syzbot
WARNING: kobject bug in __dlm_new_lockspace
Status:
moderation: reported on 2026/08/05 05:59
Subsystems:
gfs2
Labels:
prio:low
[Documentation on labels]
Reported-by: syzbot+fdbfc0c2425fb3e2280b@syzkaller.appspotmail.com
First crash: 16d, last: 3d12h
Sample crash report:
workqueue: Failed to create a rescuer kthread for wq "dlm_callback": -EINTR
dlm: can't start dlm_callback workqueue
dlm: V: can't start dlm_callback -12
------------[ cut here ]------------
kobject: '(null)' (ffff8880351ac0c8): is not initialized, yet kobject_put() is being called.
WARNING: lib/kobject.c:736 at kobject_put+0x66/0x550 lib/kobject.c:734, CPU#0: syz.4.3091/15032
Modules linked in:
CPU: 0 UID: 0 PID: 15032 Comm: syz.4.3091 Not tainted syzkaller #0 PREEMPT_{RT,(full)}
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:kobject_put+0x8e/0x550 lib/kobject.c:734
Code: 87 04 48 89 d8 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df 80 3c 08 00 74 08 48 89 df e8 0b 10 f5 f6 48 8b 33 4c 89 f7 48 89 da <67> 48 0f b9 3a eb 05 e8 76 99 8b f6 4c 8d 73 38 4c 89 f7 be 04 00
RSP: 0018:ffffc90004c879f0 EFLAGS: 00010246
RAX: 1ffff11006a35819 RBX: ffff8880351ac0c8 RCX: dffffc0000000000
RDX: ffff8880351ac0c8 RSI: 0000000000000000 RDI: ffffffff8fc15d10
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: fffffbfff1f5e9e7 R12: 1ffff11006a35820
R13: 00000000fffffff4 R14: ffffffff8fc15d10 R15: ffff8880351ac000
FS: 00007f59e1db66c0(0000) GS:ffff888125c45000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005561988f700b CR3: 0000000032e90000 CR4: 00000000003526f0
Call Trace:
<TASK>
new_lockspace fs/dlm/lockspace.c:617 [inline]
__dlm_new_lockspace+0x19f0/0x2060 fs/dlm/lockspace.c:638
device_create_lockspace+0xc7/0x350 fs/dlm/user.c:414
device_write+0x875/0xed0 fs/dlm/user.c:606
vfs_write+0x29f/0xbb0 fs/read_write.c:685
ksys_write+0x156/0x270 fs/read_write.c:739
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: 0033:0x7f59e3b5e0d9
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:00007f59e1db6028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f59e3de5fa0 RCX: 00007f59e3b5e0d9
RDX: 0000000000000070 RSI: 0000200000001380 RDI: 0000000000000003
RBP: 00007f59e3bf5024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f59e3de6038 R14: 00007f59e3de5fa0 R15: 00007ffe21b3da38
</TASK>
----------------
Code disassembly (best guess):
0: 87 04 48 xchg %eax,(%rax,%rcx,2)
3: 89 d8 mov %ebx,%eax
5: 48 c1 e8 03 shr $0x3,%rax
9: 48 b9 00 00 00 00 00 movabs $0xdffffc0000000000,%rcx
10: fc ff df
13: 80 3c 08 00 cmpb $0x0,(%rax,%rcx,1)
17: 74 08 je 0x21
19: 48 89 df mov %rbx,%rdi
1c: e8 0b 10 f5 f6 call 0xf6f5102c
21: 48 8b 33 mov (%rbx),%rsi
24: 4c 89 f7 mov %r14,%rdi
27: 48 89 da mov %rbx,%rdx
* 2a: 67 48 0f b9 3a ud1 (%edx),%rdi <-- trapping instruction
2f: eb 05 jmp 0x36
31: e8 76 99 8b f6 call 0xf68b99ac
36: 4c 8d 73 38 lea 0x38(%rbx),%r14
3a: 4c 89 f7 mov %r14,%rdi
3d: be .byte 0xbe
3e: 04 00 add $0x0,%al
* Struck through repros no longer work on HEAD.