INFO: task can't die in io_uring_setup

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 4442749a Add linux-next specific files for 20200902
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=138e7285900000
kernel config: https://syzkaller.appspot.com/x/.config?x=39134fcec6c78e33
dashboard link: https://syzkaller.appspot.com/bug?extid=3227d097b95b4207b570
compiler: gcc (GCC) 10.1.0-syz 20200507
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15306279900000

The issue was bisected to:

commit dfe127799f8e663c7e3e48b5275ca538b278177b
Author: Stefano Garzarella <sgar...@redhat.com>
Date: Thu Aug 27 14:58:31 2020 +0000

io_uring: allow disabling rings during the creation

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=15b09115900000
final oops: https://syzkaller.appspot.com/x/report.txt?x=17b09115900000
console output: https://syzkaller.appspot.com/x/log.txt?x=13b09115900000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+3227d0...@syzkaller.appspotmail.com
Fixes: dfe127799f8e ("io_uring: allow disabling rings during the creation")

INFO: task syz-executor.0:28543 can't die for more than 143 seconds.
task:syz-executor.0 state:D stack:28824 pid:28543 ppid: 6864 flags:0x00004004
Call Trace:
context_switch kernel/sched/core.c:3777 [inline]
__schedule+0xea9/0x2230 kernel/sched/core.c:4526
schedule+0xd0/0x2a0 kernel/sched/core.c:4601
schedule_timeout+0x1d8/0x250 kernel/time/timer.c:1855
do_wait_for_common kernel/sched/completion.c:85 [inline]
__wait_for_common kernel/sched/completion.c:106 [inline]
wait_for_common kernel/sched/completion.c:117 [inline]
wait_for_completion+0x163/0x260 kernel/sched/completion.c:138
io_sq_thread_stop fs/io_uring.c:6906 [inline]
io_finish_async fs/io_uring.c:6920 [inline]
io_sq_offload_create fs/io_uring.c:7595 [inline]
io_uring_create fs/io_uring.c:8671 [inline]
io_uring_setup+0x1495/0x29a0 fs/io_uring.c:8744
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45d5b9
Code: Bad RIP value.
RSP: 002b:00007fde24a51bf8 EFLAGS: 00000206 ORIG_RAX: 00000000000001a9
RAX: ffffffffffffffda RBX: 0000000020000240 RCX: 000000000045d5b9
RDX: 00000000206d5000 RSI: 0000000020000240 RDI: 0000000000007e71
RBP: 000000000118cf98 R08: 0000000020000100 R09: 0000000020000100
R10: 0000000000000000 R11: 0000000000000206 R12: 00000000206d5000
R13: 00000000206d4000 R14: 0000000020000100 R15: 0000000000000000
INFO: task syz-executor.0:28543 blocked for more than 143 seconds.
Not tainted 5.9.0-rc3-next-20200902-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor.0 state:D stack:28824 pid:28543 ppid: 6864 flags:0x00004004
Call Trace:
context_switch kernel/sched/core.c:3777 [inline]
__schedule+0xea9/0x2230 kernel/sched/core.c:4526
schedule+0xd0/0x2a0 kernel/sched/core.c:4601
schedule_timeout+0x1d8/0x250 kernel/time/timer.c:1855
do_wait_for_common kernel/sched/completion.c:85 [inline]
__wait_for_common kernel/sched/completion.c:106 [inline]
wait_for_common kernel/sched/completion.c:117 [inline]
wait_for_completion+0x163/0x260 kernel/sched/completion.c:138
io_sq_thread_stop fs/io_uring.c:6906 [inline]
io_finish_async fs/io_uring.c:6920 [inline]
io_sq_offload_create fs/io_uring.c:7595 [inline]
io_uring_create fs/io_uring.c:8671 [inline]
io_uring_setup+0x1495/0x29a0 fs/io_uring.c:8744
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45d5b9
Code: Bad RIP value.
RSP: 002b:00007fde24a51bf8 EFLAGS: 00000206 ORIG_RAX: 00000000000001a9
RAX: ffffffffffffffda RBX: 0000000020000240 RCX: 000000000045d5b9
RDX: 00000000206d5000 RSI: 0000000020000240 RDI: 0000000000007e71
RBP: 000000000118cf98 R08: 0000000020000100 R09: 0000000020000100
R10: 0000000000000000 R11: 0000000000000206 R12: 00000000206d5000
R13: 00000000206d4000 R14: 0000000020000100 R15: 0000000000000000
INFO: task io_uring-sq:28548 blocked for more than 143 seconds.
Not tainted 5.9.0-rc3-next-20200902-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:io_uring-sq state:D stack:31120 pid:28548 ppid: 2 flags:0x00004000
Call Trace:
context_switch kernel/sched/core.c:3777 [inline]
__schedule+0xea9/0x2230 kernel/sched/core.c:4526
schedule+0xd0/0x2a0 kernel/sched/core.c:4601
schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:4660
kthread+0x2ac/0x4a0 kernel/kthread.c:285
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

Showing all locks held in the system:
1 lock held by khungtaskd/1174:
#0: ffffffff89c67980 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x53/0x260 kernel/locking/lockdep.c:5829

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

NMI backtrace for cpu 1
CPU: 1 PID: 1174 Comm: khungtaskd Not tainted 5.9.0-rc3-next-20200902-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x198/0x1fd lib/dump_stack.c:118
nmi_cpu_backtrace.cold+0x44/0xd7 lib/nmi_backtrace.c:105
nmi_trigger_cpumask_backtrace+0x1b3/0x223 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:147 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:253 [inline]
watchdog+0xd89/0xf30 kernel/hung_task.c:339
kthread+0x3b5/0x4a0 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 3906 Comm: systemd-journal Not tainted 5.9.0-rc3-next-20200902-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:arch_static_branch arch/x86/include/asm/jump_label.h:25 [inline]
RIP: 0010:static_key_false include/linux/jump_label.h:200 [inline]
RIP: 0010:trace_irq_disable_rcuidle include/trace/events/preemptirq.h:36 [inline]
RIP: 0010:trace_hardirqs_off kernel/trace/trace_preemptirq.c:82 [inline]
RIP: 0010:trace_hardirqs_off+0x6c/0x210 kernel/trace/trace_preemptirq.c:74
Code: 81 e3 00 00 f0 00 31 ff 89 de e8 9f 37 fa ff 85 db 74 0d 5b 5d 41 5c 41 5d 41 5e e9 0e 3b fa ff e8 09 3b fa ff 4c 8b 6c 24 28 <0f> 1f 44 00 00 e8 fa 3a fa ff eb dd e8 f3 3a fa ff 65 8b 1d bc fe
RSP: 0018:ffffc90005357f00 EFLAGS: 00000093
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff817a9471
RDX: ffff888092cbe500 RSI: ffffffff817a9487 RDI: 0000000000000005
RBP: ffffc90005357f58 R08: 0000000000000001 R09: ffff888092cbee08
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: ffffffff87f9c83e R14: 0000000000000000 R15: 0000000000000000
FS: 00007f7fd426b8c0(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f7fd161d000 CR3: 00000000933ac000 CR4: 00000000001506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
local_irq_disable_exit_to_user include/linux/entry-common.h:166 [inline]
syscall_exit_to_user_mode+0xae/0x2e0 kernel/entry/common.c:241
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7f7fd3504f17
Code: ff ff ff 48 8b 4d a0 0f b7 51 fe 48 8b 4d a8 66 89 54 08 fe e9 1a ff ff ff 66 2e 0f 1f 84 00 00 00 00 00 b8 27 00 00 00 0f 05 <c3> 0f 1f 84 00 00 00 00 00 b8 6e 00 00 00 0f 05 c3 0f 1f 84 00 00
RSP: 002b:00007ffc0a1045c8 EFLAGS: 00000206 ORIG_RAX: 0000000000000027
RAX: 0000000000000f42 RBX: 000055ca0d4b51e0 RCX: 00007f7fd3504f17
RDX: 00007ffc0a104688 RSI: 0000000000000001 RDI: 000055ca0d4b51e0
RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000069 R11: 0000000000000206 R12: 00007ffc0a104688
R13: 0000000000000f42 R14: 00007ffc0a107470 R15: 00007ffc0a104a80


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[Jens Axboe]

This very much looks like a dupe of the issue that Hillf already
fixed, but as there's no C reproducer yet, I can't verify.

--
Jens Axboe

[syzbot]

Auto-closing this bug as obsolete.
No recent activity, existing reproducers are no longer triggering the issue.