[syzbot] [gfs2?] KASAN: slab-use-after-free Read in gfs2_quotad

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 2aa680df6806 Merge tag 'sound-6.19-rc1' of git://git.kerne..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15ac701a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=7e44d84dbc04570e
dashboard link: https://syzkaller.appspot.com/bug?extid=4cb0d0336db6bc6930e9
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1213bcc2580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/dcfbfa0a8815/disk-2aa680df.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/1a6f7574c952/vmlinux-2aa680df.xz
kernel image: https://storage.googleapis.com/syzbot-assets/be0a631aa7d7/bzImage-2aa680df.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/b2c257be04cf/mount_3.gz
fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=11ffb192580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4cb0d0...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-use-after-free in instrument_atomic_read include/linux/instrumented.h:68 [inline]
BUG: KASAN: slab-use-after-free in _test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline]
BUG: KASAN: slab-use-after-free in gfs2_withdrawn fs/gfs2/util.h:187 [inline]
BUG: KASAN: slab-use-after-free in gfs2_quotad+0x19c/0x930 fs/gfs2/quota.c:1586
Read of size 8 at addr ffff8880754740a8 by task gfs2_quotad/syz/8747

CPU: 1 UID: 0 PID: 8747 Comm: gfs2_quotad/syz Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
<TASK>
dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:378 [inline]
print_report+0xca/0x240 mm/kasan/report.c:482
kasan_report+0x118/0x150 mm/kasan/report.c:595
check_region_inline mm/kasan/generic.c:-1 [inline]
kasan_check_range+0x2b0/0x2c0 mm/kasan/generic.c:200
instrument_atomic_read include/linux/instrumented.h:68 [inline]
_test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline]
gfs2_withdrawn fs/gfs2/util.h:187 [inline]
gfs2_quotad+0x19c/0x930 fs/gfs2/quota.c:1586
kthread+0x711/0x8a0 kernel/kthread.c:463
ret_from_fork+0x599/0xb30 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
</TASK>

Allocated by task 8733:
kasan_save_stack mm/kasan/common.c:56 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:77
poison_kmalloc_redzone mm/kasan/common.c:400 [inline]
__kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:417
kasan_kmalloc include/linux/kasan.h:262 [inline]
__kmalloc_cache_noprof+0x3d5/0x6f0 mm/slub.c:5771
kmalloc_noprof include/linux/slab.h:957 [inline]
kzalloc_noprof include/linux/slab.h:1094 [inline]
init_sbd fs/gfs2/ops_fstype.c:79 [inline]
gfs2_fill_super+0x11f/0x21b0 fs/gfs2/ops_fstype.c:1121
get_tree_bdev_flags+0x40e/0x4d0 fs/super.c:1699
gfs2_get_tree+0x51/0x1e0 fs/gfs2/ops_fstype.c:1332
vfs_get_tree+0x92/0x2a0 fs/super.c:1759
fc_mount fs/namespace.c:1199 [inline]
do_new_mount_fc fs/namespace.c:3636 [inline]
do_new_mount+0x302/0xa10 fs/namespace.c:3712
do_mount fs/namespace.c:4035 [inline]
__do_sys_mount fs/namespace.c:4224 [inline]
__se_sys_mount+0x313/0x410 fs/namespace.c:4201
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 8733:
kasan_save_stack mm/kasan/common.c:56 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:77
__kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:587
kasan_save_free_info mm/kasan/kasan.h:406 [inline]
poison_slab_object mm/kasan/common.c:252 [inline]
__kasan_slab_free+0x5c/0x80 mm/kasan/common.c:284
kasan_slab_free include/linux/kasan.h:234 [inline]
slab_free_hook mm/slub.c:2540 [inline]
slab_free mm/slub.c:6663 [inline]
kfree+0x1c0/0x660 mm/slub.c:6871
free_sbd fs/gfs2/ops_fstype.c:72 [inline]
gfs2_fill_super+0x14ef/0x21b0 fs/gfs2/ops_fstype.c:1316
get_tree_bdev_flags+0x40e/0x4d0 fs/super.c:1699
gfs2_get_tree+0x51/0x1e0 fs/gfs2/ops_fstype.c:1332
vfs_get_tree+0x92/0x2a0 fs/super.c:1759
fc_mount fs/namespace.c:1199 [inline]
do_new_mount_fc fs/namespace.c:3636 [inline]
do_new_mount+0x302/0xa10 fs/namespace.c:3712
do_mount fs/namespace.c:4035 [inline]
__do_sys_mount fs/namespace.c:4224 [inline]
__se_sys_mount+0x313/0x410 fs/namespace.c:4201
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff888075474000
which belongs to the cache kmalloc-8k of size 8192
The buggy address is located 168 bytes inside of
freed 8192-byte region [ffff888075474000, ffff888075476000)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x75470
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
ksm flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801a027280 ffffea00009a8c00 dead000000000003
raw: 0000000000000000 0000000000020002 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801a027280 ffffea00009a8c00 dead000000000003
head: 0000000000000000 0000000000020002 00000000f5000000 0000000000000000
head: 00fff00000000003 ffffea0001d51c01 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
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 5660, tgid 5660 (dhcpcd-run-hook), ts 66112319039, free_ts 66011248304
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x234/0x290 mm/page_alloc.c:1845
prep_new_page mm/page_alloc.c:1853 [inline]
get_page_from_freelist+0x2365/0x2440 mm/page_alloc.c:3879
__alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5183
alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2416
alloc_slab_page mm/slub.c:3075 [inline]
allocate_slab+0x86/0x3b0 mm/slub.c:3248
new_slab mm/slub.c:3302 [inline]
___slab_alloc+0xf2b/0x1960 mm/slub.c:4651
__slab_alloc+0x65/0x100 mm/slub.c:4774
__slab_alloc_node mm/slub.c:4850 [inline]
slab_alloc_node mm/slub.c:5246 [inline]
__kmalloc_cache_noprof+0x411/0x6f0 mm/slub.c:5766
kmalloc_noprof include/linux/slab.h:957 [inline]
kzalloc_noprof include/linux/slab.h:1094 [inline]
tomoyo_print_bprm security/tomoyo/audit.c:26 [inline]
tomoyo_init_log+0x111f/0x1f70 security/tomoyo/audit.c:264
tomoyo_supervisor+0x340/0x1480 security/tomoyo/common.c:2198
tomoyo_audit_env_log security/tomoyo/environ.c:36 [inline]
tomoyo_env_perm+0x149/0x1e0 security/tomoyo/environ.c:63
tomoyo_environ security/tomoyo/domain.c:672 [inline]
tomoyo_find_next_domain+0x15ce/0x1aa0 security/tomoyo/domain.c:888
tomoyo_bprm_check_security+0x11c/0x180 security/tomoyo/tomoyo.c:102
security_bprm_check+0x89/0x270 security/security.c:794
search_binary_handler fs/exec.c:1659 [inline]
exec_binprm fs/exec.c:1701 [inline]
bprm_execve+0x887/0x1400 fs/exec.c:1753
do_execveat_common+0x510/0x6a0 fs/exec.c:1859
page last free pid 5655 tgid 5655 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
free_pages_prepare mm/page_alloc.c:1394 [inline]
__free_frozen_pages+0xbc4/0xd30 mm/page_alloc.c:2901
discard_slab mm/slub.c:3346 [inline]
__put_partials+0x146/0x170 mm/slub.c:3886
put_cpu_partial+0x1f2/0x2d0 mm/slub.c:3961
__slab_free+0x288/0x2a0 mm/slub.c:5947
qlink_free mm/kasan/quarantine.c:163 [inline]
qlist_free_all+0x97/0x100 mm/kasan/quarantine.c:179
kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286
__kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:352
kasan_slab_alloc include/linux/kasan.h:252 [inline]
slab_post_alloc_hook mm/slub.c:4948 [inline]
slab_alloc_node mm/slub.c:5258 [inline]
__do_kmalloc_node mm/slub.c:5651 [inline]
__kmalloc_node_track_caller_noprof+0x51d/0x810 mm/slub.c:5759
__kmemdup_nul mm/util.c:64 [inline]
kstrdup+0x42/0x100 mm/util.c:84
bprm_change_interp+0x82/0xc0 fs/exec.c:1479
load_script+0x6d0/0x860 fs/binfmt_script.c:125
search_binary_handler fs/exec.c:1669 [inline]
exec_binprm fs/exec.c:1701 [inline]
bprm_execve+0x92e/0x1400 fs/exec.c:1753
do_execveat_common+0x510/0x6a0 fs/exec.c:1859
do_execve fs/exec.c:1933 [inline]
__do_sys_execve fs/exec.c:2009 [inline]
__se_sys_execve fs/exec.c:2004 [inline]
__x64_sys_execve+0x94/0xb0 fs/exec.c:2004
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
ffff888075473f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888075474000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888075474080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888075474100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888075474180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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