[v6.6] KASAN: slab-use-after-free Read in list_lru_add

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Jul 30, 2026, 3:54:38 PM (22 hours ago) Jul 30
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Hello,

syzbot found the following issue on:

HEAD commit: a1153c0deb44 Linux 6.6.147
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=13b078c6580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f0bc3d90c30838b5
dashboard link: https://syzkaller.appspot.com/bug?extid=6ec01cdf045f33b48d70
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/9f646bfa1b52/disk-a1153c0d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a2aec2e8f0fd/vmlinux-a1153c0d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a7abe1f87405/bzImage-a1153c0d.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+6ec01c...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-use-after-free in __list_add_valid_or_report+0x6b/0xf0 lib/list_debug.c:32
Read of size 8 at addr ffff88805fbfd078 by task syz-executor/5771

CPU: 0 PID: 5771 Comm: syz-executor Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
Call Trace:
<TASK>
dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
print_address_description mm/kasan/report.c:364 [inline]
print_report+0xa8/0x210 mm/kasan/report.c:468
kasan_report+0x117/0x150 mm/kasan/report.c:581
__list_add_valid_or_report+0x6b/0xf0 lib/list_debug.c:32
__list_add_valid include/linux/list.h:88 [inline]
__list_add include/linux/list.h:150 [inline]
list_add_tail include/linux/list.h:183 [inline]
list_lru_add+0x246/0x400 mm/list_lru.c:129
qd_put+0x11a/0x1a0 fs/gfs2/quota.c:331
qd_unlock fs/gfs2/quota.c:519 [inline]
gfs2_quota_sync+0x4b3/0x5a0 fs/gfs2/quota.c:1347
gfs2_sync_fs+0x4c/0xb0 fs/gfs2/super.c:671
sync_filesystem+0xea/0x220 fs/sync.c:56
generic_shutdown_super+0x6f/0x2b0 fs/super.c:666
kill_block_super+0x44/0x90 fs/super.c:1660
deactivate_locked_super+0x97/0x100 fs/super.c:481
cleanup_mnt+0x3d7/0x460 fs/namespace.c:1259
task_work_run+0x1d4/0x260 kernel/task_work.c:245
resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177
exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
__syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f0c5a99f257
Code: a2 c7 05 9c 44 25 00 00 00 00 00 eb 96 e8 e1 12 00 00 90 31 f6 e9 09 00 00 00 66 0f 1f 84 00 00 00 00 00 b8 a6 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 01 c3 48 c7 c2 e8 ff ff ff f7 d8 64 89 02 b8
RSP: 002b:00007ffc31cf4c88 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 00007f0c5aa3445c RCX: 00007f0c5a99f257
RDX: 0000000000000000 RSI: 0000000000000009 RDI: 00007ffc31cf4d40
RBP: 00007ffc31cf4d40 R08: 00007ffc31cf5d40 R09: 00000000ffffffff
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffc31cf5dd0
R13: 00007f0c5aa3445c R14: 0000000000023e6d R15: 00007ffc31cf5e10
</TASK>

Allocated by task 7190:
kasan_save_stack mm/kasan/common.c:46 [inline]
kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
__kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:329
kasan_slab_alloc include/linux/kasan.h:188 [inline]
slab_post_alloc_hook+0x6a/0x4d0 mm/slab.h:770
slab_alloc_node mm/slub.c:3495 [inline]
slab_alloc mm/slub.c:3503 [inline]
__kmem_cache_alloc_lru mm/slub.c:3510 [inline]
kmem_cache_alloc+0x17e/0x2c0 mm/slub.c:3519
kmem_cache_zalloc include/linux/slab.h:711 [inline]
qd_alloc+0x50/0x260 fs/gfs2/quota.c:221
gfs2_quota_init+0x751/0xe90 fs/gfs2/quota.c:1437
gfs2_make_fs_rw+0x418/0x590 fs/gfs2/super.c:159
gfs2_fill_super+0x1977/0x1f90 fs/gfs2/ops_fstype.c:1291
get_tree_bdev+0x3e5/0x520 fs/super.c:1591
gfs2_get_tree+0x51/0x1e0 fs/gfs2/ops_fstype.c:1344
vfs_get_tree+0x8c/0x280 fs/super.c:1764
do_new_mount+0x24a/0xa40 fs/namespace.c:3386
do_mount fs/namespace.c:3726 [inline]
__do_sys_mount fs/namespace.c:3935 [inline]
__se_sys_mount+0x2e7/0x3d0 fs/namespace.c:3912
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2

Freed by task 5771:
kasan_save_stack mm/kasan/common.c:46 [inline]
kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
kasan_save_free_info+0x28/0x40 mm/kasan/generic.c:522
____kasan_slab_free+0x126/0x1f0 mm/kasan/common.c:237
kasan_slab_free include/linux/kasan.h:164 [inline]
slab_free_hook mm/slub.c:1811 [inline]
slab_free_freelist_hook+0x130/0x1a0 mm/slub.c:1837
slab_free mm/slub.c:3830 [inline]
kmem_cache_free+0xf8/0x290 mm/slub.c:3852
gfs2_qd_dealloc+0x70/0xe0 fs/gfs2/quota.c:111
rcu_do_batch kernel/rcu/tree.c:2194 [inline]
rcu_core+0x9c1/0x17f0 kernel/rcu/tree.c:2467
handle_softirqs+0x27d/0x820 kernel/softirq.c:578
__do_softirq kernel/softirq.c:612 [inline]
invoke_softirq kernel/softirq.c:452 [inline]
__irq_exit_rcu+0xd3/0x190 kernel/softirq.c:661
irq_exit_rcu+0x9/0x20 kernel/softirq.c:673
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline]
sysvec_apic_timer_interrupt+0xa4/0xc0 arch/x86/kernel/apic/apic.c:1088
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687

Last potentially related work creation:
kasan_save_stack+0x3e/0x60 mm/kasan/common.c:46
__kasan_record_aux_stack+0xaf/0xc0 mm/kasan/generic.c:492
__call_rcu_common kernel/rcu/tree.c:2721 [inline]
call_rcu+0x153/0x900 kernel/rcu/tree.c:2837
qd_unlock fs/gfs2/quota.c:519 [inline]
gfs2_quota_sync+0x4b3/0x5a0 fs/gfs2/quota.c:1347
gfs2_sync_fs+0x4c/0xb0 fs/gfs2/super.c:671
sync_filesystem+0xea/0x220 fs/sync.c:56
generic_shutdown_super+0x6f/0x2b0 fs/super.c:666
kill_block_super+0x44/0x90 fs/super.c:1660
deactivate_locked_super+0x97/0x100 fs/super.c:481
cleanup_mnt+0x3d7/0x460 fs/namespace.c:1259
task_work_run+0x1d4/0x260 kernel/task_work.c:245
resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177
exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
__syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x68/0xd2

The buggy address belongs to the object at ffff88805fbfd000
which belongs to the cache gfs2_quotad of size 272
The buggy address is located 120 bytes inside of
freed 272-byte region [ffff88805fbfd000, ffff88805fbfd110)

The buggy address belongs to the physical page:
page:ffffea00017eff40 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x5fbfd
flags: 0xfff00000000800(slab|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000800 ffff88814469c140 dead000000000122 0000000000000000
raw: 0000000000000000 00000000800c000c 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Reclaimable, gfp_mask 0x112c50(GFP_NOFS|__GFP_NOWARN|__GFP_NORETRY|__GFP_HARDWALL|__GFP_RECLAIMABLE), pid 7190, tgid 7189 (syz.1.479), ts 140096383207, free_ts 138206145784
set_page_owner include/linux/page_owner.h:31 [inline]
post_alloc_hook+0x1c1/0x200 mm/page_alloc.c:1582
prep_new_page mm/page_alloc.c:1589 [inline]
get_page_from_freelist+0x2181/0x22a0 mm/page_alloc.c:3221
__alloc_pages+0x1f0/0x460 mm/page_alloc.c:4501
alloc_slab_page+0x5d/0x180 mm/slub.c:1881
allocate_slab mm/slub.c:2028 [inline]
new_slab+0x87/0x2d0 mm/slub.c:2081
___slab_alloc+0xc5c/0x12f0 mm/slub.c:3253
__slab_alloc mm/slub.c:3339 [inline]
__slab_alloc_node mm/slub.c:3392 [inline]
slab_alloc_node mm/slub.c:3485 [inline]
slab_alloc mm/slub.c:3503 [inline]
__kmem_cache_alloc_lru mm/slub.c:3510 [inline]
kmem_cache_alloc+0x109/0x2c0 mm/slub.c:3519
kmem_cache_zalloc include/linux/slab.h:711 [inline]
qd_alloc+0x50/0x260 fs/gfs2/quota.c:221
gfs2_quota_init+0x751/0xe90 fs/gfs2/quota.c:1437
gfs2_make_fs_rw+0x418/0x590 fs/gfs2/super.c:159
gfs2_fill_super+0x1977/0x1f90 fs/gfs2/ops_fstype.c:1291
get_tree_bdev+0x3e5/0x520 fs/super.c:1591
gfs2_get_tree+0x51/0x1e0 fs/gfs2/ops_fstype.c:1344
vfs_get_tree+0x8c/0x280 fs/super.c:1764
do_new_mount+0x24a/0xa40 fs/namespace.c:3386
do_mount fs/namespace.c:3726 [inline]
__do_sys_mount fs/namespace.c:3935 [inline]
__se_sys_mount+0x2e7/0x3d0 fs/namespace.c:3912
page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1182 [inline]
free_unref_page_prepare+0x7d7/0x8f0 mm/page_alloc.c:2366
free_unref_page+0x32/0x2e0 mm/page_alloc.c:2459
__slab_free+0x35a/0x400 mm/slub.c:3736
qlink_free mm/kasan/quarantine.c:166 [inline]
qlist_free_all+0x75/0xd0 mm/kasan/quarantine.c:185
kasan_quarantine_reduce+0x143/0x160 mm/kasan/quarantine.c:292
__kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:306
kasan_slab_alloc include/linux/kasan.h:188 [inline]
slab_post_alloc_hook+0x6a/0x4d0 mm/slab.h:770
slab_alloc_node mm/slub.c:3495 [inline]
__kmem_cache_alloc_node+0x194/0x250 mm/slub.c:3534
kmalloc_trace+0x2a/0xe0 mm/slab_common.c:1098
kmalloc include/linux/slab.h:600 [inline]
kzalloc include/linux/slab.h:721 [inline]
kernfs_fop_open+0x3d2/0xc60 fs/kernfs/file.c:690
do_dentry_open+0x880/0x14b0 fs/open.c:929
do_open fs/namei.c:3640 [inline]
path_openat+0x284f/0x3270 fs/namei.c:3801
do_filp_open+0x1f2/0x430 fs/namei.c:3828
do_sys_openat2+0x134/0x1d0 fs/open.c:1422
do_sys_open fs/open.c:1437 [inline]
__do_sys_openat fs/open.c:1453 [inline]
__se_sys_openat fs/open.c:1448 [inline]
__x64_sys_openat+0x139/0x160 fs/open.c:1448
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76

Memory state around the buggy address:
ffff88805fbfcf00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88805fbfcf80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88805fbfd000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88805fbfd080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88805fbfd100: fb fb fc fc fc fc fc fc fc fc fa fb fb fb fb fb
==================================================================


---
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