| 0/0 |
2026/05/20 00:17 |
flow |
assessment-security |
45m
Results: map[DenialOfService:false Explanation:Based on the analysis of the bug report and the kernel source code, here is the
assessment of the vulnerability:
### Bug Cause
The bug occurs in `udf_expand_dir_adinicb()` in `fs/udf/namei.c`. This function
is responsible for expanding a UDF directory from inline data (stored within the
inode/ICB) to a dedicated block when the inline space is exhausted (e.g., when a
new file is added or renamed into the directory).
During this expansion, the function allocates a new block and copies the inline
data to it:
```c
memcpy(dbh->b_data, iinfo->i_data, inode->i_size);
```
However, if the directory has Extended Attributes, the `iinfo->i_data` buffer
starts with the Extended Attributes, and the actual inline directory entries
start at an offset of `iinfo->i_lenEAttr`. The correct copy operation should be
from `iinfo->i_data + iinfo->i_lenEAttr` (similar to what is done in
`udf_expand_file_adinicb()`).
Because of this incorrect offset, the function copies the Extended Attributes
and the truncated directory entries into the new block. Immediately after, it
iterates over the new block to update the tags of the directory entries. Since
the block now starts with Extended Attributes instead of valid directory
entries, `udf_verify_fi()` fails (reporting an incorrect tag, as seen in the bug
report), and the iteration returns an error (`-EFSCORRUPTED`). This triggers the
`WARN_ON_ONCE(ret)` at line 214.
### Security Impact
* **Exploitable: No**
The `memcpy()` size is bounded by `inode->i_size`. In `udf_read_inode()`,
`inode->i_size` is strictly validated to ensure it fits within the remaining
space of the block after accounting for the file entry header and Extended
Attributes. Therefore, `inode->i_size` is always less than or equal to the
size of the allocated `iinfo->i_data` buffer. There is no out-of-bounds read
from `iinfo->i_data` and no out-of-bounds write to the new block
(`dbh->b_data`). The bug only results in logical filesystem corruption on the
mounted UDF image.
* **Denial Of Service: No**
The `WARN_ON_ONCE` does not halt the system in production builds (unless
`panic_on_warn` is explicitly set). The error is handled gracefully: the
function cleans up the iterator and returns `0` (success). Subsequent
operations on the corrupted directory (like `readdir` or further lookups) will
simply fail with `-EFSCORRUPTED` or `-EIO` through normal error paths. There
are no resource leaks, deadlocks, or hangs.
* **Accessible From Unprivileged Processes / User Namespaces: No**
Triggering this bug requires mounting a crafted UDF filesystem image (one that
contains a directory with Extended Attributes and inline data). Mounting a
filesystem requires `CAP_SYS_ADMIN` in the initial namespace. Furthermore, the
UDF filesystem does not support `FS_USERNS_MOUNT`, meaning it cannot be
mounted inside an unprivileged user namespace.
* **Peripheral / Malicious Filesystem Trigger: Yes**
The bug can be triggered if a user physically plugs in a malicious USB drive
containing a crafted UDF image, and the desktop environment auto-mounts it.
However, since the bug only corrupts the attacker's own filesystem and does
not lead to privilege escalation, memory corruption, or a system crash, it
does not pose a significant security boundary violation. Exploitable:false FilesystemTrigger:true NetworkTrigger:false PeripheralTrigger:true RemoteTrigger:false Unprivileged:false UserNamespace:false VMGuestTrigger:false VMHostTrigger:false]
|
| 1/1 |
2026/05/20 00:17 |
action |
syz-repro-to-c-repro |
0m
Results: map[SimplifiedCRepro:// autogenerated by syzkaller (https://github.com/google/syzkaller)
#define _GNU_SOURCE
#include <endian.h>
#include <errno.h>
#include <fcntl.h>
#include <setjmp.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <sys/mount.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <unistd.h>
#include <linux/loop.h>
#ifndef __NR_memfd_create
#define __NR_memfd_create 319
#endif
#ifndef __NR_renameat2
#define __NR_renameat2 316
#endif
static unsigned long long procid;
//% This code is derived from puff.{c,h}, found in the zlib development. The
//% original files come with the following copyright notice:
//% Copyright (C) 2002-2013 Mark Adler, all rights reserved
//% version 2.3, 21 Jan 2013
//% This software is provided 'as-is', without any express or implied
//% warranty. In no event will the author be held liable for any damages
//% arising from the use of this software.
//% Permission is granted to anyone to use this software for any purpose,
//% including commercial applications, and to alter it and redistribute it
//% freely, subject to the following restrictions:
//% 1. The origin of this software must not be misrepresented; you must not
//% claim that you wrote the original software. If you use this software
//% in a product, an acknowledgment in the product documentation would be
//% appreciated but is not required.
//% 2. Altered source versions must be plainly marked as such, and must not be
//% misrepresented as being the original software.
//% 3. This notice may not be removed or altered from any source distribution.
//% Mark Adler madler@alumni.caltech.edu
//% BEGIN CODE DERIVED FROM puff.{c,h}
#define MAXBITS 15
#define MAXLCODES 286
#define MAXDCODES 30
#define MAXCODES (MAXLCODES + MAXDCODES)
#define FIXLCODES 288
struct puff_state {
unsigned char* out;
unsigned long outlen;
unsigned long outcnt;
const unsigned char* in;
unsigned long inlen;
unsigned long incnt;
int bitbuf;
int bitcnt;
jmp_buf env;
};
static int puff_bits(struct puff_state* s, int need)
{
long val = s->bitbuf;
while (s->bitcnt < need) {
if (s->incnt == s->inlen)
longjmp(s->env, 1);
val |= (long)(s->in[s->incnt++]) << s->bitcnt;
s->bitcnt += 8;
}
s->bitbuf = (int)(val >> need);
s->bitcnt -= need;
return (int)(val & ((1L << need) - 1));
}
static int puff_stored(struct puff_state* s)
{
s->bitbuf = 0;
s->bitcnt = 0;
if (s->incnt + 4 > s->inlen)
return 2;
unsigned len = s->in[s->incnt++];
len |= s->in[s->incnt++] << 8;
if (s->in[s->incnt++] != (~len & 0xff) ||
s->in[s->incnt++] != ((~len >> 8) & 0xff))
return -2;
if (s->incnt + len > s->inlen)
return 2;
if (s->outcnt + len > s->outlen)
return 1;
for (; len--; s->outcnt++, s->incnt++) {
if (s->in[s->incnt])
s->out[s->outcnt] = s->in[s->incnt];
}
return 0;
}
struct puff_huffman {
short* count;
short* symbol;
};
static int puff_decode(struct puff_state* s, const struct puff_huffman* h)
{
int first = 0;
int index = 0;
int bitbuf = s->bitbuf;
int left = s->bitcnt;
int code = first = index = 0;
int len = 1;
short* next = h->count + 1;
while (1) {
while (left--) {
code |= bitbuf & 1;
bitbuf >>= 1;
int count = *next++;
if (code - count < first) {
s->bitbuf = bitbuf;
s->bitcnt = (s->bitcnt - len) & 7;
return h->symbol[index + (code - first)];
}
index += count;
first += count;
first <<= 1;
code <<= 1;
len++;
}
left = (MAXBITS + 1) - len;
if (left == 0)
break;
if (s->incnt == s->inlen)
longjmp(s->env, 1);
bitbuf = s->in[s->incnt++];
if (left > 8)
left = 8;
}
return -10;
}
static int puff_construct(struct puff_huffman* h, const short* length, int n)
{
int len;
for (len = 0; len <= MAXBITS; len++)
h->count[len] = 0;
int symbol;
for (symbol = 0; symbol < n; symbol++)
(h->count[length[symbol]])++;
if (h->count[0] == n)
return 0;
int left = 1;
for (len = 1; len <= MAXBITS; len++) {
left <<= 1;
left -= h->count[len];
if (left < 0)
return left;
}
short offs[MAXBITS + 1];
offs[1] = 0;
for (len = 1; len < MAXBITS; len++)
offs[len + 1] = offs[len] + h->count[len];
for (symbol = 0; symbol < n; symbol++)
if (length[symbol] != 0)
h->symbol[offs[length[symbol]]++] = symbol;
return left;
}
static int puff_codes(struct puff_state* s,
const struct puff_huffman* lencode,
const struct puff_huffman* distcode)
{
static const short lens[29] = {
3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31,
35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258};
static const short lext[29] = {
0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2,
3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0};
static const short dists[30] = {
1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193,
257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145,
8193, 12289, 16385, 24577};
static const short dext[30] = {
0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6,
7, 7, 8, 8, 9, 9, 10, 10, 11, 11,
12, 12, 13, 13};
int symbol;
do {
symbol = puff_decode(s, lencode);
if (symbol < 0)
return symbol;
if (symbol < 256) {
if (s->outcnt == s->outlen)
return 1;
if (symbol)
s->out[s->outcnt] = symbol;
s->outcnt++;
} else if (symbol > 256) {
symbol -= 257;
if (symbol >= 29)
return -10;
int len = lens[symbol] + puff_bits(s, lext[symbol]);
symbol = puff_decode(s, distcode);
if (symbol < 0)
return symbol;
unsigned dist = dists[symbol] + puff_bits(s, dext[symbol]);
if (dist > s->outcnt)
return -11;
if (s->outcnt + len > s->outlen)
return 1;
while (len--) {
if (dist <= s->outcnt && s->out[s->outcnt - dist])
s->out[s->outcnt] = s->out[s->outcnt - dist];
s->outcnt++;
}
}
} while (symbol != 256);
return 0;
}
static int puff_fixed(struct puff_state* s)
{
static int virgin = 1;
static short lencnt[MAXBITS + 1], lensym[FIXLCODES];
static short distcnt[MAXBITS + 1], distsym[MAXDCODES];
static struct puff_huffman lencode, distcode;
if (virgin) {
lencode.count = lencnt;
lencode.symbol = lensym;
distcode.count = distcnt;
distcode.symbol = distsym;
short lengths[FIXLCODES];
int symbol;
for (symbol = 0; symbol < 144; symbol++)
lengths[symbol] = 8;
for (; symbol < 256; symbol++)
lengths[symbol] = 9;
for (; symbol < 280; symbol++)
lengths[symbol] = 7;
for (; symbol < FIXLCODES; symbol++)
lengths[symbol] = 8;
puff_construct(&lencode, lengths, FIXLCODES);
for (symbol = 0; symbol < MAXDCODES; symbol++)
lengths[symbol] = 5;
puff_construct(&distcode, lengths, MAXDCODES);
virgin = 0;
}
return puff_codes(s, &lencode, &distcode);
}
static int puff_dynamic(struct puff_state* s)
{
static const short order[19] =
{16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15};
int nlen = puff_bits(s, 5) + 257;
int ndist = puff_bits(s, 5) + 1;
int ncode = puff_bits(s, 4) + 4;
if (nlen > MAXLCODES || ndist > MAXDCODES)
return -3;
short lengths[MAXCODES];
int index;
for (index = 0; index < ncode; index++)
lengths[order[index]] = puff_bits(s, 3);
for (; index < 19; index++)
lengths[order[index]] = 0;
short lencnt[MAXBITS + 1], lensym[MAXLCODES];
struct puff_huffman lencode = {lencnt, lensym};
int err = puff_construct(&lencode, lengths, 19);
if (err != 0)
return -4;
index = 0;
while (index < nlen + ndist) {
int symbol;
int len;
symbol = puff_decode(s, &lencode);
if (symbol < 0)
return symbol;
if (symbol < 16)
lengths[index++] = symbol;
else {
len = 0;
if (symbol == 16) {
if (index == 0)
return -5;
len = lengths[index - 1];
symbol = 3 + puff_bits(s, 2);
} else if (symbol == 17)
symbol = 3 + puff_bits(s, 3);
else
symbol = 11 + puff_bits(s, 7);
if (index + symbol > nlen + ndist)
return -6;
while (symbol--)
lengths[index++] = len;
}
}
if (lengths[256] == 0)
return -9;
err = puff_construct(&lencode, lengths, nlen);
if (err && (err < 0 || nlen != lencode.count[0] + lencode.count[1]))
return -7;
short distcnt[MAXBITS + 1], distsym[MAXDCODES];
struct puff_huffman distcode = {distcnt, distsym};
err = puff_construct(&distcode, lengths + nlen, ndist);
if (err && (err < 0 || ndist != distcode.count[0] + distcode.count[1]))
return -8;
return puff_codes(s, &lencode, &distcode);
}
static int puff(
unsigned char* dest,
unsigned long* destlen,
const unsigned char* source,
unsigned long sourcelen)
{
struct puff_state s = {
.out = dest,
.outlen = *destlen,
.outcnt = 0,
.in = source,
.inlen = sourcelen,
.incnt = 0,
.bitbuf = 0,
.bitcnt = 0,
};
int err;
if (setjmp(s.env) != 0)
err = 2;
else {
int last;
do {
last = puff_bits(&s, 1);
int type = puff_bits(&s, 2);
err = type == 0 ? puff_stored(&s) : (type == 1 ? puff_fixed(&s) : (type == 2 ? puff_dynamic(&s) : -1));
if (err != 0)
break;
} while (!last);
}
*destlen = s.outcnt;
return err;
}
//% END CODE DERIVED FROM puff.{c,h}
#define ZLIB_HEADER_WIDTH 2
static int puff_zlib_to_file(const unsigned char* source, unsigned long sourcelen, int dest_fd)
{
if (sourcelen < ZLIB_HEADER_WIDTH)
return 0;
source += ZLIB_HEADER_WIDTH;
sourcelen -= ZLIB_HEADER_WIDTH;
const unsigned long max_destlen = 132 << 20;
void* ret = mmap(0, max_destlen, PROT_WRITE | PROT_READ, MAP_PRIVATE | MAP_ANON, -1, 0);
if (ret == MAP_FAILED)
return -1;
unsigned char* dest = (unsigned char*)ret;
unsigned long destlen = max_destlen;
int err = puff(dest, &destlen, source, sourcelen);
if (err) {
munmap(dest, max_destlen);
errno = -err;
return -1;
}
if (write(dest_fd, dest, destlen) != (ssize_t)destlen) {
munmap(dest, max_destlen);
return -1;
}
return munmap(dest, max_destlen);
}
static int setup_loop_device(unsigned char* data, unsigned long size, const char* loopname, int* loopfd_p)
{
int err = 0, loopfd = -1;
int memfd = syscall(__NR_memfd_create, "syzkaller", 0);
if (memfd == -1) {
err = errno;
goto error;
}
if (puff_zlib_to_file(data, size, memfd)) {
err = errno;
goto error_close_memfd;
}
loopfd = open(loopname, O_RDWR);
if (loopfd == -1) {
err = errno;
goto error_close_memfd;
}
if (ioctl(loopfd, LOOP_SET_FD, memfd)) {
if (errno != EBUSY) {
err = errno;
goto error_close_loop;
}
ioctl(loopfd, LOOP_CLR_FD, 0);
usleep(1000);
if (ioctl(loopfd, LOOP_SET_FD, memfd)) {
err = errno;
goto error_close_loop;
}
}
close(memfd);
*loopfd_p = loopfd;
return 0;
error_close_loop:
close(loopfd);
error_close_memfd:
close(memfd);
error:
errno = err;
return -1;
}
static void reset_loop_device(const char* loopname)
{
int loopfd = open(loopname, O_RDWR);
if (loopfd == -1) {
return;
}
if (ioctl(loopfd, LOOP_CLR_FD, 0)) {
}
close(loopfd);
}
static long syz_mount_image(
volatile long fsarg,
volatile long dir,
volatile long flags,
volatile long optsarg,
volatile long change_dir,
volatile unsigned long size,
volatile long image)
{
unsigned char* data = (unsigned char*)image;
int res = -1, err = 0, need_loop_device = !!size;
char* mount_opts = (char*)optsarg;
char* target = (char*)dir;
char* fs = (char*)fsarg;
char* source = NULL;
char loopname[64];
if (need_loop_device) {
int loopfd;
memset(loopname, 0, sizeof(loopname));
snprintf(loopname, sizeof(loopname), "/dev/loop%llu", procid);
if (setup_loop_device(data, size, loopname, &loopfd) == -1)
return -1;
close(loopfd);
source = loopname;
}
mkdir(target, 0777);
char opts[256];
memset(opts, 0, sizeof(opts));
if (strlen(mount_opts) > (sizeof(opts) - 32)) {
}
strncpy(opts, mount_opts, sizeof(opts) - 32);
if (strcmp(fs, "iso9660") == 0) {
flags |= MS_RDONLY;
} else if (strncmp(fs, "ext", 3) == 0) {
bool has_remount_ro = false;
char* remount_ro_start = strstr(opts, "errors=remount-ro");
if (remount_ro_start != NULL) {
char after = *(remount_ro_start + strlen("errors=remount-ro"));
char before = remount_ro_start == opts ? '\0' : *(remount_ro_start - 1);
has_remount_ro = ((before == '\0' || before == ',') && (after == '\0' || after == ','));
}
if (strstr(opts, "errors=panic") || !has_remount_ro)
strcat(opts, ",errors=continue");
} else if (strcmp(fs, "xfs") == 0) {
strcat(opts, ",nouuid");
} else if (strncmp(fs, "gfs2", 4) == 0 && (strstr(opts, "errors=panic") || strstr(opts, "debug"))) {
strcat(opts, ",errors=withdraw");
}
res = mount(source, target, fs, flags, opts);
if (res == -1) {
err = errno;
goto error_clear_loop;
}
res = open(target, O_RDONLY | O_DIRECTORY);
if (res == -1) {
err = errno;
goto error_clear_loop;
}
if (change_dir) {
res = chdir(target);
if (res == -1) {
err = errno;
}
}
error_clear_loop:
if (need_loop_device)
reset_loop_device(loopname);
errno = err;
return res;
}
uint64_t r[1] = {0xffffffffffffffff};
int main(void)
{
syscall(__NR_mmap, /*addr=*/0x1ffffffff000ul, /*len=*/0x1000ul, /*prot=*/0ul, /*flags=MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE*/0x32ul, /*fd=*/(intptr_t)-1, /*offset=*/0ul);
syscall(__NR_mmap, /*addr=*/0x200000000000ul, /*len=*/0x1000000ul, /*prot=PROT_WRITE|PROT_READ|PROT_EXEC*/7ul, /*flags=MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE*/0x32ul, /*fd=*/(intptr_t)-1, /*offset=*/0ul);
syscall(__NR_mmap, /*addr=*/0x200001000000ul, /*len=*/0x1000ul, /*prot=*/0ul, /*flags=MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE*/0x32ul, /*fd=*/(intptr_t)-1, /*offset=*/0ul);
const char* reason;
(void)reason;
intptr_t res = 0;
if (write(1, "executing program\n", sizeof("executing program\n") - 1)) {}
// syz_mount_image$udf arguments: [
// fs: ptr[in, buffer] {
// buffer: {75 64 66 00} (length 0x4)
// }
// dir: ptr[in, buffer] {
// buffer: {2e 2f 66 69 6c 65 31 00} (length 0x8)
// }
// flags: mount_flags = 0x0 (8 bytes)
// opts: ptr[inout, array[ANYUNION]] {
// array[ANYUNION] {
// union ANYUNION {
// ANYBLOB: buffer: {6e 6f 61 64 69 6e 69 63 62 2c 6e 6f 73 74 72 69 63 74 2c 6d 6f 64 65 3d 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 34 2c 75 69 64 3d 66 6f 72 67 65 74 2c 6e 6f 61 64 69 6e 69 63 62 2c 75 6d 61 73 6b 3d 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 34 30 30 30 32 30 30 30 2c 6c 61 73 74 62 6c 6f 63 6b 3d 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 31 33 2c 75 6e 64 65 6c 65 74 65 2c 70 61 72 74 69 74 69 6f 6e 3d 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 35 2c 00} (length 0xab)
// }
// }
// }
// chdir: int8 = 0x47 (1 bytes)
// size: len = 0xc15 (8 bytes)
// img: ptr[in, buffer] {
// buffer: (compressed buffer with length 0xc15)
// }
// ]
// returns fd_dir
memcpy((void*)0x200000000c40, "udf\000", 4);
memcpy((void*)0x2000000000c0, "./file1\000", 8);
memcpy((void*)0x200000000180, "... [truncated large byte array] ...", 171);
memcpy((void*)0x200000001940, "... [truncated large byte array] ...", 3093);
syz_mount_image(/*fs=*/0x200000000c40, /*dir=*/0x2000000000c0, /*flags=*/0, /*opts=*/0x200000000180, /*chdir=*/0x47, /*size=*/0xc15, /*img=*/0x200000001940);
// openat$dir arguments: [
// fd: const = 0xffffffffffffff9c (8 bytes)
// file: ptr[in, buffer] {
// buffer: {2e 00} (length 0x2)
// }
// flags: open_flags = 0x32d800 (4 bytes)
// mode: open_mode = 0x0 (2 bytes)
// ]
// returns fd_dir
memcpy((void*)0x200000000040, ".\000", 2);
res = syscall(__NR_openat, /*fd=*/0xffffffffffffff9cul, /*file=*/0x200000000040ul, /*flags=O_SYNC|O_PATH|O_NONBLOCK|O_NOFOLLOW|O_LARGEFILE|O_DIRECT*/0x32d800, /*mode=*/0);
if (res != -1)
r[0] = res;
// renameat2 arguments: [
// oldfd: fd_dir (resource)
// old: ptr[in, buffer] {
// buffer: {2e 2f 66 69 6c 65 31 00} (length 0x8)
// }
// newfd: fd_dir (resource)
// new: ptr[in, buffer] {
// buffer: {2e 2f 66 69 6c 65 30 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 00} (length 0xfd)
// }
// flags: renameat2_flags = 0x0 (8 bytes)
// ]
memcpy((void*)0x200000000080, "./file1\000", 8);
memcpy((void*)0x200000000980, "... [truncated large byte array] ...", 253);
syscall(__NR_renameat2, /*oldfd=*/0xffffff9c, /*old=*/0x200000000080ul, /*newfd=*/r[0], /*new=*/0x200000000980ul, /*flags=*/0ul);
// mount arguments: [
// src: nil
// dst: ptr[in, buffer] {
// buffer: {2e 00} (length 0x2)
// }
// type: nil
// flags: mount_flags = 0x2236824 (8 bytes)
// data: nil
// ]
memcpy((void*)0x200000000000, ".\000", 2);
syscall(__NR_mount, /*src=*/0ul, /*dst=*/0x200000000000ul, /*type=*/0ul, /*flags=MS_LAZYTIME|MS_UNBINDABLE|MS_POSIXACL|MS_REC|MS_REMOUNT|MS_RELATIME|0x2804*/0x2236824ul, /*data=*/0ul);
// unlink arguments: [
// path: ptr[in, buffer] {
// buffer: {2e 2f 66 69 6c 65 31 00} (length 0x8)
// }
// ]
memcpy((void*)0x200000000000, "./file1\000", 8);
syscall(__NR_unlink, /*path=*/0x200000000000ul);
return 0;
}
]
|
| 2/1 |
2026/05/20 00:17 |
action |
kernel-checkouter |
1m
Results: map[KernelSrc:/app/workdir/cache/src/1ba55c5f381082e9b9ad4b0c2543dbf5328402c4]
|
| 3/1 |
2026/05/20 00:18 |
action |
kernel-builder |
21m
Results: map[KernelObj:/app/workdir/cache/build/a74e49e1ca872c89e05aba79c3df5f5db83f23c5]
|
| 4/1 |
2026/05/20 00:40 |
action |
codesearch-prepare |
16m
Results: map[Index:codesearch-index]
|
| 5/1 |
2026/05/20 00:57 |
agent |
expert |
5m
Model:
Results: map[DenialOfService:false Exploitable:false FilesystemTrigger:true NetworkTrigger:false PeripheralTrigger:true RemoteTrigger:false Unprivileged:false UserNamespace:false VMGuestTrigger:false VMHostTrigger:false]
Instruction:
You are an experienced Linux kernel security engineer. Your task is to analyze given kernel bug report
and determine its security impact based on the following dimensions.
Use the provided tools to examine the source code, check for capability checks (e.g., capable(), ns_capable()),
and understand the nature of the bug. Analyze the given kernel build and configuration.
You can check the kernel config by grepping ".config" file; you can check kernel cmdline by greeping
".config" file for "CONFIG_CMDLINE=". Assume sysctl parameters have default values.
But analyze for the corresponding production build w/o debugging tools enabled (like KASAN, KMSAN, UBSAN).
Don't make assumptions; verify them with source code access. Try different strategies when analyzing the bug:
- think of ways in which the vulnerable code is unreachable
- or the other way around: try to come up with different ideas of how an unprivileged user can reach the bug
If still unsure err on the side of the bug being non-exploitable/not-accessible.
In the final reply, provide a reasoning for your assessment.
Analysis dimensions:
* Exploitable:
Determine if the bug can result in memory corruption or elevated privileges.
Memory safety issues are almost always exploitable (KASAN or UBSAN reports for use-after-free, out-of-bounds;
refcounting issues, corrupted lists, etc). When kernel is crashing on a completly wild pointer access
(e.g. user-space address, or non-canonical address, but not on NULL or address corresponding to KASAN shadow
for NULL address), including both data accesses and control tranfers, that's also usually implies possibility
of exploitation. Such reports usually say "unable to handle kernel paging request".
Uses of uninitialized values detected by KMSAN may be exploitable b/c attacker frequently can affect uninit
values with spraying techniques. However, for these exploitabability depends on how exactly the uninit value
is used in the code, and what it affects.
Think of what happens after the bug is triggered. Some bugs cause kernel panic and halt execution,
they are harder to exploit. For example, BUG reports halts the kernel. However, WARNING reports don't halt
execution in production builds. Debug bug detection tools (like KASAN, KMSAN, KCSAN, UBSAN) are also not enabled
in production builds, so attacker can freely exploit these bugs w/o being detected by these tools.
If you see an integer overflow, think how the overflowed value used later (if it's used as allocation size,
or an array index). If you see an out-of-bounds read, think if it's followed by an out-of-bounds write as well.
Some KCSAN data-races may be exploitable by skilled attackers as well. Think what data structures got corrupted
as the result of data races and how. However, note that kernel has lots of "benign" data races that don't lead
to any runtime misbehavior at all.
* Denial Of Service:
Determine if the bug can result in denial-of-service. Most bugs can, since they cause system crash,
hangs, deadlocks, or resource leaks. This is mostly applicable to WARNING bugs that won't cause system crash
in production. For these think what will be consequences of the violation of the kernel assumptions flagged
by the WARNING. In some cases the unexpected condition is also properly handled by the normal control flow
(e.g. with "if (WARN_ON(...))"), these won't cause denial-of-service. If the condition is not handled,
then it may or may not cause denial-of-service.
* Accessible From Unprivileged Processes:
Determine if the bug can be reached from a typical (non-root) user process that does NOT have any special capabilities
(like CAP_SYS_ADMIN, CAP_NET_ADMIN, CAP_NET_RAW, CAP_PERFMON) or access to device nodes restricted to root.
Assume that unprivileged_bpf_disabled=1, that is eBPF loading is not accessible. However, cBPF (classical BPF)
is still accessible to non-root processes.
Assume that user namespaces are not accessible, that is, the process cannot get the mentioned capabilities even
within a new user namespace (checked by ns_capable() function in the kernel sources).
* Accessible From User Namespaces:
Determine if the bug can be reached within a user-namespace where the process has all capabilities
(including CAP_SYS_ADMIN, CAP_NET_ADMIN, CAP_NET_RAW, CAP_PERFMON). Such capabilities are checked with ns_capable()
function in the kernel sources.
* VM Guest Trigger:
Determine if the bug can be triggered from the context of a typical KVM guest (e.g., set up by a QEMU VMM).
Consider accesses to standard Linux host paravirtualized features (virtio-blk, virtio-net, etc.),
and handling of VM exits in the KVM code.
* VM Host Trigger in The Confidetial Computing Context:
Determine if the bug can be triggered in a confidential computing guest kernel from the context of a KVM host.
Consider access to standard Linux guest paravirtualized features (virtio-blk, virtio-net, etc.).
* Ethernet Network Trigger:
Determine if the bug can be triggered by processing ingress network Ethernet traffic, either directly (network stack)
or via drivers exposed to network data.
* Other Remote Trigger:
Determine if the bug can be triggered by processing remote traffic other than Ethernet (Wifi, Bluetooth, NFC, etc).
* Peripheral Trigger:
Determine if the bug can be triggered via an untrusted peripheral device that can be physically plugged
into a system, such as a USB device or a niche hardware driver handling external hardware inputs.
This is particularly important for mobile and desktop environments where users can plug in unknown devices.
* Malicious Filesystem Trigger:
Determine if the bug can be triggered by the kernel mounting and parsing a malicious filesystem image.
This is highly critical for Desktop and Mobile environments where external media or downloaded images
might be auto-mounted.
Prefer calling several tools at the same time to save round-trips.
Use set-results tool to provide results of the analysis.
It must be called exactly once before the final reply.
Ignore results of this tool.
Prompt:
The kernel bug report is:
UDF-fs: error (device loop1): udf_verify_fi: directory (ino 1408) has entry at pos 128 with incorrect tag 1
------------[ cut here ]------------
WARNING: CPU: 1 PID: 8363 at fs/udf/namei.c:214 udf_expand_dir_adinicb+0xbf6/0xf00 fs/udf/namei.c:214
Modules linked in:
CPU: 1 UID: 0 PID: 8363 Comm: syz.1.1106 Not tainted 6.15.0-syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:udf_expand_dir_adinicb+0xbf6/0xf00 fs/udf/namei.c:214
Code: 01 00 00 00 e8 ab 1e fe ff 8b 5c 24 60 e9 aa f6 ff ff e8 0d 12 80 fe 4c 89 ef e8 c5 c8 09 ff e9 ac f8 ff ff e8 fb 11 80 fe 90 <0f> 0b 90 e9 88 fe ff ff bb 8b ff ff ff e9 80 f6 ff ff bb f4 ff ff
RSP: 0018:ffffc9000b4bf400 EFLAGS: 00010293
RAX: 0000000000000000 RBX: 00000000ffffff8b RCX: ffffffff833b31ce
RDX: ffff8880321e1e00 RSI: ffffffff833b3345 RDI: 0000000000000005
RBP: ffffc9000b4bf680 R08: 0000000000000005 R09: 0000000000000000
R10: 00000000ffffff8b R11: 0000000000000000 R12: 00000000ffffff8b
R13: ffff88805c84d740 R14: 0000000000000000 R15: 0000000000000000
FS: 00007f4d6dc3e6c0(0000) GS:ffff888124ae0000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f5509c78000 CR3: 0000000034101000 CR4: 0000000000350ef0
Call Trace:
<TASK>
udf_fiiter_add_entry+0xcf0/0x10d0 fs/udf/namei.c:262
udf_rename+0x902/0xd90 fs/udf/namei.c:843
vfs_rename+0xf64/0x2250 fs/namei.c:5121
do_renameat2+0x82b/0xc90 fs/namei.c:5270
__do_sys_renameat2 fs/namei.c:5304 [inline]
__se_sys_renameat2 fs/namei.c:5301 [inline]
__x64_sys_renameat2+0xe7/0x130 fs/namei.c:5301
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0x260 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f4d6cd8e969
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f4d6dc3e038 EFLAGS: 00000246 ORIG_RAX: 000000000000013c
RAX: ffffffffffffffda RBX: 00007f4d6cfb5fa0 RCX: 00007f4d6cd8e969
RDX: 0000000000000004 RSI: 0000200000000080 RDI: ffffffffffffff9c
RBP: 00007f4d6ce10ab1 R08: 0000000000000000 R09: 0000000000000000
R10: 0000200000000980 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f4d6cfb5fa0 R15: 00007ffeb5d70468
</TASK>
It is reproducible with the followint program.
Keep in mind that it may lack the precise threading, sandboxing, and some arguments of a working reproducer.
But it should give an idea of the involved syscalls.
// autogenerated by syzkaller (https://github.com/google/syzkaller)
#define _GNU_SOURCE
#include <endian.h>
#include <errno.h>
#include <fcntl.h>
#include <setjmp.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <sys/mount.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <unistd.h>
#include <linux/loop.h>
#ifndef __NR_memfd_create
#define __NR_memfd_create 319
#endif
#ifndef __NR_renameat2
#define __NR_renameat2 316
#endif
static unsigned long long procid;
//% This code is derived from puff.{c,h}, found in the zlib development. The
//% original files come with the following copyright notice:
//% Copyright (C) 2002-2013 Mark Adler, all rights reserved
//% version 2.3, 21 Jan 2013
//% This software is provided 'as-is', without any express or implied
//% warranty. In no event will the author be held liable for any damages
//% arising from the use of this software.
//% Permission is granted to anyone to use this software for any purpose,
//% including commercial applications, and to alter it and redistribute it
//% freely, subject to the following restrictions:
//% 1. The origin of this software must not be misrepresented; you must not
//% claim that you wrote the original software. If you use this software
//% in a product, an acknowledgment in the product documentation would be
//% appreciated but is not required.
//% 2. Altered source versions must be plainly marked as such, and must not be
//% misrepresented as being the original software.
//% 3. This notice may not be removed or altered from any source distribution.
//% Mark Adler madler@alumni.caltech.edu
//% BEGIN CODE DERIVED FROM puff.{c,h}
#define MAXBITS 15
#define MAXLCODES 286
#define MAXDCODES 30
#define MAXCODES (MAXLCODES + MAXDCODES)
#define FIXLCODES 288
struct puff_state {
unsigned char* out;
unsigned long outlen;
unsigned long outcnt;
const unsigned char* in;
unsigned long inlen;
unsigned long incnt;
int bitbuf;
int bitcnt;
jmp_buf env;
};
static int puff_bits(struct puff_state* s, int need)
{
long val = s->bitbuf;
while (s->bitcnt < need) {
if (s->incnt == s->inlen)
longjmp(s->env, 1);
val |= (long)(s->in[s->incnt++]) << s->bitcnt;
s->bitcnt += 8;
}
s->bitbuf = (int)(val >> need);
s->bitcnt -= need;
return (int)(val & ((1L << need) - 1));
}
static int puff_stored(struct puff_state* s)
{
s->bitbuf = 0;
s->bitcnt = 0;
if (s->incnt + 4 > s->inlen)
return 2;
unsigned len = s->in[s->incnt++];
len |= s->in[s->incnt++] << 8;
if (s->in[s->incnt++] != (~len & 0xff) ||
s->in[s->incnt++] != ((~len >> 8) & 0xff))
return -2;
if (s->incnt + len > s->inlen)
return 2;
if (s->outcnt + len > s->outlen)
return 1;
for (; len--; s->outcnt++, s->incnt++) {
if (s->in[s->incnt])
s->out[s->outcnt] = s->in[s->incnt];
}
return 0;
}
struct puff_huffman {
short* count;
short* symbol;
};
static int puff_decode(struct puff_state* s, const struct puff_huffman* h)
{
int first = 0;
int index = 0;
int bitbuf = s->bitbuf;
int left = s->bitcnt;
int code = first = index = 0;
int len = 1;
short* next = h->count + 1;
while (1) {
while (left--) {
code |= bitbuf & 1;
bitbuf >>= 1;
int count = *next++;
if (code - count < first) {
s->bitbuf = bitbuf;
s->bitcnt = (s->bitcnt - len) & 7;
return h->symbol[index + (code - first)];
}
index += count;
first += count;
first <<= 1;
code <<= 1;
len++;
}
left = (MAXBITS + 1) - len;
if (left == 0)
break;
if (s->incnt == s->inlen)
longjmp(s->env, 1);
bitbuf = s->in[s->incnt++];
if (left > 8)
left = 8;
}
return -10;
}
static int puff_construct(struct puff_huffman* h, const short* length, int n)
{
int len;
for (len = 0; len <= MAXBITS; len++)
h->count[len] = 0;
int symbol;
for (symbol = 0; symbol < n; symbol++)
(h->count[length[symbol]])++;
if (h->count[0] == n)
return 0;
int left = 1;
for (len = 1; len <= MAXBITS; len++) {
left <<= 1;
left -= h->count[len];
if (left < 0)
return left;
}
short offs[MAXBITS + 1];
offs[1] = 0;
for (len = 1; len < MAXBITS; len++)
offs[len + 1] = offs[len] + h->count[len];
for (symbol = 0; symbol < n; symbol++)
if (length[symbol] != 0)
h->symbol[offs[length[symbol]]++] = symbol;
return left;
}
static int puff_codes(struct puff_state* s,
const struct puff_huffman* lencode,
const struct puff_huffman* distcode)
{
static const short lens[29] = {
3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31,
35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258};
static const short lext[29] = {
0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2,
3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0};
static const short dists[30] = {
1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193,
257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145,
8193, 12289, 16385, 24577};
static const short dext[30] = {
0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6,
7, 7, 8, 8, 9, 9, 10, 10, 11, 11,
12, 12, 13, 13};
int symbol;
do {
symbol = puff_decode(s, lencode);
if (symbol < 0)
return symbol;
if (symbol < 256) {
if (s->outcnt == s->outlen)
return 1;
if (symbol)
s->out[s->outcnt] = symbol;
s->outcnt++;
} else if (symbol > 256) {
symbol -= 257;
if (symbol >= 29)
return -10;
int len = lens[symbol] + puff_bits(s, lext[symbol]);
symbol = puff_decode(s, distcode);
if (symbol < 0)
return symbol;
unsigned dist = dists[symbol] + puff_bits(s, dext[symbol]);
if (dist > s->outcnt)
return -11;
if (s->outcnt + len > s->outlen)
return 1;
while (len--) {
if (dist <= s->outcnt && s->out[s->outcnt - dist])
s->out[s->outcnt] = s->out[s->outcnt - dist];
s->outcnt++;
}
}
} while (symbol != 256);
return 0;
}
static int puff_fixed(struct puff_state* s)
{
static int virgin = 1;
static short lencnt[MAXBITS + 1], lensym[FIXLCODES];
static short distcnt[MAXBITS + 1], distsym[MAXDCODES];
static struct puff_huffman lencode, distcode;
if (virgin) {
lencode.count = lencnt;
lencode.symbol = lensym;
distcode.count = distcnt;
distcode.symbol = distsym;
short lengths[FIXLCODES];
int symbol;
for (symbol = 0; symbol < 144; symbol++)
lengths[symbol] = 8;
for (; symbol < 256; symbol++)
lengths[symbol] = 9;
for (; symbol < 280; symbol++)
lengths[symbol] = 7;
for (; symbol < FIXLCODES; symbol++)
lengths[symbol] = 8;
puff_construct(&lencode, lengths, FIXLCODES);
for (symbol = 0; symbol < MAXDCODES; symbol++)
lengths[symbol] = 5;
puff_construct(&distcode, lengths, MAXDCODES);
virgin = 0;
}
return puff_codes(s, &lencode, &distcode);
}
static int puff_dynamic(struct puff_state* s)
{
static const short order[19] =
{16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15};
int nlen = puff_bits(s, 5) + 257;
int ndist = puff_bits(s, 5) + 1;
int ncode = puff_bits(s, 4) + 4;
if (nlen > MAXLCODES || ndist > MAXDCODES)
return -3;
short lengths[MAXCODES];
int index;
for (index = 0; index < ncode; index++)
lengths[order[index]] = puff_bits(s, 3);
for (; index < 19; index++)
lengths[order[index]] = 0;
short lencnt[MAXBITS + 1], lensym[MAXLCODES];
struct puff_huffman lencode = {lencnt, lensym};
int err = puff_construct(&lencode, lengths, 19);
if (err != 0)
return -4;
index = 0;
while (index < nlen + ndist) {
int symbol;
int len;
symbol = puff_decode(s, &lencode);
if (symbol < 0)
return symbol;
if (symbol < 16)
lengths[index++] = symbol;
else {
len = 0;
if (symbol == 16) {
if (index == 0)
return -5;
len = lengths[index - 1];
symbol = 3 + puff_bits(s, 2);
} else if (symbol == 17)
symbol = 3 + puff_bits(s, 3);
else
symbol = 11 + puff_bits(s, 7);
if (index + symbol > nlen + ndist)
return -6;
while (symbol--)
lengths[index++] = len;
}
}
if (lengths[256] == 0)
return -9;
err = puff_construct(&lencode, lengths, nlen);
if (err && (err < 0 || nlen != lencode.count[0] + lencode.count[1]))
return -7;
short distcnt[MAXBITS + 1], distsym[MAXDCODES];
struct puff_huffman distcode = {distcnt, distsym};
err = puff_construct(&distcode, lengths + nlen, ndist);
if (err && (err < 0 || ndist != distcode.count[0] + distcode.count[1]))
return -8;
return puff_codes(s, &lencode, &distcode);
}
static int puff(
unsigned char* dest,
unsigned long* destlen,
const unsigned char* source,
unsigned long sourcelen)
{
struct puff_state s = {
.out = dest,
.outlen = *destlen,
.outcnt = 0,
.in = source,
.inlen = sourcelen,
.incnt = 0,
.bitbuf = 0,
.bitcnt = 0,
};
int err;
if (setjmp(s.env) != 0)
err = 2;
else {
int last;
do {
last = puff_bits(&s, 1);
int type = puff_bits(&s, 2);
err = type == 0 ? puff_stored(&s) : (type == 1 ? puff_fixed(&s) : (type == 2 ? puff_dynamic(&s) : -1));
if (err != 0)
break;
} while (!last);
}
*destlen = s.outcnt;
return err;
}
//% END CODE DERIVED FROM puff.{c,h}
#define ZLIB_HEADER_WIDTH 2
static int puff_zlib_to_file(const unsigned char* source, unsigned long sourcelen, int dest_fd)
{
if (sourcelen < ZLIB_HEADER_WIDTH)
return 0;
source += ZLIB_HEADER_WIDTH;
sourcelen -= ZLIB_HEADER_WIDTH;
const unsigned long max_destlen = 132 << 20;
void* ret = mmap(0, max_destlen, PROT_WRITE | PROT_READ, MAP_PRIVATE | MAP_ANON, -1, 0);
if (ret == MAP_FAILED)
return -1;
unsigned char* dest = (unsigned char*)ret;
unsigned long destlen = max_destlen;
int err = puff(dest, &destlen, source, sourcelen);
if (err) {
munmap(dest, max_destlen);
errno = -err;
return -1;
}
if (write(dest_fd, dest, destlen) != (ssize_t)destlen) {
munmap(dest, max_destlen);
return -1;
}
return munmap(dest, max_destlen);
}
static int setup_loop_device(unsigned char* data, unsigned long size, const char* loopname, int* loopfd_p)
{
int err = 0, loopfd = -1;
int memfd = syscall(__NR_memfd_create, "syzkaller", 0);
if (memfd == -1) {
err = errno;
goto error;
}
if (puff_zlib_to_file(data, size, memfd)) {
err = errno;
goto error_close_memfd;
}
loopfd = open(loopname, O_RDWR);
if (loopfd == -1) {
err = errno;
goto error_close_memfd;
}
if (ioctl(loopfd, LOOP_SET_FD, memfd)) {
if (errno != EBUSY) {
err = errno;
goto error_close_loop;
}
ioctl(loopfd, LOOP_CLR_FD, 0);
usleep(1000);
if (ioctl(loopfd, LOOP_SET_FD, memfd)) {
err = errno;
goto error_close_loop;
}
}
close(memfd);
*loopfd_p = loopfd;
return 0;
error_close_loop:
close(loopfd);
error_close_memfd:
close(memfd);
error:
errno = err;
return -1;
}
static void reset_loop_device(const char* loopname)
{
int loopfd = open(loopname, O_RDWR);
if (loopfd == -1) {
return;
}
if (ioctl(loopfd, LOOP_CLR_FD, 0)) {
}
close(loopfd);
}
static long syz_mount_image(
volatile long fsarg,
volatile long dir,
volatile long flags,
volatile long optsarg,
volatile long change_dir,
volatile unsigned long size,
volatile long image)
{
unsigned char* data = (unsigned char*)image;
int res = -1, err = 0, need_loop_device = !!size;
char* mount_opts = (char*)optsarg;
char* target = (char*)dir;
char* fs = (char*)fsarg;
char* source = NULL;
char loopname[64];
if (need_loop_device) {
int loopfd;
memset(loopname, 0, sizeof(loopname));
snprintf(loopname, sizeof(loopname), "/dev/loop%llu", procid);
if (setup_loop_device(data, size, loopname, &loopfd) == -1)
return -1;
close(loopfd);
source = loopname;
}
mkdir(target, 0777);
char opts[256];
memset(opts, 0, sizeof(opts));
if (strlen(mount_opts) > (sizeof(opts) - 32)) {
}
strncpy(opts, mount_opts, sizeof(opts) - 32);
if (strcmp(fs, "iso9660") == 0) {
flags |= MS_RDONLY;
} else if (strncmp(fs, "ext", 3) == 0) {
bool has_remount_ro = false;
char* remount_ro_start = strstr(opts, "errors=remount-ro");
if (remount_ro_start != NULL) {
char after = *(remount_ro_start + strlen("errors=remount-ro"));
char before = remount_ro_start == opts ? '\0' : *(remount_ro_start - 1);
has_remount_ro = ((before == '\0' || before == ',') && (after == '\0' || after == ','));
}
if (strstr(opts, "errors=panic") || !has_remount_ro)
strcat(opts, ",errors=continue");
} else if (strcmp(fs, "xfs") == 0) {
strcat(opts, ",nouuid");
} else if (strncmp(fs, "gfs2", 4) == 0 && (strstr(opts, "errors=panic") || strstr(opts, "debug"))) {
strcat(opts, ",errors=withdraw");
}
res = mount(source, target, fs, flags, opts);
if (res == -1) {
err = errno;
goto error_clear_loop;
}
res = open(target, O_RDONLY | O_DIRECTORY);
if (res == -1) {
err = errno;
goto error_clear_loop;
}
if (change_dir) {
res = chdir(target);
if (res == -1) {
err = errno;
}
}
error_clear_loop:
if (need_loop_device)
reset_loop_device(loopname);
errno = err;
return res;
}
uint64_t r[1] = {0xffffffffffffffff};
int main(void)
{
syscall(__NR_mmap, /*addr=*/0x1ffffffff000ul, /*len=*/0x1000ul, /*prot=*/0ul, /*flags=MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE*/0x32ul, /*fd=*/(intptr_t)-1, /*offset=*/0ul);
syscall(__NR_mmap, /*addr=*/0x200000000000ul, /*len=*/0x1000000ul, /*prot=PROT_WRITE|PROT_READ|PROT_EXEC*/7ul, /*flags=MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE*/0x32ul, /*fd=*/(intptr_t)-1, /*offset=*/0ul);
syscall(__NR_mmap, /*addr=*/0x200001000000ul, /*len=*/0x1000ul, /*prot=*/0ul, /*flags=MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE*/0x32ul, /*fd=*/(intptr_t)-1, /*offset=*/0ul);
const char* reason;
(void)reason;
intptr_t res = 0;
if (write(1, "executing program\n", sizeof("executing program\n") - 1)) {}
// syz_mount_image$udf arguments: [
// fs: ptr[in, buffer] {
// buffer: {75 64 66 00} (length 0x4)
// }
// dir: ptr[in, buffer] {
// buffer: {2e 2f 66 69 6c 65 31 00} (length 0x8)
// }
// flags: mount_flags = 0x0 (8 bytes)
// opts: ptr[inout, array[ANYUNION]] {
// array[ANYUNION] {
// union ANYUNION {
// ANYBLOB: buffer: {6e 6f 61 64 69 6e 69 63 62 2c 6e 6f 73 74 72 69 63 74 2c 6d 6f 64 65 3d 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 34 2c 75 69 64 3d 66 6f 72 67 65 74 2c 6e 6f 61 64 69 6e 69 63 62 2c 75 6d 61 73 6b 3d 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 34 30 30 30 32 30 30 30 2c 6c 61 73 74 62 6c 6f 63 6b 3d 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 31 33 2c 75 6e 64 65 6c 65 74 65 2c 70 61 72 74 69 74 69 6f 6e 3d 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 35 2c 00} (length 0xab)
// }
// }
// }
// chdir: int8 = 0x47 (1 bytes)
// size: len = 0xc15 (8 bytes)
// img: ptr[in, buffer] {
// buffer: (compressed buffer with length 0xc15)
// }
// ]
// returns fd_dir
memcpy((void*)0x200000000c40, "udf\000", 4);
memcpy((void*)0x2000000000c0, "./file1\000", 8);
memcpy((void*)0x200000000180, "... [truncated large byte array] ...", 171);
memcpy((void*)0x200000001940, "... [truncated large byte array] ...", 3093);
syz_mount_image(/*fs=*/0x200000000c40, /*dir=*/0x2000000000c0, /*flags=*/0, /*opts=*/0x200000000180, /*chdir=*/0x47, /*size=*/0xc15, /*img=*/0x200000001940);
// openat$dir arguments: [
// fd: const = 0xffffffffffffff9c (8 bytes)
// file: ptr[in, buffer] {
// buffer: {2e 00} (length 0x2)
// }
// flags: open_flags = 0x32d800 (4 bytes)
// mode: open_mode = 0x0 (2 bytes)
// ]
// returns fd_dir
memcpy((void*)0x200000000040, ".\000", 2);
res = syscall(__NR_openat, /*fd=*/0xffffffffffffff9cul, /*file=*/0x200000000040ul, /*flags=O_SYNC|O_PATH|O_NONBLOCK|O_NOFOLLOW|O_LARGEFILE|O_DIRECT*/0x32d800, /*mode=*/0);
if (res != -1)
r[0] = res;
// renameat2 arguments: [
// oldfd: fd_dir (resource)
// old: ptr[in, buffer] {
// buffer: {2e 2f 66 69 6c 65 31 00} (length 0x8)
// }
// newfd: fd_dir (resource)
// new: ptr[in, buffer] {
// buffer: {2e 2f 66 69 6c 65 30 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 61 00} (length 0xfd)
// }
// flags: renameat2_flags = 0x0 (8 bytes)
// ]
memcpy((void*)0x200000000080, "./file1\000", 8);
memcpy((void*)0x200000000980, "... [truncated large byte array] ...", 253);
syscall(__NR_renameat2, /*oldfd=*/0xffffff9c, /*old=*/0x200000000080ul, /*newfd=*/r[0], /*new=*/0x200000000980ul, /*flags=*/0ul);
// mount arguments: [
// src: nil
// dst: ptr[in, buffer] {
// buffer: {2e 00} (length 0x2)
// }
// type: nil
// flags: mount_flags = 0x2236824 (8 bytes)
// data: nil
// ]
memcpy((void*)0x200000000000, ".\000", 2);
syscall(__NR_mount, /*src=*/0ul, /*dst=*/0x200000000000ul, /*type=*/0ul, /*flags=MS_LAZYTIME|MS_UNBINDABLE|MS_POSIXACL|MS_REC|MS_REMOUNT|MS_RELATIME|0x2804*/0x2236824ul, /*data=*/0ul);
// unlink arguments: [
// path: ptr[in, buffer] {
// buffer: {2e 2f 66 69 6c 65 31 00} (length 0x8)
// }
// ]
memcpy((void*)0x200000000000, "./file1\000", 8);
syscall(__NR_unlink, /*path=*/0x200000000000ul);
return 0;
}
Reply: Based on the analysis of the bug report and the kernel source code, here is the assessment of the vulnerability:
### Bug Cause
The bug occurs in `udf_expand_dir_adinicb()` in `fs/udf/namei.c`. This function is responsible for expanding a UDF directory from inline data (stored within the inode/ICB) to a dedicated block when the inline space is exhausted (e.g., when a new file is added or renamed into the directory).
During this expansion, the function allocates a new block and copies the inline data to it:
```c
memcpy(dbh->b_data, iinfo->i_data, inode->i_size);
```
However, if the directory has Extended Attributes, the `iinfo->i_data` buffer starts with the Extended Attributes, and the actual inline directory entries start at an offset of `iinfo->i_lenEAttr`. The correct copy operation should be from `iinfo->i_data + iinfo->i_lenEAttr` (similar to what is done in `udf_expand_file_adinicb()`).
Because of this incorrect offset, the function copies the Extended Attributes and the truncated directory entries into the new block. Immediately after, it iterates over the new block to update the tags of the directory entries. Since the block now starts with Extended Attributes instead of valid directory entries, `udf_verify_fi()` fails (reporting an incorrect tag, as seen in the bug report), and the iteration returns an error (`-EFSCORRUPTED`). This triggers the `WARN_ON_ONCE(ret)` at line 214.
### Security Impact
* **Exploitable: No**
The `memcpy()` size is bounded by `inode->i_size`. In `udf_read_inode()`, `inode->i_size` is strictly validated to ensure it fits within the remaining space of the block after accounting for the file entry header and Extended Attributes. Therefore, `inode->i_size` is always less than or equal to the size of the allocated `iinfo->i_data` buffer. There is no out-of-bounds read from `iinfo->i_data` and no out-of-bounds write to the new block (`dbh->b_data`). The bug only results in logical filesystem corruption on the mounted UDF image.
* **Denial Of Service: No**
The `WARN_ON_ONCE` does not halt the system in production builds (unless `panic_on_warn` is explicitly set). The error is handled gracefully: the function cleans up the iterator and returns `0` (success). Subsequent operations on the corrupted directory (like `readdir` or further lookups) will simply fail with `-EFSCORRUPTED` or `-EIO` through normal error paths. There are no resource leaks, deadlocks, or hangs.
* **Accessible From Unprivileged Processes / User Namespaces: No**
Triggering this bug requires mounting a crafted UDF filesystem image (one that contains a directory with Extended Attributes and inline data). Mounting a filesystem requires `CAP_SYS_ADMIN` in the initial namespace. Furthermore, the UDF filesystem does not support `FS_USERNS_MOUNT`, meaning it cannot be mounted inside an unprivileged user namespace.
* **Peripheral / Malicious Filesystem Trigger: Yes**
The bug can be triggered if a user physically plugs in a malicious USB drive containing a crafted UDF image, and the desktop environment auto-mounts it. However, since the bug only corrupts the attacker's own filesystem and does not lead to privilege escalation, memory corruption, or a system crash, it does not pose a significant security boundary violation.
|
| 6/2 |
2026/05/20 00:57 |
llm |
expert |
0m
Model:
Tokens:
input: 14593
output: 48
thoughts: 140
Thoughts: **Analyzing a Kernel Bug Report**
Okay, so I've got this kernel bug report to look into. The system's throwing a warning, a pretty specific one: `WARNING: CPU: 1 PID: 8363 at fs/udf/namei.c:214 udf_expand_dir_adinicb+0xbf6/0xf00 fs/udf/namei.c:214`. Right away, I see the error is rooted in the UDF filesystem code, specifically within the `udf_expand_dir_adinicb` function in `fs/udf/namei.c`. The reproducer involves mounting a UDF filesystem image and running some operations, with `renameat2` being a key part of it.
Now, let's dive straight into `fs/udf/namei.c:214`. I need to understand what's happening at that exact line of code to get a handle on the bug and the implications of the warning. This is where the real work begins.
|
| 7/2 |
2026/05/20 00:57 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:fs/udf/namei.c IncludeLines:true Name:udf_expand_dir_adinicb]
Results: map[SourceCode: 133: static int udf_expand_dir_adinicb(struct inode *inode, udf_pblk_t *block)
134: {
135: udf_pblk_t newblock;
136: struct buffer_head *dbh = NULL;
137: struct kernel_lb_addr eloc;
138: struct extent_position epos;
139: uint8_t alloctype;
140: struct udf_inode_info *iinfo = UDF_I(inode);
141: struct udf_fileident_iter iter;
142: uint8_t *impuse;
143: int ret;
144:
145: if (UDF_QUERY_FLAG(inode->i_sb, UDF_FLAG_USE_SHORT_AD))
146: alloctype = ICBTAG_FLAG_AD_SHORT;
147: else
148: alloctype = ICBTAG_FLAG_AD_LONG;
149:
150: if (!inode->i_size) {
151: iinfo->i_alloc_type = alloctype;
152: mark_inode_dirty(inode);
153: return 0;
154: }
155:
156: /* alloc block, and copy data to it */
157: *block = udf_new_block(inode->i_sb, inode,
158: iinfo->i_location.partitionReferenceNum,
159: iinfo->i_location.logicalBlockNum, &ret);
160: if (!(*block))
161: return ret;
162: newblock = udf_get_pblock(inode->i_sb, *block,
163: iinfo->i_location.partitionReferenceNum,
164: 0);
165: if (newblock == 0xffffffff)
166: return -EFSCORRUPTED;
167: dbh = sb_getblk(inode->i_sb, newblock);
168: if (!dbh)
169: return -ENOMEM;
170: lock_buffer(dbh);
171: memcpy(dbh->b_data, iinfo->i_data, inode->i_size);
172: memset(dbh->b_data + inode->i_size, 0,
173: inode->i_sb->s_blocksize - inode->i_size);
174: set_buffer_uptodate(dbh);
175: unlock_buffer(dbh);
176:
177: /* Drop inline data, add block instead */
178: iinfo->i_alloc_type = alloctype;
179: memset(iinfo->i_data + iinfo->i_lenEAttr, 0, iinfo->i_lenAlloc);
180: iinfo->i_lenAlloc = 0;
181: eloc.logicalBlockNum = *block;
182: eloc.partitionReferenceNum =
183: iinfo->i_location.partitionReferenceNum;
184: iinfo->i_lenExtents = inode->i_size;
185: epos.bh = NULL;
186: epos.block = iinfo->i_location;
187: epos.offset = udf_file_entry_alloc_offset(inode);
188: ret = udf_add_aext(inode, &epos, &eloc, inode->i_size, 0);
189: brelse(epos.bh);
190: if (ret < 0) {
191: brelse(dbh);
192: udf_free_blocks(inode->i_sb, inode, &eloc, 0, 1);
193: return ret;
194: }
195: mark_inode_dirty(inode);
196:
197: /* Now fixup tags in moved directory entries */
198: for (ret = udf_fiiter_init(&iter, inode, 0);
199: !ret && iter.pos < inode->i_size;
200: ret = udf_fiiter_advance(&iter)) {
201: iter.fi.descTag.tagLocation = cpu_to_le32(*block);
202: if (iter.fi.lengthOfImpUse != cpu_to_le16(0))
203: impuse = dbh->b_data + iter.pos +
204: sizeof(struct fileIdentDesc);
205: else
206: impuse = NULL;
207: udf_fiiter_write_fi(&iter, impuse);
208: }
209: brelse(dbh);
210: /*
211: * We don't expect the iteration to fail as the directory has been
212: * already verified to be correct
213: */
214: WARN_ON_ONCE(ret);
215: udf_fiiter_release(&iter);
216:
217: return 0;
218: }
SourceFile:fs/udf/namei.c]
|
| 8/2 |
2026/05/20 00:57 |
llm |
expert |
0m
Model:
Tokens:
input: 16476
output: 45
thoughts: 136
Thoughts: **Analyzing a Potential File System Iterator Issue**
Okay, so I've hit a warning, specifically `WARN_ON_ONCE(ret);` on line 214. This is triggered when either `udf_fiiter_init` or `udf_fiiter_advance` returns an error code, which is concerning. The comment suggests we *shouldn't* see errors here because the directory has already been verified as valid. This is the crux of the problem - we validated the directory's integrity, but something, either during the initialization or subsequent advancement of the file system iterator, is failing. This makes no sense, there is clearly a bug. Now, my next step is to dive into the implementations of both `udf_fiiter_advance` and `udf_fiiter_init`. I need to understand what they're actually doing and identify the possible failure points in what should be a robust and verified process. There has to be a race condition, or a latent bug, that wasn't exposed during the initial verification.
|
| 9/2 |
2026/05/20 00:57 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:fs/udf/namei.c IncludeLines:true Name:udf_fiiter_advance]
Results: map[SourceCode: 290: int udf_fiiter_advance(struct udf_fileident_iter *iter)
291: {
292: unsigned int oldoff, len;
293: int blksize = 1 << iter->dir->i_blkbits;
294: int err;
295:
296: oldoff = iter->pos & (blksize - 1);
297: len = udf_dir_entry_len(&iter->fi);
298: iter->pos += len;
299: if (UDF_I(iter->dir)->i_alloc_type != ICBTAG_FLAG_AD_IN_ICB) {
300: if (oldoff + len >= blksize) {
301: brelse(iter->bh[0]);
302: iter->bh[0] = NULL;
303: /* Next block already loaded? */
304: if (iter->bh[1]) {
305: iter->bh[0] = iter->bh[1];
306: iter->bh[1] = NULL;
307: } else {
308: err = udf_fiiter_advance_blk(iter);
309: if (err < 0)
310: return err;
311: }
312: }
313: err = udf_fiiter_load_bhs(iter);
314: if (err < 0)
315: return err;
316: }
317: return udf_copy_fi(iter);
318: }
SourceFile:fs/udf/directory.c]
|
| 10/2 |
2026/05/20 00:57 |
llm |
expert |
0m
Model:
Tokens:
input: 17357
output: 43
thoughts: 12
Thoughts: Okay, let's dive into this. Here's my take on those thoughts, as if they're my own:
**Analyzing `udf_copy_fi`**
Alright, `udf_copy_fi`... right, that rings a bell. My mind immediately starts to run through the potential contexts. Is this a user-defined function? If so, what language? SQL? Python? Something else entirely? What's the 'fi' likely to stand for? Could be "file", "financial instrument", "foreign investment", or who knows what... need more data. My analytical gears are already turning, considering the possibilities. I'm mentally parsing the naming convention. Is it following a particular standard or is it something bespoke? That will give me clues about the organization where this is used. It makes me want to dig deeper into the codebase. Need to understand the dependencies and where this function fits into the bigger picture. I'm already formulating questions: What does it take as input? What is its output? What's the error handling like? Without knowing more, I'm already starting to categorize this function and imagine different scenarios where it would be useful. This is interesting... let's see how this unfolds.
|
| 11/2 |
2026/05/20 00:57 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:fs/udf/directory.c IncludeLines:true Name:udf_copy_fi]
Results: map[SourceCode: 67: static int udf_copy_fi(struct udf_fileident_iter *iter)
68: {
69: struct udf_inode_info *iinfo = UDF_I(iter->dir);
70: u32 blksize = 1 << iter->dir->i_blkbits;
71: u32 off, len, nameoff;
72: int err;
73:
74: /* Skip copying when we are at EOF */
75: if (iter->pos >= iter->dir->i_size) {
76: iter->name = NULL;
77: return 0;
78: }
79: if (iter->dir->i_size < iter->pos + sizeof(struct fileIdentDesc)) {
80: udf_err(iter->dir->i_sb,
81: "directory (ino %lu) has entry straddling EOF\n",
82: iter->dir->i_ino);
83: return -EFSCORRUPTED;
84: }
85: if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB) {
86: memcpy(&iter->fi, iinfo->i_data + iinfo->i_lenEAttr + iter->pos,
87: sizeof(struct fileIdentDesc));
88: err = udf_verify_fi(iter);
89: if (err < 0)
90: return err;
91: iter->name = iinfo->i_data + iinfo->i_lenEAttr + iter->pos +
92: sizeof(struct fileIdentDesc) +
93: le16_to_cpu(iter->fi.lengthOfImpUse);
94: return 0;
95: }
96:
97: off = iter->pos & (blksize - 1);
98: len = min_t(u32, sizeof(struct fileIdentDesc), blksize - off);
99: memcpy(&iter->fi, iter->bh[0]->b_data + off, len);
100: if (len < sizeof(struct fileIdentDesc))
101: memcpy((char *)(&iter->fi) + len, iter->bh[1]->b_data,
102: sizeof(struct fileIdentDesc) - len);
103: err = udf_verify_fi(iter);
104: if (err < 0)
105: return err;
106:
107: /* Handle directory entry name */
108: nameoff = off + sizeof(struct fileIdentDesc) +
109: le16_to_cpu(iter->fi.lengthOfImpUse);
110: if (off + udf_dir_entry_len(&iter->fi) <= blksize) {
111: iter->name = iter->bh[0]->b_data + nameoff;
112: } else if (nameoff >= blksize) {
113: iter->name = iter->bh[1]->b_data + (nameoff - blksize);
114: } else {
115: iter->name = iter->namebuf;
116: len = blksize - nameoff;
117: memcpy(iter->name, iter->bh[0]->b_data + nameoff, len);
118: memcpy(iter->name + len, iter->bh[1]->b_data,
119: iter->fi.lengthFileIdent - len);
120: }
121: return 0;
122: }
SourceFile:fs/udf/directory.c]
|
| 12/2 |
2026/05/20 00:57 |
llm |
expert |
0m
Model:
Tokens:
input: 18671
output: 43
thoughts: 64
Thoughts: Okay, here's my interpretation of that bug report, presented as if it were my own thought process:
**Diving into a UDF Filesystem Verification Failure**
Right, so this error message *screams* UDF filesystem corruption. Specifically, `UDF-fs: error (device loop1): udf_verify_fi: directory (ino 1408) has entry at pos 128 with incorrect tag 1`. Let's break this down. `udf_verify_fi`... that's a key function for filesystem integrity checking within the UDF implementation. It's essentially flagging a problem with a file or directory's internal structure. The "device loop1" bit suggests this is running on a loopback device, likely a disk image or something similar. Doesn't matter, we've got a UDF filesystem issue to diagnose.
The real meat is that `directory (ino 1408) has entry at pos 128 with incorrect tag 1`. Inode 1408 is the culprit. That's the specific file or, more likely, directory entry that's got something seriously wrong with its metadata. "Entry at pos 128" refers to the offset within that inode's data structure, which represents an entry in the directory, meaning a file or subdirectory. And the killer: "incorrect tag 1." The "tag" field is crucial in UDF directory entries; it identifies the type of entry. Tag 1 typically signifies a valid file or directory entry. If the code is seeing an *incorrect* tag 1, it implies the entry is malformed, corrupted, or it's incorrectly interpreted by the system. Someone may have written to the drive without correctly formatting the data.
This incorrect tag indicates an issue with the internal structure of the file or directory. This could manifest as a corrupted entry, invalid size, an unexpected field value, or even a mismatch in entry type. The UDF filesystem is flagging an inconsistency, which could have been caused by anything from a power failure during a write to a bug in some UDF manipulation code.
|
| 13/2 |
2026/05/20 00:57 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:fs/udf/directory.c IncludeLines:true Name:udf_verify_fi]
Results: map[SourceCode: 19: static int udf_verify_fi(struct udf_fileident_iter *iter)
20: {
21: unsigned int len;
22:
23: if (iter->fi.descTag.tagIdent != cpu_to_le16(TAG_IDENT_FID)) {
24: udf_err(iter->dir->i_sb,
25: "directory (ino %lu) has entry at pos %llu with incorrect tag %x\n",
26: iter->dir->i_ino, (unsigned long long)iter->pos,
27: le16_to_cpu(iter->fi.descTag.tagIdent));
28: return -EFSCORRUPTED;
29: }
30: len = udf_dir_entry_len(&iter->fi);
31: if (le16_to_cpu(iter->fi.lengthOfImpUse) & 3) {
32: udf_err(iter->dir->i_sb,
33: "directory (ino %lu) has entry at pos %llu with unaligned length of impUse field\n",
34: iter->dir->i_ino, (unsigned long long)iter->pos);
35: return -EFSCORRUPTED;
36: }
37: /*
38: * This is in fact allowed by the spec due to long impUse field but
39: * we don't support it. If there is real media with this large impUse
40: * field, support can be added.
41: */
42: if (len > 1 << iter->dir->i_blkbits) {
43: udf_err(iter->dir->i_sb,
44: "directory (ino %lu) has too big (%u) entry at pos %llu\n",
45: iter->dir->i_ino, len, (unsigned long long)iter->pos);
46: return -EFSCORRUPTED;
47: }
48: if (iter->pos + len > iter->dir->i_size) {
49: udf_err(iter->dir->i_sb,
50: "directory (ino %lu) has entry past directory size at pos %llu\n",
51: iter->dir->i_ino, (unsigned long long)iter->pos);
52: return -EFSCORRUPTED;
53: }
54: if (udf_dir_entry_len(&iter->fi) !=
55: sizeof(struct tag) + le16_to_cpu(iter->fi.descTag.descCRCLength)) {
56: udf_err(iter->dir->i_sb,
57: "directory (ino %lu) has entry where CRC length (%u) does not match entry length (%u)\n",
58: iter->dir->i_ino,
59: (unsigned)le16_to_cpu(iter->fi.descTag.descCRCLength),
60: (unsigned)(udf_dir_entry_len(&iter->fi) -
61: sizeof(struct tag)));
62: return -EFSCORRUPTED;
63: }
64: return 0;
65: }
SourceFile:fs/udf/directory.c]
|
| 14/2 |
2026/05/20 00:57 |
llm |
expert |
0m
Model:
Tokens:
input: 20119
output: 56
thoughts: 133
Thoughts: Here's my thought process, distilled:
**Analyzing a UDF Filesystem Corruption Scenario**
Okay, so `udf_verify_fi` is throwing `-EFSCORRUPTED` when the file identifier (FI) tag is off, which is a key indicator. The warning's surfacing within `udf_expand_dir_adinicb`. Now, that function is triggered if either `udf_fiiter_advance` or `udf_fiiter_init` has barfed. I need to understand that call stack in the larger context.
Right, `udf_expand_dir_adinicb` is handling the expansion of directory data *from* inline data within an ICB (specifically, using AD_IN_ICB) *to* some kind of extent structure (either AD_SHORT or AD_LONG). Effectively, it's a directory growing from an embedded state.
Now, I'm thinking about the call chain here, and want to map the calling context. The next step is to pinpoint everywhere `udf_expand_dir_adinicb` is invoked. I need the bigger picture to understand what triggers the corruption and what the recovery path looks like.
|
| 15/2 |
2026/05/20 00:57 |
tool |
codesearch-find-references |
0m
Args: map[ContextFile:fs/udf/namei.c IncludeSnippetLines:0 Name:udf_expand_dir_adinicb SourceTreePrefix:]
Results: map[References:[map[ReferenceKind:calls ReferencingEntityKind:function ReferencingEntityName:udf_fiiter_add_entry SourceFile:fs/udf/namei.c SourceLine:262]] TruncatedOutput:false]
|
| 16/2 |
2026/05/20 00:57 |
llm |
expert |
0m
Model:
Tokens:
input: 20638
output: 47
thoughts: 15
Thoughts: Okay, here's my attempt at summarizing the thought process, tailored for an expert audience, and written in the first person:
**Internal Reflection on Entry Addition**
Alright, so I'm being called from `udf_filter_add_entry`. This means I'm in the thick of managing these user-defined filter entries, likely within a larger filtering framework. My immediate focus is on ensuring the new entry integrates cleanly, without introducing any vulnerabilities or performance regressions. I need to consider a few key aspects, here. First, how is the new entry formatted or encoded? Is it safe, maybe something like a sanitization layer? Second, how does the underlying data structure handle this new information? What are the implications for lookups, insertions, and deletions? Is the chosen data structure optimized for the expected workload β that could be based on the volume of entries and frequency of operations? I'm thinking about potential collisions or conflicts. If this is a hash-based structure, are we using a robust hashing algorithm that minimizes collisions? Whatβs the worst-case lookup complexity? Further, are there any implicit dependencies on the entry content? Does the new entry need to interact with any other existing filters or lookup mechanisms? Finally, I need to verify that this entry adheres to the security constraints of the filter. I want to make sure we're not inadvertently opening a door for malicious input or abuse. Overall, my priority is maintaining the system's integrity, performance, and security while accommodating this new filter entry.
|
| 17/2 |
2026/05/20 00:57 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:fs/udf/namei.c IncludeLines:true Name:udf_fiiter_add_entry]
Results: map[SourceCode: 220: static int udf_fiiter_add_entry(struct inode *dir, struct dentry *dentry,
221: struct udf_fileident_iter *iter)
222: {
223: struct udf_inode_info *dinfo = UDF_I(dir);
224: int nfidlen, namelen = 0;
225: int ret;
226: int off, blksize = 1 << dir->i_blkbits;
227: udf_pblk_t block;
228: char name[UDF_NAME_LEN_CS0];
229:
230: if (dentry) {
231: namelen = udf_put_filename(dir->i_sb, dentry->d_name.name,
232: dentry->d_name.len,
233: name, UDF_NAME_LEN_CS0);
234: if (!namelen)
235: return -ENAMETOOLONG;
236: }
237: nfidlen = ALIGN(sizeof(struct fileIdentDesc) + namelen, UDF_NAME_PAD);
238:
239: for (ret = udf_fiiter_init(iter, dir, 0);
240: !ret && iter->pos < dir->i_size;
241: ret = udf_fiiter_advance(iter)) {
242: if (iter->fi.fileCharacteristics & FID_FILE_CHAR_DELETED) {
243: if (udf_dir_entry_len(&iter->fi) == nfidlen) {
244: iter->fi.descTag.tagSerialNum = cpu_to_le16(1);
245: iter->fi.fileVersionNum = cpu_to_le16(1);
246: iter->fi.fileCharacteristics = 0;
247: iter->fi.lengthFileIdent = namelen;
248: iter->fi.lengthOfImpUse = cpu_to_le16(0);
249: memcpy(iter->namebuf, name, namelen);
250: iter->name = iter->namebuf;
251: return 0;
252: }
253: }
254: }
255: if (ret) {
256: udf_fiiter_release(iter);
257: return ret;
258: }
259: if (dinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB &&
260: blksize - udf_ext0_offset(dir) - iter->pos < nfidlen) {
261: udf_fiiter_release(iter);
262: ret = udf_expand_dir_adinicb(dir, &block);
263: if (ret)
264: return ret;
265: ret = udf_fiiter_init(iter, dir, dir->i_size);
266: if (ret < 0)
267: return ret;
268: }
269:
270: /* Get blocknumber to use for entry tag */
271: if (dinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB) {
272: block = dinfo->i_location.logicalBlockNum;
273: } else {
274: block = iter->eloc.logicalBlockNum +
275: ((iter->elen - 1) >> dir->i_blkbits);
276: }
277: off = iter->pos & (blksize - 1);
278: if (!off)
279: off = blksize;
280: /* Entry fits into current block? */
281: if (blksize - udf_ext0_offset(dir) - off >= nfidlen)
282: goto store_fi;
283:
284: ret = udf_fiiter_append_blk(iter);
285: if (ret) {
286: udf_fiiter_release(iter);
287: return ret;
288: }
289:
290: /* Entry will be completely in the new block? Update tag location... */
291: if (!(iter->pos & (blksize - 1)))
292: block = iter->eloc.logicalBlockNum +
293: ((iter->elen - 1) >> dir->i_blkbits);
294: store_fi:
295: memset(&iter->fi, 0, sizeof(struct fileIdentDesc));
296: if (UDF_SB(dir->i_sb)->s_udfrev >= 0x0200)
297: udf_new_tag((char *)(&iter->fi), TAG_IDENT_FID, 3, 1, block,
298: sizeof(struct tag));
299: else
300: udf_new_tag((char *)(&iter->fi), TAG_IDENT_FID, 2, 1, block,
301: sizeof(struct tag));
302: iter->fi.fileVersionNum = cpu_to_le16(1);
303: iter->fi.lengthFileIdent = namelen;
304: iter->fi.lengthOfImpUse = cpu_to_le16(0);
305: memcpy(iter->namebuf, name, namelen);
306: iter->name = iter->namebuf;
307:
308: dir->i_size += nfidlen;
309: if (dinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB) {
310: dinfo->i_lenAlloc += nfidlen;
311: } else {
312: /* Truncate last extent to proper size */
313: udf_fiiter_update_elen(iter, iter->elen -
314: (dinfo->i_lenExtents - dir->i_size));
315: }
316: mark_inode_dirty(dir);
317:
318: return 0;
319: }
SourceFile:fs/udf/namei.c]
|
| 18/2 |
2026/05/20 00:57 |
llm |
expert |
0m
Model:
Tokens:
input: 22776
output: 44
thoughts: 397
Thoughts: **Analyzing Directory Expansion in UDF Filesystems**
Okay, so I'm diving into this `udf_fiiter_add_entry` function, and it's basically scanning the directory to find a spot for a new entry β either a deleted one, or it hits the end. If it hits the end, it checks a few things. First, is this directory "inline," which is indicated by `AD_IN_ICB`, and second, is there even enough space? If not, we trigger `udf_expand_dir_adinicb`.
Now, `udf_expand_dir_adinicb` is interesting. It's essentially allocating a new block, moving the inline directory data over, and then, crucially, iterating through those entries in the *new* block to update their tags. This makes sense; the block number has changed, so all those pointers in the file identifier descriptors need to be corrected.
The iteration itself in `udf_expand_dir_adinicb` is using `udf_fiiter_init` and `udf_fiiter_advance` within a `for` loop. The code snippet is:
```c
/* Now fixup tags in moved directory entries */
for (ret = udf_fiiter_init(&iter, inode, 0);
!ret && iter.pos < inode->i_size;
ret = udf_fiiter_advance(&iter)) {
iter.fi.descTag.tagLocation = cpu_to_le32(*block);
if (iter.fi.lengthOfImpUse != cpu_to_le16(0))
impuse = dbh->b_data + iter.pos +
sizeof(struct fileIdentDesc);
else
impuse = NULL;
udf_fiiter_write_fi(&iter, impuse);
}
brelse(dbh);
/*
* We don't expect the iteration to fail as the directory has been
* already verified to be correct
*/
WARN_ON_ONCE(ret);
```
The thing that bugs me is the comment. Why does the code have a `WARN_ON_ONCE(ret)`? It specifically says, "We don't expect the iteration to fail." But, if the iteration *could* fail in `udf_expand_dir_adinicb`, what would be different from the loop in `udf_fiiter_add_entry`? What's going on here that might introduce a potential failure mode that wasn't present in the initial search? I should probably investigate `udf_fiiter_init` a little more closely.
|
| 19/2 |
2026/05/20 00:58 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:fs/udf/directory.c IncludeLines:true Name:udf_fiiter_init]
Results: map[SourceCode: 244: int udf_fiiter_init(struct udf_fileident_iter *iter, struct inode *dir,
245: loff_t pos)
246: {
247: struct udf_inode_info *iinfo = UDF_I(dir);
248: int err = 0;
249: int8_t etype;
250:
251: iter->dir = dir;
252: iter->bh[0] = iter->bh[1] = NULL;
253: iter->pos = pos;
254: iter->elen = 0;
255: iter->epos.bh = NULL;
256: iter->name = NULL;
257: /*
258: * When directory is verified, we don't expect directory iteration to
259: * fail and it can be difficult to undo without corrupting filesystem.
260: * So just do not allow memory allocation failures here.
261: */
262: iter->namebuf = kmalloc(UDF_NAME_LEN_CS0, GFP_KERNEL | __GFP_NOFAIL);
263:
264: if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB) {
265: err = udf_copy_fi(iter);
266: goto out;
267: }
268:
269: err = inode_bmap(dir, iter->pos >> dir->i_blkbits, &iter->epos,
270: &iter->eloc, &iter->elen, &iter->loffset, &etype);
271: if (err <= 0 || etype != (EXT_RECORDED_ALLOCATED >> 30)) {
272: if (pos == dir->i_size)
273: return 0;
274: udf_err(dir->i_sb,
275: "position %llu not allocated in directory (ino %lu)\n",
276: (unsigned long long)pos, dir->i_ino);
277: err = -EFSCORRUPTED;
278: goto out;
279: }
280: err = udf_fiiter_load_bhs(iter);
281: if (err < 0)
282: goto out;
283: err = udf_copy_fi(iter);
284: out:
285: if (err < 0)
286: udf_fiiter_release(iter);
287: return err;
288: }
SourceFile:fs/udf/directory.c]
|
| 20/2 |
2026/05/20 00:58 |
llm |
expert |
0m
Model:
Tokens:
input: 24566
output: 48
thoughts: 1800
Thoughts: **Analyzing the UDF Directory Expansion Bug**
Okay, let's break this down. It seems there's a problem with UDF directory expansion, specifically when moving from inline data to a block. The core issue appears to be related to how file identifiers (FIDs) are handled during this transition.
My initial thought is that the function `udf_expand_dir_adinicb` modifies the `iinfo->i_alloc_type` before `udf_fiiter_init` is called. Specifically, `iinfo->i_alloc_type` becomes either `ICBTAG_FLAG_AD_SHORT` or `ICBTAG_FLAG_AD_LONG`. This change is important because it dictates how file entries are read.
I'm thinking, let's step through `udf_expand_dir_adinicb`. Here's what's happening. The inline data is dropped, and a block is added in its place. The code then copies data from `iinfo->i_data` to the newly allocated block. The crucial part is that `udf_fiiter_init` is called *after* this allocation type change. So now, the iterator is going to expect data in a different format. Specifically, it should not expect `iinfo->i_alloc_type` to be `ICBTAG_FLAG_AD_IN_ICB`.
When `udf_fiiter_init` is called, the code goes down the non-inline path, where `udf_copy_fi` is called. Inside `udf_copy_fi`, we eventually get to `udf_verify_fi`. `udf_verify_fi` checks the `tagIdent` field of each file identifier. The bug report is reporting an incorrect tag, specifically tag 1.
The problem here must be the content of the data. Tag 1 isn't supposed to be found in the directory. The tag should be `TAG_IDENT_FID`, which is 261 (0x0105).
The directory was supposedly verified earlier in `udf_fiiter_add_entry`, when the directory was still inline. All entries should have correctly had `TAG_IDENT_FID`. But it looks like `udf_fiiter_add_entry` stops iterating when it finds a deleted entry!
Now, the important question is: Why is `udf_verify_fi` failing in `udf_expand_dir_adinicb` after it succeeded earlier? Let's go back and examine `udf_expand_dir_adinicb` again. This is where the magic (or the bug) is happening. We're copying data with this line: `memcpy(dbh->b_data, iinfo->i_data, inode->i_size);`.
Wait a minute, if `iinfo->i_data` contains Extended Attributes before the inline data, this is not correct! The inline data itself starts at `iinfo->i_data + iinfo->i_lenEAttr`.
Looking back at `udf_copy_fi` when `iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB`, we see the right pointer being used in the copy: `memcpy(&iter->fi, iinfo->i_data + iinfo->i_lenEAttr + iter->pos, sizeof(struct fileIdentDesc));`. That's the correct offset!
So, the issue is, `udf_expand_dir_adinicb` is copying *all* of `iinfo->i_data`, including Extended Attributes and the start of the inline data, when it should be copying only the *inline* data, and then not from the start of the buffer. The extended attributes are the problem! If the extended attributes are present, then the newly copied block is corrupted!
|
| 21/2 |
2026/05/20 00:58 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:fs/udf/namei.c IncludeLines:true Name:udf_expand_dir_adinicb]
Results: map[SourceCode: 133: static int udf_expand_dir_adinicb(struct inode *inode, udf_pblk_t *block)
134: {
135: udf_pblk_t newblock;
136: struct buffer_head *dbh = NULL;
137: struct kernel_lb_addr eloc;
138: struct extent_position epos;
139: uint8_t alloctype;
140: struct udf_inode_info *iinfo = UDF_I(inode);
141: struct udf_fileident_iter iter;
142: uint8_t *impuse;
143: int ret;
144:
145: if (UDF_QUERY_FLAG(inode->i_sb, UDF_FLAG_USE_SHORT_AD))
146: alloctype = ICBTAG_FLAG_AD_SHORT;
147: else
148: alloctype = ICBTAG_FLAG_AD_LONG;
149:
150: if (!inode->i_size) {
151: iinfo->i_alloc_type = alloctype;
152: mark_inode_dirty(inode);
153: return 0;
154: }
155:
156: /* alloc block, and copy data to it */
157: *block = udf_new_block(inode->i_sb, inode,
158: iinfo->i_location.partitionReferenceNum,
159: iinfo->i_location.logicalBlockNum, &ret);
160: if (!(*block))
161: return ret;
162: newblock = udf_get_pblock(inode->i_sb, *block,
163: iinfo->i_location.partitionReferenceNum,
164: 0);
165: if (newblock == 0xffffffff)
166: return -EFSCORRUPTED;
167: dbh = sb_getblk(inode->i_sb, newblock);
168: if (!dbh)
169: return -ENOMEM;
170: lock_buffer(dbh);
171: memcpy(dbh->b_data, iinfo->i_data, inode->i_size);
172: memset(dbh->b_data + inode->i_size, 0,
173: inode->i_sb->s_blocksize - inode->i_size);
174: set_buffer_uptodate(dbh);
175: unlock_buffer(dbh);
176:
177: /* Drop inline data, add block instead */
178: iinfo->i_alloc_type = alloctype;
179: memset(iinfo->i_data + iinfo->i_lenEAttr, 0, iinfo->i_lenAlloc);
180: iinfo->i_lenAlloc = 0;
181: eloc.logicalBlockNum = *block;
182: eloc.partitionReferenceNum =
183: iinfo->i_location.partitionReferenceNum;
184: iinfo->i_lenExtents = inode->i_size;
185: epos.bh = NULL;
186: epos.block = iinfo->i_location;
187: epos.offset = udf_file_entry_alloc_offset(inode);
188: ret = udf_add_aext(inode, &epos, &eloc, inode->i_size, 0);
189: brelse(epos.bh);
190: if (ret < 0) {
191: brelse(dbh);
192: udf_free_blocks(inode->i_sb, inode, &eloc, 0, 1);
193: return ret;
194: }
195: mark_inode_dirty(inode);
196:
197: /* Now fixup tags in moved directory entries */
198: for (ret = udf_fiiter_init(&iter, inode, 0);
199: !ret && iter.pos < inode->i_size;
200: ret = udf_fiiter_advance(&iter)) {
201: iter.fi.descTag.tagLocation = cpu_to_le32(*block);
202: if (iter.fi.lengthOfImpUse != cpu_to_le16(0))
203: impuse = dbh->b_data + iter.pos +
204: sizeof(struct fileIdentDesc);
205: else
206: impuse = NULL;
207: udf_fiiter_write_fi(&iter, impuse);
208: }
209: brelse(dbh);
210: /*
211: * We don't expect the iteration to fail as the directory has been
212: * already verified to be correct
213: */
214: WARN_ON_ONCE(ret);
215: udf_fiiter_release(&iter);
216:
217: return 0;
218: }
SourceFile:fs/udf/namei.c]
|
| 22/2 |
2026/05/20 00:58 |
llm |
expert |
0m
Model:
Tokens:
input: 28710
output: 47
thoughts: 136
Thoughts: **Debugging a Potential Data Copying Issue**
Okay, so I'm looking at this `memcpy` call: `memcpy(dbh->b_data, iinfo->i_data, inode->i_size);`. My initial concern is that it seems to be directly copying from `iinfo->i_data`, and not accounting for a potential offset like `iinfo->i_data + iinfo->i_lenEAttr`. This could be a problem, depending on what those structures actually contain and how the data is organized. I need to be sure the data is being copied from the correct location.
Then I recalled seeing `udf_expand_file_adinicb` in `fs/udf/inode.c`, I'm pretty sure I saw something relevant in there. Let me confirm with a quick search. Ah, right, that's where the *actual* copy is done:
```c
memcpy(page_address(page), iinfo->i_data + iinfo->i_lenEAttr, inode->i_size);
```
Okay, so *that* version *does* use the offset, `iinfo->i_lenEAttr`. This is crucial. I need to figure out how these two seemingly related calls interact and what scenario they relate to. I'm going to dig into the definition of `udf_expand_file_adinicb` to understand why the second implementation is correct, and whether there is an issue to be addressed.
|
| 23/2 |
2026/05/20 00:58 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:fs/udf/inode.c IncludeLines:true Name:udf_expand_file_adinicb]
Results: map[SourceCode: 333: /*
334: * Expand file stored in ICB to a normal one-block-file
335: *
336: * This function requires i_mutex held
337: */
338: int udf_expand_file_adinicb(struct inode *inode)
339: {
340: struct folio *folio;
341: struct udf_inode_info *iinfo = UDF_I(inode);
342: int err;
343:
344: WARN_ON_ONCE(!inode_is_locked(inode));
345: if (!iinfo->i_lenAlloc) {
346: down_write(&iinfo->i_data_sem);
347: if (UDF_QUERY_FLAG(inode->i_sb, UDF_FLAG_USE_SHORT_AD))
348: iinfo->i_alloc_type = ICBTAG_FLAG_AD_SHORT;
349: else
350: iinfo->i_alloc_type = ICBTAG_FLAG_AD_LONG;
351: up_write(&iinfo->i_data_sem);
352: mark_inode_dirty(inode);
353: return 0;
354: }
355:
356: folio = __filemap_get_folio(inode->i_mapping, 0,
357: FGP_LOCK | FGP_ACCESSED | FGP_CREAT, GFP_KERNEL);
358: if (IS_ERR(folio))
359: return PTR_ERR(folio);
360:
361: if (!folio_test_uptodate(folio))
362: udf_adinicb_read_folio(folio);
363: down_write(&iinfo->i_data_sem);
364: memset(iinfo->i_data + iinfo->i_lenEAttr, 0x00,
365: iinfo->i_lenAlloc);
366: iinfo->i_lenAlloc = 0;
367: if (UDF_QUERY_FLAG(inode->i_sb, UDF_FLAG_USE_SHORT_AD))
368: iinfo->i_alloc_type = ICBTAG_FLAG_AD_SHORT;
369: else
370: iinfo->i_alloc_type = ICBTAG_FLAG_AD_LONG;
371: folio_mark_dirty(folio);
372: folio_unlock(folio);
373: up_write(&iinfo->i_data_sem);
374: err = filemap_fdatawrite(inode->i_mapping);
375: if (err) {
376: /* Restore everything back so that we don't lose data... */
377: folio_lock(folio);
378: down_write(&iinfo->i_data_sem);
379: memcpy_from_folio(iinfo->i_data + iinfo->i_lenEAttr,
380: folio, 0, inode->i_size);
381: folio_unlock(folio);
382: iinfo->i_alloc_type = ICBTAG_FLAG_AD_IN_ICB;
383: iinfo->i_lenAlloc = inode->i_size;
384: up_write(&iinfo->i_data_sem);
385: }
386: folio_put(folio);
387: mark_inode_dirty(inode);
388:
389: return err;
390: }
SourceFile:fs/udf/inode.c]
|
| 24/2 |
2026/05/20 00:58 |
llm |
expert |
0m
Model:
Tokens:
input: 30235
output: 47
thoughts: 63
Thoughts: **Analyzing the UDF ADINICB Read Process**
Okay, so I'm looking at `udf_expand_file_adinicb` and it seems pretty clear that it's calling `udf_adinicb_read_folio`. Given my understanding of how UDF structures work, and especially how folio data is handled, I strongly suspect that `udf_adinicb_read_folio` is actually the function responsible for reading data from a specific location within the file's information structure. That location, I'm guessing, is probably calculated as `iinfo->i_data + iinfo->i_lenEAttr`. In essence, we're probably reading from a data area offset by the extended attributes length.
To be absolutely sure, I need to verify that hypothesis. The next logical step is to dive right into the `udf_adinicb_read_folio` function itself. I'll need to confirm if it's operating on that assumed memory location or if there's something else at play. Time to get into the details!
|
| 25/2 |
2026/05/20 00:58 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:fs/udf/inode.c IncludeLines:true Name:udf_adinicb_read_folio]
Results: map[SourceCode: 211: static void udf_adinicb_read_folio(struct folio *folio)
212: {
213: struct inode *inode = folio->mapping->host;
214: struct udf_inode_info *iinfo = UDF_I(inode);
215: loff_t isize = i_size_read(inode);
216:
217: folio_fill_tail(folio, 0, iinfo->i_data + iinfo->i_lenEAttr, isize);
218: folio_mark_uptodate(folio);
219: }
SourceFile:fs/udf/inode.c]
|
| 26/2 |
2026/05/20 00:58 |
llm |
expert |
0m
Model:
Tokens:
input: 30769
output: 46
thoughts: 432
Thoughts: **Bug Analysis: Directory Extended Attributes and `memcpy` Offset**
Okay, so `udf_adinicb_read_folio` clearly utilizes `iinfo->i_data + iinfo->i_lenEAttr`. That's the baseline. Right off the bat, I can see that `udf_expand_dir_adinicb` has a serious flaw. It's copying from `iinfo->i_data` when it should be offsetting by `iinfo->i_data + iinfo->i_lenEAttr`. Let me double-check that `memcpy` call in `udf_expand_dir_adinicb`:
```c
memcpy(dbh->b_data, iinfo->i_data, inode->i_size);
```
Yep, exactly what I thought. If `iinfo->i_lenEAttr` is non-zero, this *will* copy the Extended Attributes right into the directory block. The subsequent directory entries will be shifted. In essence, the directory block becomes a mishmash: the first `iinfo->i_lenEAttr` bytes will be the Extended Attributes, and the following bytes will be truncated directory entries.
And then `udf_fiiter_init` goes and reads from that directory block! Itβll see those EAs instead of the directory entries, which will then inevitably cause `udf_verify_fi` to choke because the tag will be incorrect. Bang! That perfectly explains the failure. That's a textbook demonstration of the problem.
Now, just to be absolutely certain, can directories *actually* have Extended Attributes? Yup, a quick refresher shows that's indeed possible.
Now, the important question...is this exploitable? Let me think this through. The core of the bug is an incorrect `memcpy` offset. It's copying `inode->i_size` bytes from `iinfo->i_data` to `dbh->b_data`. So, what exactly is `iinfo->i_data`? Is it a buffer of size `UDF_I(inode)->i_data`, or is it, as seems more likely, a flexible array member or a pointer? I'll need to double check the `struct udf_inode_info` definition to make sure. Okay, I'll go check that now...
|
| 27/2 |
2026/05/20 00:58 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:fs/udf/udf_i.h IncludeLines:true Name:udf_inode_info]
Results: map[SourceCode: 30: struct udf_inode_info {
31: struct timespec64 i_crtime;
32: /* Physical address of inode */
33: struct kernel_lb_addr i_location;
34: __u64 i_unique;
35: __u32 i_lenEAttr;
36: __u32 i_lenAlloc;
37: __u64 i_lenExtents;
38: __u32 i_next_alloc_block;
39: __u32 i_next_alloc_goal;
40: __u32 i_checkpoint;
41: __u32 i_extraPerms;
42: unsigned i_alloc_type : 3;
43: unsigned i_efe : 1; /* extendedFileEntry */
44: unsigned i_use : 1; /* unallocSpaceEntry */
45: unsigned i_strat4096 : 1;
46: unsigned i_streamdir : 1;
47: unsigned i_hidden : 1; /* hidden system inode */
48: unsigned reserved : 24;
49: __u8 *i_data;
50: struct kernel_lb_addr i_locStreamdir;
51: __u64 i_lenStreams;
52: struct rw_semaphore i_data_sem;
53: struct udf_ext_cache cached_extent;
54: /* Spinlock for protecting extent cache */
55: spinlock_t i_extent_cache_lock;
56: struct inode vfs_inode;
57: };
SourceFile:fs/udf/udf_i.h]
|
| 28/2 |
2026/05/20 00:58 |
llm |
expert |
0m
Model:
Tokens:
input: 32236
output: 58
thoughts: 20
Thoughts: Okay, here's my interpretation of those thoughts, tailored for an expert audience, presented in the first person:
**Navigating the Byte-Level Landscape**
Right, so `i_data` is a pointer. It's pointing to something of type `__u8`, which I immediately recognize as an unsigned 8-bit integer. That's our basic building block, essentially a single byte. My brain immediately jumps to the critical question: where is this byte actually *located* in memory? The declaration provides the *type* of data it points to, but it doesn't give me any clues about its origin, its allocation context. Is it on the stack? Heap? Is it statically allocated? Knowing *where* it resides in memory is absolutely crucial for proper memory management and understanding how it interacts with the rest of my program. This is the first question I need to answer.
|
| 29/2 |
2026/05/20 00:58 |
tool |
codesearch-find-references |
0m
Args: map[ContextFile:fs/udf/udf_i.h IncludeSnippetLines:0 Name:udf_inode_info::i_data SourceTreePrefix:]
Results: map[References:[map[ReferenceKind:writes ReferencingEntityKind:function ReferencingEntityName:init_once SourceFile:fs/udf/super.c SourceLine:182] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_add_extendedattr SourceFile:fs/udf/misc.c SourceLine:35] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_add_extendedattr SourceFile:fs/udf/misc.c SourceLine:37] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_adinicb_read_folio SourceFile:fs/udf/inode.c SourceLine:217] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_adinicb_writepage SourceFile:fs/udf/inode.c SourceLine:192] map[ReferenceKind:writes ReferencingEntityKind:function ReferencingEntityName:udf_alloc_i_data SourceFile:fs/udf/inode.c SourceLine:1661] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_alloc_i_data SourceFile:fs/udf/inode.c SourceLine:1662] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_copy_fi SourceFile:fs/udf/directory.c SourceLine:86] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_copy_fi SourceFile:fs/udf/directory.c SourceLine:86] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_copy_fi SourceFile:fs/udf/directory.c SourceLine:86] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_copy_fi SourceFile:fs/udf/directory.c SourceLine:91] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_current_aext SourceFile:fs/udf/inode.c SourceLine:2253] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_evict_inode SourceFile:fs/udf/inode.c SourceLine:159] map[ReferenceKind:writes ReferencingEntityKind:function ReferencingEntityName:udf_evict_inode SourceFile:fs/udf/inode.c SourceLine:160] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_expand_dir_adinicb SourceFile:fs/udf/namei.c SourceLine:171] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_expand_dir_adinicb SourceFile:fs/udf/namei.c SourceLine:171] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_expand_dir_adinicb SourceFile:fs/udf/namei.c SourceLine:171] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_expand_dir_adinicb SourceFile:fs/udf/namei.c SourceLine:179] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_expand_dir_adinicb SourceFile:fs/udf/namei.c SourceLine:179] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_expand_dir_adinicb SourceFile:fs/udf/namei.c SourceLine:179] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_expand_file_adinicb SourceFile:fs/udf/inode.c SourceLine:364] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_expand_file_adinicb SourceFile:fs/udf/inode.c SourceLine:364] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_expand_file_adinicb SourceFile:fs/udf/inode.c SourceLine:364] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_expand_file_adinicb SourceFile:fs/udf/inode.c SourceLine:379] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_fiiter_write_fi SourceFile:fs/udf/directory.c SourceLine:416] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_get_extendedattr SourceFile:fs/udf/misc.c SourceLine:136] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_get_pblock_virt15 SourceFile:fs/udf/partition.c SourceLine:65] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_ioctl SourceFile:fs/udf/file.c SourceLine:165] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_load_vat SourceFile:fs/udf/super.c SourceLine:1261] map[ReferenceKind:writes ReferencingEntityKind:function ReferencingEntityName:udf_new_inode SourceFile:fs/udf/ialloc.c SourceLine:51] map[ReferenceKind:writes ReferencingEntityKind:function ReferencingEntityName:udf_new_inode SourceFile:fs/udf/ialloc.c SourceLine:56] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_new_inode SourceFile:fs/udf/ialloc.c SourceLine:60] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_read_inode SourceFile:fs/udf/inode.c SourceLine:1455] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_read_inode SourceFile:fs/udf/inode.c SourceLine:1455] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_read_inode SourceFile:fs/udf/inode.c SourceLine:1455] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_read_inode SourceFile:fs/udf/inode.c SourceLine:1464] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_read_inode SourceFile:fs/udf/inode.c SourceLine:1464] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_read_inode SourceFile:fs/udf/inode.c SourceLine:1464] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_read_inode SourceFile:fs/udf/inode.c SourceLine:1477] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_read_inode SourceFile:fs/udf/inode.c SourceLine:1477] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_read_inode SourceFile:fs/udf/inode.c SourceLine:1477] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_setsize SourceFile:fs/udf/inode.c SourceLine:1302] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_setsize SourceFile:fs/udf/inode.c SourceLine:1302] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_setsize SourceFile:fs/udf/inode.c SourceLine:1302] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_symlink SourceFile:fs/udf/namei.c SourceLine:644] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_symlink_filler SourceFile:fs/udf/symlink.c SourceLine:116] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_update_inode SourceFile:fs/udf/inode.c SourceLine:1752] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_update_inode SourceFile:fs/udf/inode.c SourceLine:1752] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_update_inode SourceFile:fs/udf/inode.c SourceLine:1752] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_update_inode SourceFile:fs/udf/inode.c SourceLine:1822] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_update_inode SourceFile:fs/udf/inode.c SourceLine:1822] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_update_inode SourceFile:fs/udf/inode.c SourceLine:1822] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_update_inode SourceFile:fs/udf/inode.c SourceLine:1841] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_update_inode SourceFile:fs/udf/inode.c SourceLine:1841] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_update_inode SourceFile:fs/udf/inode.c SourceLine:1841] map[ReferenceKind:reads ReferencingEntityKind:function ReferencingEntityName:udf_write_aext SourceFile:fs/udf/inode.c SourceLine:2151]] TruncatedOutput:false]
|
| 30/2 |
2026/05/20 00:58 |
llm |
expert |
0m
Model:
Tokens:
input: 35461
output: 45
thoughts: 14
Thoughts: Okay, here's my summary, presented as a stream of thought:
**Diving into `udf_alloc_i_data`**
Alright, let's get down to it. Time to dissect `udf_alloc_i_data`. Based on the name, I'm expecting this to be a core function involved in allocating data structures related to UDFs (User Defined Functions) with an emphasis on "i" data. That "i" likely suggests initialization or internal data, possibly related to state management within the UDF context. I need to understand how these UDFs are managing their internal data. Is it memory, references, resource handles, etc? Is it just the UDF metadata structure that is being populated?
I need to see what's being allocated, how it's being handled. Does this work with an existing allocator? Are there considerations to concurrency? What kind of error handling is implemented if allocation fails? I'm looking for potential bottlenecks, memory leaks, and any unusual resource management strategies. I'm thinking about potential thread-safety concerns, especially if multiple UDFs can be running concurrently. And what about error-handling scenarios? Does the code anticipate out-of-memory conditions or other allocation failures?
I need to determine the purpose of this allocation, and how it relates to the wider UDF architecture.
|
| 31/2 |
2026/05/20 00:58 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:fs/udf/inode.c IncludeLines:true Name:udf_alloc_i_data]
Results: map[SourceCode:1658: static int udf_alloc_i_data(struct inode *inode, size_t size)
1659: {
1660: struct udf_inode_info *iinfo = UDF_I(inode);
1661: iinfo->i_data = kmalloc(size, GFP_KERNEL);
1662: if (!iinfo->i_data)
1663: return -ENOMEM;
1664: return 0;
1665: }
SourceFile:fs/udf/inode.c]
|
| 32/2 |
2026/05/20 00:58 |
llm |
expert |
0m
Model:
Tokens:
input: 35965
output: 53
thoughts: 40
Thoughts: Okay, here's my take on those thoughts, framed as an expert's self-reflection:
**Deep Dive into i_data Allocation**
Alright, let's see, I'm looking at this `iinfo->i_data` pointer. Right, so it's pointing to memory allocated using `kmalloc`. The size of this allocated buffer is, from what I'm seeing, defined by `size`.
Now, the real question that pops into my head is, where exactly is `udf_alloc_i_data` being invoked? I need to trace back from this allocation point to understand the call flow and ensure everything is set up correctly. Specifically, I need to know where and when this crucial `kmalloc` is done. This will help me understand why this buffer exists and what the expectations of its contents will be. I need to understand this callsite and its context to make sure there are no memory leaks or issues in sizing.
|
| 33/2 |
2026/05/20 00:58 |
tool |
codesearch-find-references |
0m
Args: map[ContextFile:fs/udf/inode.c IncludeSnippetLines:0 Name:udf_alloc_i_data SourceTreePrefix:]
Results: map[References:[map[ReferenceKind:calls ReferencingEntityKind:function ReferencingEntityName:udf_read_inode SourceFile:fs/udf/inode.c SourceLine:1451] map[ReferenceKind:calls ReferencingEntityKind:function ReferencingEntityName:udf_read_inode SourceFile:fs/udf/inode.c SourceLine:1461] map[ReferenceKind:calls ReferencingEntityKind:function ReferencingEntityName:udf_read_inode SourceFile:fs/udf/inode.c SourceLine:1473]] TruncatedOutput:false]
|
| 34/2 |
2026/05/20 00:58 |
llm |
expert |
0m
Model:
Tokens:
input: 36436
output: 43
thoughts: 12
Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience:
**Analyzing `udf_read_inode`**
Alright, let's dive into `udf_read_inode`. I immediately start thinking about its role in the UDF filesystem implementation. I need to understand how it's interfacing with the on-disk data structures. What's the typical flow? Is it called from the VFS layer, perhaps in response to an `iget` call or a similar inode retrieval request? I need to consider what information the function expects as input, typically something like the device, the block number of the inode, and possibly some context flags.
Then, the focus shifts to what the function *does*. I'm immediately interested in the access pattern. Does it involve a simple direct read from the disk, or does it utilize some kind of caching or buffering mechanism? If so, what cache layers are involved and what are their implications on performance and concurrency? I want to understand how it handles error conditions. Are there checks for corrupted data, bad sector reads, or inconsistencies in the UDF metadata? What's the strategy for reporting and handling those errors to the calling process?
Furthermore, I have to consider the potential for complex scenarios like multi-extent inodes. Does `udf_read_inode` need to handle chained extent descriptors, scattered across the disk? How does it deal with sparse files and allocated blocks? I need to think about how it verifies the integrity of the data it's reading, perhaps through checksums or other validity checks within the UDF structure. I would want to look at the function's interaction with the underlying block device driver. Does it call a generic block layer function, or are there UDF-specific optimizations or device-specific considerations?
Finally, I'm thinking about the return value. What information does it populate in the returned inode structure? Is there an opportunity for pre-fetching data or optimising block access, depending on the file's type? How does it handle setting file attributes, permissions, size, timestamps, and extended attributes? I'm trying to get a complete picture of the UDF inode retrieval process.
|
| 35/2 |
2026/05/20 00:59 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:fs/udf/inode.c IncludeLines:true Name:udf_read_inode]
Results: map[SourceCode:1338: static int udf_read_inode(struct inode *inode, bool hidden_inode)
1339: {
1340: struct buffer_head *bh = NULL;
1341: struct fileEntry *fe;
1342: struct extendedFileEntry *efe;
1343: uint16_t ident;
1344: struct udf_inode_info *iinfo = UDF_I(inode);
1345: struct udf_sb_info *sbi = UDF_SB(inode->i_sb);
1346: struct kernel_lb_addr *iloc = &iinfo->i_location;
1347: unsigned int link_count;
1348: unsigned int indirections = 0;
1349: int bs = inode->i_sb->s_blocksize;
1350: int ret = -EIO;
1351: uint32_t uid, gid;
1352: struct timespec64 ts;
1353:
1354: reread:
1355: if (iloc->partitionReferenceNum >= sbi->s_partitions) {
1356: udf_debug("partition reference: %u > logical volume partitions: %u\n",
1357: iloc->partitionReferenceNum, sbi->s_partitions);
1358: return -EIO;
1359: }
1360:
1361: if (iloc->logicalBlockNum >=
1362: sbi->s_partmaps[iloc->partitionReferenceNum].s_partition_len) {
1363: udf_debug("block=%u, partition=%u out of range\n",
1364: iloc->logicalBlockNum, iloc->partitionReferenceNum);
1365: return -EIO;
1366: }
1367:
1368: /*
1369: * Set defaults, but the inode is still incomplete!
1370: * Note: get_new_inode() sets the following on a new inode:
1371: * i_sb = sb
1372: * i_no = ino
1373: * i_flags = sb->s_flags
1374: * i_state = 0
1375: * clean_inode(): zero fills and sets
1376: * i_count = 1
1377: * i_nlink = 1
1378: * i_op = NULL;
1379: */
1380: bh = udf_read_ptagged(inode->i_sb, iloc, 0, &ident);
1381: if (!bh) {
1382: udf_err(inode->i_sb, "(ino %lu) failed !bh\n", inode->i_ino);
1383: return -EIO;
1384: }
1385:
1386: if (ident != TAG_IDENT_FE && ident != TAG_IDENT_EFE &&
1387: ident != TAG_IDENT_USE) {
1388: udf_err(inode->i_sb, "(ino %lu) failed ident=%u\n",
1389: inode->i_ino, ident);
1390: goto out;
1391: }
1392:
1393: fe = (struct fileEntry *)bh->b_data;
1394: efe = (struct extendedFileEntry *)bh->b_data;
1395:
1396: if (fe->icbTag.strategyType == cpu_to_le16(4096)) {
1397: struct buffer_head *ibh;
1398:
1399: ibh = udf_read_ptagged(inode->i_sb, iloc, 1, &ident);
1400: if (ident == TAG_IDENT_IE && ibh) {
1401: struct kernel_lb_addr loc;
1402: struct indirectEntry *ie;
1403:
1404: ie = (struct indirectEntry *)ibh->b_data;
1405: loc = lelb_to_cpu(ie->indirectICB.extLocation);
1406:
1407: if (ie->indirectICB.extLength) {
1408: brelse(ibh);
1409: memcpy(&iinfo->i_location, &loc,
1410: sizeof(struct kernel_lb_addr));
1411: if (++indirections > UDF_MAX_ICB_NESTING) {
1412: udf_err(inode->i_sb,
1413: "too many ICBs in ICB hierarchy"
1414: " (max %d supported)\n",
1415: UDF_MAX_ICB_NESTING);
1416: goto out;
1417: }
1418: brelse(bh);
1419: goto reread;
1420: }
1421: }
1422: brelse(ibh);
1423: } else if (fe->icbTag.strategyType != cpu_to_le16(4)) {
1424: udf_err(inode->i_sb, "unsupported strategy type: %u\n",
1425: le16_to_cpu(fe->icbTag.strategyType));
1426: goto out;
1427: }
1428: if (fe->icbTag.strategyType == cpu_to_le16(4))
1429: iinfo->i_strat4096 = 0;
1430: else /* if (fe->icbTag.strategyType == cpu_to_le16(4096)) */
1431: iinfo->i_strat4096 = 1;
1432:
1433: iinfo->i_alloc_type = le16_to_cpu(fe->icbTag.flags) &
1434: ICBTAG_FLAG_AD_MASK;
1435: if (iinfo->i_alloc_type != ICBTAG_FLAG_AD_SHORT &&
1436: iinfo->i_alloc_type != ICBTAG_FLAG_AD_LONG &&
1437: iinfo->i_alloc_type != ICBTAG_FLAG_AD_IN_ICB) {
1438: ret = -EIO;
1439: goto out;
1440: }
1441: iinfo->i_hidden = hidden_inode;
1442: iinfo->i_unique = 0;
1443: iinfo->i_lenEAttr = 0;
1444: iinfo->i_lenExtents = 0;
1445: iinfo->i_lenAlloc = 0;
1446: iinfo->i_next_alloc_block = 0;
1447: iinfo->i_next_alloc_goal = 0;
1448: if (fe->descTag.tagIdent == cpu_to_le16(TAG_IDENT_EFE)) {
1449: iinfo->i_efe = 1;
1450: iinfo->i_use = 0;
1451: ret = udf_alloc_i_data(inode, bs -
1452: sizeof(struct extendedFileEntry));
1453: if (ret)
1454: goto out;
1455: memcpy(iinfo->i_data,
1456: bh->b_data + sizeof(struct extendedFileEntry),
1457: bs - sizeof(struct extendedFileEntry));
1458: } else if (fe->descTag.tagIdent == cpu_to_le16(TAG_IDENT_FE)) {
1459: iinfo->i_efe = 0;
1460: iinfo->i_use = 0;
1461: ret = udf_alloc_i_data(inode, bs - sizeof(struct fileEntry));
1462: if (ret)
1463: goto out;
1464: memcpy(iinfo->i_data,
1465: bh->b_data + sizeof(struct fileEntry),
1466: bs - sizeof(struct fileEntry));
1467: } else if (fe->descTag.tagIdent == cpu_to_le16(TAG_IDENT_USE)) {
1468: iinfo->i_efe = 0;
1469: iinfo->i_use = 1;
1470: iinfo->i_lenAlloc = le32_to_cpu(
1471: ((struct unallocSpaceEntry *)bh->b_data)->
1472: lengthAllocDescs);
1473: ret = udf_alloc_i_data(inode, bs -
1474: sizeof(struct unallocSpaceEntry));
1475: if (ret)
1476: goto out;
1477: memcpy(iinfo->i_data,
1478: bh->b_data + sizeof(struct unallocSpaceEntry),
1479: bs - sizeof(struct unallocSpaceEntry));
1480: return 0;
1481: }
1482:
1483: ret = -EIO;
1484: read_lock(&sbi->s_cred_lock);
1485: uid = le32_to_cpu(fe->uid);
1486: if (uid == UDF_INVALID_ID ||
1487: UDF_QUERY_FLAG(inode->i_sb, UDF_FLAG_UID_SET))
1488: inode->i_uid = sbi->s_uid;
1489: else
1490: i_uid_write(inode, uid);
1491:
1492: gid = le32_to_cpu(fe->gid);
1493: if (gid == UDF_INVALID_ID ||
1494: UDF_QUERY_FLAG(inode->i_sb, UDF_FLAG_GID_SET))
1495: inode->i_gid = sbi->s_gid;
1496: else
1497: i_gid_write(inode, gid);
1498:
1499: if (fe->icbTag.fileType != ICBTAG_FILE_TYPE_DIRECTORY &&
1500: sbi->s_fmode != UDF_INVALID_MODE)
1501: inode->i_mode = sbi->s_fmode;
1502: else if (fe->icbTag.fileType == ICBTAG_FILE_TYPE_DIRECTORY &&
1503: sbi->s_dmode != UDF_INVALID_MODE)
1504: inode->i_mode = sbi->s_dmode;
1505: else
1506: inode->i_mode = udf_convert_permissions(fe);
1507: inode->i_mode &= ~sbi->s_umask;
1508: iinfo->i_extraPerms = le32_to_cpu(fe->permissions) & ~FE_MAPPED_PERMS;
1509:
1510: read_unlock(&sbi->s_cred_lock);
1511:
1512: link_count = le16_to_cpu(fe->fileLinkCount);
1513: if (!link_count) {
1514: if (!hidden_inode) {
1515: ret = -ESTALE;
1516: goto out;
1517: }
1518: link_count = 1;
1519: }
1520: set_nlink(inode, link_count);
1521:
1522: inode->i_size = le64_to_cpu(fe->informationLength);
1523: iinfo->i_lenExtents = inode->i_size;
1524:
1525: if (iinfo->i_efe == 0) {
1526: inode->i_blocks = le64_to_cpu(fe->logicalBlocksRecorded) <<
1527: (inode->i_sb->s_blocksize_bits - 9);
1528:
1529: udf_disk_stamp_to_time(&ts, fe->accessTime);
1530: inode_set_atime_to_ts(inode, ts);
1531: udf_disk_stamp_to_time(&ts, fe->modificationTime);
1532: inode_set_mtime_to_ts(inode, ts);
1533: udf_disk_stamp_to_time(&ts, fe->attrTime);
1534: inode_set_ctime_to_ts(inode, ts);
1535:
1536: iinfo->i_unique = le64_to_cpu(fe->uniqueID);
1537: iinfo->i_lenEAttr = le32_to_cpu(fe->lengthExtendedAttr);
1538: iinfo->i_lenAlloc = le32_to_cpu(fe->lengthAllocDescs);
1539: iinfo->i_checkpoint = le32_to_cpu(fe->checkpoint);
1540: iinfo->i_streamdir = 0;
1541: iinfo->i_lenStreams = 0;
1542: } else {
1543: inode->i_blocks = le64_to_cpu(efe->logicalBlocksRecorded) <<
1544: (inode->i_sb->s_blocksize_bits - 9);
1545:
1546: udf_disk_stamp_to_time(&ts, efe->accessTime);
1547: inode_set_atime_to_ts(inode, ts);
1548: udf_disk_stamp_to_time(&ts, efe->modificationTime);
1549: inode_set_mtime_to_ts(inode, ts);
1550: udf_disk_stamp_to_time(&ts, efe->attrTime);
1551: inode_set_ctime_to_ts(inode, ts);
1552: udf_disk_stamp_to_time(&iinfo->i_crtime, efe->createTime);
1553:
1554: iinfo->i_unique = le64_to_cpu(efe->uniqueID);
1555: iinfo->i_lenEAttr = le32_to_cpu(efe->lengthExtendedAttr);
1556: iinfo->i_lenAlloc = le32_to_cpu(efe->lengthAllocDescs);
1557: iinfo->i_checkpoint = le32_to_cpu(efe->checkpoint);
1558:
1559: /* Named streams */
1560: iinfo->i_streamdir = (efe->streamDirectoryICB.extLength != 0);
1561: iinfo->i_locStreamdir =
1562: lelb_to_cpu(efe->streamDirectoryICB.extLocation);
1563: iinfo->i_lenStreams = le64_to_cpu(efe->objectSize);
1564: if (iinfo->i_lenStreams >= inode->i_size)
1565: iinfo->i_lenStreams -= inode->i_size;
1566: else
1567: iinfo->i_lenStreams = 0;
1568: }
1569: inode->i_generation = iinfo->i_unique;
1570:
1571: /*
1572: * Sanity check length of allocation descriptors and extended attrs to
1573: * avoid integer overflows
1574: */
1575: if (iinfo->i_lenEAttr > bs || iinfo->i_lenAlloc > bs)
1576: goto out;
1577: /* Now do exact checks */
1578: if (udf_file_entry_alloc_offset(inode) + iinfo->i_lenAlloc > bs)
1579: goto out;
1580: /* Sanity checks for files in ICB so that we don't get confused later */
1581: if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB) {
1582: /*
1583: * For file in ICB data is stored in allocation descriptor
1584: * so sizes should match
1585: */
1586: if (iinfo->i_lenAlloc != inode->i_size)
1587: goto out;
1588: /* File in ICB has to fit in there... */
1589: if (inode->i_size > bs - udf_file_entry_alloc_offset(inode))
1590: goto out;
1591: }
1592:
1593: switch (fe->icbTag.fileType) {
1594: case ICBTAG_FILE_TYPE_DIRECTORY:
1595: inode->i_op = &udf_dir_inode_operations;
1596: inode->i_fop = &udf_dir_operations;
1597: inode->i_mode |= S_IFDIR;
1598: inc_nlink(inode);
1599: break;
1600: case ICBTAG_FILE_TYPE_REALTIME:
1601: case ICBTAG_FILE_TYPE_REGULAR:
1602: case ICBTAG_FILE_TYPE_UNDEF:
1603: case ICBTAG_FILE_TYPE_VAT20:
1604: inode->i_data.a_ops = &udf_aops;
1605: inode->i_op = &udf_file_inode_operations;
1606: inode->i_fop = &udf_file_operations;
1607: inode->i_mode |= S_IFREG;
1608: break;
1609: case ICBTAG_FILE_TYPE_BLOCK:
1610: inode->i_mode |= S_IFBLK;
1611: break;
1612: case ICBTAG_FILE_TYPE_CHAR:
1613: inode->i_mode |= S_IFCHR;
1614: break;
1615: case ICBTAG_FILE_TYPE_FIFO:
1616: init_special_inode(inode, inode->i_mode | S_IFIFO, 0);
1617: break;
1618: case ICBTAG_FILE_TYPE_SOCKET:
1619: init_special_inode(inode, inode->i_mode | S_IFSOCK, 0);
1620: break;
1621: case ICBTAG_FILE_TYPE_SYMLINK:
1622: inode->i_data.a_ops = &udf_symlink_aops;
1623: inode->i_op = &udf_symlink_inode_operations;
1624: inode_nohighmem(inode);
1625: inode->i_mode = S_IFLNK | 0777;
1626: break;
1627: case ICBTAG_FILE_TYPE_MAIN:
1628: udf_debug("METADATA FILE-----\n");
1629: break;
1630: case ICBTAG_FILE_TYPE_MIRROR:
1631: udf_debug("METADATA MIRROR FILE-----\n");
1632: break;
1633: case ICBTAG_FILE_TYPE_BITMAP:
1634: udf_debug("METADATA BITMAP FILE-----\n");
1635: break;
1636: default:
1637: udf_err(inode->i_sb, "(ino %lu) failed unknown file type=%u\n",
1638: inode->i_ino, fe->icbTag.fileType);
1639: goto out;
1640: }
1641: if (S_ISCHR(inode->i_mode) || S_ISBLK(inode->i_mode)) {
1642: struct deviceSpec *dsea =
1643: (struct deviceSpec *)udf_get_extendedattr(inode, 12, 1);
1644: if (dsea) {
1645: init_special_inode(inode, inode->i_mode,
1646: MKDEV(le32_to_cpu(dsea->majorDeviceIdent),
1647: le32_to_cpu(dsea->minorDeviceIdent)));
1648: /* Developer ID ??? */
1649: } else
1650: goto out;
1651: }
1652: ret = 0;
1653: out:
1654: brelse(bh);
1655: return ret;
1656: }
SourceFile:fs/udf/inode.c]
|
| 36/2 |
2026/05/20 00:59 |
llm |
expert |
0m
Model:
Tokens:
input: 42594
output: 46
thoughts: 2013
Thoughts: **Analysis of UDF Directory Expansion**
Okay, so the initial allocation in `udf_alloc_i_data` seems straightforward enough, allocating space and copying data. The critical bit is the size calculation: using the block size minus the `fileEntry` size. This `i_data` buffer holds extended attributes and allocation descriptors/inline data, its size dictated by the block size less the size of `fileEntry`. When it comes to `udf_expand_dir_adinicb`, it appears that we copy from `iinfo->i_data` to a directory buffer. This copying depends on `inode->i_size` and `iinfo->i_lenEAttr`.
Here's where the corruption comes in. We're copying the extended attributes *first*, and *then* the directory entries, truncating the directory entries due to shifting. Because the copy is done from `iinfo->i_data`, which begins with the extended attributes, only part of the directory is copied. The directory entries are shifted, and the end is truncated and zeroed. We need to verify there isn't an out-of-bounds read, but given the relationship between `i_size` and the size of `iinfo->i_data`, that seems unlikely.
The key observation is that the iteration through the directory entries is now using corrupted data. `udf_fiiter_init` and `udf_fiiter_advance` will read the corrupted data, causing `udf_verify_fi` to fail. Although the `WARN_ON_ONCE` indicates an error, the code *continues* on the assumption that it's already verified as correct. So the program continues, even though the directory block is now malformed. The `udf_fiiter_release` does a cleanup.
Then, the code tries to iterate through the directory, expecting valid directory entries. The `WARN_ON_ONCE` here hides the fact that the directory's contents are incorrect, containing the extended attributes and possibly partial directory entries instead of complete directory entries. Then, it seems we change `iinfo->i_alloc_type` to `ICBTAG_FLAG_AD_SHORT`, set `iinfo->i_lenAlloc` to zero, and the block is added to the inode's extents. The directory is *expanded*, but its contents are *corrupted*.
The next part is where the problem gets interesting. The loop might re-expand the directory if it's not large enough, calling `udf_expand_dir_adinicb` and then initializing the iterator again. Crucially, the size passed to the iterator is the *old* directory size. This is how the iterator now correctly handles the newly added extent and avoids out-of-bounds reads.
So, the second `udf_fiiter_init` now correctly sets the iterator to a valid position in the new extent, and `udf_fiiter_add_entry` works as expected. The logic seems correct, but it's operating on a directory with corrupted data that now occupies the space. The code correctly handles adding the new entry, but the directory is messed up.
In conclusion: the issue appears to be an initial corruption of the directory block's contents during expansion due to incorrect offset calculations during the copy from `iinfo->i_data`, which is masked by an error message. The corruption is then successfully expanded to be the appropriate size, but with the data still corrupted. This likely manifests as file system corruption, but it is masked and continues on with corrupted directory data.
|
| 37/2 |
2026/05/20 00:59 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:fs/udf/udfdecl.h IncludeLines:true Name:udf_ext0_offset]
Results: map[SourceCode: 57: static inline size_t udf_ext0_offset(struct inode *inode)
58: {
59: if (UDF_I(inode)->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB)
60: return udf_file_entry_alloc_offset(inode);
61: else
62: return 0;
63: }
SourceFile:fs/udf/udfdecl.h]
|
| 38/2 |
2026/05/20 00:59 |
llm |
expert |
0m
Model:
Tokens:
input: 45555
output: 42
thoughts: 521
Thoughts: **Analyzing the UDF File Identifier Entry Addition**
Okay, so I'm looking at how new file identifier entries are added in this UDF file system code. Let's break this down.
First, `udf_ext0_offset(dir)` is zero, which is expected. Then, `off` is calculated as `iter->pos & (blksize - 1)`. And `iter->pos` is set to `dir->i_size`. So, the check `blksize - off >= nfidlen` essentially confirms if the new entry fits within the currently allocated block. If it does, then it proceeds to the `store_fi` block.
In `store_fi`, it looks like the `fileIdentDesc` struct, which is `iter->fi`, is initialized. The tag is created using `udf_new_tag`, with different versions based on the superblock revision. The `fileVersionNum`, `lengthFileIdent`, and `lengthOfImpUse` fields are populated, and the file name is copied into `iter->namebuf`. Important; this doesn't allocate anything, but just prepares the data!
The directory's `i_size` is incremented by `nfidlen`. This updates the on-disk size. Then, depending on `i_alloc_type`, we potentially update either the `i_lenAlloc` (if allocation is in the ICB) or update `iter->elen` in the case of extent allocation. Finally, the inode is marked as dirty.
Now, hold on. This `store_fi` function *doesn't* actually write to disk. I was assuming it would but it seems it only updates `iter->fi` and `iter->namebuf`. So where's the actual write? This `udf_fiiter_add_entry` must be called from elsewhere.
Let's see where `udf_fiiter_add_entry` is called. It looks like it's being called from either `udf_rename`, `udf_add_nondir`, or `udf_add_entry`. We will need to investigate those to figure out how the actual writing to disk occurs. I'll need to go back and examine those functions to figure out when this data is actually flushed.
|
| 39/2 |
2026/05/20 00:59 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:fs/udf/namei.c IncludeLines:true Name:udf_rename]
Results: map[SourceCode: 762: /* Anybody can rename anything with this: the permission checks are left to the
763: * higher-level routines.
764: */
765: static int udf_rename(struct mnt_idmap *idmap, struct inode *old_dir,
766: struct dentry *old_dentry, struct inode *new_dir,
767: struct dentry *new_dentry, unsigned int flags)
768: {
769: struct inode *old_inode = d_inode(old_dentry);
770: struct inode *new_inode = d_inode(new_dentry);
771: struct udf_fileident_iter oiter, niter, diriter;
772: bool has_diriter = false, is_dir = false;
773: int retval;
774: struct kernel_lb_addr tloc;
775:
776: if (flags & ~RENAME_NOREPLACE)
777: return -EINVAL;
778:
779: retval = udf_fiiter_find_entry(old_dir, &old_dentry->d_name, &oiter);
780: if (retval)
781: return retval;
782:
783: tloc = lelb_to_cpu(oiter.fi.icb.extLocation);
784: if (udf_get_lb_pblock(old_dir->i_sb, &tloc, 0) != old_inode->i_ino) {
785: retval = -ENOENT;
786: goto out_oiter;
787: }
788:
789: if (S_ISDIR(old_inode->i_mode)) {
790: if (new_inode) {
791: retval = -ENOTEMPTY;
792: if (!empty_dir(new_inode))
793: goto out_oiter;
794: retval = -EFSCORRUPTED;
795: if (new_inode->i_nlink != 2)
796: goto out_oiter;
797: }
798: retval = -EFSCORRUPTED;
799: if (old_dir->i_nlink < 3)
800: goto out_oiter;
801: is_dir = true;
802: } else if (new_inode) {
803: retval = -EFSCORRUPTED;
804: if (new_inode->i_nlink < 1)
805: goto out_oiter;
806: }
807: if (is_dir && old_dir != new_dir) {
808: retval = udf_fiiter_find_entry(old_inode, &dotdot_name,
809: &diriter);
810: if (retval == -ENOENT) {
811: udf_err(old_inode->i_sb,
812: "directory (ino %lu) has no '..' entry\n",
813: old_inode->i_ino);
814: retval = -EFSCORRUPTED;
815: }
816: if (retval)
817: goto out_oiter;
818: has_diriter = true;
819: tloc = lelb_to_cpu(diriter.fi.icb.extLocation);
820: if (udf_get_lb_pblock(old_inode->i_sb, &tloc, 0) !=
821: old_dir->i_ino) {
822: retval = -EFSCORRUPTED;
823: udf_err(old_inode->i_sb,
824: "directory (ino %lu) has parent entry pointing to another inode (%lu != %u)\n",
825: old_inode->i_ino, old_dir->i_ino,
826: udf_get_lb_pblock(old_inode->i_sb, &tloc, 0));
827: goto out_oiter;
828: }
829: }
830:
831: retval = udf_fiiter_find_entry(new_dir, &new_dentry->d_name, &niter);
832: if (retval && retval != -ENOENT)
833: goto out_oiter;
834: /* Entry found but not passed by VFS? */
835: if (!retval && !new_inode) {
836: retval = -EFSCORRUPTED;
837: udf_fiiter_release(&niter);
838: goto out_oiter;
839: }
840: /* Entry not found? Need to add one... */
841: if (retval) {
842: udf_fiiter_release(&niter);
843: retval = udf_fiiter_add_entry(new_dir, new_dentry, &niter);
844: if (retval)
845: goto out_oiter;
846: }
847:
848: /*
849: * Like most other Unix systems, set the ctime for inodes on a
850: * rename.
851: */
852: inode_set_ctime_current(old_inode);
853: mark_inode_dirty(old_inode);
854:
855: /*
856: * ok, that's it
857: */
858: niter.fi.fileVersionNum = oiter.fi.fileVersionNum;
859: niter.fi.fileCharacteristics = oiter.fi.fileCharacteristics;
860: memcpy(&(niter.fi.icb), &(oiter.fi.icb), sizeof(oiter.fi.icb));
861: udf_fiiter_write_fi(&niter, NULL);
862: udf_fiiter_release(&niter);
863:
864: /*
865: * The old entry may have moved due to new entry allocation. Find it
866: * again.
867: */
868: udf_fiiter_release(&oiter);
869: retval = udf_fiiter_find_entry(old_dir, &old_dentry->d_name, &oiter);
870: if (retval) {
871: udf_err(old_dir->i_sb,
872: "failed to find renamed entry again in directory (ino %lu)\n",
873: old_dir->i_ino);
874: } else {
875: udf_fiiter_delete_entry(&oiter);
876: udf_fiiter_release(&oiter);
877: }
878:
879: if (new_inode) {
880: inode_set_ctime_current(new_inode);
881: inode_dec_link_count(new_inode);
882: udf_add_fid_counter(old_dir->i_sb, S_ISDIR(new_inode->i_mode),
883: -1);
884: }
885: inode_set_mtime_to_ts(old_dir, inode_set_ctime_current(old_dir));
886: inode_set_mtime_to_ts(new_dir, inode_set_ctime_current(new_dir));
887: mark_inode_dirty(old_dir);
888: mark_inode_dirty(new_dir);
889:
890: if (has_diriter) {
891: diriter.fi.icb.extLocation =
892: cpu_to_lelb(UDF_I(new_dir)->i_location);
893: udf_fiiter_write_fi(&diriter, NULL);
894: udf_fiiter_release(&diriter);
895: }
896:
897: if (is_dir) {
898: inode_dec_link_count(old_dir);
899: if (new_inode)
900: inode_dec_link_count(new_inode);
901: else {
902: inc_nlink(new_dir);
903: mark_inode_dirty(new_dir);
904: }
905: }
906: return 0;
907: out_oiter:
908: if (has_diriter)
909: udf_fiiter_release(&diriter);
910: udf_fiiter_release(&oiter);
911:
912: return retval;
913: }
SourceFile:fs/udf/namei.c]
|
| 40/2 |
2026/05/20 00:59 |
llm |
expert |
0m
Model:
Tokens:
input: 49124
output: 52
thoughts: 771
Thoughts: **Analyzing a UDF Filesystem Corruption Bug**
Okay, so `udf_fiiter_add_entry` returned 0, meaning it likely succeeded, and then `udf_rename` called `udf_fiiter_write_fi(&niter, NULL)`. Hang on, `udf_fiiter_write_fi` is *writing* the entry to disk, right? It looks like it's copying `oiter.fi`'s data into `niter.fi` and then writing that.
I see... `niter` was initialized in `udf_fiiter_add_entry`. If `udf_expand_dir_adinicb` corrupted the directory block, `udf_fiiter_add_entry` appended the new entry at the *end* of the corrupted block, at `dir->i_size`. `dir->i_size` is the size of the directory.
Right, `udf_expand_dir_adinicb` copies `inode->i_size` bytes from `iinfo->i_data` to `dbh->b_data`. So, the first `inode->i_size` bytes of `dbh->b_data` contain the Extended Attributes and the truncated directory entries. Then `udf_fiiter_add_entry` appends the new entry at `dir->i_size`. That new entry *should* be written correctly. But the *previous* entries are definitely corrupted!
Hmm, is this exploitable? It looks like a filesystem corruption bug. A user mounts a crafted UDF image (or a valid one with Extended Attributes on a directory). They rename a file in that directory, which causes the directory to expand from inline to a block. The directory block becomes corrupted, with Extended Attributes interpreted as directory entries. Then, when the user reads the directory, the kernel parses those Extended Attributes as directory entries!
Wait, though! `udf_verify_fi` will likely fail when reading the directory, because the tags will be incorrect. If `udf_verify_fi` fails, `readdir` will return an error, likely something like `-EIO` or `-EFSCORRUPTED`.
Okay, so the challenge is... can the user *craft* the Extended Attributes such that they form *valid* directory entries? The answer is *yes*! The user *controls* the Extended Attributes. But, can they *really* use this to get anything extra? The user can already create valid directory entries by just creating files.
Does this bug let the user do something they couldn't otherwise? For example, could they craft a directory entry that points to an arbitrary block on the disk, and then read/write that block as a file?
Wait! If the user can mount a *crafted* UDF image, they can *already* create a directory entry that points to an arbitrary block because they control the entire image! So this bug *doesn't* give them any new privileges if they can mount a crafted image.
So, what if the user *can't* mount a crafted image, but *can* create Extended Attributes and rename files on an existing UDF filesystem? Can an unprivileged user even set Extended Attributes on a UDF directory? Let's check if UDF supports `setxattr`. That's the key question now... is the user able to cause this behavior on a filesystem they didn't create?
|
| 41/2 |
2026/05/20 00:59 |
tool |
codesearch-find-references |
0m
Error:
Args: map[ContextFile:fs/udf/namei.c IncludeSnippetLines:0 Name:udf_setxattr SourceTreePrefix:]
Results: map[References:<nil> TruncatedOutput:false]
|
| 42/2 |
2026/05/20 00:59 |
llm |
expert |
0m
Model:
Tokens:
input: 50703
output: 19
thoughts: 12
Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience:
**Investigating Extended Attributes within the UDF Filesystem**
Alright, time to get my hands dirty. My immediate thought is to zero in on the use of `xattr` within a UDF (Universal Disk Format) context. Given the potential for metadata storage in UDF, especially for features beyond the basic ISO 9660 compatibility, this seems like a logical first point of investigation. I need to understand how (or if) extended attributes are being leveraged to store application-specific information, security descriptors, or even alternative data streams within this particular implementation. I want to know the strategy for encoding, retrieving, and interpreting these attributes; what tools are available, and whether there are any potential pitfalls or incompatibilities.
|
| 43/2 |
2026/05/20 00:59 |
tool |
grepper |
0m
Error:
Args: map[Expression:udf.*xattr]
Results:
|
| 44/2 |
2026/05/20 01:00 |
llm |
expert |
0m
Model:
Tokens:
input: 50915
output: 45
thoughts: 14
Thoughts: Okay, let's dive into this. Here's my take on those thoughts, as if they're my own:
**Analyzing `udf_file_inode_operations`**
Right, let's take a look at `udf_file_inode_operations`. I need to understand this structure intimately. This probably handles file-specific operations within the UDF filesystem, which means things like reading, writing, seeking, locking, and so on. Understanding this is crucial to optimizing performance or debugging any UDF-related issues. I'll need to drill down into each function pointer it contains. Are they all implemented? Are there any potential bottlenecks in any of the handlers? What specific data structures does each function take as input, and what does it return? Are there any common coding practices employed here that I can exploit if I were to be modifying the filesystem for my own purposes? I will examine each field, cross-referencing it with the UDF specifications and any relevant kernel documentation. I will be looking for: potential race conditions, inefficient memory access patterns, and anything that jumps out as unusual or needing specific attention for security reasons. Let's see what we can find.
|
| 45/2 |
2026/05/20 01:00 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:fs/udf/file.c IncludeLines:true Name:udf_file_inode_operations]
Results: map[SourceCode: 250: const struct inode_operations udf_file_inode_operations = {
251: .setattr = udf_setattr,
252: };
SourceFile:fs/udf/file.c]
|
| 46/2 |
2026/05/20 01:00 |
llm |
expert |
0m
Model:
Tokens:
input: 51298
output: 46
thoughts: 14
Thoughts: Here's my attempt at summarizing the thought process, tailored for an expert audience:
**Diving into `udf_dir_inode_operations`**
Okay, time to zero in on this `udf_dir_inode_operations` structure. I need to understand its role within the UDF filesystem implementation. I'm thinking about the critical directory operations it likely handles β things like creating, reading, writing, and deleting directory entries. The nuances of UDF's metadata management are always interesting, especially when dealing with the extent descriptors and logical volumes. I want to see how this structure interfaces with the underlying block device and the various sector allocation strategies UDF might employ. Is there any obvious optimization or potential area for subtle bugs in the implementation? I'll specifically look at how the inode-specific logic interacts with the generic VFS layer. Let's start with a thorough examination of the code and any associated documentation...
|
| 47/2 |
2026/05/20 01:00 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:fs/udf/namei.c IncludeLines:true Name:udf_dir_inode_operations]
Results: map[SourceCode:1017: const struct inode_operations udf_dir_inode_operations = {
1018: .lookup = udf_lookup,
1019: .create = udf_create,
1020: .link = udf_link,
1021: .unlink = udf_unlink,
1022: .symlink = udf_symlink,
1023: .mkdir = udf_mkdir,
1024: .rmdir = udf_rmdir,
1025: .mknod = udf_mknod,
1026: .rename = udf_rename,
1027: .tmpfile = udf_tmpfile,
1028: };
SourceFile:fs/udf/namei.c]
|
| 48/2 |
2026/05/20 01:00 |
llm |
expert |
0m
Model:
Tokens:
input: 51772
output: 44
thoughts: 2175
Thoughts: **Analysis of the UDF Filesystem Bug**
Okay, so I'm diving into this UDF filesystem issue. First, it seems that Extended Attributes aren't directly supported via `setxattr` or `getxattr` on a UDF filesystem. The only way to get them is if they're *already* in the image. If a user can mount a crafted image, this bug *could* be triggered. But, if they can mount a crafted image, they can already do some pretty nasty things by just adding entries. So, this isn't a privilege escalation or memory corruption scenario. It's really just a `WARN_ON_ONCE` and some directory corruption β which the user, in theory, already controls.
Now, wait, is there any memory corruption? I see this `memcpy` operation: `memcpy(dbh->b_data, iinfo->i_data, inode->i_size);`. `inode->i_size` is the directory size. Is it possible that `inode->i_size` could be larger than `bs`? No, because `ICBTAG_FLAG_AD_IN_ICB`, `inode->i_size` must be `<= bs - udf_file_entry_alloc_offset(inode)`. I can see this check within `udf_read_inode`. Basically, the code ensures directory sizes fit within the allocated space. And `udf_file_entry_alloc_offset(inode)` is `sizeof(struct fileEntry) + iinfo->i_lenEAttr`. So `inode->i_size` is strictly less than the size of `iinfo->i_data`. So, no out-of-bounds read from `iinfo->i_data`, and no out-of-bounds write to `dbh->b_data` either, since `dbh->b_data` size is `bs`. So, it's safe.
But, wait, what if `inode->i_size` changes after `udf_read_inode`? Can the size of an inline directory be increased? Yep, by adding entries through `udf_fiiter_add_entry`. It increments `dir->i_size`. But, `udf_fiiter_add_entry` checks if the new entry fits. It checks that `blksize - (sizeof(struct fileEntry) + iinfo->i_lenEAttr) - dir->i_size < nfidlen`. If it doesn't fit, `udf_expand_dir_adinicb` is called. So, the directory size (`dir->i_size`) only increases if it fits. Therefore, `dir->i_size` will never exceed that bounded value and `memcpy` stays safe.
Okay, is there *anything* else to worry about? What if `iinfo->i_lenEAttr` is really big? Looking at `udf_read_inode`, there's a size check to make sure `iinfo->i_lenEAttr` is within bounds! It is at most `bs - sizeof(struct fileEntry)`. So, everything is properly bounded.
Now, that bug report says "WARNING: CPU: 1 PID: 8363 at fs/udf/namei.c:214 udf_expand_dir_adinicb+0xbf6/0xf00 fs/udf/namei.c:214". That's a `WARN_ON_ONCE`. Does that cause a panic? By default, `WARN_ON_ONCE` doesn't cause a panic unless `panic_on_warn` is set. What are the consequences? Let's check how the condition is handled in `udf_expand_dir_adinicb`. If the iterator fails, then `WARN_ON_ONCE` is executed, then `udf_fiiter_release(&iter)` is called, then the function returns success. The caller will continue as if the directory was successfully expanded. Now, `udf_fiiter_init` will be called again with `pos = dir->i_size`. And the directory block on disk will be corrupted, because the old entries will be overwritten by Extended Attributes and truncated.
Is this a Denial of Service? Since the filesystem is mounted from a crafted image the user provides, corrupting their own filesystem is not really a DoS. But, what if the filesystem is a real USB drive? If a user plugs in a USB drive with a UDF filesystem, and renames a file in a directory with Extended Attributes, the directory will be corrupted. Is that a DoS? Usually, filesystem corruption bugs that only affect the mounted filesystem and don't crash the kernel or cause resource leaks are not considered
|
| 49/2 |
2026/05/20 01:00 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:fs/udf/directory.c IncludeLines:true Name:udf_fiiter_init]
Results: map[SourceCode: 244: int udf_fiiter_init(struct udf_fileident_iter *iter, struct inode *dir,
245: loff_t pos)
246: {
247: struct udf_inode_info *iinfo = UDF_I(dir);
248: int err = 0;
249: int8_t etype;
250:
251: iter->dir = dir;
252: iter->bh[0] = iter->bh[1] = NULL;
253: iter->pos = pos;
254: iter->elen = 0;
255: iter->epos.bh = NULL;
256: iter->name = NULL;
257: /*
258: * When directory is verified, we don't expect directory iteration to
259: * fail and it can be difficult to undo without corrupting filesystem.
260: * So just do not allow memory allocation failures here.
261: */
262: iter->namebuf = kmalloc(UDF_NAME_LEN_CS0, GFP_KERNEL | __GFP_NOFAIL);
263:
264: if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB) {
265: err = udf_copy_fi(iter);
266: goto out;
267: }
268:
269: err = inode_bmap(dir, iter->pos >> dir->i_blkbits, &iter->epos,
270: &iter->eloc, &iter->elen, &iter->loffset, &etype);
271: if (err <= 0 || etype != (EXT_RECORDED_ALLOCATED >> 30)) {
272: if (pos == dir->i_size)
273: return 0;
274: udf_err(dir->i_sb,
275: "position %llu not allocated in directory (ino %lu)\n",
276: (unsigned long long)pos, dir->i_ino);
277: err = -EFSCORRUPTED;
278: goto out;
279: }
280: err = udf_fiiter_load_bhs(iter);
281: if (err < 0)
282: goto out;
283: err = udf_copy_fi(iter);
284: out:
285: if (err < 0)
286: udf_fiiter_release(iter);
287: return err;
288: }
SourceFile:fs/udf/directory.c]
|
| 50/2 |
2026/05/20 01:00 |
llm |
expert |
0m
Model:
Tokens:
input: 55774
output: 44
thoughts: 91
Thoughts: Here's my thought process, as if I were analyzing this code:
**Double Release Concern**
Okay, so I see a potential double-free scenario here, and that immediately sets off alarm bells. The code indicates that if `err` is less than zero, we call `udf_fiiter_release(iter)`. That's standard error handling. However, the subsequent line, `udf_expand_dir_adinicb` calls `udf_fiiter_release(&iter)` again. And then, there's a `WARN_ON_ONCE` before the second call to `udf_fiiter_release(&iter)`. This is definitely suspicious. A double release of a resource can lead to memory corruption, crashes, and other nasty bugs, and the fact that we're getting a warning suggests this might be happening.
I need to dive into `udf_fiiter_release` to understand exactly what it does. I need to know if it does indeed free the `iter` resource, and if so, what its internal state is, to understand how a second release is happening. I need to verify that `WARN_ON_ONCE` isn't masking a serious issue. I'll need to trace the execution path and identify the conditions under which this double release occurs, if it actually *is* a double release. This warrants careful inspection. The fact that the first call is conditional while the second one is unconditional is another point to investigate.
|
| 51/2 |
2026/05/20 01:00 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:fs/udf/directory.c IncludeLines:true Name:udf_fiiter_release]
Results: map[SourceCode: 320: void udf_fiiter_release(struct udf_fileident_iter *iter)
321: {
322: iter->dir = NULL;
323: brelse(iter->bh[0]);
324: brelse(iter->bh[1]);
325: iter->bh[0] = iter->bh[1] = NULL;
326: kfree(iter->namebuf);
327: iter->namebuf = NULL;
328: }
SourceFile:fs/udf/directory.c]
|
| 52/2 |
2026/05/20 01:00 |
llm |
expert |
0m
Model:
Tokens:
input: 56394
output: 44
thoughts: 146
Thoughts: **Double-Checking UDF Iterator Release**
Okay, so I'm revisiting the `udf_fiiter_release` function to confirm its safety, especially regarding potential double-frees. My thought process is as follows: it seems that `udf_fiiter_release` sets `iter->dir = NULL`, `iter->bh[0] = iter->bh[1] = NULL`, and `iter->namebuf = NULL`. This is good, because these nullifications should make subsequent calls harmless. A `brelse(NULL)` is a no-op, and similarly, `kfree(NULL)` is also a no-op. Therefore, directly calling `udf_fiiter_release` twice shouldn't lead to any memory corruption. I can't see an obvious double-free issue.
However, I need to consider a different scenario. What happens if `udf_fiiter_init` succeeds, but `udf_fiiter_advance` then fails? Does this create an inconsistent state that could be problematic when `udf_fiiter_release` is called? If `udf_fiiter_advance` encounters a problem, it should return an error, but I need to make sure that the previous state won't allow a double-free. To be completely sure, I should check the implementation of `udf_fiiter_advance` to confirm how it handles such errors. I'll take a look at its code now.
|
| 53/2 |
2026/05/20 01:00 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:fs/udf/directory.c IncludeLines:true Name:udf_fiiter_advance]
Results: map[SourceCode: 290: int udf_fiiter_advance(struct udf_fileident_iter *iter)
291: {
292: unsigned int oldoff, len;
293: int blksize = 1 << iter->dir->i_blkbits;
294: int err;
295:
296: oldoff = iter->pos & (blksize - 1);
297: len = udf_dir_entry_len(&iter->fi);
298: iter->pos += len;
299: if (UDF_I(iter->dir)->i_alloc_type != ICBTAG_FLAG_AD_IN_ICB) {
300: if (oldoff + len >= blksize) {
301: brelse(iter->bh[0]);
302: iter->bh[0] = NULL;
303: /* Next block already loaded? */
304: if (iter->bh[1]) {
305: iter->bh[0] = iter->bh[1];
306: iter->bh[1] = NULL;
307: } else {
308: err = udf_fiiter_advance_blk(iter);
309: if (err < 0)
310: return err;
311: }
312: }
313: err = udf_fiiter_load_bhs(iter);
314: if (err < 0)
315: return err;
316: }
317: return udf_copy_fi(iter);
318: }
SourceFile:fs/udf/directory.c]
|
| 54/2 |
2026/05/20 01:00 |
llm |
expert |
0m
Model:
Tokens:
input: 57373
output: 46
thoughts: 651
Thoughts: **Analyzing a Potential Directory Corruption Issue in UDF Filesystem Code**
Okay, so I'm looking at this UDF filesystem code and trying to understand a reported warning. If `udf_fiiter_advance` fails, it doesn't call `udf_fiiter_release`, which seems a bit odd, but `udf_expand_dir_adinicb` later calls `udf_fiiter_release` anyway, so that seems safe enough. The bug report is pointing me to `fs/udf/namei.c:214` within `udf_expand_dir_adinicb`. It's just a WARNING, which is good in a production environment as a kernel panic isn't triggered, unless `panic_on_warn` is set. But, what are the potential consequences? The report states the directory might be corrupted. Okay, let's dive into the code.
The immediate question that springs to mind is whether `udf_fiiter_add_entry` could potentially write out of bounds. The code calculates a `block` number and an `off`set. The key part is this section:
```c
/* Get blocknumber to use for entry tag */
if (dinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB) {
block = dinfo->i_location.logicalBlockNum;
} else {
block = iter->eloc.logicalBlockNum +
((iter->elen - 1) >> dir->i_blkbits);
}
off = iter->pos & (blksize - 1);
if (!off)
off = blksize;
/* Entry fits into current block? */
if (blksize - udf_ext0_offset(dir) - off >= nfidlen)
goto store_fi;
ret = udf_fiiter_append_blk(iter);
```
I'm thinking, `iter->pos` is actually `dir->i_size`, and `dir->i_size` is the directory's size. So `off` becomes `dir->i_size & (blksize - 1)`. I am concerned, could there be a wraparound if `dir->i_size` is large? But wait, `dir->i_size` is limited by `blksize - sizeof(struct fileEntry) - iinfo->i_lenEAttr`, which means the size can't wrap around. So `off` is just `dir->i_size`. Therefore, `blksize - off` represents the remaining space in the block. If this is greater than or equal to `nfidlen`, we go to the `store_fi` label.
Crucially, in `store_fi`:
```c
store_fi:
memset(&iter->fi, 0, sizeof(struct fileIdentDesc));
```
Aha! `store_fi` is *just* setting `iter->fi` and `iter->namebuf`! No direct block writes happen there. The block writing actually happens later in `udf_fiiter_write_fi`. So I need to go look at *that* function next to see where the actual potential corruption could occur. I need to understand what writes happen there, what the preconditions are, and whether any of those preconditions could be violated given this context.
|
| 55/2 |
2026/05/20 01:01 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:fs/udf/directory.c IncludeLines:true Name:udf_fiiter_write_fi]
Results: map[SourceCode: 407: void udf_fiiter_write_fi(struct udf_fileident_iter *iter, uint8_t *impuse)
408: {
409: struct udf_inode_info *iinfo = UDF_I(iter->dir);
410: void *buf1, *buf2 = NULL;
411: int len1, len2 = 0, off;
412: int blksize = 1 << iter->dir->i_blkbits;
413:
414: off = iter->pos & (blksize - 1);
415: if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB) {
416: buf1 = iinfo->i_data + iinfo->i_lenEAttr;
417: len1 = iter->dir->i_size;
418: } else {
419: buf1 = iter->bh[0]->b_data;
420: len1 = blksize;
421: if (iter->bh[1]) {
422: buf2 = iter->bh[1]->b_data;
423: len2 = blksize;
424: }
425: }
426:
427: udf_copy_fi_to_bufs(buf1, len1, buf2, len2, off, &iter->fi, impuse,
428: iter->name == iter->namebuf ? iter->name : NULL);
429:
430: if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB) {
431: mark_inode_dirty(iter->dir);
432: } else {
433: mark_buffer_dirty_inode(iter->bh[0], iter->dir);
434: if (iter->bh[1])
435: mark_buffer_dirty_inode(iter->bh[1], iter->dir);
436: }
437: inode_inc_iversion(iter->dir);
438: }
SourceFile:fs/udf/directory.c]
|
| 56/2 |
2026/05/20 01:01 |
llm |
expert |
0m
Model:
Tokens:
input: 59419
output: 47
thoughts: 227
Thoughts: **Analyzing a Potential NULL Pointer Dereference in UDF File System Code**
Okay, so I'm looking at this `udf_fiiter_write_fi` function, and it seems like it's writing to `iter->bh[0]->b_data` at an offset calculated as `iter->pos & (blksize - 1)`. That offset (`off`) is interesting, as is the pointer itself, `iter->bh[0]`. The function `udf_copy_fi_to_bufs` is called to copy the file information `iter->fi` and the name `iter->name` into buffers `buf1` and `buf2`, so far, so good.
But here's where my alarm bells start ringing: is it *possible* that `iter->bh[0]` is NULL at this point? This could lead to a really nasty NULL pointer dereference, which is something I want to catch *before* it becomes a problem. The current logic in `udf_fiiter_add_entry` calls `udf_expand_dir_adinicb` and `udf_fiiter_init`, the latter is the one that calls `udf_fiiter_load_bhs(iter)`. If `udf_fiiter_init` fails, then a return value is generated and control is returned, so now I really need to check `udf_fiiter_load_bhs` to see what is happening! Let's get to the bottom of this.
|
| 57/2 |
2026/05/20 01:01 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:fs/udf/directory.c IncludeLines:true Name:udf_fiiter_load_bhs]
Results: map[SourceCode: 194: static int udf_fiiter_load_bhs(struct udf_fileident_iter *iter)
195: {
196: int blksize = 1 << iter->dir->i_blkbits;
197: int off = iter->pos & (blksize - 1);
198: int err;
199: struct fileIdentDesc *fi;
200:
201: /* Is there any further extent we can map from? */
202: if (!iter->bh[0] && iter->elen) {
203: iter->bh[0] = udf_fiiter_bread_blk(iter);
204: if (!iter->bh[0]) {
205: err = -ENOMEM;
206: goto out_brelse;
207: }
208: if (!buffer_uptodate(iter->bh[0])) {
209: err = -EIO;
210: goto out_brelse;
211: }
212: }
213: /* There's no next block so we are done */
214: if (iter->pos >= iter->dir->i_size)
215: return 0;
216: /* Need to fetch next block as well? */
217: if (off + sizeof(struct fileIdentDesc) > blksize)
218: goto fetch_next;
219: fi = (struct fileIdentDesc *)(iter->bh[0]->b_data + off);
220: /* Need to fetch next block to get name? */
221: if (off + udf_dir_entry_len(fi) > blksize) {
222: fetch_next:
223: err = udf_fiiter_advance_blk(iter);
224: if (err)
225: goto out_brelse;
226: iter->bh[1] = udf_fiiter_bread_blk(iter);
227: if (!iter->bh[1]) {
228: err = -ENOMEM;
229: goto out_brelse;
230: }
231: if (!buffer_uptodate(iter->bh[1])) {
232: err = -EIO;
233: goto out_brelse;
234: }
235: }
236: return 0;
237: out_brelse:
238: brelse(iter->bh[0]);
239: brelse(iter->bh[1]);
240: iter->bh[0] = iter->bh[1] = NULL;
241: return err;
242: }
SourceFile:fs/udf/directory.c]
|
| 58/2 |
2026/05/20 01:01 |
llm |
expert |
0m
Model:
Tokens:
input: 60817
output: 52
thoughts: 906
Thoughts: **Analyzing the UDF Filesystem Corruption**
Okay, let me break this down systematically. If `iter->pos` exceeds `iter->dir->i_size` in `udf_fiiter_load_bhs`, the function returns 0. But crucially, before that check, `iter->bh[0]` is loaded if `iter->elen` is non-zero, which means that the block is always loaded. So `iter->bh[0]` will never be NULL if it gets to the write. Then, `udf_fiiter_write_fi` writes to `iter->bh[0]->b_data` at an offset `off` which is equal to `dir->i_size & (blksize - 1)`. Since `dir->i_size` is less than `blksize`, that's just `dir->i_size`, meaning the new entry goes *precisely* where I expect it to go: at the end of the directory data. This confirms the initial hypothesis that the new entry is written correctly.
I'm thinking, however, the problem is corruption of existing entries, not an out-of-bounds write. There's no memory corruption, no panic (unless `panic_on_warn` is set, which is a separate concern), and no resource leak. This is definitely filesystem corruption. But no matter the outcome, this corruption must be at the user's discretion.
Now, a critical point: could `dir->i_size` be larger than `blksize`? No, since this is an inline directory, its size cannot exceed `blksize - sizeof(struct fileEntry)`. So the offset (`off`) will always be within bounds. What if `off + nfidlen` exceeds `blksize`? The `udf_fiiter_add_entry` function handles this, and checks if it fits. If it *doesn't* fit, it calls `udf_fiiter_append_blk(iter)`, allocating a new block and updating `iter->bh[0]` and `iter->bh[1]`. So writes would be correct. Still no out-of-bounds write.
Let me double-check for other related issues. What about a case where `iinfo->i_lenEAttr` is very large, making `inode->i_size` small, while the `memcpy` is still trying to copy a large amount from `iinfo->i_data`? Wait, `memcpy(dbh->b_data, iinfo->i_data, inode->i_size)` copies `inode->i_size` bytes *from the start* of `iinfo->i_data`. So, it copies `min(inode->i_size, iinfo->i_lenEAttr)` bytes of extended attributes, and the rest from inline data. This would be *data* corruption, not memory corruption.
The next question: Is there a way to trigger this from a local unprivileged user? No. UDF doesn't support `setxattr`. The only way to get a directory with Extended Attributes is through a crafted image. Mounting the image requires `CAP_SYS_ADMIN` in the initial user namespace (or potentially in a user namespace if `fs_userns_mount` is supported by UDF). Hmm, does UDF support user namespace mounts? That could be a possible attack vector...
|
| 59/2 |
2026/05/20 01:01 |
tool |
codesearch-find-references |
0m
Error:
Args: map[ContextFile:fs/udf/super.c IncludeSnippetLines:0 Name:FS_USERNS_MOUNT SourceTreePrefix:]
Results: map[References:<nil> TruncatedOutput:false]
|
| 60/2 |
2026/05/20 01:01 |
llm |
expert |
0m
Model:
Tokens:
input: 62517
output: 43
thoughts: 12
Thoughts: Here's a summary of my thought process:
**Diving into File System Type**
Okay, first things first, let's zero in on this `udf_fs_type` thing. I need to understand what's happening with the file system. Knowing the type is absolutely crucial β it dictates everything from performance characteristics and supported features to potential compatibility issues. It's the foundation we're building on, so understanding it is the necessary first step. Let's see what that variable is holding.
|
| 61/2 |
2026/05/20 01:01 |
tool |
codesearch-definition-source |
0m
Error:
Args: map[ContextFile:fs/udf/super.c IncludeLines:true Name:udf_fs_type]
Results: map[SourceCode: SourceFile:]
|
| 62/2 |
2026/05/20 01:01 |
llm |
expert |
0m
Model:
Tokens:
input: 62701
output: 42
thoughts: 11
Thoughts: Here's my take on those thoughts:
**Analyzing `udf_fstype`**
Okay, let's dive into this. The initial impulse here is to verify the status of `udf_fstype`. I need to assess its current state and functionality. What is it doing? How is it performing? Are there any obvious issues or areas for optimization? Essentially, I'm thinking, this is a critical component, and I need to get a handle on its behavior right now. Time to investigate!
|
| 63/2 |
2026/05/20 01:01 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:fs/udf/super.c IncludeLines:true Name:udf_fstype]
Results: map[SourceCode: 138: static struct file_system_type udf_fstype = {
139: .owner = THIS_MODULE,
140: .name = "udf",
141: .kill_sb = kill_block_super,
142: .fs_flags = FS_REQUIRES_DEV,
143: .init_fs_context = udf_init_fs_context,
144: .parameters = udf_param_spec,
145: };
SourceFile:fs/udf/super.c]
|
| 64/2 |
2026/05/20 01:01 |
llm |
expert |
0m
Model:
Tokens:
input: 63029
output: 47
thoughts: 2507
Thoughts: **My Analysis of the UDF Filesystem Vulnerability**
Okay, so here's what I've got after this deep dive: the original report suggested a potential issue with UDF. My initial thoughts were, "Can unprivileged users mount UDF? No, it's not `FS_USERNS_MOUNT`." I then considered auto-mounting, especially on a desktop environment, and the possibility of triggering a bug by renaming a file on a UDF-formatted USB drive.
My subsequent analysis confirmed that it doesn't lead to any *true* security vulnerability, though. It just results in a file system corruption on the mounted image. Specifically:
* **Exploitability:** No, just filesystem corruption.
* **Denial of Service:** No. The `WARN_ON_ONCE` doesn't halt the system.
* **Privilege:** No, requires mount access.
* **User Namespaces:** No, UDF doesn't support it.
* **Triggers:** Yes, malicious or crafted filesystem image. Peripheral trigger via USB auto-mounting also possible, but since no DOS or exploitability, not a security issue.
I was concerned about potential out-of-bounds reads or writes during the `memcpy` operation. I dug into the `udf_read_inode` code and found that the size calculations for `iinfo->i_data` and `inode->i_size` are carefully done. `iinfo->i_data`'s size is controlled by the block size and the size of the file/extended file entry (FE/EFE). Furthermore, the code checks to ensure `inode->i_size` is no larger than `iinfo->i_data`. This means any `memcpy` will read at most `inode->i_size` bytes from a valid buffer, and no out-of-bounds read is possible. And the `dbh->b_data` buffer is also checked to ensure the data fits. There's also no wrap-around issue for `iinfo->i_lenEAttr` since it is bounded by the block size.
My analysis also looked into other code paths, specifically `udf_setsize`, directory modifications, and memory initialization. It all looked solid. However, I got caught up on the logic surrounding directory expansion, and more specifically what happens during a rename operation. If the *old* directory is the same as the *new* directory, then a call to `udf_fiiter_delete_entry(&oiter)` after expanding the old directory could lead to trying to find the *old* entry in a corrupted directory. This could be a problem! I'll need to dig into `udf_fiiter_find_entry` more deeply.
|
| 65/2 |
2026/05/20 01:02 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:fs/udf/namei.c IncludeLines:true Name:udf_fiiter_find_entry]
Results: map[SourceCode: 40: /**
41: * udf_fiiter_find_entry - find entry in given directory.
42: *
43: * @dir: directory inode to search in
44: * @child: qstr of the name
45: * @iter: iter to use for searching
46: *
47: * This function searches in the directory @dir for a file name @child. When
48: * found, @iter points to the position in the directory with given entry.
49: *
50: * Returns 0 on success, < 0 on error (including -ENOENT).
51: */
52: static int udf_fiiter_find_entry(struct inode *dir, const struct qstr *child,
53: struct udf_fileident_iter *iter)
54: {
55: int flen;
56: unsigned char *fname = NULL;
57: struct super_block *sb = dir->i_sb;
58: int isdotdot = child->len == 2 &&
59: child->name[0] == '.' && child->name[1] == '.';
60: int ret;
61:
62: fname = kmalloc(UDF_NAME_LEN, GFP_KERNEL);
63: if (!fname)
64: return -ENOMEM;
65:
66: for (ret = udf_fiiter_init(iter, dir, 0);
67: !ret && iter->pos < dir->i_size;
68: ret = udf_fiiter_advance(iter)) {
69: if (iter->fi.fileCharacteristics & FID_FILE_CHAR_DELETED) {
70: if (!UDF_QUERY_FLAG(sb, UDF_FLAG_UNDELETE))
71: continue;
72: }
73:
74: if (iter->fi.fileCharacteristics & FID_FILE_CHAR_HIDDEN) {
75: if (!UDF_QUERY_FLAG(sb, UDF_FLAG_UNHIDE))
76: continue;
77: }
78:
79: if ((iter->fi.fileCharacteristics & FID_FILE_CHAR_PARENT) &&
80: isdotdot)
81: goto out_ok;
82:
83: if (!iter->fi.lengthFileIdent)
84: continue;
85:
86: flen = udf_get_filename(sb, iter->name,
87: iter->fi.lengthFileIdent, fname, UDF_NAME_LEN);
88: if (flen < 0) {
89: ret = flen;
90: goto out_err;
91: }
92:
93: if (udf_match(flen, fname, child->len, child->name))
94: goto out_ok;
95: }
96: if (!ret)
97: ret = -ENOENT;
98:
99: out_err:
100: udf_fiiter_release(iter);
101: out_ok:
102: kfree(fname);
103:
104: return ret;
105: }
SourceFile:fs/udf/namei.c]
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| 66/2 |
2026/05/20 01:02 |
llm |
expert |
0m
Model:
Tokens:
input: 67106
output: 66
thoughts: 1909
Thoughts: **Bug Analysis: UDF Filesystem Directory Corruption during Rename**
Okay, let's break this down. If the UDF directory is corrupted, the core issue seems to stem from `udf_fiiter_init` or `udf_fiiter_advance` returning `-EFSCORRUPTED`. This propagates to `udf_fiiter_find_entry`, and eventually leads to an error message in `udf_rename`. Importantly, `udf_fiiter_delete_entry` *isn't* called in the corrupted scenario. This means the rename is effectively a copy, not a move, which in itself is problematic *if* we could still read the old entry. But wait, `readdir` will also fail due to the corruption, so the user can't *see* either the old or the new entry. So itβs a file system corruption, plain and simple. Not a security issue, right?
But, wait. What if that corrupted directory *somehow* tricks `udf_fiiter_find_entry` into *succeeding*? Could this happen through cleverly crafted Extended Attributes? Yes, because the user controls the contents of the Extended Attributes. They could manipulate them to match the old name, then `udf_fiiter_delete_entry` would get called on this fabricated entry. And what does `udf_fiiter_delete_entry` *do*? It just sets `FID_FILE_CHAR_DELETED` and writes back... so it just modifies the crafted entry in the Extended Attributes. Still not a security issue, just an oddity.
So, the root cause is a bad offset in a `memcpy`, triggering a `WARN_ON_ONCE`. No crash, no memory corruption, no leaks. Itβs not accessible from unprivileged processes or user namespaces. It's triggered by a malicious filesystem image, like one on a USB drive. Let's make sure our parameters are correct: Exploitable: False, DenialOfService: False, Unprivileged: False, UserNamespace: False, and so on... PeripheralTrigger: True (because of the USB) and FilesystemTrigger: True.
Hmm, let's think again about other consequences. Is `udf_expand_dir_adinicb` involved? No, just a normal function call. Now, letβs go back to the bug report: We see the `WARN_ON_ONCE` in `udf_expand_dir_adinicb`, and the error from `udf_verify_fi` - exactly what we expect. Mounting an image, calling `renameat2`β¦ matches the analysis.
Is there any impact from `WARN_ON_ONCE`? Some systems set `panic_on_warn`. But this is a handled warning, so it doesn't cause a DoS. The code handles the corruption gracefully; it appends the new entry and later fails to find the old one. So, it's not a DoS.
What about `udf_fiiter_add_entry` or `readdir` called on the corrupted directory? They also hit `-EFSCORRUPTED`, which is normal error handling. Still no DoS. The bug is handled by normal error paths.
Can we exploit this for privilege escalation? The user *could* craft an image, putting Extended Attributes into a directory. Then, these become directory entries. But they already control the image. They already control the directory entries. It's pointless. Now, what if they don't *fully* control the filesystem? The UDF does not support `setxattr`. So, they can't *add* Extended Attributes. They can only trigger this on an image that *already* has them. So, an admin created the UDF image and added sensitive EA and the user renames a file?
Wait! If that EA has sensitive data, it could be exposed via directory entries using `readdir`! So the `readdir` call would return the contents of the Extended Attributes as filenames. But, can they normally get at the Extended Attributes anyway? No, UDF has no `getxattr`. So the Extended Attributes are hidden, unless the user *renames a file* in a directory where an administrator added Extended Attributes.
But... why would the admin add Extended Attributes and not provide access to read them with `getxattr`? Extended Attributes are usually for device nodes, symlinks, or OS-specific metadata (like Mac OS Finder info), not user data. And even if they *did*, the user needs write access to rename the file. And if they have write access, they have access anyway. This is a very weak information leak if at all. It's not exploitable for privilege escalation or significant information disclosure.
Okay, let's review the `set-results` parameters again: Explo
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| 67/2 |
2026/05/20 01:02 |
tool |
set-results |
0m
Args: map[DenialOfService:false Exploitable:false FilesystemTrigger:true NetworkTrigger:false PeripheralTrigger:true RemoteTrigger:false Unprivileged:false UserNamespace:false VMGuestTrigger:false VMHostTrigger:false]
Results: map[DenialOfService:false Exploitable:false FilesystemTrigger:true NetworkTrigger:false PeripheralTrigger:true RemoteTrigger:false Unprivileged:false UserNamespace:false VMGuestTrigger:false VMHostTrigger:false]
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| 68/2 |
2026/05/20 01:02 |
llm |
expert |
0m
Model:
Tokens:
input: 70170
output: 793
thoughts: 591
Thoughts: **My Analysis of the UDF Filesystem Bug**
Okay, the deep dive is done, and it's time to craft the final response. My findings are pretty clear. It looks like we have a bug in `udf_expand_dir_adinicb`, specifically in `fs/udf/namei.c`. The root cause is centered around how inline data (AD_IN_ICB) is handled when a UDF directory is expanded to a block.
Essentially, when the kernel goes to expand a directory with inline data into a regular block, it allocates a new block, copies the inline data over, and then updates the tags. The critical flaw is in the `memcpy`. Instead of properly accounting for extended attributes (EAs) that might be present, the code uses a flawed offset. It's using `memcpy(dbh->b_data, iinfo->i_data, inode->i_size);` instead of `memcpy(dbh->b_data, iinfo->i_data + iinfo->i_lenEAttr, inode->i_size);`. This means itβs copying *both* the extended attributes and then a truncated portion of the directory entries, directly into the newly allocated block.
The problem quickly escalates from there. When it tries to iterate through the directory entries to update their tags, `udf_verify_fi` fails because the copied block now starts with these incorrect EAs and corrupted directory data instead of valid tags (e.g., encountering tag 1 instead of TAG_IDENT_FID). That leads `udf_fiiter_init` or `udf_fiiter_advance` to return `-EFSCORRUPTED`. The loop in `udf_expand_dir_adinicb` breaks early, triggering a `WARN_ON_ONCE(ret)`. The function then returns 0 (success) but it's fundamentally incorrect, leading to further corruption when the caller goes on to append a new entry to that garbage-filled directory block.
Regarding impact, the good news is that itβs not exploitable in a classic sense. No out-of-bounds reads or writes. `memcpy`'s size limitation is bound by `inode->i_size`, and the buffer allocation is sufficient, so we're safe from memory corruption in that respect. It will, however, cause filesystem corruption on any UDF image that triggers the bug, which is a major concern.
In terms of denial of service, it's limited. The `WARN_ON_ONCE` isn't a showstopper for production systems. The usual control flow handles the error without halting the system. Further operations on the corrupted directory will just return `-EFSCORRUPTED` or `-EIO`, but at least we aren't at risk of deadlocks, hangs, or resource leaks.
The trigger is a crafted UDF filesystem image and a rename operation on a directory with extended attributes. One needs `CAP_SYS_ADMIN` to mount the image, or it can be triggered by automatic mounting of a USB drive (Peripheral Trigger / Malicious Filesystem Trigger). Fortunately, UDF does not support user namespace mounts.
I'll use this summary as a solid foundation for the final response.
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| 69/1 |
2026/05/20 01:02 |
action |
format-explanation |
0m
Results: map[Explanation:Based on the analysis of the bug report and the kernel source code, here is the
assessment of the vulnerability:
### Bug Cause
The bug occurs in `udf_expand_dir_adinicb()` in `fs/udf/namei.c`. This function
is responsible for expanding a UDF directory from inline data (stored within the
inode/ICB) to a dedicated block when the inline space is exhausted (e.g., when a
new file is added or renamed into the directory).
During this expansion, the function allocates a new block and copies the inline
data to it:
```c
memcpy(dbh->b_data, iinfo->i_data, inode->i_size);
```
However, if the directory has Extended Attributes, the `iinfo->i_data` buffer
starts with the Extended Attributes, and the actual inline directory entries
start at an offset of `iinfo->i_lenEAttr`. The correct copy operation should be
from `iinfo->i_data + iinfo->i_lenEAttr` (similar to what is done in
`udf_expand_file_adinicb()`).
Because of this incorrect offset, the function copies the Extended Attributes
and the truncated directory entries into the new block. Immediately after, it
iterates over the new block to update the tags of the directory entries. Since
the block now starts with Extended Attributes instead of valid directory
entries, `udf_verify_fi()` fails (reporting an incorrect tag, as seen in the bug
report), and the iteration returns an error (`-EFSCORRUPTED`). This triggers the
`WARN_ON_ONCE(ret)` at line 214.
### Security Impact
* **Exploitable: No**
The `memcpy()` size is bounded by `inode->i_size`. In `udf_read_inode()`,
`inode->i_size` is strictly validated to ensure it fits within the remaining
space of the block after accounting for the file entry header and Extended
Attributes. Therefore, `inode->i_size` is always less than or equal to the
size of the allocated `iinfo->i_data` buffer. There is no out-of-bounds read
from `iinfo->i_data` and no out-of-bounds write to the new block
(`dbh->b_data`). The bug only results in logical filesystem corruption on the
mounted UDF image.
* **Denial Of Service: No**
The `WARN_ON_ONCE` does not halt the system in production builds (unless
`panic_on_warn` is explicitly set). The error is handled gracefully: the
function cleans up the iterator and returns `0` (success). Subsequent
operations on the corrupted directory (like `readdir` or further lookups) will
simply fail with `-EFSCORRUPTED` or `-EIO` through normal error paths. There
are no resource leaks, deadlocks, or hangs.
* **Accessible From Unprivileged Processes / User Namespaces: No**
Triggering this bug requires mounting a crafted UDF filesystem image (one that
contains a directory with Extended Attributes and inline data). Mounting a
filesystem requires `CAP_SYS_ADMIN` in the initial namespace. Furthermore, the
UDF filesystem does not support `FS_USERNS_MOUNT`, meaning it cannot be
mounted inside an unprivileged user namespace.
* **Peripheral / Malicious Filesystem Trigger: Yes**
The bug can be triggered if a user physically plugs in a malicious USB drive
containing a crafted UDF image, and the desktop environment auto-mounts it.
However, since the bug only corrupts the attacker's own filesystem and does
not lead to privilege escalation, memory corruption, or a system crash, it
does not pose a significant security boundary violation.]
|