[moderation] [fs?] KASAN: null-ptr-deref Write in d_delete_notify

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 7d31f578f323 Add linux-next specific files for 20251128
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=110bc112580000
kernel config: https://syzkaller.appspot.com/x/.config?x=6336d8e94a7c517d
dashboard link: https://syzkaller.appspot.com/bug?extid=cc864ee4e028e41b567d
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
CC: [bra...@kernel.org ja...@suse.cz linux-...@vger.kernel.org linux-...@vger.kernel.org vi...@zeniv.linux.org.uk]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/6b49d8ad90de/disk-7d31f578.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/dbe2d4988ca7/vmlinux-7d31f578.xz
kernel image: https://storage.googleapis.com/syzbot-assets/fc0448ab2411/bzImage-7d31f578.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+cc864e...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: null-ptr-deref in instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
BUG: KASAN: null-ptr-deref in atomic_inc_return include/linux/atomic/atomic-instrumented.h:453 [inline]
BUG: KASAN: null-ptr-deref in ihold+0x1f/0x60 fs/inode.c:529
Write of size 4 at addr 0000000000000200 by task syz.6.969/10547

CPU: 1 UID: 0 PID: 10547 Comm: syz.6.969 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
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_write include/linux/instrumented.h:96 [inline]
atomic_inc_return include/linux/atomic/atomic-instrumented.h:453 [inline]
ihold+0x1f/0x60 fs/inode.c:529
d_delete_notify+0x46/0x190 include/linux/fsnotify.h:374
vfs_unlink+0x435/0x640 fs/namei.c:5384
__do_sys_mq_unlink ipc/mqueue.c:969 [inline]
__se_sys_mq_unlink+0x2b2/0x360 ipc/mqueue.c:944
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
RIP: 0033:0x7f6ede38f749
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f6edc5b4038 EFLAGS: 00000246 ORIG_RAX: 00000000000000f1
RAX: ffffffffffffffda RBX: 00007f6ede5e6180 RCX: 00007f6ede38f749
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000200000000000
RBP: 00007f6ede413f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f6ede5e6218 R14: 00007f6ede5e6180 R15: 00007ffdc96a7d68
</TASK>
==================================================================


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