[v5.15] KASAN: use-after-free Read in quotad_error

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 68efe5a6c16a Linux 5.15.197
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=10ec6852580000
kernel config: https://syzkaller.appspot.com/x/.config?x=30e28339904629ca
dashboard link: https://syzkaller.appspot.com/bug?extid=f2b6e998ff712cb4660d
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/a778cfe5926b/disk-68efe5a6.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/d2cfafb4eb48/vmlinux-68efe5a6.xz
kernel image: https://storage.googleapis.com/syzbot-assets/845a4677be47/bzImage-68efe5a6.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f2b6e9...@syzkaller.appspotmail.com

kthread+0x436/0x520 kernel/kthread.c:334
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
</TASK>
==================================================================
BUG: KASAN: use-after-free in instrument_atomic_read include/linux/instrumented.h:71 [inline]
BUG: KASAN: use-after-free in test_bit include/asm-generic/bitops/instrumented-non-atomic.h:134 [inline]
BUG: KASAN: use-after-free in gfs2_withdrawn fs/gfs2/util.h:207 [inline]
BUG: KASAN: use-after-free in quotad_error+0x60/0x170 fs/gfs2/quota.c:1506
Read of size 8 at addr ffff8880772340a8 by task gfs2_quotad/4576

CPU: 0 PID: 4576 Comm: gfs2_quotad Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
<TASK>
dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
print_address_description+0x60/0x2d0 mm/kasan/report.c:248
__kasan_report mm/kasan/report.c:434 [inline]
kasan_report+0xdf/0x130 mm/kasan/report.c:451
check_region_inline mm/kasan/generic.c:-1 [inline]
kasan_check_range+0x235/0x290 mm/kasan/generic.c:189
instrument_atomic_read include/linux/instrumented.h:71 [inline]
test_bit include/asm-generic/bitops/instrumented-non-atomic.h:134 [inline]
gfs2_withdrawn fs/gfs2/util.h:207 [inline]
quotad_error+0x60/0x170 fs/gfs2/quota.c:1506
quotad_check_timeo fs/gfs2/quota.c:1520 [inline]
gfs2_quotad+0x414/0x890 fs/gfs2/quota.c:1586
kthread+0x436/0x520 kernel/kthread.c:334
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
</TASK>

Allocated by task 4562:
kasan_save_stack mm/kasan/common.c:38 [inline]
kasan_set_track mm/kasan/common.c:46 [inline]
set_alloc_info mm/kasan/common.c:434 [inline]
____kasan_kmalloc mm/kasan/common.c:513 [inline]
__kasan_kmalloc+0xb5/0xf0 mm/kasan/common.c:522
kmalloc include/linux/slab.h:607 [inline]
kzalloc include/linux/slab.h:738 [inline]
init_sbd fs/gfs2/ops_fstype.c:77 [inline]
gfs2_fill_super+0x17d/0x1f00 fs/gfs2/ops_fstype.c:1151
get_tree_bdev+0x3f1/0x610 fs/super.c:1325
gfs2_get_tree+0x4d/0x1e0 fs/gfs2/ops_fstype.c:1332
vfs_get_tree+0x88/0x270 fs/super.c:1530
do_new_mount+0x24a/0xa40 fs/namespace.c:3034
do_mount fs/namespace.c:3377 [inline]
__do_sys_mount fs/namespace.c:3585 [inline]
__se_sys_mount+0x2e3/0x3d0 fs/namespace.c:3562
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

Freed by task 4189:
kasan_save_stack mm/kasan/common.c:38 [inline]
kasan_set_track+0x4b/0x70 mm/kasan/common.c:46
kasan_set_free_info+0x1f/0x40 mm/kasan/generic.c:360
____kasan_slab_free+0xd5/0x110 mm/kasan/common.c:366
kasan_slab_free include/linux/kasan.h:230 [inline]
slab_free_hook mm/slub.c:1710 [inline]
slab_free_freelist_hook+0xea/0x170 mm/slub.c:1736
slab_free mm/slub.c:3504 [inline]
kfree+0xef/0x2a0 mm/slub.c:4564
generic_shutdown_super+0x130/0x300 fs/super.c:475
kill_block_super+0x7c/0xe0 fs/super.c:1427
deactivate_locked_super+0x93/0xf0 fs/super.c:335
cleanup_mnt+0x42d/0x4e0 fs/namespace.c:1148
task_work_run+0x125/0x1a0 kernel/task_work.c:188
tracehook_notify_resume include/linux/tracehook.h:189 [inline]
exit_to_user_mode_loop+0x10f/0x130 kernel/entry/common.c:181
exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:214
__syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:307
do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x66/0xd0

The buggy address belongs to the object at ffff888077234000
which belongs to the cache kmalloc-8k of size 8192
The buggy address is located 168 bytes inside of
8192-byte region [ffff888077234000, ffff888077236000)
The buggy address belongs to the page:
page:ffffea0001dc8c00 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff888077230000 pfn:0x77230
head:ffffea0001dc8c00 order:3 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 ffffea0001fa7008 ffffea0000b08608 ffff888016c42280
raw: ffff888077230000 0000000000020001 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd2040(__GFP_IO|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 4017, ts 43044204282, free_ts 43037888759
prep_new_page mm/page_alloc.c:2426 [inline]
get_page_from_freelist+0x1bbd/0x1ca0 mm/page_alloc.c:4192
__alloc_pages+0x1ee/0x480 mm/page_alloc.c:5487
alloc_slab_page mm/slub.c:1780 [inline]
allocate_slab mm/slub.c:1917 [inline]
new_slab+0xc0/0x4b0 mm/slub.c:1980
___slab_alloc+0x80a/0xdd0 mm/slub.c:3013
__slab_alloc mm/slub.c:3100 [inline]
slab_alloc_node mm/slub.c:3191 [inline]
slab_alloc mm/slub.c:3233 [inline]
kmem_cache_alloc_trace+0x1a5/0x2a0 mm/slub.c:3250
kmalloc include/linux/slab.h:607 [inline]
kzalloc include/linux/slab.h:738 [inline]
tomoyo_print_bprm security/tomoyo/audit.c:26 [inline]
tomoyo_init_log+0x1008/0x1e90 security/tomoyo/audit.c:264
tomoyo_supervisor+0x38d/0x11f0 security/tomoyo/common.c:2097
tomoyo_audit_env_log security/tomoyo/environ.c:36 [inline]
tomoyo_env_perm+0x14e/0x1f0 security/tomoyo/environ.c:63
tomoyo_environ security/tomoyo/domain.c:672 [inline]
tomoyo_find_next_domain+0x1591/0x1a60 security/tomoyo/domain.c:882
tomoyo_bprm_check_security+0xdd/0x120 security/tomoyo/tomoyo.c:101
security_bprm_check+0x5e/0x90 security/security.c:868
search_binary_handler fs/exec.c:1730 [inline]
exec_binprm fs/exec.c:1783 [inline]
bprm_execve+0xa53/0x1840 fs/exec.c:1852
do_execveat_common+0x51e/0x6d0 fs/exec.c:1957
do_execve fs/exec.c:2027 [inline]
__do_sys_execve fs/exec.c:2103 [inline]
__se_sys_execve fs/exec.c:2098 [inline]
__x64_sys_execve+0x8e/0xa0 fs/exec.c:2098
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1340 [inline]
free_pcp_prepare mm/page_alloc.c:1391 [inline]
free_unref_page_prepare+0x637/0x6c0 mm/page_alloc.c:3317
free_unref_page+0x8f/0x2a0 mm/page_alloc.c:3396
free_slab mm/slub.c:2020 [inline]
discard_slab mm/slub.c:2026 [inline]
__unfreeze_partials+0x1a5/0x200 mm/slub.c:2512
put_cpu_partial+0x12d/0x190 mm/slub.c:2592
qlist_free_all+0x35/0x90 mm/kasan/quarantine.c:176
kasan_quarantine_reduce+0x150/0x160 mm/kasan/quarantine.c:283
__kasan_slab_alloc+0x2f/0xd0 mm/kasan/common.c:444
kasan_slab_alloc include/linux/kasan.h:254 [inline]
slab_post_alloc_hook+0x4c/0x380 mm/slab.h:519
slab_alloc_node mm/slub.c:3225 [inline]
__kmalloc_node+0x15a/0x3b0 mm/slub.c:4456
kmalloc_node include/linux/slab.h:630 [inline]
kvmalloc_node+0x84/0x130 mm/util.c:619
kvmalloc include/linux/mm.h:816 [inline]
seq_buf_alloc fs/seq_file.c:38 [inline]
seq_read_iter+0x1f6/0xd50 fs/seq_file.c:210
proc_reg_read_iter+0x1a9/0x270 fs/proc/inode.c:300
call_read_iter include/linux/fs.h:2167 [inline]
new_sync_read fs/read_write.c:404 [inline]
vfs_read+0x759/0xd60 fs/read_write.c:485
ksys_read+0x152/0x260 fs/read_write.c:623
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

Memory state around the buggy address:
ffff888077233f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888077234000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888077234080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888077234100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888077234180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


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