[moderation] [fs?] WARNING in cleanup_mnt (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 33e02dc69afb Merge tag 'sound-6.10-rc1' of git://git.kerne..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1306ddb8980000
kernel config: https://syzkaller.appspot.com/x/.config?x=39878f1ce91ccfda
dashboard link: https://syzkaller.appspot.com/bug?extid=96de35645722f82062b1
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: i386
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 (non-bootable): https://storage.googleapis.com/syzbot-assets/7bc7510fe41f/non_bootable_disk-33e02dc6.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a7597d9cd2b5/vmlinux-33e02dc6.xz
kernel image: https://storage.googleapis.com/syzbot-assets/93cadb45c580/bzImage-33e02dc6.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+96de35...@syzkaller.appspotmail.com

------------[ cut here ]------------
WARNING: CPU: 1 PID: 5232 at fs/namespace.c:1258 cleanup_mnt+0x397/0x450 fs/namespace.c:1258
Modules linked in:
CPU: 1 PID: 5232 Comm: syz-executor.3 Not tainted 6.9.0-syzkaller-07370-g33e02dc69afb #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:cleanup_mnt+0x397/0x450 fs/namespace.c:1258
Code: 03 38 d0 7c 08 84 d2 0f 85 b1 00 00 00 c7 83 3c 01 00 00 00 00 00 00 48 89 df e8 f4 ee ff ff e9 34 fe ff ff e8 3a 09 89 ff 90 <0f> 0b 90 e9 8e fc ff ff e8 2c 09 89 ff 4c 89 ef e8 a4 09 07 00 e9
RSP: 0018:ffffc9000329fe18 EFLAGS: 00010293
RAX: 0000000000000000 RBX: 0000000000000001 RCX: ffffffff82059ec5
RDX: ffff88801f41c880 RSI: ffffffff8205a236 RDI: 0000000000000005
RBP: 0000000000000000 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: ffff88801f41d1e8
R13: ffff888027057a40 R14: ffffed1003e83a3d R15: ffff888027057a80
FS: 0000000000000000(0000) GS:ffff88802c100000(0063) knlGS:0000000056d15400
CS: 0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 000000c0010c6000 CR3: 000000004c32c000 CR4: 0000000000350ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
task_work_run+0x14e/0x250 kernel/task_work.c:180
resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
exit_to_user_mode_loop kernel/entry/common.c:114 [inline]
exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
__syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
syscall_exit_to_user_mode+0x278/0x2a0 kernel/entry/common.c:218
__do_fast_syscall_32+0x82/0x120 arch/x86/entry/common.c:389
do_fast_syscall_32+0x32/0x80 arch/x86/entry/common.c:411
entry_SYSENTER_compat_after_hwframe+0x84/0x8e
RIP: 0023:0xf72a3579
Code: b8 01 10 06 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 00 00 00 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 8d b4 26 00 00 00 00 8d b4 26 00 00 00 00
RSP: 002b:00000000ffe57518 EFLAGS: 00000292 ORIG_RAX: 0000000000000034
RAX: 0000000000000000 RBX: 00000000ffe575c0 RCX: 0000000000000009
RDX: 00000000f73f9ff4 RSI: 00000000f734a361 RDI: 00000000ffe58664
RBP: 00000000ffe575c0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000292 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
</TASK>
----------------
Code disassembly (best guess), 2 bytes skipped:
0: 10 06 adc %al,(%rsi)
2: 03 74 b4 01 add 0x1(%rsp,%rsi,4),%esi
6: 10 07 adc %al,(%rdi)
8: 03 74 b0 01 add 0x1(%rax,%rsi,4),%esi
c: 10 08 adc %cl,(%rax)
e: 03 74 d8 01 add 0x1(%rax,%rbx,8),%esi
1e: 00 51 52 add %dl,0x52(%rcx)
21: 55 push %rbp
22: 89 e5 mov %esp,%ebp
24: 0f 34 sysenter
26: cd 80 int $0x80
* 28: 5d pop %rbp <-- trapping instruction
29: 5a pop %rdx
2a: 59 pop %rcx
2b: c3 ret
2c: 90 nop
2d: 90 nop
2e: 90 nop
2f: 90 nop
30: 8d b4 26 00 00 00 00 lea 0x0(%rsi,%riz,1),%esi
37: 8d b4 26 00 00 00 00 lea 0x0(%rsi,%riz,1),%esi


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