[moderation] [fs?] WARNING in chmod_common (5)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 1791c390149f Merge tag 'char-misc-7.0-rc7' of git://git.ke..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16f175da580000
kernel config: https://syzkaller.appspot.com/x/.config?x=d46eab0cfd31c214
dashboard link: https://syzkaller.appspot.com/bug?extid=86293893403f963dc291
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
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 (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-1791c390.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/b381e1a524fb/vmlinux-1791c390.xz
kernel image: https://storage.googleapis.com/syzbot-assets/de59bbdaba20/bzImage-1791c390.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+862938...@syzkaller.appspotmail.com

------------[ cut here ]------------
DEBUG_RWSEMS_WARN_ON((rwsem_owner(sem) != current) && !rwsem_test_oflags(sem, RWSEM_NONSPINNABLE)): count = 0x0, magic = 0xffff888046ff9b58, owner = 0x0, curr 0xffff88801cce0000, list empty
WARNING: kernel/locking/rwsem.c:1381 at __up_write kernel/locking/rwsem.c:1380 [inline], CPU#0: syz.0.0/5348
WARNING: kernel/locking/rwsem.c:1381 at up_write+0x2d6/0x410 kernel/locking/rwsem.c:1643, CPU#0: syz.0.0/5348
Modules linked in:
CPU: 0 UID: 0 PID: 5348 Comm: syz.0.0 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:__up_write kernel/locking/rwsem.c:1380 [inline]
RIP: 0010:up_write+0x388/0x410 kernel/locking/rwsem.c:1643
Code: cc 8b 49 c7 c2 a0 ec cc 8b 4c 0f 44 d0 48 8b 7c 24 08 48 c7 c6 00 ef cc 8b 48 8b 14 24 4c 89 f1 4d 89 e0 4c 8b 4c 24 10 41 52 <67> 48 0f b9 3a 48 83 c4 08 e8 6a 96 0c 03 e9 67 fd ff ff 48 c7 c1
RSP: 0018:ffffc9000a71fc20 EFLAGS: 00010246
RAX: ffffffff8bccec80 RBX: ffff888046ff9b58 RCX: ffff888046ff9b58
RDX: 0000000000000000 RSI: ffffffff8bccef00 RDI: ffffffff90154990
RBP: ffff888046ff9bb0 R08: 0000000000000000 R09: ffff88801cce0000
R10: ffffffff8bccec80 R11: ffffed1008dff36d R12: 0000000000000000
R13: dffffc0000000000 R14: ffff888046ff9b58 R15: 1ffff11008dff36c
FS: 00007f45a04746c0(0000) GS:ffff88808ca49000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f45a0473fe8 CR3: 0000000012a5b000 CR4: 0000000000352ef0
Call Trace:
<TASK>
inode_unlock include/linux/fs.h:1038 [inline]
chmod_common+0x27e/0x4a0 fs/open.c:642
do_fchmodat+0x12d/0x230 fs/open.c:684
__do_sys_fchmodat fs/open.c:703 [inline]
__se_sys_fchmodat fs/open.c:700 [inline]
__x64_sys_fchmodat+0x7d/0x90 fs/open.c:700
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f459f59c819
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f45a0473fe8 EFLAGS: 00000246 ORIG_RAX: 000000000000010c
RAX: ffffffffffffffda RBX: 00007f459f816180 RCX: 00007f459f59c819
RDX: 00000000000001ff RSI: 0000200000000300 RDI: ffffffffffffff9c
RBP: 00007f459f632c91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f459f816218 R14: 00007f459f816180 R15: 00007fff226bf148
</TASK>
----------------
Code disassembly (best guess):
0: cc int3
1: 8b 49 c7 mov -0x39(%rcx),%ecx
4: c2 a0 ec ret $0xeca0
7: cc int3
8: 8b 4c 0f 44 mov 0x44(%rdi,%rcx,1),%ecx
c: d0 48 8b rorb $1,-0x75(%rax)
f: 7c 24 jl 0x35
11: 08 48 c7 or %cl,-0x39(%rax)
14: c6 00 ef movb $0xef,(%rax)
17: cc int3
18: 8b 48 8b mov -0x75(%rax),%ecx
1b: 14 24 adc $0x24,%al
1d: 4c 89 f1 mov %r14,%rcx
20: 4d 89 e0 mov %r12,%r8
23: 4c 8b 4c 24 10 mov 0x10(%rsp),%r9
28: 41 52 push %r10
* 2a: 67 48 0f b9 3a ud1 (%edx),%rdi <-- trapping instruction
2f: 48 83 c4 08 add $0x8,%rsp
33: e8 6a 96 0c 03 call 0x30c96a2
38: e9 67 fd ff ff jmp 0xfffffda4
3d: 48 rex.W
3e: c7 .byte 0xc7
3f: c1 .byte 0xc1


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