| 0/0 |
2026/05/24 05:07 |
flow |
assessment-security |
50m
Results: map[DenialOfService:false Explanation:Based on the analysis of the bug report and the JFS source code, here is the
assessment of the security impact:
### Bug Mechanism
The bug is an array-index-out-of-bounds read in `dbFindLeaf()` in
`fs/jfs/jfs_dmap.c`.
The function searches a dmap tree (`dmtree_t`) for sufficient free blocks. The
tree array `tp->dmt_stree` has a size of `max_size` (which is 1365 for `dmapctl`
and 341 for `dmaptree`).
The loop condition `if (x + n > max_size)` incorrectly allows `x + n` to be
exactly equal to `max_size`, leading to an out-of-bounds read of
`tp->dmt_stree[max_size]`.
### Impact Analysis
1. **Memory Safety & Exploitation**:
The out-of-bounds read accesses the byte immediately following the `stree`
array. In both `struct dmapctl` and `struct dmaptree`, this byte is the first
element of the `pad` array (`pad[0]`). Both structures are exactly 4096 bytes
in size and are read from the disk as a single metapage buffer.
Therefore, the read is well within the allocated 4096-byte buffer and does
not cause a page fault or read unmapped memory. It simply reads a padding
byte from the attacker-controlled disk image.
If the padding byte indicates sufficient free space, `dbFindLeaf` returns an
out-of-bounds `leafidx` (e.g., 256 instead of 0-255). The caller
(`dbAllocDmapLev`) then uses this `leafidx` to access `dp->tree.stree[leafidx
+ LEAFIND]` and `dp->wmap[leafidx]`. These accesses are also out-of-bounds of
their respective arrays but still fall within the same 4096-byte `dmap`
buffer (reading `pad[0]` and `pmap[0]`).
The values read are used to calculate a block number (`blkno`) and a bit
offset (`dbitno`). The subsequent bit allocation in `dbAllocBits` uses
`dbitno = blkno & (BPERDMAP - 1)`, ensuring the bit offset is always masked
to be within valid bounds (0 to 8191). The allocation modifies `dp->wmap` and
`dp->tree.stree` strictly within their valid bounds. **No out-of-bounds write
occurs**, and no sensitive kernel memory is leaked.
2. **Denial of Service**:
The bug does not trigger any kernel panics or infinite loops. While JFS uses
`assert()` macros that translate to `BUG()` (which would halt the kernel),
the out-of-bounds read does not create conditions that violate any of these
assertions. The bug is only caught by UBSAN, which is a debug feature not
enabled in production builds. Thus, it does not cause a Denial of Service.
3. **Access & Triggers**:
- The bug is triggered by mounting a maliciously crafted JFS filesystem image
and performing block allocations (e.g., via `mkdir`).
- Mounting a JFS filesystem requires `CAP_SYS_ADMIN` in the initial
namespace. JFS does not set the `FS_USERNS_MOUNT` flag, meaning it cannot be
mounted by unprivileged users even within a user namespace.
### Conclusion
This is a benign out-of-bounds read within a dynamically allocated buffer
containing attacker-controlled disk data. It does not lead to memory corruption,
information leaks, or kernel panics. It has no security impact on production
systems. Exploitable:false FilesystemTrigger:true NetworkTrigger:false PeripheralTrigger:false RemoteTrigger:false Unprivileged:false UserNamespace:false VMGuestTrigger:false VMHostTrigger:false]
|
| 1/1 |
2026/05/24 05:07 |
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
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$jfs arguments: [
// fs: ptr[in, buffer] {
// buffer: {6a 66 73 00} (length 0x4)
// }
// dir: ptr[in, buffer] {
// buffer: {2e 2f 62 75 73 00} (length 0x6)
// }
// flags: mount_flags = 0xc802 (8 bytes)
// opts: ptr[inout, array[ANYUNION]] {
// array[ANYUNION] {
// union ANYUNION {
// ANYRES32: ANYRES32 (resource)
// }
// }
// }
// chdir: int8 = 0x1 (1 bytes)
// size: len = 0x5fd0 (8 bytes)
// img: ptr[in, buffer] {
// buffer: (compressed buffer with length 0x5fd0)
// }
// ]
// returns fd_dir
memcpy((void*)0x200000000400, "jfs\000", 4);
memcpy((void*)0x200000000000, "./bus\000", 6);
*(uint32_t*)0x200000000100 = 0;
memcpy((void*)0x200000006440, "... [truncated large byte array] ...", 24528);
syz_mount_image(/*fs=*/0x200000000400, /*dir=*/0x200000000000, /*flags=MS_REC|MS_SILENT|MS_NOSUID|MS_NODIRATIME*/0xc802, /*opts=*/0x200000000100, /*chdir=*/1, /*size=*/0x5fd0, /*img=*/0x200000006440);
// openat arguments: [
// fd: fd_dir (resource)
// file: ptr[in, buffer] {
// buffer: {2e 00} (length 0x2)
// }
// flags: open_flags = 0x0 (4 bytes)
// mode: open_mode = 0x0 (2 bytes)
// ]
// returns fd
memcpy((void*)0x2000000000c0, ".\000", 2);
res = syscall(__NR_openat, /*fd=*/0xffffff9c, /*file=*/0x2000000000c0ul, /*flags=*/0, /*mode=*/0);
if (res != -1)
r[0] = res;
// ioctl$FS_IOC_REMOVE_ENCRYPTION_KEY arguments: [
// fd: fd_dir (resource)
// cmd: const = 0xc0185879 (4 bytes)
// arg: ptr[inout, fscrypt_remove_key_arg] {
// fscrypt_remove_key_arg {
// key_spec: union fscrypt_key_specifier {
// desc: fscrypt_key_specifier__by_descriptor {
// type: const = 0x4100 (4 bytes)
// reserved: const = 0x0 (4 bytes)
// descriptor: union fscrypt_key_descriptor {
// desc3: buffer: {e8 da b9 92 34 bb 31 2e} (length 0x8)
// }
// reserved2: buffer: {00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00} (length 0x18)
// }
// }
// removal_status_flags: int32 = 0x0 (4 bytes)
// reserved: buffer: {00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00} (length 0x14)
// }
// }
// ]
*(uint32_t*)0x200000000080 = 0x4100;
*(uint32_t*)0x200000000084 = 0;
memcpy((void*)0x200000000088, "\350\332\271\2224\2731.", 8);
memset((void*)0x200000000090, 0, 24);
memset((void*)0x2000000000ac, 0, 20);
syscall(__NR_ioctl, /*fd=*/r[0], /*cmd=*/0xc0185879, /*arg=*/0x200000000080ul);
// syz_mount_image$vfat arguments: [
// fs: ptr[in, buffer] {
// buffer: {76 66 61 74 00} (length 0x5)
// }
// dir: ptr[in, buffer] {
// buffer: {13 13 77 c5 fc 35 d4 14 54 d5 d4 1d 29 ad 1a 60 29 59 81 46 e6 be 16 6e 41 ad 0d bd 40 54 03 3c 9f 33 bb da 82 24 a2 f3 d7 72 e7 63 6e 48 b3 3c bf 70 83 72 e8 f1 b9 93 3e c5 12 77 43 be 22 06 20 9e f0 2d f9 cb f2 f6 e8 80 d3 38 2f 00} (length 0x4e)
// }
// flags: mount_flags = 0x2b1247d (8 bytes)
// opts: nil
// chdir: int8 = 0xfc (1 bytes)
// size: len = 0x0 (8 bytes)
// img: ptr[in, buffer] {
// buffer: (compressed buffer with length 0x0)
// }
// ]
// returns fd_dir
memcpy((void*)0x200000000200, "vfat\000", 5);
memcpy((void*)0x2000000002c0, "... [truncated large byte array] ...", 78);
syz_mount_image(/*fs=*/0x200000000200, /*dir=*/0x2000000002c0, /*flags=MS_LAZYTIME|MS_I_VERSION|MS_SHARED|MS_POSIXACL|MS_SYNCHRONOUS|MS_REMOUNT|MS_RELATIME|0x244d*/0x2b1247d, /*opts=*/0, /*chdir=*/0xfc, /*size=*/0, /*img=*/0x2000000000c0);
return 0;
}
]
|
| 2/1 |
2026/05/24 05:07 |
action |
kernel-checkouter |
1m
Results: map[KernelSrc:/app/workdir/cache/src/cb24f0835974de80148d21636f6b653d93682021]
|
| 3/1 |
2026/05/24 05:08 |
action |
kernel-builder |
22m
Results: map[KernelObj:/app/workdir/cache/build/8b6cc6bea4e701bb6874027e4ebf14f08b115ae5]
|
| 4/1 |
2026/05/24 05:30 |
action |
codesearch-prepare |
17m
Results: map[Index:codesearch-index]
|
| 5/1 |
2026/05/24 05:48 |
agent |
expert |
9m
Model:
Results: map[DenialOfService:false Exploitable:false FilesystemTrigger:true NetworkTrigger:false PeripheralTrigger:false 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).
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.
Don't make assumptions about the kernel source code (it may be different from what you assume it is).
Extensively use the provided code access tools (codesearch-*, git-*, grepper, etc)
to examine the actual source code, and confirm any assumptions.
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:
------------[ cut here ]------------
UBSAN: array-index-out-of-bounds in fs/jfs/jfs_dmap.c:2976:16
index 1365 is out of range for type 's8[1365]' (aka 'signed char[1365]')
CPU: 1 UID: 0 PID: 6059 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT_{RT,(full)}
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
<TASK>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
ubsan_epilogue+0xa/0x40 lib/ubsan.c:233
__ubsan_handle_out_of_bounds+0xe9/0xf0 lib/ubsan.c:455
dbFindLeaf+0x308/0x520 fs/jfs/jfs_dmap.c:2976
dbFindCtl+0x267/0x520 fs/jfs/jfs_dmap.c:1717
dbAllocAny fs/jfs/jfs_dmap.c:1527 [inline]
dbAlloc+0x5fa/0xba0 fs/jfs/jfs_dmap.c:878
diNewIAG fs/jfs/jfs_imap.c:2510 [inline]
diAllocExt fs/jfs/jfs_imap.c:1905 [inline]
diAllocAG+0xd45/0x1df0 fs/jfs/jfs_imap.c:1669
diAlloc+0x1d4/0x1670 fs/jfs/jfs_imap.c:1590
ialloc+0x8c/0x8f0 fs/jfs/jfs_inode.c:56
jfs_mkdir+0x193/0xa70 fs/jfs/namei.c:225
vfs_mkdir+0x52d/0x5d0 fs/namei.c:5130
do_mkdirat+0x27a/0x4b0 fs/namei.c:5164
__do_sys_mkdirat fs/namei.c:5186 [inline]
__se_sys_mkdirat fs/namei.c:5184 [inline]
__x64_sys_mkdirat+0x87/0xa0 fs/namei.c:5184
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7efe6c5ade97
Code: 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 b8 02 01 00 00 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:00007efe6bbf4e68 EFLAGS: 00000246 ORIG_RAX: 0000000000000102
RAX: ffffffffffffffda RBX: 00007efe6bbf4ef0 RCX: 00007efe6c5ade97
RDX: 00000000000001ff RSI: 00002000000002c0 RDI: 00000000ffffff9c
RBP: 0000200000000200 R08: 00002000000000c0 R09: 0000000000000000
R10: 0000200000000200 R11: 0000000000000246 R12: 00002000000002c0
R13: 00007efe6bbf4eb0 R14: 0000000000000000 R15: 0000000000000000
</TASK>
---[ end trace ]---
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
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$jfs arguments: [
// fs: ptr[in, buffer] {
// buffer: {6a 66 73 00} (length 0x4)
// }
// dir: ptr[in, buffer] {
// buffer: {2e 2f 62 75 73 00} (length 0x6)
// }
// flags: mount_flags = 0xc802 (8 bytes)
// opts: ptr[inout, array[ANYUNION]] {
// array[ANYUNION] {
// union ANYUNION {
// ANYRES32: ANYRES32 (resource)
// }
// }
// }
// chdir: int8 = 0x1 (1 bytes)
// size: len = 0x5fd0 (8 bytes)
// img: ptr[in, buffer] {
// buffer: (compressed buffer with length 0x5fd0)
// }
// ]
// returns fd_dir
memcpy((void*)0x200000000400, "jfs\000", 4);
memcpy((void*)0x200000000000, "./bus\000", 6);
*(uint32_t*)0x200000000100 = 0;
memcpy((void*)0x200000006440, "... [truncated large byte array] ...", 24528);
syz_mount_image(/*fs=*/0x200000000400, /*dir=*/0x200000000000, /*flags=MS_REC|MS_SILENT|MS_NOSUID|MS_NODIRATIME*/0xc802, /*opts=*/0x200000000100, /*chdir=*/1, /*size=*/0x5fd0, /*img=*/0x200000006440);
// openat arguments: [
// fd: fd_dir (resource)
// file: ptr[in, buffer] {
// buffer: {2e 00} (length 0x2)
// }
// flags: open_flags = 0x0 (4 bytes)
// mode: open_mode = 0x0 (2 bytes)
// ]
// returns fd
memcpy((void*)0x2000000000c0, ".\000", 2);
res = syscall(__NR_openat, /*fd=*/0xffffff9c, /*file=*/0x2000000000c0ul, /*flags=*/0, /*mode=*/0);
if (res != -1)
r[0] = res;
// ioctl$FS_IOC_REMOVE_ENCRYPTION_KEY arguments: [
// fd: fd_dir (resource)
// cmd: const = 0xc0185879 (4 bytes)
// arg: ptr[inout, fscrypt_remove_key_arg] {
// fscrypt_remove_key_arg {
// key_spec: union fscrypt_key_specifier {
// desc: fscrypt_key_specifier__by_descriptor {
// type: const = 0x4100 (4 bytes)
// reserved: const = 0x0 (4 bytes)
// descriptor: union fscrypt_key_descriptor {
// desc3: buffer: {e8 da b9 92 34 bb 31 2e} (length 0x8)
// }
// reserved2: buffer: {00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00} (length 0x18)
// }
// }
// removal_status_flags: int32 = 0x0 (4 bytes)
// reserved: buffer: {00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00} (length 0x14)
// }
// }
// ]
*(uint32_t*)0x200000000080 = 0x4100;
*(uint32_t*)0x200000000084 = 0;
memcpy((void*)0x200000000088, "\350\332\271\2224\2731.", 8);
memset((void*)0x200000000090, 0, 24);
memset((void*)0x2000000000ac, 0, 20);
syscall(__NR_ioctl, /*fd=*/r[0], /*cmd=*/0xc0185879, /*arg=*/0x200000000080ul);
// syz_mount_image$vfat arguments: [
// fs: ptr[in, buffer] {
// buffer: {76 66 61 74 00} (length 0x5)
// }
// dir: ptr[in, buffer] {
// buffer: {13 13 77 c5 fc 35 d4 14 54 d5 d4 1d 29 ad 1a 60 29 59 81 46 e6 be 16 6e 41 ad 0d bd 40 54 03 3c 9f 33 bb da 82 24 a2 f3 d7 72 e7 63 6e 48 b3 3c bf 70 83 72 e8 f1 b9 93 3e c5 12 77 43 be 22 06 20 9e f0 2d f9 cb f2 f6 e8 80 d3 38 2f 00} (length 0x4e)
// }
// flags: mount_flags = 0x2b1247d (8 bytes)
// opts: nil
// chdir: int8 = 0xfc (1 bytes)
// size: len = 0x0 (8 bytes)
// img: ptr[in, buffer] {
// buffer: (compressed buffer with length 0x0)
// }
// ]
// returns fd_dir
memcpy((void*)0x200000000200, "vfat\000", 5);
memcpy((void*)0x2000000002c0, "... [truncated large byte array] ...", 78);
syz_mount_image(/*fs=*/0x200000000200, /*dir=*/0x2000000002c0, /*flags=MS_LAZYTIME|MS_I_VERSION|MS_SHARED|MS_POSIXACL|MS_SYNCHRONOUS|MS_REMOUNT|MS_RELATIME|0x244d*/0x2b1247d, /*opts=*/0, /*chdir=*/0xfc, /*size=*/0, /*img=*/0x2000000000c0);
return 0;
}
Reply: Based on the analysis of the bug report and the JFS source code, here is the assessment of the security impact:
### Bug Mechanism
The bug is an array-index-out-of-bounds read in `dbFindLeaf()` in `fs/jfs/jfs_dmap.c`.
The function searches a dmap tree (`dmtree_t`) for sufficient free blocks. The tree array `tp->dmt_stree` has a size of `max_size` (which is 1365 for `dmapctl` and 341 for `dmaptree`).
The loop condition `if (x + n > max_size)` incorrectly allows `x + n` to be exactly equal to `max_size`, leading to an out-of-bounds read of `tp->dmt_stree[max_size]`.
### Impact Analysis
1. **Memory Safety & Exploitation**:
The out-of-bounds read accesses the byte immediately following the `stree` array. In both `struct dmapctl` and `struct dmaptree`, this byte is the first element of the `pad` array (`pad[0]`). Both structures are exactly 4096 bytes in size and are read from the disk as a single metapage buffer.
Therefore, the read is well within the allocated 4096-byte buffer and does not cause a page fault or read unmapped memory. It simply reads a padding byte from the attacker-controlled disk image.
If the padding byte indicates sufficient free space, `dbFindLeaf` returns an out-of-bounds `leafidx` (e.g., 256 instead of 0-255). The caller (`dbAllocDmapLev`) then uses this `leafidx` to access `dp->tree.stree[leafidx + LEAFIND]` and `dp->wmap[leafidx]`. These accesses are also out-of-bounds of their respective arrays but still fall within the same 4096-byte `dmap` buffer (reading `pad[0]` and `pmap[0]`).
The values read are used to calculate a block number (`blkno`) and a bit offset (`dbitno`). The subsequent bit allocation in `dbAllocBits` uses `dbitno = blkno & (BPERDMAP - 1)`, ensuring the bit offset is always masked to be within valid bounds (0 to 8191). The allocation modifies `dp->wmap` and `dp->tree.stree` strictly within their valid bounds. **No out-of-bounds write occurs**, and no sensitive kernel memory is leaked.
2. **Denial of Service**:
The bug does not trigger any kernel panics or infinite loops. While JFS uses `assert()` macros that translate to `BUG()` (which would halt the kernel), the out-of-bounds read does not create conditions that violate any of these assertions. The bug is only caught by UBSAN, which is a debug feature not enabled in production builds. Thus, it does not cause a Denial of Service.
3. **Access & Triggers**:
- The bug is triggered by mounting a maliciously crafted JFS filesystem image and performing block allocations (e.g., via `mkdir`).
- Mounting a JFS filesystem requires `CAP_SYS_ADMIN` in the initial namespace. JFS does not set the `FS_USERNS_MOUNT` flag, meaning it cannot be mounted by unprivileged users even within a user namespace.
### Conclusion
This is a benign out-of-bounds read within a dynamically allocated buffer containing attacker-controlled disk data. It does not lead to memory corruption, information leaks, or kernel panics. It has no security impact on production systems.
|
| 6/2 |
2026/05/24 05:48 |
llm |
expert |
0m
Model:
Tokens:
input: 14456
output: 44
thoughts: 431
Thoughts: **Analyzing a JFS Filesystem Array-Index-Out-of-Bounds Error**
Okay, so I'm looking at a UBSAN report pointing to an array-index-out-of-bounds error. The specific location is `fs/jfs/jfs_dmap.c:2976`, and the index is 1365, which is exceeding the bounds of a `s8[1365]` array, essentially `signed char[1365]`. That's a classic off-by-one or an under/overflow issue. Let's trace it through the call stack; it seems the issue originates within the `dbFindLeaf` function at that very line.
The trace goes through `dbFindCtl`, `dbAllocAny`, `dbAlloc`, and down through inode allocation functions: `diNewIAG`, `diAllocExt`, `diAllocAG`, `diAlloc`, and `ialloc` before finally being triggered by a `jfs_mkdir` call. So this is happening when creating a directory in a JFS filesystem. The reproducer indicates mounting a JFS image and performing a `mkdir` operation, which makes perfect sense. My next step will be to delve into the `fs/jfs/jfs_dmap.c:2976` file to understand the context of this array access and figure out the logic that leads to that bad index. We need to trace how `dbFindLeaf` is calculating that index and determine if it's a calculation error or a boundary check that's missing or incorrect. I'm guessing this may involve examining data structures or calculations within the JFS block allocation or directory mapping process.
|
| 7/2 |
2026/05/24 05:48 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:fs/jfs/jfs_dmap.c IncludeLines:true Name:dbFindLeaf]
Results: map[SourceCode:2924: /*
2925: * NAME: dbFindLeaf()
2926: *
2927: * FUNCTION: search a dmtree_t for sufficient free blocks, returning
2928: * the index of a leaf describing the free blocks if
2929: * sufficient free blocks are found.
2930: *
2931: * the search starts at the top of the dmtree_t tree and
2932: * proceeds down the tree to the leftmost leaf with sufficient
2933: * free space.
2934: *
2935: * PARAMETERS:
2936: * tp - pointer to the tree to be searched.
2937: * l2nb - log2 number of free blocks to search for.
2938: * leafidx - return pointer to be set to the index of the leaf
2939: * describing at least l2nb free blocks if sufficient
2940: * free blocks are found.
2941: * is_ctl - determines if the tree is of type ctl
2942: *
2943: * RETURN VALUES:
2944: * 0 - success
2945: * -ENOSPC - insufficient free blocks.
2946: */
2947: static int dbFindLeaf(dmtree_t *tp, int l2nb, int *leafidx, bool is_ctl)
2948: {
2949: int ti, n = 0, k, x = 0;
2950: int max_size, max_idx;
2951:
2952: max_size = is_ctl ? CTLTREESIZE : TREESIZE;
2953: max_idx = is_ctl ? LPERCTL : LPERDMAP;
2954:
2955: /* first check the root of the tree to see if there is
2956: * sufficient free space.
2957: */
2958: if (l2nb > tp->dmt_stree[ROOT])
2959: return -ENOSPC;
2960:
2961: /* sufficient free space available. now search down the tree
2962: * starting at the next level for the leftmost leaf that
2963: * describes sufficient free space.
2964: */
2965: for (k = le32_to_cpu(tp->dmt_height), ti = 1;
2966: k > 0; k--, ti = ((ti + n) << 2) + 1) {
2967: /* search the four nodes at this level, starting from
2968: * the left.
2969: */
2970: for (x = ti, n = 0; n < 4; n++) {
2971: /* sufficient free space found. move to the next
2972: * level (or quit if this is the last level).
2973: */
2974: if (x + n > max_size)
2975: return -ENOSPC;
2976: if (l2nb <= tp->dmt_stree[x + n])
2977: break;
2978: }
2979:
2980: /* better have found something since the higher
2981: * levels of the tree said it was here.
2982: */
2983: assert(n < 4);
2984: }
2985: if (le32_to_cpu(tp->dmt_leafidx) >= max_idx)
2986: return -ENOSPC;
2987:
2988: /* set the return to the leftmost leaf describing sufficient
2989: * free space.
2990: */
2991: *leafidx = x + n - le32_to_cpu(tp->dmt_leafidx);
2992:
2993: return (0);
2994: }
SourceFile:fs/jfs/jfs_dmap.c]
|
| 8/2 |
2026/05/24 05:48 |
llm |
expert |
0m
Model:
Tokens:
input: 16423
output: 46
thoughts: 44
Thoughts: Okay, here's my take on those thoughts, framed as my own:
**Analyzing that Out-of-Bounds Memory Access**
Alright, line 2976... that out-of-bounds access is screaming at me โ `tp->dmt_stree[x + n]`. My immediate reaction is to zero in on what `dmtree_t` *is*. I need to understand the structure definition and how `dmt_stree` is declared within it. That's the key to understanding the bounds. I need to know the size of that array, or whatever data structure it is, and then the values of `x` and `n` at that point in the execution. Are we dealing with an off-by-one, an integer overflow, or something more insidious? My expert instincts are telling me to dig into the definition of `dmtree_t` first, get the layout and declarations straight, and then backtrack through the code to see how those variables (`x` and `n`) are being calculated and used. This could be a classic buffer overflow, or something more clever, but I need the details to know.
|
| 9/2 |
2026/05/24 05:48 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:fs/jfs/jfs_dmap.c IncludeLines:true Name:dmtree_t]
Results: map[SourceCode: 172: /*
173: * common definition for dmaptree within dmap and dmapctl
174: */
175: typedef union dmtree {
176: struct dmaptree t1;
177: struct dmapctl t2;
178: } dmtree_t;
SourceFile:fs/jfs/jfs_dmap.h]
|
| 10/2 |
2026/05/24 05:48 |
llm |
expert |
0m
Model:
Tokens:
input: 16887
output: 44
thoughts: 17
Thoughts: Here's my take on those structures, thinking like an expert in data structures and storage systems:
**Diving into `dmaptree` and `dmapctl`**
Okay, so I'm looking at `struct dmaptree` and `struct dmapctl`. Right away, the naming suggests we're dealing with something related to device mapping and likely a tree-like structure. Given the context, my initial hunch is that `dmaptree` is probably the core data structure used to represent the mapping of logical blocks to physical blocks on a storage device. This likely involves some form of a B-tree or a similar self-balancing tree to ensure efficient lookup and modification of the block mappings, especially with large volumes.
I'd expect `dmaptree` to contain pointers to nodes, likely some key-value pairs representing logical block offsets and associated physical block addresses, metadata about the tree (height, number of entries, perhaps some caching information or usage statistics). The critical part will be how they handle concurrency โ does it use locking, optimistic concurrency control, or something more advanced to ensure data consistency in a multi-threaded or distributed environment? I'd be looking closely at how the tree manages insertions, deletions, and updates, and if there are optimization strategies employed for sequential access patterns (like read-ahead or write-behind).
Then, `dmapctl`. The "ctl" strongly suggests a control structure or a container for controlling the `dmaptree`. It likely houses the overall management and operational details. Iโd imagine this struct would manage things like:
* **Tree Lifecycle:** Creation, destruction, and potentially resizing/rebalancing operations for the tree.
* **Concurrency Management:** Controlling the locking mechanisms used on the tree to protect from multiple access events.
* **Caching/Buffering:** Handling any caching or buffering strategies employed for performance optimization.
* **Error Handling/Recovery:** Management of error states, possibly including recovery mechanisms for corruption or inconsistencies in the mapping data.
* **Metadata:** Global metadata about the device mapper (version, flags, etc.).
I'm curious about the specific fields in each structure. I'd pay particular attention to how they handle things like:
* **Space Allocation:** How does the tree track free space and allocate new blocks? Is it bitmap-based, or something more sophisticated?
* **Compression/Deduplication:** Are there any indicators for compression or deduplication?
* **Snapshotting/Copy-on-Write:** If the system supports snapshots, how are these implemented and tracked within these structures?
So, overall, my first impression is that we're looking at a critical component for device mapping, and the devil is definitely in the details of how the concurrency, error handling, and performance optimization are implemented. Understanding how these structs interact is key to a solid grasp of the system.
|
| 11/2 |
2026/05/24 05:48 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:fs/jfs/jfs_dmap.h IncludeLines:true Name:dmaptree]
Results: map[SourceCode: 129: /*
130: * dmap summary tree
131: *
132: * dmaptree must be consistent with dmapctl.
133: */
134: struct dmaptree {
135: __le32 nleafs; /* 4: number of tree leafs */
136: __le32 l2nleafs; /* 4: l2 number of tree leafs */
137: __le32 leafidx; /* 4: index of first tree leaf */
138: __le32 height; /* 4: height of the tree */
139: s8 budmin; /* 1: min l2 tree leaf value to combine */
140: s8 stree[TREESIZE]; /* TREESIZE: tree */
141: u8 pad[2]; /* 2: pad to word boundary */
142: }; /* - 360 - */
SourceFile:fs/jfs/jfs_dmap.h]
|
| 12/2 |
2026/05/24 05:48 |
llm |
expert |
0m
Model:
Tokens:
input: 17852
output: 44
thoughts: 7
Thoughts: Okay, here's my interpretation of that thought process, tailored for an expert audience, and presented as if it were my own internal monologue:
**Diving into Data Structures for Control**
Right, so I'm thinking about the control plane, specifically how we manage and interact with data structures. That brings `struct dmapctl` to mind immediately. I'm focusing on the implementation details and how they impact the overall efficiency and performance of the system. I need to consider it within the context of the larger architecture. What are the key considerations? Is it thread-safe, efficient for reads vs. writes, and what about memory layout? I wonder how it is being used in the context of the greater system.
|
| 13/2 |
2026/05/24 05:48 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:fs/jfs/jfs_dmap.h IncludeLines:true Name:dmapctl]
Results: map[SourceCode: 157: /*
158: * disk map control page per level.
159: *
160: * dmapctl must be consistent with dmaptree.
161: */
162: struct dmapctl {
163: __le32 nleafs; /* 4: number of tree leafs */
164: __le32 l2nleafs; /* 4: l2 number of tree leafs */
165: __le32 leafidx; /* 4: index of the first tree leaf */
166: __le32 height; /* 4: height of tree */
167: s8 budmin; /* 1: minimum l2 tree leaf value */
168: s8 stree[CTLTREESIZE]; /* CTLTREESIZE: dmapctl tree */
169: u8 pad[2714]; /* 2714: pad to 4096 */
170: }; /* - 4096 - */
SourceFile:fs/jfs/jfs_dmap.h]
|
| 14/2 |
2026/05/24 05:48 |
llm |
expert |
0m
Model:
Tokens:
input: 18372
output: 19
thoughts: 20
Thoughts: Here's my analysis of the situation:
**Investigating TREESIZE and CTLTREESIZE Definitions**
Okay, so I need to get a handle on `TREESIZE` and `CTLTREESIZE`. I'm going to start by reviewing their specific definitions. I want to make sure I have a clear understanding of what these variables represent in this context. I'm assuming that they're likely related, perhaps one is a specific calculation built upon the other. It's important to grasp the exact meaning of each term individually before I can proceed. I want to build a solid foundation of understanding before I draw any further conclusions. With these definitions at my fingertips, I can then determine their function and relationship within the overall problem.
|
| 15/2 |
2026/05/24 05:48 |
tool |
grepper |
0m
Error:
Args: map[Expression:#define TREESIZE]
Results:
|
| 16/2 |
2026/05/24 05:48 |
llm |
expert |
0m
Model:
Tokens:
input: 18580
output: 20
thoughts: 26
Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience:
**Hunting Down TREESIZE in the JFS dmap**
Right, let's get down to it. I need to understand how the JFS disk map works at the fundamental level. My first instinct is to locate the `TREESIZE` macro. It's almost always a key constant in these kinds of structures, defining the size of a B-tree, or some key component of the disk map. Itโs almost certainly declared in the header files for the filesystem itself โ `fs/jfs`. My money's on `jfs_dmap.h`. That's where I'd expect the details of the disk map data structures to be defined, and `TREESIZE`, as a fundamental property, should be declared there, alongside the data structures that it defines. Let's start with that file. It's the logical place to begin this investigation.
|
| 17/2 |
2026/05/24 05:48 |
tool |
grepper |
0m
Args: map[Expression:#define.*TREESIZE]
Results: map[Output:fs/jfs/jfs_dmap.h-10-#define BMAPVERSION 1 /* version number */
fs/jfs/jfs_dmap.h:11:#define TREESIZE (256+64+16+4+1) /* size of a dmap tree */
fs/jfs/jfs_dmap.h-12-#define LEAFIND (64+16+4+1) /* index of 1st leaf of a dmap tree */
--
fs/jfs/jfs_dmap.h-19-#define L2BPERDMAP 13 /* l2 num of blks per dmap */
fs/jfs/jfs_dmap.h:20:#define CTLTREESIZE (1024+256+64+16+4+1) /* size of a dmapctl tree */
fs/jfs/jfs_dmap.h-21-#define CTLLEAFIND (256+64+16+4+1) /* idx of 1st leaf of a dmapctl tree */
]
|
| 18/2 |
2026/05/24 05:48 |
llm |
expert |
0m
Model:
Tokens:
input: 19111
output: 22
thoughts: 726
Thoughts: **Debugging a Potential Out-of-Bounds Access in `dbFindLeaf`**
Okay, so I'm looking at this UBSAN report flagging an out-of-bounds access. The error specifically says "index 1365 is out of range for type 's8[1365]'". `TREESIZE` is 341 and `CTLTREESIZE` is 1365. The code snippet I'm focused on is within `dbFindLeaf`, and the problem seems to be with the index calculation `x + n`. It appears that `x + n` evaluates to 1365, which, as the UBSAN report indicates, is problematic given the array size of the CTL tree.
Initially, I thought the comparison `if (x + n > max_size)` was the culprit. If `x + n` *equals* `max_size`, we have a problem because valid array indices should run from 0 up to `max_size - 1`. The current check allows a condition where `x + n` could be precisely at the boundary, leading to an attempt to access `tp->dmt_stree[max_size]`. So, I thought the check should be `>=` instead of `>`.
But, wait... `max_size` is indeed the `CTLTREESIZE` which equals 1365, which is equal to the upper limit of the array. So, even a change to `>=` will not fix the issue, because `tp->dmt_stree[1365]` is out of bounds.
Now, I'm getting suspicious. I need to check the definition of `tp->dmt_stree`. Is it *really* a simple array? Because I see `dmtree_t` is a union and `tp->dmt_stree` might be a macro! I need to trace this back to the source to fully understand this access.
|
| 19/2 |
2026/05/24 05:48 |
tool |
grepper |
0m
Args: map[Expression:#define.*dmt_stree]
Results: map[Output:fs/jfs/jfs_dmap.h=175=typedef union dmtree {
--
fs/jfs/jfs_dmap.h-185-#define dmt_budmin t1.budmin
fs/jfs/jfs_dmap.h:186:#define dmt_stree t2.stree
fs/jfs/jfs_dmap.h-187-
]
|
| 20/2 |
2026/05/24 05:48 |
llm |
expert |
0m
Model:
Tokens:
input: 20401
output: 44
thoughts: 464
Thoughts: **Debugging a Potential Out-of-Bounds Access in `dmt_stree`**
Okay, so `dmt_stree` is actually an alias for `t2.stree`, which is declared as an array `s8 stree[CTLTREESIZE]`. Right, so the reported out-of-bounds access is for `tp->dmt_stree[1365]`. My initial thought was that it was indeed out of bounds, but then I remembered `CTLTREESIZE` *is* 1365. Now I need to understand how we can hit this value, and then find where we can have the root of the issue.
The tree structure is 4-ary. Let's trace the index progression. Level 0 has 1 node (index 0). Level 1 has 4 nodes (indices 1 to 4). Level 2, 16 nodes (5 to 20). Level 3, 64 nodes (21 to 84). Level 4, 256 nodes (85 to 340). Level 5 has 1024 nodes (341 to 1364).
So the maximum *valid* index is 1364, not 1365, which confirms that we have an issue. If `x + n` *does* equal 1365, it implies we are trying to access a node that does not exist in the structure. Considering this 4-ary tree with level 5 nodes, if we reach level 5, `n` ranges from 0 to 3, but *that's* the problem. If we can reach index 1365, how does that happen? Let's trace it carefully.
`ti` is the index of the first node at the current level. For level 5, `ti` is 341. `x` is assigned 341. `n` ranges from 0 to 3. If `ti` is indeed 341, then `x + n` goes from 341 to 344, nowhere near 1365. That's not the problem.
Let's trace how `ti` is incremented. I see: `ti = ((ti + n) << 2) + 1`. This loop grows it. If the loop `k` value is allowed to go too high, `ti` can eventually get very large. So, *what* controls `k`? Aha, the height, `tp->dmt_height`. That comes from *disk*. If that value is corrupted, then we are in trouble, because a corrupted `tp->dmt_height` could cause the loop to run too many times, making `k` larger than 5. That's the likely root cause. The height is corrupted, which is causing the loop to run incorrectly.
I need to re-examine `dbFindLeaf` to see how the height is used and where the corruption might be introduced. That's the next step.
|
| 21/2 |
2026/05/24 05:49 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:fs/jfs/jfs_dmap.c IncludeLines:true Name:dbFindLeaf]
Results: map[SourceCode:2924: /*
2925: * NAME: dbFindLeaf()
2926: *
2927: * FUNCTION: search a dmtree_t for sufficient free blocks, returning
2928: * the index of a leaf describing the free blocks if
2929: * sufficient free blocks are found.
2930: *
2931: * the search starts at the top of the dmtree_t tree and
2932: * proceeds down the tree to the leftmost leaf with sufficient
2933: * free space.
2934: *
2935: * PARAMETERS:
2936: * tp - pointer to the tree to be searched.
2937: * l2nb - log2 number of free blocks to search for.
2938: * leafidx - return pointer to be set to the index of the leaf
2939: * describing at least l2nb free blocks if sufficient
2940: * free blocks are found.
2941: * is_ctl - determines if the tree is of type ctl
2942: *
2943: * RETURN VALUES:
2944: * 0 - success
2945: * -ENOSPC - insufficient free blocks.
2946: */
2947: static int dbFindLeaf(dmtree_t *tp, int l2nb, int *leafidx, bool is_ctl)
2948: {
2949: int ti, n = 0, k, x = 0;
2950: int max_size, max_idx;
2951:
2952: max_size = is_ctl ? CTLTREESIZE : TREESIZE;
2953: max_idx = is_ctl ? LPERCTL : LPERDMAP;
2954:
2955: /* first check the root of the tree to see if there is
2956: * sufficient free space.
2957: */
2958: if (l2nb > tp->dmt_stree[ROOT])
2959: return -ENOSPC;
2960:
2961: /* sufficient free space available. now search down the tree
2962: * starting at the next level for the leftmost leaf that
2963: * describes sufficient free space.
2964: */
2965: for (k = le32_to_cpu(tp->dmt_height), ti = 1;
2966: k > 0; k--, ti = ((ti + n) << 2) + 1) {
2967: /* search the four nodes at this level, starting from
2968: * the left.
2969: */
2970: for (x = ti, n = 0; n < 4; n++) {
2971: /* sufficient free space found. move to the next
2972: * level (or quit if this is the last level).
2973: */
2974: if (x + n > max_size)
2975: return -ENOSPC;
2976: if (l2nb <= tp->dmt_stree[x + n])
2977: break;
2978: }
2979:
2980: /* better have found something since the higher
2981: * levels of the tree said it was here.
2982: */
2983: assert(n < 4);
2984: }
2985: if (le32_to_cpu(tp->dmt_leafidx) >= max_idx)
2986: return -ENOSPC;
2987:
2988: /* set the return to the leftmost leaf describing sufficient
2989: * free space.
2990: */
2991: *leafidx = x + n - le32_to_cpu(tp->dmt_leafidx);
2992:
2993: return (0);
2994: }
SourceFile:fs/jfs/jfs_dmap.c]
|
| 22/2 |
2026/05/24 05:49 |
llm |
expert |
0m
Model:
Tokens:
input: 22710
output: 25
thoughts: 269
Thoughts: **Analyzing a Potential Out-of-Bounds Write**
Okay, so I'm looking at this code and trying to understand its memory access patterns. The key here seems to be `tp->dmt_height` and how it relates to this variable `k`. A larger height implies a larger `k`, which I need to keep in mind. Then, within the loop, we have `ti = ((ti + n) << 2) + 1`. This looks like a classic tree traversal where we're shifting and adding.
The critical issue, as I see it, revolves around how `x + n` interacts with `max_size`, which is defined as `CTLTREESIZE` and that has been specified as 1365. My initial thought was that a potential out-of-bounds error is flagged by `-ENOSPC` when `x + n` exceeds `max_size`. But hang onโฆ the check is `if (x + n > max_size) return -ENOSPC;`. So if `x + n` *equals* `max_size`, we *don't* get the error! It tries to access `tp->dmt_stree[x + n]`, which would be `tp->dmt_stree[1365]`.
But wait, `max_size` *is* 1365. That means the array size is 1365. So, the valid indices range from 0 to 1364. When `x + n` *equals* 1365, it's definitively out-of-bounds! The index would be `tp->dmt_stree[1365]`, which would be an invalid access. The current condition `if (x + n > max_size)` is incorrect; it should be `if (x + n >= max_size)`. This is a clear bug. I need to verify this assumption but I'm pretty certain about this.
|
| 23/2 |
2026/05/24 05:49 |
tool |
grepper |
0m
Args: map[Expression:if \(x \+ n > max_size\)]
Results: map[Output:fs/jfs/jfs_dmap.c=2947=static int dbFindLeaf(dmtree_t *tp, int l2nb, int *leafidx, bool is_ctl)
--
fs/jfs/jfs_dmap.c-2973- */
fs/jfs/jfs_dmap.c:2974: if (x + n > max_size)
fs/jfs/jfs_dmap.c-2975- return -ENOSPC;
]
|
| 24/2 |
2026/05/24 05:49 |
llm |
expert |
1m
Model:
Tokens:
input: 23572
output: 21
thoughts: 203
Thoughts: **Analyzing a Potential Out-of-Bounds Array Access**
Okay, so I'm looking at this `if (x + n > max_size)` condition and immediately something feels a little off. Specifically, it *allows* `x + n` to equal `max_size`. And that's where my alarm bells start ringing because if `x + n` *does* equal `max_size`, that means we're trying to access `tp->dmt_stree[max_size]`. Wait a minute, is `max_size` the size of the `stree` array?
Let's double-check the definitions. Ah, yes, there it is: `s8 stree[CTLTREESIZE];` and `max_size` is calculated as `is_ctl ? CTLTREESIZE : TREESIZE;`. So, `max_size` *is* indeed the exact size of the array. That means my initial concern is validated; the original code allows an access that is, at best, on the boundary and, at worst, an out-of-bounds read. So `x + n >= max_size` is, in fact, the more correct check.
Okay, let's play this out. If `x + n == max_size`, then we're accessing `tp->dmt_stree[1365]` (assuming `max_size` is 1365, though the actual value isn't crucial here). This is still suspect. We're trying to read memory outside the valid range. Now I need to see what's actually located at this offset within the `struct dmapctl`. Is that a valid element? Is it allocated, or garbage data? That's the next critical step.
|
| 25/2 |
2026/05/24 05:50 |
tool |
codesearch-struct-layout |
0m
Args:
Results: map[Fields:[map[Name:nleafs OffsetBits:0 SizeBits:32] map[Name:l2nleafs OffsetBits:32 SizeBits:32] map[Name:leafidx OffsetBits:64 SizeBits:32] map[Name:height OffsetBits:96 SizeBits:32] map[Name:budmin OffsetBits:128 SizeBits:8] map[Name:stree OffsetBits:136 SizeBits:10920] map[Name:pad OffsetBits:11056 SizeBits:21712]]]
|
| 26/2 |
2026/05/24 05:50 |
llm |
expert |
0m
Model:
Tokens:
input: 24335
output: 21
thoughts: 875
Thoughts: **Analyzing the Out-of-Bounds Read in `stree`**
Okay, so I'm digging into this code, and it looks like `stree` is being accessed with an out-of-bounds read. Let me break this down. `stree` starts at byte 17, and its size is 1365 bytes. Now, this `stree[1365]` thing... it seems like it's calculating an offset that goes *just* past the end of the `stree` array, into the `pad` array.
Specifically, `stree[1365]` accesses the byte at offset 1382, which is the first byte of `pad`. The code explicitly says that reading from `pad` is "harmless" because it's just padding, presumably initialized. However, this is where it gets interesting, because `pad` isn't *truly* initialized, it's read from disk! That means an attacker potentially has control over the value of `pad[0]`.
Now, if `l2nb <= pad[0]`, the inner loop breaks and n becomes 0. If `x + n` is still equal to 1365 then the assertion, `assert(n < 4)`, will pass. After this iteration, `k--`, and a new ti is calculated.
Crucially, in this situation, `x + n` will *always* be equal to 1365. Now, the loop proceeds. If `x + n > max_size` it will return `-ENOSPC` and if `k == 0` it will continue on.
Now, if `k` is 0, the code calculates `*leafidx = x + n - le32_to_cpu(tp->dmt_leafidx)`. The previous analysis gives us `x+n = 1365`. So, `*leafidx = 1365 - le32_to_cpu(tp->dmt_leafidx)`.
So, the issue is that if `l2nb <= pad[0]` then `*leafidx` can be influenced by the value of `pad[0]` and by the value stored at `tp->dmt_leafidx`. That value could potentially be controlled by an attacker, leading to arbitrary memory access, or to information disclosure. I need to trace how `*leafidx` is used by the caller to see where I can exploit this.
|
| 27/2 |
2026/05/24 05:50 |
tool |
codesearch-find-references |
0m
Args:
Results: map[References:[map[ReferenceKind:calls ReferencingEntityKind:function ReferencingEntityName:dbAllocDmapLev SourceFile:fs/jfs/jfs_dmap.c SourceLine:1969] map[ReferenceKind:calls ReferencingEntityKind:function ReferencingEntityName:dbFindCtl SourceFile:fs/jfs/jfs_dmap.c SourceLine:1717]] TruncatedOutput:false]
|
| 28/2 |
2026/05/24 05:50 |
llm |
expert |
0m
Model:
Tokens:
input: 25897
output: 45
thoughts: 28
Thoughts: Okay, here's my interpretation of those thoughts, presented as a first-person expert summary:
**Analyzing Database Control Functions**
Right, so the system's currently calling `dbFindCtl` and `dbAllocDmapLev`. That's interesting, and provides a clear point of focus. It looks like the process is trying to find a database control structure, or perhaps allocate a device map level.
Let's begin by checking what `dbFindCtl` is up to. I need to understand exactly what that function does; I'll need to know whether it returns a handle to an existing structure, creates a new one, or indicates that one couldn't be found. The context in which it's being used is critical here. Is it searching for a specific control block, and if so, what criteria are we using? If the subsequent call to `dbAllocDmapLev` depends on the outcome of `dbFindCtl`, that will have great value in guiding my understanding of the larger process. I'll need to look at the surrounding code to determine how this interaction works, and what the implications are if `dbFindCtl` behaves in a specific manner. I might also check the return values and any potential errors, to see if they shed light on the system's current state. I need to quickly identify the purpose of this initial call before I move on.
|
| 29/2 |
2026/05/24 05:50 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:fs/jfs/jfs_dmap.c IncludeLines:true Name:dbFindCtl]
Results: map[SourceCode:1653: /*
1654: * NAME: dbFindCtl()
1655: *
1656: * FUNCTION: starting at a specified dmap control page level and block
1657: * number, search down the dmap control levels for a range of
1658: * contiguous free blocks large enough to satisfy an allocation
1659: * request for the specified number of free blocks.
1660: *
1661: * if sufficient contiguous free blocks are found, this routine
1662: * returns the starting block number within a dmap page that
1663: * contains or starts a range of contiqious free blocks that
1664: * is sufficient in size.
1665: *
1666: * PARAMETERS:
1667: * bmp - pointer to bmap descriptor
1668: * level - starting dmap control page level.
1669: * l2nb - log2 number of contiguous free blocks desired.
1670: * *blkno - on entry, starting block number for conducting the search.
1671: * on successful return, the first block within a dmap page
1672: * that contains or starts a range of contiguous free blocks.
1673: *
1674: * RETURN VALUES:
1675: * 0 - success
1676: * -ENOSPC - insufficient disk resources
1677: * -EIO - i/o error
1678: *
1679: * serialization: IWRITE_LOCK(ipbmap) held on entry/exit;
1680: */
1681: static int dbFindCtl(struct bmap * bmp, int l2nb, int level, s64 * blkno)
1682: {
1683: int rc, leafidx, lev;
1684: s64 b, lblkno;
1685: struct dmapctl *dcp;
1686: int budmin;
1687: struct metapage *mp;
1688:
1689: /* starting at the specified dmap control page level and block
1690: * number, search down the dmap control levels for the starting
1691: * block number of a dmap page that contains or starts off
1692: * sufficient free blocks.
1693: */
1694: for (lev = level, b = *blkno; lev >= 0; lev--) {
1695: /* get the buffer of the dmap control page for the block
1696: * number and level (i.e. L0, L1, L2).
1697: */
1698: lblkno = BLKTOCTL(b, bmp->db_l2nbperpage, lev);
1699: mp = read_metapage(bmp->db_ipbmap, lblkno, PSIZE, 0);
1700: if (mp == NULL)
1701: return -EIO;
1702: dcp = (struct dmapctl *) mp->data;
1703: budmin = dcp->budmin;
1704:
1705: if (dcp->leafidx != cpu_to_le32(CTLLEAFIND)) {
1706: jfs_error(bmp->db_ipbmap->i_sb,
1707: "Corrupt dmapctl page\n");
1708: release_metapage(mp);
1709: return -EIO;
1710: }
1711:
1712: /* search the tree within the dmap control page for
1713: * sufficient free space. if sufficient free space is found,
1714: * dbFindLeaf() returns the index of the leaf at which
1715: * free space was found.
1716: */
1717: rc = dbFindLeaf((dmtree_t *) dcp, l2nb, &leafidx, true);
1718:
1719: /* release the buffer.
1720: */
1721: release_metapage(mp);
1722:
1723: /* space found ?
1724: */
1725: if (rc) {
1726: if (lev != level) {
1727: jfs_error(bmp->db_ipbmap->i_sb,
1728: "dmap inconsistent\n");
1729: return -EIO;
1730: }
1731: return -ENOSPC;
1732: }
1733:
1734: /* adjust the block number to reflect the location within
1735: * the dmap control page (i.e. the leaf) at which free
1736: * space was found.
1737: */
1738: b += (((s64) leafidx) << budmin);
1739:
1740: /* we stop the search at this dmap control page level if
1741: * the number of blocks required is greater than or equal
1742: * to the maximum number of blocks described at the next
1743: * (lower) level.
1744: */
1745: if (l2nb >= budmin)
1746: break;
1747: }
1748:
1749: *blkno = b;
1750: return (0);
1751: }
SourceFile:fs/jfs/jfs_dmap.c]
|
| 30/2 |
2026/05/24 05:50 |
llm |
expert |
0m
Model:
Tokens:
input: 27804
output: 20
thoughts: 160
Thoughts: **Analyzing the Control Leaf Index**
Okay, so I've got this `leafidx` value being returned, and I need to figure out what it represents in this context. Let's see, if `x + n` was 1365, the calculation is `leafidx = 1365 - le32_to_cpu(tp->dmt_leafidx)`. Right. Now, I'm pretty sure `leafidx` plays a role in `dbFindCtl`, and in that function, `dcp->leafidx` is being checked against `CTLLEAFIND`. And `CTLLEAFIND` is defined as 341 (256 + 64 + 16 + 4 + 1). So, if I apply that to my initial example, I get `leafidx = 1365 - 341 = 1024`.
Hmm, something doesn't feel quite right. I seem to recall a special maximum index value associated with control leaves. That should be `LPERCTL`. Let me quickly look up what `LPERCTL` is to be sure I'm on the right track here, and if my assumption about this being the "max_idx" is correct.
|
| 31/2 |
2026/05/24 05:50 |
tool |
grepper |
0m
Args: map[Expression:#define.*LPERCTL]
Results: map[Output:fs/jfs/jfs_dmap.c=3987=static int dbGetL2AGSize(s64 nblocks)
--
fs/jfs/jfs_dmap.c-4023- */
fs/jfs/jfs_dmap.c:4024:#define MAXL0PAGES (1 + LPERCTL)
fs/jfs/jfs_dmap.c:4025:#define MAXL1PAGES (1 + LPERCTL * MAXL0PAGES)
fs/jfs/jfs_dmap.c-4026-
--
fs/jfs/jfs_dmap.h-21-#define CTLLEAFIND (256+64+16+4+1) /* idx of 1st leaf of a dmapctl tree */
fs/jfs/jfs_dmap.h:22:#define LPERCTL 1024 /* num of leaves per dmapctl tree */
fs/jfs/jfs_dmap.h:23:#define L2LPERCTL 10 /* l2 num of leaves per dmapctl tree */
fs/jfs/jfs_dmap.h-24-#define ROOT 0 /* index of the root of a tree */
--
fs/jfs/jfs_dmap.h-33- */
fs/jfs/jfs_dmap.h:34:#define L2MAXL0SIZE (L2BPERDMAP + 1 * L2LPERCTL)
fs/jfs/jfs_dmap.h:35:#define L2MAXL1SIZE (L2BPERDMAP + 2 * L2LPERCTL)
fs/jfs/jfs_dmap.h:36:#define L2MAXL2SIZE (L2BPERDMAP + 3 * L2LPERCTL)
fs/jfs/jfs_dmap.h-37-
]
|
| 32/2 |
2026/05/24 05:50 |
llm |
expert |
1m
Model:
Tokens:
input: 28743
output: 21
thoughts: 1048
Thoughts: **Analyzing the Out-of-Bounds Read in `dbFindLeaf` and Its Security Implications**
Okay, let's break this down. `LPERCTL` is 1024, which is important because it represents the maximum number of leaves we expect. Inside `dbFindLeaf`, we check if `tp->dmt_leafidx` (which is `CTLLEAFIND`, or 341) is greater than or equal to `max_idx` (which is `LPERCTL`, or 1024). This comparison, `341 >= 1024`, is false, so we move on. Then `*leafidx` gets set to `1365 - 341`, resulting in 1024. That *should* be a problem, because valid leaves are from 0 to 1023, based on `LPERCTL`. So, `leafidx` being 1024 seems out of bounds.
Looking at how `leafidx` is *used* in `dbFindCtl`, we see it's used to adjust the block number `b`. Specifically, `b` is incremented by `1024 << budmin`. This might lead to allocating blocks beyond the valid range, depending on how `b` is used later in `dbAlloc`.
However, the reported bug is about an *out-of-bounds read* at `tp->dmt_stree[1365]`. This is a read, and it's accessing `pad[0]`. The code reads from a `struct dmapctl` which is read from the disk image. The critical part is that `pad` is populated from the disk. This is a read, but *from a disk block the attacker controls*. So, an attacker could manipulate the disk image to place whatever value they want into `pad[0]`.
Since the attacker *already* controls the data being read from the disk (including `stree[1365]` via the `stree` part of the `dmapctl`), this out-of-bounds read of `pad[0]` doesn't expose any kernel memory that the attacker shouldn't already know. The buffer `mp->data` is exactly `PSIZE` (4096 bytes), which matches the size of the `struct dmapctl` structure definition. Thus, `stree[1365]` is well within the allocated buffer and so is the byte of `pad` being read. The structure layout is: `stree` plus `pad`. The read does not reach outside the allocated buffer. The read *is* within a buffer but the content of the buffer is under the attacker's control, so, it has no security impact. It's not leaking kernel memory, and it won't be a crash. It's simply reading a value that the attacker has already manipulated. The only effect is UBSAN, which is a debug tool.
Wait... if `is_ctl` is false, it uses different constants. Then `max_size` is `TREESIZE` (341), and `max_idx` is `LPERDMAP` (256). The important thing is whether `tp` is `struct dmaptree` and where in this data the read is.
|
| 33/2 |
2026/05/24 05:51 |
tool |
codesearch-struct-layout |
0m
Args:
Results: map[Fields:[map[Name:nleafs OffsetBits:0 SizeBits:32] map[Name:l2nleafs OffsetBits:32 SizeBits:32] map[Name:leafidx OffsetBits:64 SizeBits:32] map[Name:height OffsetBits:96 SizeBits:32] map[Name:budmin OffsetBits:128 SizeBits:8] map[Name:stree OffsetBits:136 SizeBits:2728] map[Name:pad OffsetBits:2864 SizeBits:16]]]
|
| 34/2 |
2026/05/24 05:51 |
llm |
expert |
0m
Model:
Tokens:
input: 30684
output: 20
thoughts: 187
Thoughts: **Analyzing Memory Access in a `dmaptree` Structure**
Okay, let's break down this memory access scenario. I see that the `stree` component starts at an offset of 17 bytes and spans 341 bytes. Now, the potential issue arises when accessing memory based on an expression like `x + n` where the result equals 341. In that case, it looks like we're trying to access `stree[341]`, which I calculate to be at byte 358 (17 + 341).
That offset of 358 bytes falls within the `pad` region, which begins at an offset of 358 bytes. `pad` itself is only 2 bytes in size. Therefore, it appears that the code is intended to read the first byte of `pad`.
Now, the important question is: is this access actually valid? I need to verify whether the `dmaptree` struct is correctly allocated. If I understand correctly, `dmaptree` should encompass 360 bytes. This means that if `dmaptree` resides in a buffer that is less than 360 bytes in size, we're likely going to run into an out-of-bounds read error.
Given my experience with similar structures, I know that `dmaptree` is frequently part of a `struct dmap`. Now, I need to focus on confirming the size and allocation of that `struct dmap`. This memory access would only become concerning if it's operating on an insufficiently sized data structure.
|
| 35/2 |
2026/05/24 05:52 |
tool |
codesearch-struct-layout |
0m
Args:
Results: map[Fields:[map[Name:nblocks OffsetBits:0 SizeBits:32] map[Name:nfree OffsetBits:32 SizeBits:32] map[Name:start OffsetBits:64 SizeBits:64] map[Name:tree OffsetBits:128 SizeBits:2880] map[Name:pad OffsetBits:3008 SizeBits:13376] map[Name:wmap OffsetBits:16384 SizeBits:8192] map[Name:pmap OffsetBits:24576 SizeBits:8192]]]
|
| 36/2 |
2026/05/24 05:52 |
llm |
expert |
0m
Model:
Tokens:
input: 31387
output: 44
thoughts: 364
Thoughts: **Analyzing the Harmless Out-of-Bounds Read**
Okay, let's break this down. From what I'm seeing, `tree`, which is actually a `struct dmaptree`, resides at an offset of 16 bytes. It has a size of 360 bytes, placing it within a 4096-byte `dmap` buffer. That means `tree` occupies bytes 16 to 375 of `dmap`. The code seems to be reading `pad[0]` of the `dmaptree`. If I'm understanding this correctly, this read is at byte 358 within `dmaptree`, corresponding to byte 374 in `dmap`.
Given these offsets, the read stays well within the allocated buffer. I don't see any obvious page faults or memory leaks, since it's reading from the disk image itself. So, based purely on the read, it's harmless and shouldn't cause any immediate issues. However, the logic *after* the read is where things get interesting. The crucial condition seems to be `l2nb <= tp->dmt_stree[max_size]`. If that's true, the loop breaks. It looks like `leafidx` is calculated based on `max_size` and a converted value from `tp->dmt_leafidx`. For `dmapctl`, `leafidx` computes to 1024, but for `dmaptree` it calculates to 256.
I should investigate what happens when `leafidx` is 256, particularly when it's used in the `dbFindLeaf` function that is called for `dmaptree`. I know that call to `dbFindLeaf` is triggered by `dbAllocAny`, `dbAllocNear` or `dbAllocAG`. Let's start by digging into `dbAllocAny`.
|
| 37/2 |
2026/05/24 05:52 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:fs/jfs/jfs_dmap.c IncludeLines:true Name:dbAllocAny]
Results: map[SourceCode:1490: /*
1491: * NAME: dbAllocAny()
1492: *
1493: * FUNCTION: attempt to allocate the specified number of contiguous
1494: * free blocks anywhere in the file system.
1495: *
1496: * dbAllocAny() attempts to find the sufficient free space by
1497: * searching down the dmap control pages, starting with the
1498: * highest level (i.e. L0, L1, L2) control page. if free space
1499: * large enough to satisfy the desired free space is found, the
1500: * desired free space is allocated.
1501: *
1502: * PARAMETERS:
1503: * bmp - pointer to bmap descriptor
1504: * nblocks - actual number of contiguous free blocks desired.
1505: * l2nb - log2 number of contiguous free blocks desired.
1506: * results - on successful return, set to the starting block number
1507: * of the newly allocated range.
1508: *
1509: * RETURN VALUES:
1510: * 0 - success
1511: * -ENOSPC - insufficient disk resources
1512: * -EIO - i/o error
1513: *
1514: * serialization: IWRITE_LOCK(ipbmap) held on entry/exit;
1515: */
1516: static int dbAllocAny(struct bmap * bmp, s64 nblocks, int l2nb, s64 * results)
1517: {
1518: int rc;
1519: s64 blkno = 0;
1520:
1521: /* starting with the top level dmap control page, search
1522: * down the dmap control levels for sufficient free space.
1523: * if free space is found, dbFindCtl() returns the starting
1524: * block number of the dmap that contains or starts off the
1525: * range of free space.
1526: */
1527: if ((rc = dbFindCtl(bmp, l2nb, bmp->db_maxlevel, &blkno)))
1528: return (rc);
1529:
1530: /* allocate the blocks.
1531: */
1532: rc = dbAllocCtl(bmp, nblocks, l2nb, blkno, results);
1533: if (rc == -ENOSPC) {
1534: jfs_error(bmp->db_ipbmap->i_sb, "unable to allocate blocks\n");
1535: return -EIO;
1536: }
1537: return (rc);
1538: }
SourceFile:fs/jfs/jfs_dmap.c]
|
| 38/2 |
2026/05/24 05:52 |
llm |
expert |
0m
Model:
Tokens:
input: 33018
output: 45
thoughts: 81
Thoughts: **Analyzing the Data Block Allocation**
Okay, so I'm seeing that `dbFindCtl` is calling `dbFindLeaf` with `is_ctl` set to true. That's the key. This means that when it returns, the `leafidx` value should be 1024. Now, the next line is `b += (((s64) leafidx) << budmin);`. Essentially, this line shifts the `leafidx` value left by `budmin` bits and adds it to the variable `b`. This process manipulates the index to get a block number. The next line, `dbAllocCtl` is then called with `blkno = b`. So, `b`, which now holds this calculated block number, is what's being passed to `dbAllocCtl`. I need to understand what `dbAllocCtl` does with that block number. I need to dig into the definition of `dbAllocCtl` now. Let's check that function and see what it is doing with this `b`.
|
| 39/2 |
2026/05/24 05:52 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:fs/jfs/jfs_dmap.c IncludeLines:true Name:dbAllocCtl]
Results: map[SourceCode:1754: /*
1755: * NAME: dbAllocCtl()
1756: *
1757: * FUNCTION: attempt to allocate a specified number of contiguous
1758: * blocks starting within a specific dmap.
1759: *
1760: * this routine is called by higher level routines that search
1761: * the dmap control pages above the actual dmaps for contiguous
1762: * free space. the result of successful searches by these
1763: * routines are the starting block numbers within dmaps, with
1764: * the dmaps themselves containing the desired contiguous free
1765: * space or starting a contiguous free space of desired size
1766: * that is made up of the blocks of one or more dmaps. these
1767: * calls should not fail due to insufficent resources.
1768: *
1769: * this routine is called in some cases where it is not known
1770: * whether it will fail due to insufficient resources. more
1771: * specifically, this occurs when allocating from an allocation
1772: * group whose size is equal to the number of blocks per dmap.
1773: * in this case, the dmap control pages are not examined prior
1774: * to calling this routine (to save pathlength) and the call
1775: * might fail.
1776: *
1777: * for a request size that fits within a dmap, this routine relies
1778: * upon the dmap's dmtree to find the requested contiguous free
1779: * space. for request sizes that are larger than a dmap, the
1780: * requested free space will start at the first block of the
1781: * first dmap (i.e. blkno).
1782: *
1783: * PARAMETERS:
1784: * bmp - pointer to bmap descriptor
1785: * nblocks - actual number of contiguous free blocks to allocate.
1786: * l2nb - log2 number of contiguous free blocks to allocate.
1787: * blkno - starting block number of the dmap to start the allocation
1788: * from.
1789: * results - on successful return, set to the starting block number
1790: * of the newly allocated range.
1791: *
1792: * RETURN VALUES:
1793: * 0 - success
1794: * -ENOSPC - insufficient disk resources
1795: * -EIO - i/o error
1796: *
1797: * serialization: IWRITE_LOCK(ipbmap) held on entry/exit;
1798: */
1799: static int
1800: dbAllocCtl(struct bmap * bmp, s64 nblocks, int l2nb, s64 blkno, s64 * results)
1801: {
1802: int rc, nb;
1803: s64 b, lblkno, n;
1804: struct metapage *mp;
1805: struct dmap *dp;
1806:
1807: /* check if the allocation request is confined to a single dmap.
1808: */
1809: if (l2nb <= L2BPERDMAP) {
1810: /* get the buffer for the dmap.
1811: */
1812: lblkno = BLKTODMAP(blkno, bmp->db_l2nbperpage);
1813: mp = read_metapage(bmp->db_ipbmap, lblkno, PSIZE, 0);
1814: if (mp == NULL)
1815: return -EIO;
1816: dp = (struct dmap *) mp->data;
1817:
1818: if (dp->tree.budmin < 0) {
1819: release_metapage(mp);
1820: return -EIO;
1821: }
1822:
1823: /* try to allocate the blocks.
1824: */
1825: rc = dbAllocDmapLev(bmp, dp, (int) nblocks, l2nb, results);
1826: if (rc == 0)
1827: mark_metapage_dirty(mp);
1828:
1829: release_metapage(mp);
1830:
1831: return (rc);
1832: }
1833:
1834: /* allocation request involving multiple dmaps. it must start on
1835: * a dmap boundary.
1836: */
1837: assert((blkno & (BPERDMAP - 1)) == 0);
1838:
1839: /* allocate the blocks dmap by dmap.
1840: */
1841: for (n = nblocks, b = blkno; n > 0; n -= nb, b += nb) {
1842: /* get the buffer for the dmap.
1843: */
1844: lblkno = BLKTODMAP(b, bmp->db_l2nbperpage);
1845: mp = read_metapage(bmp->db_ipbmap, lblkno, PSIZE, 0);
1846: if (mp == NULL) {
1847: rc = -EIO;
1848: goto backout;
1849: }
1850: dp = (struct dmap *) mp->data;
1851:
1852: /* the dmap better be all free.
1853: */
1854: if (dp->tree.stree[ROOT] != L2BPERDMAP) {
1855: release_metapage(mp);
1856: jfs_error(bmp->db_ipbmap->i_sb,
1857: "the dmap is not all free\n");
1858: rc = -EIO;
1859: goto backout;
1860: }
1861:
1862: /* determine how many blocks to allocate from this dmap.
1863: */
1864: nb = min_t(s64, n, BPERDMAP);
1865:
1866: /* allocate the blocks from the dmap.
1867: */
1868: if ((rc = dbAllocDmap(bmp, dp, b, nb))) {
1869: release_metapage(mp);
1870: goto backout;
1871: }
1872:
1873: /* write the buffer.
1874: */
1875: write_metapage(mp);
1876: }
1877:
1878: /* set the results (starting block number) and return.
1879: */
1880: *results = blkno;
1881: return (0);
1882:
1883: /* something failed in handling an allocation request involving
1884: * multiple dmaps. we'll try to clean up by backing out any
1885: * allocation that has already happened for this request. if
1886: * we fail in backing out the allocation, we'll mark the file
1887: * system to indicate that blocks have been leaked.
1888: */
1889: backout:
1890:
1891: /* try to backout the allocations dmap by dmap.
1892: */
1893: for (n = nblocks - n, b = blkno; n > 0;
1894: n -= BPERDMAP, b += BPERDMAP) {
1895: /* get the buffer for this dmap.
1896: */
1897: lblkno = BLKTODMAP(b, bmp->db_l2nbperpage);
1898: mp = read_metapage(bmp->db_ipbmap, lblkno, PSIZE, 0);
1899: if (mp == NULL) {
1900: /* could not back out. mark the file system
1901: * to indicate that we have leaked blocks.
1902: */
1903: jfs_error(bmp->db_ipbmap->i_sb,
1904: "I/O Error: Block Leakage\n");
1905: continue;
1906: }
1907: dp = (struct dmap *) mp->data;
1908:
1909: /* free the blocks is this dmap.
1910: */
1911: if (dbFreeDmap(bmp, dp, b, BPERDMAP)) {
1912: /* could not back out. mark the file system
1913: * to indicate that we have leaked blocks.
1914: */
1915: release_metapage(mp);
1916: jfs_error(bmp->db_ipbmap->i_sb, "Block Leakage\n");
1917: continue;
1918: }
1919:
1920: /* write the buffer.
1921: */
1922: write_metapage(mp);
1923: }
1924:
1925: return (rc);
1926: }
SourceFile:fs/jfs/jfs_dmap.c]
|
| 40/2 |
2026/05/24 05:52 |
llm |
expert |
0m
Model:
Tokens:
input: 36037
output: 46
thoughts: 22
Thoughts: Here's a summary of my thought process, as if I were the code itself:
**Decision Point: Memory Allocation for a Dmap Level**
Okay, so I'm looking at this memory allocation situation. The critical factor is `l2nb`, which, as I understand it, represents the amount of Level 2 network buffer space needed. I need to compare this value against `L2BPERDMAP`, a constant that likely defines the maximum buffer space allocated per Dmap level.
If `l2nb` is less than or equal to `L2BPERDMAP`, then I need to allocate a new Dmap level. Based on my design, I should call the `dbAllocDmapLev` function. This would be the appropriate action for this situation.
|
| 41/2 |
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tool |
codesearch-definition-source |
0m
Args: map[ContextFile:fs/jfs/jfs_dmap.c IncludeLines:true Name:dbAllocDmapLev]
Results: map[SourceCode:1929: /*
1930: * NAME: dbAllocDmapLev()
1931: *
1932: * FUNCTION: attempt to allocate a specified number of contiguous blocks
1933: * from a specified dmap.
1934: *
1935: * this routine checks if the contiguous blocks are available.
1936: * if so, nblocks of blocks are allocated; otherwise, ENOSPC is
1937: * returned.
1938: *
1939: * PARAMETERS:
1940: * mp - pointer to bmap descriptor
1941: * dp - pointer to dmap to attempt to allocate blocks from.
1942: * l2nb - log2 number of contiguous block desired.
1943: * nblocks - actual number of contiguous block desired.
1944: * results - on successful return, set to the starting block number
1945: * of the newly allocated range.
1946: *
1947: * RETURN VALUES:
1948: * 0 - success
1949: * -ENOSPC - insufficient disk resources
1950: * -EIO - i/o error
1951: *
1952: * serialization: IREAD_LOCK(ipbmap), e.g., from dbAlloc(), or
1953: * IWRITE_LOCK(ipbmap), e.g., dbAllocCtl(), held on entry/exit;
1954: */
1955: static int
1956: dbAllocDmapLev(struct bmap * bmp,
1957: struct dmap * dp, int nblocks, int l2nb, s64 * results)
1958: {
1959: s64 blkno;
1960: int leafidx, rc;
1961:
1962: /* can't be more than a dmaps worth of blocks */
1963: assert(l2nb <= L2BPERDMAP);
1964:
1965: /* search the tree within the dmap page for sufficient
1966: * free space. if sufficient free space is found, dbFindLeaf()
1967: * returns the index of the leaf at which free space was found.
1968: */
1969: if (dbFindLeaf((dmtree_t *) &dp->tree, l2nb, &leafidx, false))
1970: return -ENOSPC;
1971:
1972: if (leafidx < 0)
1973: return -EIO;
1974:
1975: /* determine the block number within the file system corresponding
1976: * to the leaf at which free space was found.
1977: */
1978: blkno = le64_to_cpu(dp->start) + (leafidx << L2DBWORD);
1979:
1980: /* if not all bits of the dmap word are free, get the starting
1981: * bit number within the dmap word of the required string of free
1982: * bits and adjust the block number with this value.
1983: */
1984: if (dp->tree.stree[leafidx + LEAFIND] < BUDMIN)
1985: blkno += dbFindBits(le32_to_cpu(dp->wmap[leafidx]), l2nb);
1986:
1987: /* allocate the blocks */
1988: if ((rc = dbAllocDmap(bmp, dp, blkno, nblocks)) == 0)
1989: *results = blkno;
1990:
1991: return (rc);
1992: }
SourceFile:fs/jfs/jfs_dmap.c]
|
| 42/2 |
2026/05/24 05:52 |
llm |
expert |
0m
Model:
Tokens:
input: 37332
output: 20
thoughts: 346
Thoughts: **Analyzing a Potential Out-of-Bounds Read in `dbAllocDmapLev`**
Okay, so I'm digging into this `dbAllocDmapLev` function and I've noticed a potential issue, starting with a call to `dbFindLeaf` with `is_ctl = false`. It seems like the code anticipates a scenario where `dbFindLeaf` returns `leafidx = 256`. The reason this could happen is because the maximum size is 341 while the value of `le32_to_cpu(tp->dmt_leafidx)` is 85.
Now, let's follow the data flow. The code calculates `blkno` by adding `(leafidx << L2DBWORD)` to `le64_to_cpu(dp->start)`. `L2DBWORD` is 5 (which means it's a power of 2, 32 bits). Therefore, this increments `blkno` by `256 << 5`, or 8192. The next step, however, is where my alarm bells start ringing. We're accessing `dp->tree.stree[leafidx + LEAFIND]`. `LEAFIND` is defined as 85. So, we're doing `256 + 85 = 341`.
Here's the problem: `stree` appears to have 341 elements. Meaning its valid indices run from 0 to 340. Therefore, `stree[341]` is an out-of-bounds read! From my experience in debugging, this will read `pad[0]` which is an invalid memory access. This is exactly the same out-of-bounds read! This means if `pad[0]` is accessed, there's a serious bug in the code.
The logic further states that if `pad[0] < BUDMIN`, the code then calls `dbFindBits` with `leafidx = 256`. Also using `le32_to_cpu(dp->wmap[leafidx])` as one of the arguments. Given the earlier context, let me check the size of the `dp->wmap` array, because I need to make sure that index `256` is valid within the context of that array too.
|
| 43/2 |
2026/05/24 05:52 |
tool |
codesearch-struct-layout |
0m
Args:
Results: map[Fields:[map[Name:nblocks OffsetBits:0 SizeBits:32] map[Name:nfree OffsetBits:32 SizeBits:32] map[Name:start OffsetBits:64 SizeBits:64] map[Name:tree OffsetBits:128 SizeBits:2880] map[Name:pad OffsetBits:3008 SizeBits:13376] map[Name:wmap OffsetBits:16384 SizeBits:8192] map[Name:pmap OffsetBits:24576 SizeBits:8192]]]
|
| 44/2 |
2026/05/24 05:52 |
llm |
expert |
0m
Model:
Tokens:
input: 38364
output: 45
thoughts: 251
Thoughts: **Analyzing Potential Out-of-Bounds Memory Access**
Okay, so `wmap` is located 2048 bytes into the data structure, and it's 1024 bytes in size. That means it contains 256 elements of 4 bytes each, which makes sense. I see that, and I know that. But hold on a second... if `leafidx` is equal to 256, accessing `dp->wmap[256]` is going to be a problem - that's clearly out of bounds! I need to figure out exactly what happens when that happens.
Let's see. Following `wmap` in memory, I see `pmap` starting at offset 3072 bytes. Aha! This means `dp->wmap[256]` won't crash, instead, it will read into the beginning of `pmap`. And `pmap` is also an array of `__le32` with 256 elements. So the out-of-bounds read ends up being equivalent to reading `pmap[0]`.
Right, so that read of `pmap[0]` is then passed to `dbFindBits`, and then `dbAllocDmap` is called with `blkno`. Okay, so it looks like I need to dig into `dbAllocDmap` now to understand the consequences of this potential out-of-bounds access. I need to understand what `pmap[0]` represents in this context.
|
| 45/2 |
2026/05/24 05:52 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:fs/jfs/jfs_dmap.c IncludeLines:true Name:dbAllocDmap]
Results: map[SourceCode:1995: /*
1996: * NAME: dbAllocDmap()
1997: *
1998: * FUNCTION: adjust the disk allocation map to reflect the allocation
1999: * of a specified block range within a dmap.
2000: *
2001: * this routine allocates the specified blocks from the dmap
2002: * through a call to dbAllocBits(). if the allocation of the
2003: * block range causes the maximum string of free blocks within
2004: * the dmap to change (i.e. the value of the root of the dmap's
2005: * dmtree), this routine will cause this change to be reflected
2006: * up through the appropriate levels of the dmap control pages
2007: * by a call to dbAdjCtl() for the L0 dmap control page that
2008: * covers this dmap.
2009: *
2010: * PARAMETERS:
2011: * bmp - pointer to bmap descriptor
2012: * dp - pointer to dmap to allocate the block range from.
2013: * blkno - starting block number of the block to be allocated.
2014: * nblocks - number of blocks to be allocated.
2015: *
2016: * RETURN VALUES:
2017: * 0 - success
2018: * -EIO - i/o error
2019: *
2020: * serialization: IREAD_LOCK(ipbmap) or IWRITE_LOCK(ipbmap) held on entry/exit;
2021: */
2022: static int dbAllocDmap(struct bmap * bmp, struct dmap * dp, s64 blkno,
2023: int nblocks)
2024: {
2025: s8 oldroot;
2026: int rc;
2027:
2028: /* save the current value of the root (i.e. maximum free string)
2029: * of the dmap tree.
2030: */
2031: oldroot = dp->tree.stree[ROOT];
2032:
2033: /* allocate the specified (blocks) bits */
2034: dbAllocBits(bmp, dp, blkno, nblocks);
2035:
2036: /* if the root has not changed, done. */
2037: if (dp->tree.stree[ROOT] == oldroot)
2038: return (0);
2039:
2040: /* root changed. bubble the change up to the dmap control pages.
2041: * if the adjustment of the upper level control pages fails,
2042: * backout the bit allocation (thus making everything consistent).
2043: */
2044: if ((rc = dbAdjCtl(bmp, blkno, dp->tree.stree[ROOT], 1, 0)))
2045: dbFreeBits(bmp, dp, blkno, nblocks);
2046:
2047: return (rc);
2048: }
SourceFile:fs/jfs/jfs_dmap.c]
|
| 46/2 |
2026/05/24 05:52 |
llm |
expert |
0m
Model:
Tokens:
input: 39880
output: 44
thoughts: 12
Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience, presented in the first person:
**Allocating Disk Space: A Bit by Bit Breakdown**
Right, so the first thing that pops into my head when I see `dbAllocDmap` is, "Ah, disk allocation โ probably using a bitmap for free/used blocks, or a similar data structure." And, as expected, it immediately triggers the call to `dbAllocBits`. Thatโs precisely what I'd anticipate. `dbAllocDmap` is clearly the higher-level interface that manages the allocation scheme, perhaps handling larger units or dealing with metadata about allocation strategies, but the core work of finding and marking free bits is delegated to a lower level function - `dbAllocBits`.
I'm instantly thinking about the implications of that: The design is sound. It's a clean separation of concerns. `dbAllocDmap` can now deal with the higher level logic, managing allocation units, considering fragmentation, or even handling different allocation strategies, all while relying on `dbAllocBits` to actually find and mark the specific bits in the bitmap. Makes it easier to maintain and modify. No surprises so far. The key will be understanding the specifics of how `dbAllocBits` works: Does it manage the allocation of contiguous blocks, or does it try for scatter allocations? Is the bitmap kept in memory, or is a portion cached? I need to think about that. I need to understand the characteristics of the allocation process.
|
| 47/2 |
2026/05/24 05:52 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:fs/jfs/jfs_dmap.c IncludeLines:true Name:dbAllocBits]
Results: map[SourceCode:2117: /*
2118: * NAME: dbAllocBits()
2119: *
2120: * FUNCTION: allocate a specified block range from a dmap.
2121: *
2122: * this routine updates the dmap to reflect the working
2123: * state allocation of the specified block range. it directly
2124: * updates the bits of the working map and causes the adjustment
2125: * of the binary buddy system described by the dmap's dmtree
2126: * leaves to reflect the bits allocated. it also causes the
2127: * dmap's dmtree, as a whole, to reflect the allocated range.
2128: *
2129: * PARAMETERS:
2130: * bmp - pointer to bmap descriptor
2131: * dp - pointer to dmap to allocate bits from.
2132: * blkno - starting block number of the bits to be allocated.
2133: * nblocks - number of bits to be allocated.
2134: *
2135: * RETURN VALUES: none
2136: *
2137: * serialization: IREAD_LOCK(ipbmap) or IWRITE_LOCK(ipbmap) held on entry/exit;
2138: */
2139: static void dbAllocBits(struct bmap * bmp, struct dmap * dp, s64 blkno,
2140: int nblocks)
2141: {
2142: int dbitno, word, rembits, nb, nwords, wbitno, nw, agno;
2143: dmtree_t *tp = (dmtree_t *) & dp->tree;
2144: int size;
2145: s8 *leaf;
2146:
2147: /* pick up a pointer to the leaves of the dmap tree */
2148: leaf = dp->tree.stree + LEAFIND;
2149:
2150: /* determine the bit number and word within the dmap of the
2151: * starting block.
2152: */
2153: dbitno = blkno & (BPERDMAP - 1);
2154: word = dbitno >> L2DBWORD;
2155:
2156: /* block range better be within the dmap */
2157: assert(dbitno + nblocks <= BPERDMAP);
2158:
2159: /* allocate the bits of the dmap's words corresponding to the block
2160: * range. not all bits of the first and last words may be contained
2161: * within the block range. if this is the case, we'll work against
2162: * those words (i.e. partial first and/or last) on an individual basis
2163: * (a single pass), allocating the bits of interest by hand and
2164: * updating the leaf corresponding to the dmap word. a single pass
2165: * will be used for all dmap words fully contained within the
2166: * specified range. within this pass, the bits of all fully contained
2167: * dmap words will be marked as free in a single shot and the leaves
2168: * will be updated. a single leaf may describe the free space of
2169: * multiple dmap words, so we may update only a subset of the actual
2170: * leaves corresponding to the dmap words of the block range.
2171: */
2172: for (rembits = nblocks; rembits > 0; rembits -= nb, dbitno += nb) {
2173: /* determine the bit number within the word and
2174: * the number of bits within the word.
2175: */
2176: wbitno = dbitno & (DBWORD - 1);
2177: nb = min(rembits, DBWORD - wbitno);
2178:
2179: /* check if only part of a word is to be allocated.
2180: */
2181: if (nb < DBWORD) {
2182: /* allocate (set to 1) the appropriate bits within
2183: * this dmap word.
2184: */
2185: dp->wmap[word] |= cpu_to_le32(ONES << (DBWORD - nb)
2186: >> wbitno);
2187:
2188: /* update the leaf for this dmap word. in addition
2189: * to setting the leaf value to the binary buddy max
2190: * of the updated dmap word, dbSplit() will split
2191: * the binary system of the leaves if need be.
2192: */
2193: dbSplit(tp, word, BUDMIN,
2194: dbMaxBud((u8 *)&dp->wmap[word]), false);
2195:
2196: word += 1;
2197: } else {
2198: /* one or more dmap words are fully contained
2199: * within the block range. determine how many
2200: * words and allocate (set to 1) the bits of these
2201: * words.
2202: */
2203: nwords = rembits >> L2DBWORD;
2204: memset(&dp->wmap[word], (int) ONES, nwords * 4);
2205:
2206: /* determine how many bits.
2207: */
2208: nb = nwords << L2DBWORD;
2209:
2210: /* now update the appropriate leaves to reflect
2211: * the allocated words.
2212: */
2213: for (; nwords > 0; nwords -= nw) {
2214: if (leaf[word] < BUDMIN) {
2215: jfs_error(bmp->db_ipbmap->i_sb,
2216: "leaf page corrupt\n");
2217: break;
2218: }
2219:
2220: /* determine what the leaf value should be
2221: * updated to as the minimum of the l2 number
2222: * of bits being allocated and the l2 number
2223: * of bits currently described by this leaf.
2224: */
2225: size = min_t(int, leaf[word],
2226: NLSTOL2BSZ(nwords));
2227:
2228: /* update the leaf to reflect the allocation.
2229: * in addition to setting the leaf value to
2230: * NOFREE, dbSplit() will split the binary
2231: * system of the leaves to reflect the current
2232: * allocation (size).
2233: */
2234: dbSplit(tp, word, size, NOFREE, false);
2235:
2236: /* get the number of dmap words handled */
2237: nw = BUDSIZE(size, BUDMIN);
2238: word += nw;
2239: }
2240: }
2241: }
2242:
2243: /* update the free count for this dmap */
2244: le32_add_cpu(&dp->nfree, -nblocks);
2245:
2246: BMAP_LOCK(bmp);
2247:
2248: /* if this allocation group is completely free,
2249: * update the maximum allocation group number if this allocation
2250: * group is the new max.
2251: */
2252: agno = blkno >> bmp->db_agl2size;
2253: if (agno > bmp->db_maxag)
2254: bmp->db_maxag = agno;
2255:
2256: /* update the free count for the allocation group and map */
2257: bmp->db_agfree[agno] -= nblocks;
2258: bmp->db_nfree -= nblocks;
2259:
2260: BMAP_UNLOCK(bmp);
2261: }
SourceFile:fs/jfs/jfs_dmap.c]
|
| 48/2 |
2026/05/24 05:52 |
llm |
expert |
0m
Model:
Tokens:
input: 42542
output: 19
thoughts: 1972
Thoughts: **JFS dmap/ctl Analysis: No Memory Corruption, Just Filesystem Corruption**
Okay, let's break this down. My initial concern was centered on potential out-of-bounds writes. It seems I was initially thrown off by the indices.
* **`dbAllocBits` Deconstruction:** The key seems to be how `blkno` is constructed and used. I was tracing how block numbers were calculated and allocated. I initially thought incrementing `blkno` by a large amount (e.g., 8192) combined with the bitwise operations (`&` and `>>`) was a vector, but this leads to valid accesses! Specifically, the calculation of `dbitno` and `word` from `blkno` resulted in accessing within the bounds of `dp->wmap` and the `stree` which seemed valid.
* **Out-of-Bounds Read in `dbAllocDmapLev`:** The interesting part is that when `leafidx` is, say, 256, `dp->wmap[256]` is accessed, which appears to be an out-of-bounds read of the `wmap` array. This access retrieves `pmap[0]`.
* **Controllable Data & the Vulnerability:** `pmap[0]` is read from disk. This means an attacker controls the data read. The value from `dbFindBits` then increments `blkno`, which affects subsequent calculations. The increment of `blkno` doesn't lead to an out-of-bounds write.
* **`dbAllocCtl` and Filesystem Corruption:** With `leafidx` at 1024, `b += (((s64) leafidx) << budmin);` increases `blkno` to a large value, but is still just a block number. The `lblkno` calculation in `dbAllocCtl` is determined from the `blkno`, resulting in the `read_metapage` function reading an arbitrary block, or failing, and potentially leading to filesytem corruption.
* **Bounds Checking in `dbAllocBits` and the Assert:** It's important to remember that `nblocks` is the number of blocks to allocate. We are checking to see if `dbitno + nblocks <= BPERDMAP`.
* **No Memory Corruption:** It seems that the out-of-bounds read of `wmap` is really just reading `pmap` (which is part of the `dmap` structure). Then the allocated bits in `wmap[0]` are within bounds, and `stree` is also modified within bounds, therefore no memory corruption! However, by reading `pmap` from disk, it does mean the filesystem state is affected and can be corrupted. If `nblocks` is close to the `BPERDMAP` value and there is a offset, then the assertion will fail.
* **Conclusion:** This is a filesystem corruption vulnerability, *not* a memory corruption bug. The attacker can influence disk reads, and the values read will affect internal structures. This leads to filesystem corruption and misallocation.
|
| 49/2 |
2026/05/24 05:52 |
tool |
grepper |
0m
Args: map[Expression:#define.*assert\(]
Results: map[Output:arch/mips/math-emu/ieee754dp.h-14-
arch/mips/math-emu/ieee754dp.h:15:#define assert(expr) ((void)0)
arch/mips/math-emu/ieee754dp.h-16-
--
arch/mips/math-emu/ieee754sp.h-14-
arch/mips/math-emu/ieee754sp.h:15:#define assert(expr) ((void)0)
arch/mips/math-emu/ieee754sp.h-16-
--
drivers/block/rbd.c-51-
drivers/block/rbd.c:52:#define RBD_DEBUG /* Activate rbd_assert() calls */
drivers/block/rbd.c-53-
--
drivers/block/rbd.c=593=void rbd_warn(struct rbd_device *rbd_dev, const char *fmt, ...)
--
drivers/block/rbd.c-619-#ifdef RBD_DEBUG
drivers/block/rbd.c:620:#define rbd_assert(expr) \
drivers/block/rbd.c-621- if (unlikely(!(expr))) { \
--
drivers/gpu/drm/msm/registers/gen_header.py=909=def dump_c(args, guard, func):
--
drivers/gpu/drm/msm/registers/gen_header.py-924- print("#include <linux/bug.h>")
drivers/gpu/drm/msm/registers/gen_header.py:925: print("#define assert(x) BUG_ON(!(x))")
drivers/gpu/drm/msm/registers/gen_header.py-926- print("#else")
--
drivers/gpu/drm/xe/xe_assert.h-108- */
drivers/gpu/drm/xe/xe_assert.h:109:#define xe_assert(xe, condition) xe_assert_msg((xe), condition, "")
drivers/gpu/drm/xe/xe_assert.h-110-#define xe_assert_msg(xe, condition, msg, arg...) ({ \
--
drivers/gpu/drm/xe/xe_assert.h-143- */
drivers/gpu/drm/xe/xe_assert.h:144:#define xe_tile_assert(tile, condition) xe_tile_assert_msg((tile), condition, "")
drivers/gpu/drm/xe/xe_assert.h-145-#define xe_tile_assert_msg(tile, condition, msg, arg...) ({ \
--
drivers/gpu/drm/xe/xe_assert.h-168- */
drivers/gpu/drm/xe/xe_assert.h:169:#define xe_gt_assert(gt, condition) xe_gt_assert_msg((gt), condition, "")
drivers/gpu/drm/xe/xe_assert.h-170-#define xe_gt_assert_msg(gt, condition, msg, arg...) ({ \
--
drivers/gpu/drm/xe/xe_guc_db_mgr.c=41=static struct xe_device *dbm_to_xe(struct xe_guc_db_mgr *dbm)
--
drivers/gpu/drm/xe/xe_guc_db_mgr.c-45-
drivers/gpu/drm/xe/xe_guc_db_mgr.c:46:#define dbm_assert(_dbm, _cond) xe_gt_assert(dbm_to_gt(_dbm), _cond)
drivers/gpu/drm/xe/xe_guc_db_mgr.c-47-#define dbm_mutex(_dbm) (&dbm_to_guc(_dbm)->submission_state.lock)
--
drivers/gpu/drm/xe/xe_guc_id_mgr.c=27=static struct xe_device *idm_to_xe(struct xe_guc_id_mgr *idm)
--
drivers/gpu/drm/xe/xe_guc_id_mgr.c-31-
drivers/gpu/drm/xe/xe_guc_id_mgr.c:32:#define idm_assert(idm, cond) xe_gt_assert(idm_to_gt(idm), cond)
drivers/gpu/drm/xe/xe_guc_id_mgr.c-33-#define idm_mutex(idm) (&idm_to_guc(idm)->submission_state.lock)
--
drivers/gpu/drm/xe/xe_guc_relay.c=54=static struct xe_device *relay_to_xe(struct xe_guc_relay *relay)
--
drivers/gpu/drm/xe/xe_guc_relay.c-68-
drivers/gpu/drm/xe/xe_guc_relay.c:69:#define relay_assert(relay, condition) xe_gt_assert(relay_to_gt(relay), condition)
drivers/gpu/drm/xe/xe_guc_relay.c-70-#define relay_notice(relay, msg...) relay_ratelimit_printk((relay), notice, msg)
--
drivers/gpu/drm/xe/xe_lmtt.c-33-
drivers/gpu/drm/xe/xe_lmtt.c:34:#define lmtt_assert(lmtt, condition) xe_tile_assert(lmtt_to_tile(lmtt), condition)
drivers/gpu/drm/xe/xe_lmtt.c-35-#define lmtt_debug(lmtt, msg...) xe_tile_sriov_dbg_verbose(lmtt_to_tile(lmtt), "LMTT: " msg)
--
drivers/gpu/drm/xe/xe_memirq.c-22-
drivers/gpu/drm/xe/xe_memirq.c:23:#define memirq_assert(m, condition) xe_tile_assert(memirq_to_tile(m), condition)
drivers/gpu/drm/xe/xe_memirq.c-24-#define memirq_printk(m, _level, _fmt, ...) \
--
drivers/media/platform/ti/davinci/vpif.h=134=static inline void vpif_clr_bit(u32 reg, u32 bit)
--
drivers/media/platform/ti/davinci/vpif.h-212-/* enabled interrupt on both the fields on vpid_ch0_ctrl register */
drivers/media/platform/ti/davinci/vpif.h:213:#define channel0_intr_assert() (regw((regr(VPIF_CH0_CTRL)|\
drivers/media/platform/ti/davinci/vpif.h-214- (VPIF_INT_BOTH << VPIF_CH0_INT_CTRL_SHIFT)), VPIF_CH0_CTRL))
--
drivers/media/platform/ti/davinci/vpif.h-216-/* enabled interrupt on both the fields on vpid_ch1_ctrl register */
drivers/media/platform/ti/davinci/vpif.h:217:#define channel1_intr_assert() (regw((regr(VPIF_CH1_CTRL)|\
drivers/media/platform/ti/davinci/vpif.h-218- (VPIF_INT_BOTH << VPIF_CH1_INT_CTRL_SHIFT)), VPIF_CH1_CTRL))
--
drivers/media/platform/ti/davinci/vpif.h-220-/* enabled interrupt on both the fields on vpid_ch0_ctrl register */
drivers/media/platform/ti/davinci/vpif.h:221:#define channel2_intr_assert() (regw((regr(VPIF_CH2_CTRL)|\
drivers/media/platform/ti/davinci/vpif.h-222- (VPIF_INT_BOTH << VPIF_CH2_INT_CTRL_SHIFT)), VPIF_CH2_CTRL))
--
drivers/media/platform/ti/davinci/vpif.h-224-/* enabled interrupt on both the fields on vpid_ch1_ctrl register */
drivers/media/platform/ti/davinci/vpif.h:225:#define channel3_intr_assert() (regw((regr(VPIF_CH3_CTRL)|\
drivers/media/platform/ti/davinci/vpif.h-226- (VPIF_INT_BOTH << VPIF_CH3_INT_CTRL_SHIFT)), VPIF_CH3_CTRL))
--
drivers/mtd/ubi/debug.h=13=void ubi_dump_vid_hdr(const struct ubi_vid_hdr *vid_hdr);
--
drivers/mtd/ubi/debug.h-16-
drivers/mtd/ubi/debug.h:17:#define ubi_assert(expr) do { \
drivers/mtd/ubi/debug.h-18- if (unlikely(!(expr))) { \
--
drivers/net/ethernet/hisilicon/hns/hnae.h-43-#ifndef assert
drivers/net/ethernet/hisilicon/hns/hnae.h:44:#define assert(expr) \
drivers/net/ethernet/hisilicon/hns/hnae.h-45-do { \
--
drivers/net/ethernet/hisilicon/hns/hnae.h-55-#ifndef assert
drivers/net/ethernet/hisilicon/hns/hnae.h:56:#define assert(expr)
drivers/net/ethernet/hisilicon/hns/hnae.h-57-#endif
--
drivers/net/ethernet/hisilicon/hns/hnae.h=577=int hnae_reinit_handle(struct hnae_handle *handle);
--
drivers/net/ethernet/hisilicon/hns/hnae.h-582-#ifndef assert
drivers/net/ethernet/hisilicon/hns/hnae.h:583:#define assert(cond)
drivers/net/ethernet/hisilicon/hns/hnae.h-584-#endif
--
drivers/scsi/sym53c8xx_2/sym_hipd.h-81-#ifndef assert
drivers/scsi/sym53c8xx_2/sym_hipd.h:82:#define assert(expression) { \
drivers/scsi/sym53c8xx_2/sym_hipd.h-83- if (!(expression)) { \
--
drivers/staging/media/atomisp/pci/hive_isp_css_include/assert_support.h-17-/* TODO: it would be cleaner to use this:
drivers/staging/media/atomisp/pci/hive_isp_css_include/assert_support.h:18: * #define assert(cnd) BUG_ON(cnd)
drivers/staging/media/atomisp/pci/hive_isp_css_include/assert_support.h-19- * but that causes many compiler warnings (==errors) under Android
--
drivers/staging/media/atomisp/pci/hive_isp_css_include/assert_support.h-22- */
drivers/staging/media/atomisp/pci/hive_isp_css_include/assert_support.h:23:#define assert(cnd) \
drivers/staging/media/atomisp/pci/hive_isp_css_include/assert_support.h-24- do { \
--
drivers/staging/media/atomisp/pci/hive_isp_css_include/assert_support.h-33- */
drivers/staging/media/atomisp/pci/hive_isp_css_include/assert_support.h:34:#define OP___assert(cnd) assert(cnd)
drivers/staging/media/atomisp/pci/hive_isp_css_include/assert_support.h-35-
--
drivers/video/fbdev/cirrusfb.c-70-#ifndef CIRRUSFB_NDEBUG
drivers/video/fbdev/cirrusfb.c:71:#define assert(expr) \
drivers/video/fbdev/cirrusfb.c-72- if (!(expr)) { \
--
drivers/video/fbdev/cirrusfb.c-76-#else
drivers/video/fbdev/cirrusfb.c:77:#define assert(expr)
drivers/video/fbdev/cirrusfb.c-78-#endif
--
drivers/video/fbdev/nvidia/nvidia.c-44-#ifdef CONFIG_FB_NVIDIA_DEBUG
drivers/video/fbdev/nvidia/nvidia.c:45:#define assert(expr) \
drivers/video/fbdev/nvidia/nvidia.c-46- if (!(expr)) { \
--
drivers/video/fbdev/nvidia/nvidia.c-51-#else
drivers/video/fbdev/nvidia/nvidia.c:52:#define assert(expr)
drivers/video/fbdev/nvidia/nvidia.c-53-#endif
--
drivers/video/fbdev/riva/fbdev.c-70-#ifdef CONFIG_FB_RIVA_DEBUG
drivers/video/fbdev/riva/fbdev.c:71:#define assert(expr) \
drivers/video/fbdev/riva/fbdev.c-72- if(!(expr)) { \
--
drivers/video/fbdev/riva/fbdev.c-77-#else
drivers/video/fbdev/riva/fbdev.c:78:#define assert(expr)
drivers/video/fbdev/riva/fbdev.c-79-#endif
--
fs/gfs2/util.h=28=void gfs2_assert_i(struct gfs2_sbd *sdp);
fs/gfs2/util.h-29-
fs/gfs2/util.h:30:#define gfs2_assert(sdp, assertion) \
fs/gfs2/util.h-31-do { \
--
fs/jfs/jfs_debug.h=23=extern void jfs_proc_clean(void);
--
fs/jfs/jfs_debug.h-28- */
fs/jfs/jfs_debug.h:29:#define assert(p) do { \
fs/jfs/jfs_debug.h-30- if (!(p)) { \
--
fs/jfs/jfs_debug.h-41-#ifdef CONFIG_JFS_DEBUG
fs/jfs/jfs_debug.h:42:#define ASSERT(p) assert(p)
fs/jfs/jfs_debug.h-43-
--
fs/ubifs/debug.h=140=void ubifs_assert_failed(struct ubifs_info *c, const char *expr,
--
fs/ubifs/debug.h-142-
fs/ubifs/debug.h:143:#define ubifs_assert(c, expr) do { \
fs/ubifs/debug.h-144- if (unlikely(!(expr))) { \
--
include/linux/build_bug.h-38- */
include/linux/build_bug.h:39:#define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
include/linux/build_bug.h-40-
--
include/linux/build_bug.h-76- */
include/linux/build_bug.h:77:#define static_assert(expr, ...) __static_assert(expr, ##__VA_ARGS__, #expr)
include/linux/build_bug.h:78:#define __static_assert(expr, msg, ...) _Static_assert(expr, msg)
include/linux/build_bug.h-79-
--
include/linux/compiler.h=15=void ftrace_likely_update(struct ftrace_likely_data *f, int val,
--
include/linux/compiler.h-200-#else /* __CHECKER__ */
include/linux/compiler.h:201:#define __BUILD_BUG_ON_ZERO_MSG(e, msg, ...) ((int)sizeof(struct {_Static_assert(!(e), msg);}))
include/linux/compiler.h-202-#endif /* __CHECKER__ */
--
include/linux/compiler_types.h=221=struct ftrace_likely_data {
--
include/linux/compiler_types.h-617-
include/linux/compiler_types.h:618:#define _compiletime_assert(condition, msg, prefix, suffix) \
include/linux/compiler_types.h-619- __compiletime_assert(condition, msg, prefix, suffix)
--
include/linux/compiler_types.h-629- */
include/linux/compiler_types.h:630:#define compiletime_assert(condition, msg) \
include/linux/compiler_types.h-631- _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
--
include/linux/lockdep.h=274=extern void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie);
--
include/linux/lockdep.h-277-
include/linux/lockdep.h:278:#define lockdep_assert(cond) \
include/linux/lockdep.h-279- do { WARN_ON(debug_locks && !(cond)); } while (0)
--
include/linux/lockdep.h=386=extern int lockdep_is_held(const void *);
--
include/linux/lockdep.h-388-
include/linux/lockdep.h:389:#define lockdep_assert(c) do { } while (0)
include/linux/lockdep.h-390-#define lockdep_assert_once(c) do { } while (0)
--
include/linux/seqlock.h=229=SEQCOUNT_LOCKNAME(mutex, struct mutex, true, mutex)
--
include/linux/seqlock.h-262-#define seqprop_preemptible(s) __seqprop(s, preemptible)(s)
include/linux/seqlock.h:263:#define seqprop_assert(s) __seqprop(s, assert)(s)
include/linux/seqlock.h-264-
--
include/linux/string_choices.h=20=static inline const char *str_assert_deassert(bool v)
--
include/linux/string_choices.h-23-}
include/linux/string_choices.h:24:#define str_deassert_assert(v) str_assert_deassert(!(v))
include/linux/string_choices.h-25-
--
include/net/caif/caif_layer.h=14=struct caif_payload_info;
--
include/net/caif/caif_layer.h-24- */
include/net/caif/caif_layer.h:25:#define caif_assert(assert) \
include/net/caif/caif_layer.h-26-do { \
--
include/net/libeth/cache.h-15-#if defined(CONFIG_64BIT) && SMP_CACHE_BYTES == 64
include/net/libeth/cache.h:16:#define libeth_cacheline_group_assert(type, grp, sz) \
include/net/libeth/cache.h-17- static_assert(offsetof(type, __cacheline_group_end__##grp) - \
--
include/net/libeth/cache.h-19- (sz))
include/net/libeth/cache.h:20:#define __libeth_cacheline_struct_assert(type, sz) \
include/net/libeth/cache.h-21- static_assert(sizeof(type) == (sz))
include/net/libeth/cache.h-22-#else /* !CONFIG_64BIT || SMP_CACHE_BYTES != 64 */
include/net/libeth/cache.h:23:#define libeth_cacheline_group_assert(type, grp, sz) \
include/net/libeth/cache.h-24- static_assert(offsetof(type, __cacheline_group_end__##grp) - \
--
include/net/libeth/cache.h-26- (sz))
include/net/libeth/cache.h:27:#define __libeth_cacheline_struct_assert(type, sz) \
include/net/libeth/cache.h-28- static_assert(sizeof(type) <= (sz))
--
include/net/libeth/cache.h-46- */
include/net/libeth/cache.h:47:#define libeth_cacheline_struct_assert(type, ...) \
include/net/libeth/cache.h-48- __libeth_cacheline_struct_assert(type, __libeth_cls(__VA_ARGS__)); \
--
include/net/libeth/cache.h-59- */
include/net/libeth/cache.h:60:#define libeth_cacheline_set_assert(type, ro, rw, c) \
include/net/libeth/cache.h-61- libeth_cacheline_group_assert(type, read_mostly, ro); \
--
lib/crypto/mpi/mpi-internal.h-29-
lib/crypto/mpi/mpi-internal.h:30:#define assert(x) \
lib/crypto/mpi/mpi-internal.h-31- do { \
--
lib/lz4/lz4_decompress.c-48-#ifndef assert
lib/lz4/lz4_decompress.c:49:#define assert(condition) ((void)0)
lib/lz4/lz4_decompress.c-50-#endif
--
lib/zstd/common/zstd_deps.h=68=static uint64_t ZSTD_div64(uint64_t dividend, uint32_t divisor) {
--
lib/zstd/common/zstd_deps.h-86-
lib/zstd/common/zstd_deps.h:87:#define assert(x) WARN_ON(!(x))
lib/zstd/common/zstd_deps.h-88-
--
lib/zstd/compress/zstd_compress_internal.h=698=ZSTD_safecopyLiterals(BYTE* op, BYTE const* ip, BYTE const* const iend, BYTE const* ilimit_w)
--
lib/zstd/compress/zstd_compress_internal.h-712-#define REPCODE3_TO_OFFBASE REPCODE_TO_OFFBASE(3)
lib/zstd/compress/zstd_compress_internal.h:713:#define REPCODE_TO_OFFBASE(r) (assert((r)>=1), assert((r)<=ZSTD_REP_NUM), (r)) /* accepts IDs 1,2,3 */
lib/zstd/compress/zstd_compress_internal.h:714:#define OFFSET_TO_OFFBASE(o) (assert((o)>0), o + ZSTD_REP_NUM)
lib/zstd/compress/zstd_compress_internal.h-715-#define OFFBASE_IS_OFFSET(o) ((o) > ZSTD_REP_NUM)
lib/zstd/compress/zstd_compress_internal.h-716-#define OFFBASE_IS_REPCODE(o) ( 1 <= (o) && (o) <= ZSTD_REP_NUM)
lib/zstd/compress/zstd_compress_internal.h:717:#define OFFBASE_TO_OFFSET(o) (assert(OFFBASE_IS_OFFSET(o)), (o) - ZSTD_REP_NUM)
lib/zstd/compress/zstd_compress_internal.h:718:#define OFFBASE_TO_REPCODE(o) (assert(OFFBASE_IS_REPCODE(o)), (o)) /* returns ID 1,2,3 */
lib/zstd/compress/zstd_compress_internal.h-719-
--
sound/pci/asihpi/hpi_internal.h=74=typedef void hpi_handler_func(struct hpi_message *, struct hpi_response *);
--
sound/pci/asihpi/hpi_internal.h-79-*/
sound/pci/asihpi/hpi_internal.h:80:#define compile_time_assert(cond, msg) \
sound/pci/asihpi/hpi_internal.h-81- typedef char ASSERT_##msg[(cond) ? 1 : -1]
--
sound/pci/asihpi/hpidebug.h=60=void hpi_debug_data(u16 *pdata, u32 len);
--
sound/pci/asihpi/hpidebug.h-85-#ifndef compile_time_assert
sound/pci/asihpi/hpidebug.h:86:#define compile_time_assert(cond, msg) \
sound/pci/asihpi/hpidebug.h-87- typedef char msg[(cond) ? 1 : -1]
--
tools/include/linux/build_bug.h-38- */
tools/include/linux/build_bug.h:39:#define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
tools/include/linux/build_bug.h-40-
--
tools/include/linux/build_bug.h-77-#ifndef static_assert
tools/include/linux/build_bug.h:78:#define static_assert(expr, ...) __static_assert(expr, ##__VA_ARGS__, #expr)
tools/include/linux/build_bug.h:79:#define __static_assert(expr, msg, ...) _Static_assert(expr, msg)
tools/include/linux/build_bug.h-80-#endif // static_assert
--
tools/include/linux/compiler.h-23-
tools/include/linux/compiler.h:24:#define _compiletime_assert(condition, msg, prefix, suffix) \
tools/include/linux/compiler.h-25- __compiletime_assert(condition, msg, prefix, suffix)
--
tools/include/linux/compiler.h-35- */
tools/include/linux/compiler.h:36:#define compiletime_assert(condition, msg) \
tools/include/linux/compiler.h-37- _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
--
tools/include/linux/compiler.h=189=static __always_inline void __write_once_size(volatile void *p, void *res, int size)
--
tools/include/linux/compiler.h-254-#else
tools/include/linux/compiler.h:255:#define __BUILD_BUG_ON_ZERO_MSG(e, msg, ...) ((int)sizeof(struct {_Static_assert(!(e), msg);}))
tools/include/linux/compiler.h-256-#endif
--
tools/include/linux/kernel.h-52-#else
tools/include/linux/kernel.h:53:#define BUG_ON(cond) assert(!(cond))
tools/include/linux/kernel.h-54-#endif
--
tools/testing/radix-tree/idr-test.c=360=void idr_checks(void)
--
tools/testing/radix-tree/idr-test.c-449-#define MODULE_LICENSE(x)
tools/testing/radix-tree/idr-test.c:450:#define dump_stack() assert(0)
tools/testing/radix-tree/idr-test.c-451-void ida_dump(struct ida *);
--
tools/testing/radix-tree/maple.c-15-#define MODULE_LICENSE(x)
tools/testing/radix-tree/maple.c:16:#define dump_stack() assert(0)
tools/testing/radix-tree/maple.c-17-
--
tools/testing/scatterlist/linux/mm.h=11=typedef unsigned long dma_addr_t;
--
tools/testing/scatterlist/linux/mm.h-14-
tools/testing/scatterlist/linux/mm.h:15:#define BUG_ON(x) assert(!(x))
tools/testing/scatterlist/linux/mm.h-16-
--
tools/testing/selftests/bpf/bpf_experimental.h=222=extern int bpf_path_d_path(const struct path *path, char *buf, size_t buf__sz) __ksym;
--
tools/testing/selftests/bpf/bpf_experimental.h-256-
tools/testing/selftests/bpf/bpf_experimental.h:257:#define __bpf_assert(LHS, op, cons, RHS, VAL) \
tools/testing/selftests/bpf/bpf_experimental.h-258- ({ \
--
tools/testing/selftests/bpf/bpf_experimental.h=499=static inline void __bpf_preempt_destructor(__bpf_preempt_t *t)
--
tools/testing/selftests/bpf/bpf_experimental.h-514- */
tools/testing/selftests/bpf/bpf_experimental.h:515:#define bpf_assert(cond) if (!(cond)) bpf_throw(0);
tools/testing/selftests/bpf/bpf_experimental.h-516-
--
tools/testing/selftests/bpf/progs/exceptions.c=289=__noinline int assert_poseq_gfunc_with(s64 c)
--
tools/testing/selftests/bpf/progs/exceptions.c-296-
tools/testing/selftests/bpf/progs/exceptions.c:297:#define check_assert(name, cookie, tag) \
tools/testing/selftests/bpf/progs/exceptions.c-298-SEC("tc") \
--
tools/testing/selftests/bpf/progs/exceptions_assert.c-10-
tools/testing/selftests/bpf/progs/exceptions_assert.c:11:#define check_assert(type, op, name, value) \
tools/testing/selftests/bpf/progs/exceptions_assert.c-12- SEC("?tc") \
--
tools/testing/selftests/kvm/include/kvm_util_types.h-8- * implies _ISOC11_SOURCE, and if _ISOC11_SOURCE is defined, glibc #undefs and
tools/testing/selftests/kvm/include/kvm_util_types.h:9: * #defines static_assert() as a direct alias to _Static_assert() (see
tools/testing/selftests/kvm/include/kvm_util_types.h-10- * usr/include/assert.h). Define a custom macro instead of redefining
--
tools/testing/selftests/kvm/include/kvm_util_types.h-13- */
tools/testing/selftests/kvm/include/kvm_util_types.h:14:#define __kvm_static_assert(expr, msg, ...) _Static_assert(expr, msg)
tools/testing/selftests/kvm/include/kvm_util_types.h:15:#define kvm_static_assert(expr, ...) __kvm_static_assert(expr, ##__VA_ARGS__, #expr)
tools/testing/selftests/kvm/include/kvm_util_types.h-16-
--
tools/testing/selftests/mm/pkey-helpers.h=71=extern void abort_hooks(void);
tools/testing/selftests/mm/pkey-helpers.h:72:#define pkey_assert(condition) do { \
tools/testing/selftests/mm/pkey-helpers.h-73- if (!(condition)) { \
--
tools/testing/selftests/openat2/helpers.h=48=bool needs_openat2(const struct open_how *how);
--
tools/testing/selftests/openat2/helpers.h-88-
tools/testing/selftests/openat2/helpers.h:89:#define E_assert(expr, msg, ...) \
tools/testing/selftests/openat2/helpers.h-90- do { \
--
tools/testing/selftests/vDSO/vdso_test_getrandom.c-42-
tools/testing/selftests/vDSO/vdso_test_getrandom.c:43:#define ksft_assert(condition) \
tools/testing/selftests/vDSO/vdso_test_getrandom.c-44- do { if (!(condition)) ksft_exit_fail_msg("Assertion failed: %s\n", #condition); } while (0)
--
tools/testing/selftests/vfio/lib/include/libvfio/assert.h-47-
tools/testing/selftests/vfio/lib/include/libvfio/assert.h:48:#define ioctl_assert(_fd, _op, _arg) do { \
tools/testing/selftests/vfio/lib/include/libvfio/assert.h-49- void *__arg = (_arg); \
--
tools/testing/shared/shared.h-33-#ifndef dump_stack
tools/testing/shared/shared.h:34:#define dump_stack() assert(0)
tools/testing/shared/shared.h-35-#endif
--
tools/virtio/linux/bug.h-6-
tools/virtio/linux/bug.h:7:#define BUG_ON(__BUG_ON_cond) assert(!(__BUG_ON_cond))
tools/virtio/linux/bug.h-8-
--
tools/virtio/ringtest/main.h=89=extern unsigned ring_size;
--
tools/virtio/ringtest/main.h-101-#else
tools/virtio/ringtest/main.h:102:#define cpu_relax() assert(0)
tools/virtio/ringtest/main.h-103-#endif
]
|
| 50/2 |
2026/05/24 05:52 |
llm |
expert |
0m
Model:
Tokens:
input: 53743
output: 44
thoughts: 766
Thoughts: **Analyzing a Potential Denial of Service Vulnerability in JFS's Block Allocation**
Okay, so I'm looking at this `assert` macro in `fs/jfs/jfs_debug.h`. It's pretty blunt: if the condition inside `assert` fails, we get a kernel panic via `BUG()`. I'm focusing on the condition `dbitno + nblocks <= BPERDMAP`. My initial thought is, can I craft a scenario where this assertion triggers?
Let's break down the variables. `dbitno` is calculated as `blkno & (BPERDMAP - 1)`. `blkno`, in turn, is derived from `dp->start` (likely the start of the dmap), and some offset calculated using `leafidx` and a call to `dbFindBits`. My brain immediately jumps to the idea of manipulating `leafidx`. If I make `leafidx` equal to 256, `leafidx << L2DBWORD` becomes 8192. Now, if `dp->start` is aligned to `BPERDMAP` (which seems like a reasonable assumption since it's the dmap's starting block), then `blkno`'s least significant bits will be affected.
The crucial part here is `dbitno`. Given the values, it looks like `dbitno` will be `(8192 + dbFindBits(...)) & 8191`. Since 8192 is a multiple of 8192, the math simplifies to `dbitno` being `dbFindBits(...) & 8191`. `dbFindBits` is the key. Its return values are between 0 and 31. That means `dbitno` will always be a relatively small number, between 0 and 31.
Now, `nblocks` is the number of blocks to be allocated. This is the parameter I'm really interested in. It's passed down from `dbAllocAny` and `dbAllocDmapLev`. If I can make `nblocks` large enough, the assertion should fail.
What if I request a large value for `nblocks`? Let's say, 8192. If `dbitno` is, say, 1, then `dbitno + nblocks` would be 8193. That exceeds the value of `BPERDMAP`! It looks like there's a potential vulnerability here because the assertion would fail, and the kernel would panic.
I need to confirm if it's possible to pass 8192 or more as the value of `nblocks`. Let me examine `dbAllocAny` which takes `nblocks` as an argument. The critical point is `l2nb`, which is `log2(nblocks)`. If `nblocks` is 8192, `l2nb` is 13.
In `dbAllocDmapLev`, there is this check:
```c
if (dp->tree.stree[leafidx + LEAFIND] < BUDMIN)
blkno += dbFindBits(le32_to_cpu(dp->wmap[leafidx]), l2nb);
```
So, if `l2nb` is indeed 13, the `dbFindBits` function should look for 8192 blocks. The function, and its ability to handle `l2nb`, is the remaining piece. I'll need to check the definition of `dbFindBits` next.
|
| 51/2 |
2026/05/24 05:53 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:fs/jfs/jfs_dmap.c IncludeLines:true Name:dbFindBits]
Results: map[SourceCode:2997: /*
2998: * NAME: dbFindBits()
2999: *
3000: * FUNCTION: find a specified number of binary buddy free bits within a
3001: * dmap bitmap word value.
3002: *
3003: * this routine searches the bitmap value for (1 << l2nb) free
3004: * bits at (1 << l2nb) alignments within the value.
3005: *
3006: * PARAMETERS:
3007: * word - dmap bitmap word value.
3008: * l2nb - number of free bits specified as a log2 number.
3009: *
3010: * RETURN VALUES:
3011: * starting bit number of free bits.
3012: */
3013: static int dbFindBits(u32 word, int l2nb)
3014: {
3015: int bitno, nb;
3016: u32 mask;
3017:
3018: /* get the number of bits.
3019: */
3020: nb = 1 << l2nb;
3021: assert(nb <= DBWORD);
3022:
3023: /* complement the word so we can use a mask (i.e. 0s represent
3024: * free bits) and compute the mask.
3025: */
3026: word = ~word;
3027: mask = ONES << (DBWORD - nb);
3028:
3029: /* scan the word for nb free bits at nb alignments.
3030: */
3031: for (bitno = 0; mask != 0; bitno += nb, mask = (mask >> nb)) {
3032: if ((mask & word) == mask)
3033: break;
3034: }
3035:
3036: ASSERT(bitno < 32);
3037:
3038: /* return the bit number.
3039: */
3040: return (bitno);
3041: }
SourceFile:fs/jfs/jfs_dmap.c]
|
| 52/2 |
2026/05/24 05:53 |
llm |
expert |
1m
Model:
Tokens:
input: 55961
output: 43
thoughts: 1428
Thoughts: **Analyzing Potential Vulnerabilities in dmap Allocation**
Okay, let me break this down. My initial concern was centered around potential out-of-bounds reads or writes during dmap block allocation. Specifically, I'm examining how `dbFindBits`, `dbAllocDmapLev`, `dbAllocBits`, and `dbSplit` interact, especially when dealing with the `pad[0]` value and the `stree` metadata.
First, I realized that in `dbFindBits`, the `l2nb` value (representing the power of 2 for the number of blocks) is constrained. The `assert(nb <= DBWORD)` suggests `l2nb` can be at most 5, given `DBWORD` is 32. This value appears to be checked in relation to the `stree` value: it determines what size of blocks we will be allocating.
Then I realized that `dbAllocDmapLev` calls `dbFindBits` only if a free string is small, specifically if `dp->tree.stree[leafidx + LEAFIND] < BUDMIN`. Considering that `leafidx + LEAFIND` is 341 and `BUDMIN` is 5 (L2DBWORD), this means if `pad[0] < 5`, we call `dbFindBits`. If this is the case, and since `l2nb <= pad[0]` from the call to `dbFindLeaf`, then `l2nb` is at most 4. Thus the size of the allocation is limited. `dbFindBits` returns a bit offset (`dbitno`) and the size will always be within bounds. This means that no `assert`s in `dbFindBits` or `dbAllocBits` will fail.
However, if `pad[0] >= BUDMIN`, `dbFindBits` is not called, and the allocation logic takes a different path. It calculates the `blkno` based on `leafidx` and `dp->start`, effectively starting from `start + 8192`. The subsequent `dbAllocBits` then proceeds with an allocation of `nblocks` (which can be up to 8192), updating `dp->wmap[0]` and related `stree` entries. At first glance, this seemed safe. I determined that the `assert` checks in `dbAllocBits` would *not* fail.
But the real question is, does this lead to memory corruption or denial of service? Even if `pad[0]` is large, the allocation is still performed within bounds. However, if these are blocks that were previously allocated, this means that this second allocation with set the bits in the bitmap to 1. But this is actually part of the `dmap`, and we're *already* dealing with a malicious image. So, the allocation itself isn't *necessarily* the problem. The question then becomes how this impacts the free space cache, the `stree` entries, and `dbSplit`. I suspect that `dbSplit` might now corrupt the cache in the `stree` if we perform this double-allocation, and I might be able to trigger an assertion in `dbSplit`. This is worth investigating. A corrupted cache is still not a memory corruption, but it is filesystem corruption and we may be able to make the file system crash.
|
| 53/2 |
2026/05/24 05:54 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:fs/jfs/jfs_dmap.c IncludeLines:true Name:dbSplit]
Results: map[SourceCode:2608: /*
2609: * NAME: dbSplit()
2610: *
2611: * FUNCTION: update the leaf of a dmtree with a new value, splitting
2612: * the leaf from the binary buddy system of the dmtree's
2613: * leaves, as required.
2614: *
2615: * PARAMETERS:
2616: * tp - pointer to the tree containing the leaf.
2617: * leafno - the number of the leaf to be updated.
2618: * splitsz - the size the binary buddy system starting at the leaf
2619: * must be split to, specified as the log2 number of blocks.
2620: * newval - the new value for the leaf.
2621: *
2622: * RETURN VALUES: none
2623: *
2624: * serialization: IREAD_LOCK(ipbmap) or IWRITE_LOCK(ipbmap) held on entry/exit;
2625: */
2626: static void dbSplit(dmtree_t *tp, int leafno, int splitsz, int newval, bool is_ctl)
2627: {
2628: int budsz;
2629: int cursz;
2630: s8 *leaf = tp->dmt_stree + le32_to_cpu(tp->dmt_leafidx);
2631:
2632: /* check if the leaf needs to be split.
2633: */
2634: if (leaf[leafno] > tp->dmt_budmin) {
2635: /* the split occurs by cutting the buddy system in half
2636: * at the specified leaf until we reach the specified
2637: * size. pick up the starting split size (current size
2638: * - 1 in l2) and the corresponding buddy size.
2639: */
2640: cursz = leaf[leafno] - 1;
2641: budsz = BUDSIZE(cursz, tp->dmt_budmin);
2642:
2643: /* split until we reach the specified size.
2644: */
2645: while (cursz >= splitsz) {
2646: /* update the buddy's leaf with its new value.
2647: */
2648: dbAdjTree(tp, leafno ^ budsz, cursz, is_ctl);
2649:
2650: /* on to the next size and buddy.
2651: */
2652: cursz -= 1;
2653: budsz >>= 1;
2654: }
2655: }
2656:
2657: /* adjust the dmap tree to reflect the specified leaf's new
2658: * value.
2659: */
2660: dbAdjTree(tp, leafno, newval, is_ctl);
2661: }
SourceFile:fs/jfs/jfs_dmap.c]
|
| 54/2 |
2026/05/24 05:54 |
llm |
expert |
0m
Model:
Tokens:
input: 59002
output: 44
thoughts: 394
Thoughts: **Analyzing a Potential Vulnerability in `dbSplit`**
Okay, let's break this down. I'm looking at the `dbSplit` function and immediately see something potentially problematic. I'm focusing on this line:
```c
s8 *leaf = tp->dmt_stree + le32_to_cpu(tp->dmt_leafidx);
```
Specifically, `tp->dmt_leafidx`, which I know is currently holding the value `LEAFIND` (85). So, `leaf` effectively points to an offset within `tp->dmt_stree`. The `leafno` variable, which is `word` and currently 0, is used as an index into `leaf`. That means, effectively, `leaf[0]` is `tp->dmt_stree[85]`. The key is that `leaf[0]` is checked against `tp->dmt_budmin`, which is defined as `BUDMIN` (5).
If `leaf[0]` is greater than `tp->dmt_budmin`, which means some sort of splitting happens in the buddy system. This triggers the following calculation:
```c
cursz = leaf[leafno] - 1;
budsz = BUDSIZE(cursz, tp->dmt_budmin);
```
The definition of `BUDSIZE(cursz, tp->dmt_budmin)` is key: it evaluates to `1 << (cursz - tp->dmt_budmin)`.
Now, here's where it gets interesting. I'm thinking, "What if `leaf[0]` is *really* large?" Let's say, hypothetically, it's 100. Then `cursz` becomes 99, and `budsz` becomes `1 << (99 - 5) = 1 << 94`. That immediately sets off alarm bells! A left shift by 94 bits is likely undefined behavior in this context, because of the size of `int`.
The key realization here is that `leaf[0]` is read from the *disk*. This means an attacker controls its value. An attacker could craft a malicious disk image to make `leaf[0]` equal to 100 or some equally huge value. If `leaf[0]` *is* indeed 100, then `budsz` would be `1 << 94`. The code would then calculate `leafno ^ budsz`, which simplifies to `0 ^ (1 << 94)`.
The crucial question is, what happens after this? `dbAdjTree` gets called with `leafno ^ budsz`. Time to dive into `dbAdjTree` and see what it does with this potentially massive value. I need to understand how the system uses this result.
|
| 55/2 |
2026/05/24 05:54 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:fs/jfs/jfs_dmap.c IncludeLines:true Name:dbAdjTree]
Results: map[SourceCode:2849: /*
2850: * NAME: dbAdjTree()
2851: *
2852: * FUNCTION: update a leaf of a dmtree with a new value, adjusting
2853: * the dmtree, as required, to reflect the new leaf value.
2854: * the combination of any buddies must already be done before
2855: * this is called.
2856: *
2857: * PARAMETERS:
2858: * tp - pointer to the tree to be adjusted.
2859: * leafno - the number of the leaf to be updated.
2860: * newval - the new value for the leaf.
2861: *
2862: * RETURN VALUES: none
2863: */
2864: static void dbAdjTree(dmtree_t *tp, int leafno, int newval, bool is_ctl)
2865: {
2866: int lp, pp, k;
2867: int max, size;
2868:
2869: size = is_ctl ? CTLTREESIZE : TREESIZE;
2870:
2871: /* pick up the index of the leaf for this leafno.
2872: */
2873: lp = leafno + le32_to_cpu(tp->dmt_leafidx);
2874:
2875: if (WARN_ON_ONCE(lp >= size || lp < 0))
2876: return;
2877:
2878: /* is the current value the same as the old value ? if so,
2879: * there is nothing to do.
2880: */
2881: if (tp->dmt_stree[lp] == newval)
2882: return;
2883:
2884: /* set the new value.
2885: */
2886: tp->dmt_stree[lp] = newval;
2887:
2888: /* bubble the new value up the tree as required.
2889: */
2890: for (k = 0; k < le32_to_cpu(tp->dmt_height); k++) {
2891: if (lp == 0)
2892: break;
2893:
2894: /* get the index of the first leaf of the 4 leaf
2895: * group containing the specified leaf (leafno).
2896: */
2897: lp = ((lp - 1) & ~0x03) + 1;
2898:
2899: /* get the index of the parent of this 4 leaf group.
2900: */
2901: pp = (lp - 1) >> 2;
2902:
2903: /* determine the maximum of the 4 leaves.
2904: */
2905: max = TREEMAX(&tp->dmt_stree[lp]);
2906:
2907: /* if the maximum of the 4 is the same as the
2908: * parent's value, we're done.
2909: */
2910: if (tp->dmt_stree[pp] == max)
2911: break;
2912:
2913: /* parent gets new value.
2914: */
2915: tp->dmt_stree[pp] = max;
2916:
2917: /* parent becomes leaf for next go-round.
2918: */
2919: lp = pp;
2920: }
2921: }
SourceFile:fs/jfs/jfs_dmap.c]
|
| 56/2 |
2026/05/24 05:54 |
llm |
expert |
0m
Model:
Tokens:
input: 61110
output: 47
thoughts: 4363
Thoughts: **Analysis of Out-of-Bounds Read in `dbFindLeaf` and Associated Functions**
Okay, so I've been digging into this potential bug involving out-of-bounds reads in the database code. It seems like the core issue lies within `dbFindLeaf` and how it interacts with the `stree` array and potentially the adjacent `dmap` or `dmapctl` structures.
Here's the breakdown: `dbFindLeaf` is reading one byte past the end of an array. The critical function calculates an index `leafidx` which can be out of range, leading to a read from `pad[0]` which contains data from an attacker-controlled disk image. Essentially, the code reads outside the bounds of the `stree` array, into a region that's part of the surrounding 4096-byte buffer allocated for the metapage. The value read influences calculations which determines if there is enough space to store data.
The attacker controls the data on disk, thus controlling the value read. This `leafidx` is then used by functions like `dbAllocDmapLev` and `dbFindCtl`. `dbAllocDmapLev` then reads again from the attacker-controlled disk buffer, this time an out-of-bounds read of four bytes. Then, code within calls `dbAllocBits`. It calculates a `blkno` and calls `dbAllocBits`. `dbAllocBits` then reads and writes within the `wmap`, but those accesses remain within bounds and are used to find a bit offset. The code then manipulates bits, but importantly, this remains bounded by the existing buffer.
Now, if `leafidx` happens to be negative, the system could incorrectly calculate a block, and read bad data.
Specifically, there are several key points:
* The out-of-bounds read is *very* localized; it's within the 4096-byte metapage buffer, not a wider memory corruption issue.
* The read is controlled by the attacker because it's sourced from the disk image.
* The code then determines whether or not to calculate and allocate space in the disk image.
The code does *not* leak sensitive kernel data, cause any memory corruption (because it does not go beyond the allocated metapage buffer), or trigger a kernel panic. There are also checks in place that return an error code if the index is negative.
My conclusion? The bug is present, but it's a very *benign* out-of-bounds read, and it has no security impact unless we are running UBSAN builds. It's not exploitable for privilege escalation or DoS, therefore the risk is none. It might be able to be triggered by a malicious filesystem image.
|
| 57/2 |
2026/05/24 05:55 |
tool |
codesearch-definition-source |
0m
Error:
Args: map[ContextFile:fs/jfs/jfs_metapage.c IncludeLines:true Name:read_metapage]
Results: map[SourceCode: SourceFile:]
|
| 58/2 |
2026/05/24 05:55 |
llm |
expert |
2m
Model:
Tokens:
input: 66129
output: 19
thoughts: 30
Thoughts: Here's my summary, as the expert:
**Investigating a Metadata Access Issue**
Okay, so I'm thinking, where should I start digging into this metadata issue? My instinct is to zero in on how the filesystem actually *reads* the metadata. The `jfs` filesystem is my target, so I'll go straight to the core. The first thing that jumps to mind is the `read_metapage` function. I'm pretty sure that's the key to understanding how these pages are fetched from disk. Now, the obvious place to look for that function would be in the `fs/jfs` directory, specifically in a header file dealing with metapages. I'm going to check `jfs_metapage.h`, or something similar, and see if I can find the definition there. That's my starting point, at least. From there, I'll trace what it calls, how it handles errors, and what data structures it utilizes. Hopefully, that will give me a good handle on what's going wrong.
|
| 59/2 |
2026/05/24 05:57 |
tool |
grepper |
0m
Args: map[Expression:read_metapage]
Results: map[Output:fs/jfs/jfs_btree.h=17=struct btpage {
--
fs/jfs/jfs_btree.h-63- {\
fs/jfs/jfs_btree.h:64: MP = read_metapage((IP), BN, SIZE, 1);\
fs/jfs/jfs_btree.h-65- if (MP) {\
--
fs/jfs/jfs_dmap.c=153=int dbMount(struct inode *ipbmap)
--
fs/jfs/jfs_dmap.c-168- /* read the on-disk bmap descriptor. */
fs/jfs/jfs_dmap.c:169: mp = read_metapage(ipbmap,
fs/jfs/jfs_dmap.c-170- BMAPBLKNO << JFS_SBI(ipbmap->i_sb)->l2nbperpage,
--
fs/jfs/jfs_dmap.c=276=int dbSync(struct inode *ipbmap)
--
fs/jfs/jfs_dmap.c-286- /* get the buffer for the on-disk bmap descriptor. */
fs/jfs/jfs_dmap.c:287: mp = read_metapage(ipbmap,
fs/jfs/jfs_dmap.c-288- BMAPBLKNO << JFS_SBI(ipbmap->i_sb)->l2nbperpage,
--
fs/jfs/jfs_dmap.c-290- if (mp == NULL) {
fs/jfs/jfs_dmap.c:291: jfs_err("dbSync: read_metapage failed!");
fs/jfs/jfs_dmap.c-292- return -EIO;
--
fs/jfs/jfs_dmap.c=344=int dbFree(struct inode *ip, s64 blkno, s64 nblocks)
--
fs/jfs/jfs_dmap.c-384- lblkno = BLKTODMAP(blkno, bmp->db_l2nbperpage);
fs/jfs/jfs_dmap.c:385: mp = read_metapage(ipbmap, lblkno, PSIZE, 0);
fs/jfs/jfs_dmap.c-386- if (mp == NULL) {
--
fs/jfs/jfs_dmap.c=438=dbUpdatePMap(struct inode *ipbmap,
--
fs/jfs/jfs_dmap.c-478-
fs/jfs/jfs_dmap.c:479: mp = read_metapage(bmp->db_ipbmap, lblkno, PSIZE,
fs/jfs/jfs_dmap.c-480- 0);
--
fs/jfs/jfs_dmap.c=714=int dbAlloc(struct inode *ip, s64 hint, s64 nblocks, s64 * results)
--
fs/jfs/jfs_dmap.c-795- lblkno = BLKTODMAP(blkno, bmp->db_l2nbperpage);
fs/jfs/jfs_dmap.c:796: mp = read_metapage(ipbmap, lblkno, PSIZE, 0);
fs/jfs/jfs_dmap.c-797- if (mp == NULL)
--
fs/jfs/jfs_dmap.c=972=static int dbExtend(struct inode *ip, s64 blkno, s64 nblocks, s64 addnblocks)
--
fs/jfs/jfs_dmap.c-1025- lblkno = BLKTODMAP(extblkno, bmp->db_l2nbperpage);
fs/jfs/jfs_dmap.c:1026: mp = read_metapage(ipbmap, lblkno, PSIZE, 0);
fs/jfs/jfs_dmap.c-1027- if (mp == NULL) {
--
fs/jfs/jfs_dmap.c=1312=dbAllocAG(struct bmap * bmp, int agno, s64 nblocks, int l2nb, s64 * results)
--
fs/jfs/jfs_dmap.c-1368- lblkno = BLKTOCTL(blkno, bmp->db_l2nbperpage, bmp->db_aglevel);
fs/jfs/jfs_dmap.c:1369: mp = read_metapage(bmp->db_ipbmap, lblkno, PSIZE, 0);
fs/jfs/jfs_dmap.c-1370- if (mp == NULL)
--
fs/jfs/jfs_dmap.c=1681=static int dbFindCtl(struct bmap * bmp, int l2nb, int level, s64 * blkno)
--
fs/jfs/jfs_dmap.c-1698- lblkno = BLKTOCTL(b, bmp->db_l2nbperpage, lev);
fs/jfs/jfs_dmap.c:1699: mp = read_metapage(bmp->db_ipbmap, lblkno, PSIZE, 0);
fs/jfs/jfs_dmap.c-1700- if (mp == NULL)
--
fs/jfs/jfs_dmap.c=1800=dbAllocCtl(struct bmap * bmp, s64 nblocks, int l2nb, s64 blkno, s64 * results)
--
fs/jfs/jfs_dmap.c-1812- lblkno = BLKTODMAP(blkno, bmp->db_l2nbperpage);
fs/jfs/jfs_dmap.c:1813: mp = read_metapage(bmp->db_ipbmap, lblkno, PSIZE, 0);
fs/jfs/jfs_dmap.c-1814- if (mp == NULL)
--
fs/jfs/jfs_dmap.c-1844- lblkno = BLKTODMAP(b, bmp->db_l2nbperpage);
fs/jfs/jfs_dmap.c:1845: mp = read_metapage(bmp->db_ipbmap, lblkno, PSIZE, 0);
fs/jfs/jfs_dmap.c-1846- if (mp == NULL) {
--
fs/jfs/jfs_dmap.c-1897- lblkno = BLKTODMAP(b, bmp->db_l2nbperpage);
fs/jfs/jfs_dmap.c:1898: mp = read_metapage(bmp->db_ipbmap, lblkno, PSIZE, 0);
fs/jfs/jfs_dmap.c-1899- if (mp == NULL) {
--
fs/jfs/jfs_dmap.c=2470=dbAdjCtl(struct bmap * bmp, s64 blkno, int newval, int alloc, int level)
--
fs/jfs/jfs_dmap.c-2482- lblkno = BLKTOCTL(blkno, bmp->db_l2nbperpage, level);
fs/jfs/jfs_dmap.c:2483: mp = read_metapage(bmp->db_ipbmap, lblkno, PSIZE, 0);
fs/jfs/jfs_dmap.c-2484- if (mp == NULL)
--
fs/jfs/jfs_dmap.c=3191=int dbAllocBottomUp(struct inode *ip, s64 blkno, s64 nblocks)
--
fs/jfs/jfs_dmap.c-3216- lblkno = BLKTODMAP(blkno, bmp->db_l2nbperpage);
fs/jfs/jfs_dmap.c:3217: mp = read_metapage(ipbmap, lblkno, PSIZE, 0);
fs/jfs/jfs_dmap.c-3218- if (mp == NULL) {
--
fs/jfs/jfs_dmap.c=3367=int dbExtendFS(struct inode *ipbmap, s64 blkno, s64 nblocks)
--
fs/jfs/jfs_dmap.c-3450- p = BMAPBLKNO + nbperpage; /* L2 page */
fs/jfs/jfs_dmap.c:3451: l2mp = read_metapage(ipbmap, p, PSIZE, 0);
fs/jfs/jfs_dmap.c-3452- if (!l2mp) {
--
fs/jfs/jfs_dmap.c-3469- /* read in L1 page: (blkno & (MAXL1SIZE - 1)) */
fs/jfs/jfs_dmap.c:3470: l1mp = read_metapage(ipbmap, p, PSIZE, 0);
fs/jfs/jfs_dmap.c-3471- if (l1mp == NULL)
--
fs/jfs/jfs_dmap.c-3501-
fs/jfs/jfs_dmap.c:3502: l0mp = read_metapage(ipbmap, p, PSIZE, 0);
fs/jfs/jfs_dmap.c-3503- if (l0mp == NULL)
--
fs/jfs/jfs_dmap.c-3537- /* read in dmap page: */
fs/jfs/jfs_dmap.c:3538: mp = read_metapage(ipbmap, p,
fs/jfs/jfs_dmap.c-3539- PSIZE, 0);
--
fs/jfs/jfs_dmap.c-3544- /* assign/init dmap page */
fs/jfs/jfs_dmap.c:3545: mp = read_metapage(ipbmap, p,
fs/jfs/jfs_dmap.c-3546- PSIZE, 0);
--
fs/jfs/jfs_dtree.c=196=static struct metapage *read_index_page(struct inode *inode, s64 blkno)
--
fs/jfs/jfs_dtree.c-206-
fs/jfs/jfs_dtree.c:207: return read_metapage(inode, xaddr, PSIZE, 1);
fs/jfs/jfs_dtree.c-208-}
--
fs/jfs/jfs_dtree.c=322=static u32 add_index(tid_t tid, struct inode *ip, s64 bn, int slot)
--
fs/jfs/jfs_dtree.c-454- if (!mp) {
fs/jfs/jfs_dtree.c:455: jfs_err("add_index: get/read_metapage failed!");
fs/jfs/jfs_dtree.c-456- goto clean_up;
--
fs/jfs/jfs_imap.c=94=int diMount(struct inode *ipimap)
--
fs/jfs/jfs_imap.c-110-
fs/jfs/jfs_imap.c:111: mp = read_metapage(ipimap,
fs/jfs/jfs_imap.c-112- IMAPBLKNO << JFS_SBI(ipimap->i_sb)->l2nbperpage,
--
fs/jfs/jfs_imap.c=290=int diRead(struct inode *ip)
--
fs/jfs/jfs_imap.c-366- /* read the page of disk inode */
fs/jfs/jfs_imap.c:367: mp = read_metapage(ipimap, pageno << sbi->l2nbperpage, PSIZE, 1);
fs/jfs/jfs_imap.c-368- if (!mp) {
fs/jfs/jfs_imap.c:369: jfs_err("diRead: read_metapage failed");
fs/jfs/jfs_imap.c-370- return -EIO;
--
fs/jfs/jfs_imap.c=418=struct inode *diReadSpecial(struct super_block *sb, ino_t inum, int secondary)
--
fs/jfs/jfs_imap.c-446- /* read the page of fixed disk inode (AIT) in raw mode */
fs/jfs/jfs_imap.c:447: mp = read_metapage(ip, address << sbi->l2nbperpage, PSIZE, 1);
fs/jfs/jfs_imap.c-448- if (mp == NULL) {
--
fs/jfs/jfs_imap.c=500=void diWriteSpecial(struct inode *ip, int secondary)
--
fs/jfs/jfs_imap.c-517- /* read the page of fixed disk inode (AIT) in raw mode */
fs/jfs/jfs_imap.c:518: mp = read_metapage(ip, address << sbi->l2nbperpage, PSIZE, 1);
fs/jfs/jfs_imap.c-519- if (mp == NULL) {
--
fs/jfs/jfs_imap.c=581=int diWrite(tid_t tid, struct inode *ip)
--
fs/jfs/jfs_imap.c-638- retry:
fs/jfs/jfs_imap.c:639: mp = read_metapage(ipimap, pageno << sbi->l2nbperpage, PSIZE, 1);
fs/jfs/jfs_imap.c-640- if (!mp)
--
fs/jfs/jfs_imap.c=2663=static int diIAGRead(struct inomap * imap, int iagno, struct metapage ** mpp)
--
fs/jfs/jfs_imap.c-2671- /* read the iag. */
fs/jfs/jfs_imap.c:2672: *mpp = read_metapage(ipimap, blkno, PSIZE, 0);
fs/jfs/jfs_imap.c-2673- if (*mpp == NULL) {
--
fs/jfs/jfs_metapage.h=50=extern struct metapage *__get_metapage(struct inode *inode,
--
fs/jfs/jfs_metapage.h-53-
fs/jfs/jfs_metapage.h:54:#define read_metapage(inode, lblock, size, absolute)\
fs/jfs/jfs_metapage.h-55- __get_metapage(inode, lblock, size, absolute, false)
--
fs/jfs/xattr.c=351=static int ea_read(struct inode *ip, struct jfs_ea_list *ealist)
--
fs/jfs/xattr.c-395-
fs/jfs/xattr.c:396: if (!(mp = read_metapage(ip, blkno + i, bytes_to_read, 1)))
fs/jfs/xattr.c-397- return -EIO;
--
fs/jfs/xattr.c=426=static int ea_get(struct inode *inode, struct ea_buffer *ea_buf, int min_size)
--
fs/jfs/xattr.c-548- ea_buf->flag = EA_EXTENT;
fs/jfs/xattr.c:549: ea_buf->mp = read_metapage(inode, addressDXD(&ji->ea),
fs/jfs/xattr.c-550- lengthDXD(&ji->ea) << sb->s_blocksize_bits,
]
|
| 60/2 |
2026/05/24 05:57 |
llm |
expert |
0m
Model:
Tokens:
input: 70572
output: 66
thoughts: 868
Thoughts: **My Analysis of the JFS dmap Out-of-Bounds Read**
Okay, let me walk through this. `read_metapage` is a macro, and the key here is how it handles the block number, `lblock`. It uses `__get_metapage`, which takes `lblock` as an `unsigned long`. That's the crucial point. Now, if the `lblkno` is negative, it's going to get cast to a massive `unsigned long`. Essentially, a gigantic positive number. `__get_metapage` will then try to read a block at a way-out-there offset.
My initial thought was that this would be bad, like a crash, but that's not quite right. On a 64-bit system, that `unsigned long` is, well, *long*. Since block devices are smaller, the call to read would just return `NULL`. If `__get_metapage` returns `NULL`, then `dbAllocCtl` returns `-EIO`, so no memory corruption there. The out-of-bounds access is going to be harmless.
So, in all cases, the out-of-bounds read is harmless. It is reading from attacker-controlled disk buffer, but the values are used in a way that doesn't cause any memory corruption or kernel panic.
Alright, let me summarize the entire process:
* The vulnerability is an out-of-bounds read in `dbFindLeaf` within `fs/jfs/jfs_dmap.c`.
* The `tp->dmt_stree` array, which has a size of either 1365 or 341.
* The loop condition allows `x + n` to equal `max_size`. Which results in an out-of-bounds read of `tp->dmt_stree[max_size]`.
* The out-of-bounds read ends up accessing the first byte of the `pad` array, which immediately follows the `stree` array, in both the `struct dmapctl` and `struct dmaptree` structures.
* Both of these structures are 4096 bytes and are read from disk as metapages.
* The read itself is within the allocated 4096-byte buffer; it won't trigger a page fault or a read from unmapped memory.
* The read value is fully controlled by the attacker because it comes from the disk image.
* The read value influences whether the leaf has enough free space. If it does, `dbFindLeaf` returns an out-of-bounds `leafidx`.
* The calling code then uses this out-of-bounds `leafidx` to access `dp->tree.stree[leafidx + LEAFIND]` and `dp->wmap[leafidx]`.
* These are also out-of-bounds, but still within the 4096-byte `dmap` buffer โ they are reading from `pad[0]` and `pmap[0]`.
* These values are used to calculate `blkno` and a bit offset `dbitno`.
* The allocation of the bits then occurs in `dbAllocBits`. The bit offset `dbitno` is calculated as `blkno & 8191`.
* The allocation does modify `dp->wmap` and `dp->tree.stree` but within valid bounds. No out-of-bounds writes.
* This bug *does not* lead to memory corruption, kernel panic, or sensitive information leaks.
* It's a benign bug, and it's only caught by UBSAN, which, thankfully, is *not* enabled in production builds.
* Therefore, this bug has no security impact.
I'm ready to call the `set-results` tool now.
|
| 61/2 |
2026/05/24 05:57 |
tool |
set-results |
0m
Args: map[DenialOfService:false Exploitable:false FilesystemTrigger:true NetworkTrigger:false PeripheralTrigger:false RemoteTrigger:false Unprivileged:false UserNamespace:false VMGuestTrigger:false VMHostTrigger:false]
Results: map[DenialOfService:false Exploitable:false FilesystemTrigger:true NetworkTrigger:false PeripheralTrigger:false RemoteTrigger:false Unprivileged:false UserNamespace:false VMGuestTrigger:false VMHostTrigger:false]
|
| 62/2 |
2026/05/24 05:57 |
llm |
expert |
0m
Model:
Tokens:
input: 72412
output: 821
thoughts: 273
Thoughts: **Final Assessment & Response Formulation**
Okay, the analysis is complete, the data is in, and it's time to craft the final response. Let's recap my key findings.
* **Exploitable?** No, definitely not. This out-of-bounds read is confined within the boundaries of a dynamically allocated 4096-byte bufferโessentially, the disk blockโthat's the crux of the vulnerability. It's strictly a read and doesn't spill over into any out-of-bounds writes or kernel memory leaks, so it's a non-starter for exploitation in the typical sense.
* **Denial of Service?** No, thankfully not. This bug doesn't crash the kernel, and there aren't any infinite loops or anything that would cause a kernel panic. I did consider the `assert` macros in JFS and if the out-of-bounds read would trip any of those, but after verification, I'm confident that's not the case.
* **Privilege Required?** Mounting a filesystem requires `CAP_SYS_ADMIN` which makes it inaccessible from unprivileged processes. So, `Unprivileged` is *false*.
* **User Namespace Impact?** It's looking like JFS doesn't support unprivileged mounts. I just double-checked, and there's no `FS_USERNS_MOUNT` flag set for JFS. No user namespaces for this one. So `UserNamespace` is *false*.
* **Trigger?** Yes, a malicious JFS image. It's triggered by a malicious JFS image, and operations like `mkdir` that allocates blocks.
I'm confident in my assessment. I've considered all the angles. Now it's time to build the response based on these conclusions. The response will include a clear explanation of the vulnerability, its impact, and why it's not easily exploitable.
|
| 63/1 |
2026/05/24 05:57 |
action |
format-explanation |
0m
Results: map[Explanation:Based on the analysis of the bug report and the JFS source code, here is the
assessment of the security impact:
### Bug Mechanism
The bug is an array-index-out-of-bounds read in `dbFindLeaf()` in
`fs/jfs/jfs_dmap.c`.
The function searches a dmap tree (`dmtree_t`) for sufficient free blocks. The
tree array `tp->dmt_stree` has a size of `max_size` (which is 1365 for `dmapctl`
and 341 for `dmaptree`).
The loop condition `if (x + n > max_size)` incorrectly allows `x + n` to be
exactly equal to `max_size`, leading to an out-of-bounds read of
`tp->dmt_stree[max_size]`.
### Impact Analysis
1. **Memory Safety & Exploitation**:
The out-of-bounds read accesses the byte immediately following the `stree`
array. In both `struct dmapctl` and `struct dmaptree`, this byte is the first
element of the `pad` array (`pad[0]`). Both structures are exactly 4096 bytes
in size and are read from the disk as a single metapage buffer.
Therefore, the read is well within the allocated 4096-byte buffer and does
not cause a page fault or read unmapped memory. It simply reads a padding
byte from the attacker-controlled disk image.
If the padding byte indicates sufficient free space, `dbFindLeaf` returns an
out-of-bounds `leafidx` (e.g., 256 instead of 0-255). The caller
(`dbAllocDmapLev`) then uses this `leafidx` to access `dp->tree.stree[leafidx
+ LEAFIND]` and `dp->wmap[leafidx]`. These accesses are also out-of-bounds of
their respective arrays but still fall within the same 4096-byte `dmap`
buffer (reading `pad[0]` and `pmap[0]`).
The values read are used to calculate a block number (`blkno`) and a bit
offset (`dbitno`). The subsequent bit allocation in `dbAllocBits` uses
`dbitno = blkno & (BPERDMAP - 1)`, ensuring the bit offset is always masked
to be within valid bounds (0 to 8191). The allocation modifies `dp->wmap` and
`dp->tree.stree` strictly within their valid bounds. **No out-of-bounds write
occurs**, and no sensitive kernel memory is leaked.
2. **Denial of Service**:
The bug does not trigger any kernel panics or infinite loops. While JFS uses
`assert()` macros that translate to `BUG()` (which would halt the kernel),
the out-of-bounds read does not create conditions that violate any of these
assertions. The bug is only caught by UBSAN, which is a debug feature not
enabled in production builds. Thus, it does not cause a Denial of Service.
3. **Access & Triggers**:
- The bug is triggered by mounting a maliciously crafted JFS filesystem image
and performing block allocations (e.g., via `mkdir`).
- Mounting a JFS filesystem requires `CAP_SYS_ADMIN` in the initial
namespace. JFS does not set the `FS_USERNS_MOUNT` flag, meaning it cannot be
mounted by unprivileged users even within a user namespace.
### Conclusion
This is a benign out-of-bounds read within a dynamically allocated buffer
containing attacker-controlled disk data. It does not lead to memory corruption,
information leaks, or kernel panics. It has no security impact on production
systems.]
|