[moderation] [gfs2?] KASAN: slab-use-after-free Read in gfs2_withdraw_func

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Oct 24, 2025, 6:32:37 AM (3 days ago) Oct 24
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Hello,

syzbot found the following issue on:

HEAD commit: 606da5bb1655 Add linux-next specific files for 20251020
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=104c9492580000
kernel config: https://syzkaller.appspot.com/x/.config?x=cc275090905d8fd7
dashboard link: https://syzkaller.appspot.com/bug?extid=36ecab4bf8925eaec8f4
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
CC: [agru...@redhat.com gf...@lists.linux.dev linux-...@vger.kernel.org]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/dfd005041711/disk-606da5bb.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c92ee475612c/vmlinux-606da5bb.xz
kernel image: https://storage.googleapis.com/syzbot-assets/54c20315c52c/bzImage-606da5bb.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+36ecab...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-use-after-free in gfs2_withdraw_func+0x42/0x430 fs/gfs2/util.c:221
Read of size 8 at addr ffff888079a24348 by task kworker/1:3/986

CPU: 1 UID: 0 PID: 986 Comm: kworker/1:3 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Workqueue: events gfs2_withdraw_func
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
gfs2_withdraw_func+0x42/0x430 fs/gfs2/util.c:221
process_one_work kernel/workqueue.c:3263 [inline]
process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3346
worker_thread+0x8a0/0xda0 kernel/workqueue.c:3427
kthread+0x711/0x8a0 kernel/kthread.c:463
ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>

Allocated by task 6051:
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:397 [inline]
__kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:414
kasan_kmalloc include/linux/kasan.h:262 [inline]
__kmalloc_cache_noprof+0x3e2/0x700 mm/slub.c:5755
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+0x11c/0x2230 fs/gfs2/ops_fstype.c:1121
get_tree_bdev_flags+0x40e/0x4d0 fs/super.c:1691
gfs2_get_tree+0x51/0x1e0 fs/gfs2/ops_fstype.c:1333
vfs_get_tree+0x92/0x2b0 fs/super.c:1751
fc_mount fs/namespace.c:1208 [inline]
do_new_mount_fc fs/namespace.c:3651 [inline]
do_new_mount+0x302/0xa10 fs/namespace.c:3727
do_mount fs/namespace.c:4050 [inline]
__do_sys_mount fs/namespace.c:4238 [inline]
__se_sys_mount+0x313/0x410 fs/namespace.c:4215
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 6051:
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:584
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:2530 [inline]
slab_free mm/slub.c:6619 [inline]
kfree+0x19a/0x6d0 mm/slub.c:6826
free_sbd fs/gfs2/ops_fstype.c:72 [inline]
gfs2_fill_super+0x1552/0x2230 fs/gfs2/ops_fstype.c:1317
get_tree_bdev_flags+0x40e/0x4d0 fs/super.c:1691
gfs2_get_tree+0x51/0x1e0 fs/gfs2/ops_fstype.c:1333
vfs_get_tree+0x92/0x2b0 fs/super.c:1751
fc_mount fs/namespace.c:1208 [inline]
do_new_mount_fc fs/namespace.c:3651 [inline]
do_new_mount+0x302/0xa10 fs/namespace.c:3727
do_mount fs/namespace.c:4050 [inline]
__do_sys_mount fs/namespace.c:4238 [inline]
__se_sys_mount+0x313/0x410 fs/namespace.c:4215
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Last potentially related work creation:
kasan_save_stack+0x3e/0x60 mm/kasan/common.c:56
kasan_record_aux_stack+0xbd/0xd0 mm/kasan/generic.c:556
insert_work+0x3d/0x330 kernel/workqueue.c:2186
__queue_work+0xcd2/0xfb0 kernel/workqueue.c:2341
queue_work_on+0x181/0x270 kernel/workqueue.c:2392
gfs2_jdesc_check+0x17d/0x2f0 fs/gfs2/super.c:-1
check_journal_clean+0x158/0x310 fs/gfs2/util.c:69
init_journal+0x19b3/0x2180 fs/gfs2/ops_fstype.c:789
init_inodes+0xdb/0x320 fs/gfs2/ops_fstype.c:844
gfs2_fill_super+0x1a5d/0x2230 fs/gfs2/ops_fstype.c:1250
get_tree_bdev_flags+0x40e/0x4d0 fs/super.c:1691
gfs2_get_tree+0x51/0x1e0 fs/gfs2/ops_fstype.c:1333
vfs_get_tree+0x92/0x2b0 fs/super.c:1751
fc_mount fs/namespace.c:1208 [inline]
do_new_mount_fc fs/namespace.c:3651 [inline]
do_new_mount+0x302/0xa10 fs/namespace.c:3727
do_mount fs/namespace.c:4050 [inline]
__do_sys_mount fs/namespace.c:4238 [inline]
__se_sys_mount+0x313/0x410 fs/namespace.c:4215
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff888079a24000
which belongs to the cache kmalloc-8k of size 8192
The buggy address is located 840 bytes inside of
freed 8192-byte region [ffff888079a24000, ffff888079a26000)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x79a20
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88813fe27280 ffffea0001ee6e00 0000000000000002
raw: 0000000000000000 0000000080020002 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88813fe27280 ffffea0001ee6e00 0000000000000002
head: 0000000000000000 0000000080020002 00000000f5000000 0000000000000000
head: 00fff00000000003 ffffea0001e68801 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 5505, tgid 5505 (dhcpcd-run-hook), ts 56982616331, free_ts 56981166052
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x240/0x2a0 mm/page_alloc.c:1851
prep_new_page mm/page_alloc.c:1859 [inline]
get_page_from_freelist+0x2365/0x2440 mm/page_alloc.c:3920
__alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5214
alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2418
alloc_slab_page mm/slub.c:3046 [inline]
allocate_slab+0x96/0x3a0 mm/slub.c:3219
new_slab mm/slub.c:3273 [inline]
___slab_alloc+0xe94/0x18a0 mm/slub.c:4643
__slab_alloc+0x65/0x100 mm/slub.c:4762
__slab_alloc_node mm/slub.c:4838 [inline]
slab_alloc_node mm/slub.c:5260 [inline]
__kmalloc_cache_noprof+0x41e/0x700 mm/slub.c:5750
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+0x15cf/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:1341
search_binary_handler fs/exec.c:1660 [inline]
exec_binprm fs/exec.c:1702 [inline]
bprm_execve+0x8ee/0x1450 fs/exec.c:1754
do_execveat_common+0x510/0x6a0 fs/exec.c:1860
page last free pid 5505 tgid 5505 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
free_pages_prepare mm/page_alloc.c:1395 [inline]
__free_frozen_pages+0xbc8/0xd30 mm/page_alloc.c:2948
__slab_free+0x2e7/0x390 mm/slub.c:5954
qlink_free mm/kasan/quarantine.c:163 [inline]
qlist_free_all+0x97/0x140 mm/kasan/quarantine.c:179
kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286
__kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:349
kasan_slab_alloc include/linux/kasan.h:252 [inline]
slab_post_alloc_hook mm/slub.c:4962 [inline]
slab_alloc_node mm/slub.c:5272 [inline]
__kmalloc_cache_noprof+0x37c/0x700 mm/slub.c:5750
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+0x15cf/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:1341
search_binary_handler fs/exec.c:1660 [inline]
exec_binprm fs/exec.c:1702 [inline]
bprm_execve+0x8ee/0x1450 fs/exec.c:1754
do_execveat_common+0x510/0x6a0 fs/exec.c:1860
do_execve fs/exec.c:1934 [inline]
__do_sys_execve fs/exec.c:2010 [inline]
__se_sys_execve fs/exec.c:2005 [inline]
__x64_sys_execve+0x94/0xb0 fs/exec.c:2005
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94

Memory state around the buggy address:
ffff888079a24200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888079a24280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888079a24300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888079a24380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888079a24400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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