[syzbot] INFO: task hung in io_sq_thread_park (3)

From: syzbot
Date: Fri Dec 03 2021 - 03:37:26 EST

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=17cbc8c5b00000
kernel config: https://syzkaller.appspot.com/x/.config?x=5b0eee8ab3ea1839
dashboard link: https://syzkaller.appspot.com/bug?extid=0fad9252b67f73124db9
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+0fad9252b67f73124db9@xxxxxxxxxxxxxxxxxxxxxxxxx

INFO: task kworker/u4:4:964 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:kworker/u4:4 state:D stack:23392 pid: 964 ppid: 2 flags:0x00004000
Workqueue: events_unbound io_ring_exit_work
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
io_sq_thread_park+0x83/0xc1 fs/io_uring.c:7985
io_ring_exit_work+0x132/0xbd0 fs/io_uring.c:9488
process_one_work+0x9b2/0x1690 kernel/workqueue.c:2298
worker_thread+0x658/0x11f0 kernel/workqueue.c:2445
kthread+0x405/0x4f0 kernel/kthread.c:327
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
</TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/27:
#0: ffffffff8bb83b60 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x53/0x260 kernel/locking/lockdep.c:6458
3 locks held by kworker/u4:4/964:
#0: ffff888010c69138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
#0: ffff888010c69138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: arch_atomic_long_set include/linux/atomic/atomic-long.h:41 [inline]
#0: ffff888010c69138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: atomic_long_set include/linux/atomic/atomic-instrumented.h:1198 [inline]
#0: ffff888010c69138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:635 [inline]
#0: ffff888010c69138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:662 [inline]
#0: ffff888010c69138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x896/0x1690 kernel/workqueue.c:2269
#1: ffffc9000469fdb0 ((work_completion)(&ctx->exit_work)){+.+.}-{0:0}, at: process_one_work+0x8ca/0x1690 kernel/workqueue.c:2273
#2: ffff888072ba4870 (&sqd->lock){+.+.}-{3:3}, at: io_sq_thread_park+0x83/0xc1 fs/io_uring.c:7985
1 lock held by in:imklog/6214:
#0: ffff888073710370 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0xe9/0x100 fs/file.c:990
4 locks held by iou-sqp-18541/18543:

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

NMI backtrace for cpu 0
CPU: 0 PID: 27 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: 2956 Comm: systemd-journal Not tainted 5.16.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:security_cred_free+0xae/0x130 security/security.c:1686
Code: 80 3c 28 00 75 67 48 8b 1b 48 85 db 75 cb e8 69 4b d8 fd 4c 89 ea 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 80 3c 02 00 75 6e <49> 8b ac 24 88 00 00 00 e8 45 4b d8 fd 48 89 ef e8 ed 6d 1e fe 4c
RSP: 0018:ffffc90001a4fde8 EFLAGS: 00000246
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 1ffff110039675f1 RSI: ffffffff839f5f57 RDI: ffff88801cb3af00
RBP: dffffc0000000000 R08: 0000000000000000 R09: ffff888010db4ab3
R10: ffffffff83a776d6 R11: 0000000000000000 R12: ffff88801cb3af00
R13: ffff88801cb3af88 R14: 0000000000000000 R15: 0000000000000000
FS: 00007fea3d76c8c0(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fea3abe6000 CR3: 000000007e621000 CR4: 0000000000350ee0
Call Trace:
<TASK>
put_cred_rcu+0x122/0x520 kernel/cred.c:115
__put_cred+0x1de/0x250 kernel/cred.c:151
put_cred include/linux/cred.h:288 [inline]
put_cred include/linux/cred.h:281 [inline]
revert_creds+0x1a8/0x1f0 kernel/cred.c:608
do_faccessat+0x2e7/0x850 fs/open.c:462
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: 0033:0x7fea3ca279c7
Code: 83 c4 08 48 3d 01 f0 ff ff 73 01 c3 48 8b 0d c8 d4 2b 00 f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 b8 15 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d a1 d4 2b 00 f7 d8 64 89 01 48
RSP: 002b:00007ffe79700ca8 EFLAGS: 00000246 ORIG_RAX: 0000000000000015
RAX: ffffffffffffffda RBX: 00007ffe79703cd0 RCX: 00007fea3ca279c7
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000561873cda9a3
RBP: 00007ffe79700df0 R08: 0000561873cd03e5 R09: 0000000000000018
R10: 0000000000000069 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 000056187561e8a0 R15: 00007ffe797012e0
</TASK>
----------------
Code disassembly (best guess):
0: 80 3c 28 00 cmpb $0x0,(%rax,%rbp,1)
4: 75 67 jne 0x6d
6: 48 8b 1b mov (%rbx),%rbx
9: 48 85 db test %rbx,%rbx
c: 75 cb jne 0xffffffd9
e: e8 69 4b d8 fd callq 0xfdd84b7c
13: 4c 89 ea mov %r13,%rdx
16: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
1d: fc ff df
20: 48 c1 ea 03 shr $0x3,%rdx
24: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1)
28: 75 6e jne 0x98
* 2a: 49 8b ac 24 88 00 00 mov 0x88(%r12),%rbp <-- trapping instruction
31: 00
32: e8 45 4b d8 fd callq 0xfdd84b7c
37: 48 89 ef mov %rbp,%rdi
3a: e8 ed 6d 1e fe callq 0xfe1e6e2c
3f: 4c rex.WR


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