KASAN: null-ptr-deref Write in get_block (2)

Status: upstream: reported C repro on 2023/05/22 22:36
Labels: fs (incorrect?)
First crash: 14d, last: 14d

Cause bisection: failed (error log, bisect log)
Discussions (3)
Title Replies (including bot) Last reply
[PATCH v3] fs/sysv: Null check to prevent null-ptr-deref bug 6 (6) 2023/06/01 07:55
[PATCH] Null check to prevent null-ptr-deref bug 2 (2) 2023/05/28 17:52
[syzbot] [fs?] KASAN: null-ptr-deref Write in get_block (2) 0 (1) 2023/05/22 22:36
Similar bugs (3)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: null-ptr-deref Write in get_block fs C done 101 1054d 1168d 17/24 fixed on 2020/09/16 22:51
linux-4.14 BUG: unable to handle kernel NULL pointer dereference in get_block (2) C 1 92d 175d 0/1 upstream: reported C repro on 2022/12/09 08:52
upstream KASAN: slab-out-of-bounds Read in get_block (2) fs 1 144d 144d 0/24 auto-obsoleted due to no activity on 2023/05/09 01:15

Sample crash report:
memfd_create() without MFD_EXEC nor MFD_NOEXEC_SEAL, pid=4996 'syz-executor412'
loop0: detected capacity change from 0 to 128
VFS: Found a Xenix FS (block size = 512) on device loop0
sysv_free_block: trying to free block not in datazone
BUG: KASAN: null-ptr-deref in instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
BUG: KASAN: null-ptr-deref in test_and_set_bit_lock include/asm-generic/bitops/instrumented-lock.h:57 [inline]
BUG: KASAN: null-ptr-deref in trylock_buffer include/linux/buffer_head.h:399 [inline]
BUG: KASAN: null-ptr-deref in lock_buffer include/linux/buffer_head.h:405 [inline]
BUG: KASAN: null-ptr-deref in alloc_branch fs/sysv/itree.c:148 [inline]
BUG: KASAN: null-ptr-deref in get_block+0x567/0x16a0 fs/sysv/itree.c:251
Write of size 8 at addr 0000000000000000 by task syz-executor412/4996

CPU: 1 PID: 4996 Comm: syz-executor412 Not tainted 6.4.0-rc2-syzkaller-00018-g4d6d4c7f541d #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/28/2023
Call Trace:
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e7/0x2d0 lib/dump_stack.c:106
 print_report+0xe6/0x540 mm/kasan/report.c:465
 kasan_report+0x176/0x1b0 mm/kasan/report.c:572
 kasan_check_range+0x283/0x290 mm/kasan/generic.c:187
 instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
 test_and_set_bit_lock include/asm-generic/bitops/instrumented-lock.h:57 [inline]
 trylock_buffer include/linux/buffer_head.h:399 [inline]
 lock_buffer include/linux/buffer_head.h:405 [inline]
 alloc_branch fs/sysv/itree.c:148 [inline]
 get_block+0x567/0x16a0 fs/sysv/itree.c:251
 __block_write_begin_int+0x548/0x1a50 fs/buffer.c:2064
 __block_write_begin fs/buffer.c:2114 [inline]
 block_write_begin+0x9c/0x1f0 fs/buffer.c:2175
 sysv_write_begin+0x31/0x70 fs/sysv/itree.c:485
 generic_perform_write+0x300/0x5e0 mm/filemap.c:3923
 __generic_file_write_iter+0x17a/0x400 mm/filemap.c:4051
 generic_file_write_iter+0xaf/0x310 mm/filemap.c:4083
 do_iter_write+0x7b1/0xcb0 fs/read_write.c:860
 vfs_writev fs/read_write.c:933 [inline]
 do_pwritev+0x21a/0x360 fs/read_write.c:1030
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
RIP: 0033:0x7f3233222b19
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 51 14 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffecf15f268 EFLAGS: 00000246 ORIG_RAX: 0000000000000128
RAX: ffffffffffffffda RBX: 0031656c69662f2e RCX: 00007f3233222b19
RDX: 0000000000000005 RSI: 0000000020000480 RDI: 0000000000000004
RBP: 00007f32331e2150 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000007fff R11: 0000000000000246 R12: 00007f32331e21e0
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets Manager Title
2023/05/18 22:41 upstream 4d6d4c7f541d 3bb7af1d .config strace log report syz C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-upstream-fs KASAN: null-ptr-deref Write in get_block
2023/05/18 22:22 upstream 4d6d4c7f541d 3bb7af1d .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs KASAN: null-ptr-deref Write in get_block
* Struck through repros no longer work on HEAD.