[syzbot] INFO: task hung in io_uring_register

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 58e1100fdc59 MAINTAINERS: co-maintain random.c
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1221a1adb00000
kernel config: https://syzkaller.appspot.com/x/.config?x=5b0eee8ab3ea1839
dashboard link: https://syzkaller.appspot.com/bug?extid=7daefdd84ee7b8170aa6
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+7daefd...@syzkaller.appspotmail.com

INFO: task syz-executor.5:3737 blocked for more than 143 seconds.
Not tainted 5.16.0-rc3-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor.5 state:D stack:29592 pid: 3737 ppid: 7406 flags:0x00000004
Call Trace:
<TASK>
context_switch kernel/sched/core.c:4972 [inline]
__schedule+0xa9a/0x4940 kernel/sched/core.c:6253
schedule+0xd2/0x260 kernel/sched/core.c:6326
schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6385
__mutex_lock_common kernel/locking/mutex.c:680 [inline]
__mutex_lock+0xa32/0x12f0 kernel/locking/mutex.c:740
__do_sys_io_uring_register+0x2e0/0x15a0 fs/io_uring.c:11087
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f8f023f9ae9
RSP: 002b:00007f8eff94e188 EFLAGS: 00000246 ORIG_RAX: 00000000000001ab
RAX: ffffffffffffffda RBX: 00007f8f0250d020 RCX: 00007f8f023f9ae9
RDX: 0000000000000000 RSI: 0000000000000009 RDI: 0000000000000003
RBP: 00007f8f02453f6d R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f8f02a40b2f R14: 00007f8eff94e300 R15: 0000000000022000
</TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/26:
#0: ffffffff8bb83b60 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x53/0x260 kernel/locking/lockdep.c:6458
4 locks held by kworker/1:1/35:
#0: ffff8880b9c39a98 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested kernel/sched/core.c:486 [inline]
#0: ffff8880b9c39a98 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x8c/0x120 kernel/sched/core.c:471
#1: ffff8880b9d279c8 (&per_cpu_ptr(group->pcpu, cpu)->seq){-.-.}-{0:0}, at: psi_task_switch+0x3a6/0x490 kernel/sched/psi.c:880
#2: ffff8880b9d28298 (&base->lock){-.-.}-{2:2}, at: lock_timer_base+0x5a/0x1f0 kernel/time/timer.c:946
#3: ffffffff9064b2c8 (&obj_hash[i].lock){-.-.}-{2:2}, at: debug_object_activate+0x12e/0x3e0 lib/debugobjects.c:661
1 lock held by in:imklog/6232:
#0: ffff88807b8334f0 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0xe9/0x100 fs/file.c:990
2 locks held by kworker/u4:11/22134:
1 lock held by syz-executor.5/3735:
1 lock held by syz-executor.5/3737:
#0: ffff888073e690a8 (&ctx->uring_lock){+.+.}-{3:3}, at: __do_sys_io_uring_register+0x2e0/0x15a0 fs/io_uring.c:11087
1 lock held by syz-executor.5/3780:
#0: ffff88807c96d0a8 (&ctx->uring_lock){+.+.}-{3:3}, at: io_uring_del_tctx_node+0x109/0x20a fs/io_uring.c:9777
1 lock held by syz-executor.5/3782:

=============================================

NMI backtrace for cpu 0
CPU: 0 PID: 26 Comm: khungtaskd Not tainted 5.16.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
nmi_cpu_backtrace.cold+0x47/0x144 lib/nmi_backtrace.c:111
nmi_trigger_cpumask_backtrace+0x1b3/0x230 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:210 [inline]
watchdog+0xc1d/0xf50 kernel/hung_task.c:295
kthread+0x405/0x4f0 kernel/kthread.c:327
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
</TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 6232 Comm: in:imklog Not tainted 5.16.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:__switch_to_asm+0x2a/0x40 arch/x86/entry/entry_64.S:259
Code: 55 53 41 54 41 55 41 56 41 57 48 89 a7 98 17 00 00 48 8b a6 98 17 00 00 48 8b 9e d0 05 00 00 65 48 89 1c 25 28 00 00 00 41 5f <41> 5e 41 5d 41 5c 5b 5d e9 19 97 28 00 66 0f 1f 84 00 00 00 00 00
RSP: 0018:ffffc90001adfa40 EFLAGS: 00000046
RAX: dffffc0000000000 RBX: 38aea85631ad7d00 RCX: ffffc900081e7930
RDX: 1ffff11017387352 RSI: ffff888017d13a00 RDI: ffff88807f371d00
RBP: ffffc900081e7ac0 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 000000000000003f R12: ffff888017d13a00
R13: ffff8880b9c39a80 R14: ffff88807f372218 R15: ffff88801a3abf10
FS: 00007f1dbd29c700(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fe56da98000 CR3: 0000000018b09000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
----------------
Code disassembly (best guess):
0: 55 push %rbp
1: 53 push %rbx
2: 41 54 push %r12
4: 41 55 push %r13
6: 41 56 push %r14
8: 41 57 push %r15
a: 48 89 a7 98 17 00 00 mov %rsp,0x1798(%rdi)
11: 48 8b a6 98 17 00 00 mov 0x1798(%rsi),%rsp
18: 48 8b 9e d0 05 00 00 mov 0x5d0(%rsi),%rbx
1f: 65 48 89 1c 25 28 00 mov %rbx,%gs:0x28
26: 00 00
28: 41 5f pop %r15
* 2a: 41 5e pop %r14 <-- trapping instruction
2c: 41 5d pop %r13
2e: 41 5c pop %r12
30: 5b pop %rbx
31: 5d pop %rbp
32: e9 19 97 28 00 jmpq 0x289750
37: 66 0f 1f 84 00 00 00 nopw 0x0(%rax,%rax,1)
3e: 00 00


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.