syzbot
WARNING in do_new_mount (6)
Status:
moderation: reported on 2026/02/18 14:16
Subsystems:
fs
Labels:
prio:normal
[Documentation on labels]
Reported-by: syzbot+aa9301d3b66961eb2421@syzkaller.appspotmail.com
First crash: 163d, last: 3d00h
Sample crash report:
------------[ cut here ]------------
DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) != current)
WARNING: kernel/locking/rtmutex_common.h:193 at debug_rt_mutex_unlock kernel/locking/rtmutex_common.h:193 [inline], CPU#1: syz.5.194/6862
WARNING: kernel/locking/rtmutex_common.h:193 at rt_mutex_slowunlock+0x732/0xa20 kernel/locking/rtmutex.c:1432, CPU#1: syz.5.194/6862
Modules linked in:
CPU: 1 UID: 0 PID: 6862 Comm: syz.5.194 Not tainted syzkaller #0 PREEMPT_{RT,(full)}
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
RIP: 0010:debug_rt_mutex_unlock kernel/locking/rtmutex_common.h:193 [inline]
RIP: 0010:rt_mutex_slowunlock+0x739/0xa20 kernel/locking/rtmutex.c:1432
Code: af 8f 48 c1 e8 03 42 0f b6 04 20 84 c0 0f 85 cf 02 00 00 83 3d 1b 6c 6a 04 00 75 13 48 8d 3d de b1 6d 04 48 c7 c6 a0 0f 6d 8b <67> 48 0f b9 3a 90 e9 d1 f9 ff ff 48 8d 3d d5 b1 6d 04 67 48 0f b9
RSP: 0018:ffffc90007cafbc0 EFLAGS: 00010046
RAX: 0000000000000000 RBX: ffff888063189a68 RCX: 0000000000080000
RDX: ffffc9001d414000 RSI: ffffffff8b6d0fa0 RDI: ffffffff8fb2ed50
RBP: ffffc90007cafcb0 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: fffffbfff1f5f4f1 R12: dffffc0000000000
R13: 1ffff92000f95f80 R14: ffff888063189a18 R15: 0000000000000246
FS: 00007f04009e56c0(0000) GS:ffff888125d42000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f04009c3ff8 CR3: 0000000060940000 CR4: 00000000003526f0
Call Trace:
<TASK>
inode_unlock include/linux/fs.h:1034 [inline]
__unlock_mount fs/namespace.c:2808 [inline]
unlock_mount fs/namespace.c:2818 [inline]
do_new_mount_fc fs/namespace.c:3788 [inline]
do_new_mount+0x82d/0xdc0 fs/namespace.c:3841
do_mount fs/namespace.c:4174 [inline]
__do_sys_mount fs/namespace.c:4390 [inline]
__se_sys_mount+0x31d/0x420 fs/namespace.c:4367
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f04027ade99
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:00007f04009e5028 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f0402a36090 RCX: 00007f04027ade99
RDX: 0000200000000300 RSI: 0000200000000200 RDI: 0000200000000100
RBP: 00007f0402843eaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f0402a36128 R14: 00007f0402a36090 R15: 00007ffc37ffdef8
</TASK>
----------------
Code disassembly (best guess), 2 bytes skipped:
0: 48 c1 e8 03 shr $0x3,%rax
4: 42 0f b6 04 20 movzbl (%rax,%r12,1),%eax
9: 84 c0 test %al,%al
b: 0f 85 cf 02 00 00 jne 0x2e0
11: 83 3d 1b 6c 6a 04 00 cmpl $0x0,0x46a6c1b(%rip) # 0x46a6c33
18: 75 13 jne 0x2d
1a: 48 8d 3d de b1 6d 04 lea 0x46db1de(%rip),%rdi # 0x46db1ff
21: 48 c7 c6 a0 0f 6d 8b mov $0xffffffff8b6d0fa0,%rsi
* 28: 67 48 0f b9 3a ud1 (%edx),%rdi <-- trapping instruction
2d: 90 nop
2e: e9 d1 f9 ff ff jmp 0xfffffa04
33: 48 8d 3d d5 b1 6d 04 lea 0x46db1d5(%rip),%rdi # 0x46db20f
3a: 67 addr32
3b: 48 rex.W
3c: 0f .byte 0xf
3d: b9 .byte 0xb9
* Struck through repros no longer work on HEAD.