public inbox for [email protected]
 help / color / mirror / Atom feed
* [syzbot] possible deadlock in __io_commit_cqring_flush
@ 2021-11-26 12:40 syzbot
  2021-11-26 14:28 ` Pavel Begunkov
  0 siblings, 1 reply; 2+ messages in thread
From: syzbot @ 2021-11-26 12:40 UTC (permalink / raw)
  To: asml.silence, axboe, io-uring, linux-kernel, syzkaller-bugs

Hello,

syzbot found the following issue on:

HEAD commit:    a4849f6000e2 Merge tag 'drm-fixes-2021-11-26' of git://ano..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10d5f726b00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=75f05fb8d1a152d3
dashboard link: https://syzkaller.appspot.com/bug?extid=ff49a3059d49b0ca0eec
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: [email protected]

============================================
WARNING: possible recursive locking detected
5.16.0-rc2-syzkaller #0 Not tainted
--------------------------------------------
syz-executor.1/8766 is trying to acquire lock:
ffff888096b57418 (&ctx->timeout_lock){+.+.}-{2:2}, at: spin_lock_irq include/linux/spinlock.h:374 [inline]
ffff888096b57418 (&ctx->timeout_lock){+.+.}-{2:2}, at: io_flush_timeouts fs/io_uring.c:1587 [inline]
ffff888096b57418 (&ctx->timeout_lock){+.+.}-{2:2}, at: __io_commit_cqring_flush+0x108/0x50d fs/io_uring.c:1618

but task is already holding lock:
ffff888096b57418 (&ctx->timeout_lock){+.+.}-{2:2}, at: spin_lock_irq include/linux/spinlock.h:374 [inline]
ffff888096b57418 (&ctx->timeout_lock){+.+.}-{2:2}, at: io_poll_remove_all+0x50/0x235 fs/io_uring.c:5702

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(&ctx->timeout_lock);
  lock(&ctx->timeout_lock);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

2 locks held by syz-executor.1/8766:
 #0: ffff888096b573d8 (&ctx->completion_lock#2){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:349 [inline]
 #0: ffff888096b573d8 (&ctx->completion_lock#2){+.+.}-{2:2}, at: io_poll_remove_all+0x48/0x235 fs/io_uring.c:5701
 #1: ffff888096b57418 (&ctx->timeout_lock){+.+.}-{2:2}, at: spin_lock_irq include/linux/spinlock.h:374 [inline]
 #1: ffff888096b57418 (&ctx->timeout_lock){+.+.}-{2:2}, at: io_poll_remove_all+0x50/0x235 fs/io_uring.c:5702

stack backtrace:
CPU: 0 PID: 8766 Comm: syz-executor.1 Not tainted 5.16.0-rc2-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
 print_deadlock_bug kernel/locking/lockdep.c:2956 [inline]
 check_deadlock kernel/locking/lockdep.c:2999 [inline]
 validate_chain kernel/locking/lockdep.c:3788 [inline]
 __lock_acquire.cold+0x149/0x3ab kernel/locking/lockdep.c:5027
 lock_acquire kernel/locking/lockdep.c:5637 [inline]
 lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5602
 __raw_spin_lock_irq include/linux/spinlock_api_smp.h:119 [inline]
 _raw_spin_lock_irq+0x32/0x50 kernel/locking/spinlock.c:170
 spin_lock_irq include/linux/spinlock.h:374 [inline]
 io_flush_timeouts fs/io_uring.c:1587 [inline]
 __io_commit_cqring_flush+0x108/0x50d fs/io_uring.c:1618
 io_commit_cqring fs/io_uring.c:1626 [inline]
 io_poll_remove_one fs/io_uring.c:5684 [inline]
 io_poll_remove_one.cold+0xd/0x12 fs/io_uring.c:5674
 io_poll_remove_all+0x1af/0x235 fs/io_uring.c:5709
 io_ring_ctx_wait_and_kill+0x1cc/0x322 fs/io_uring.c:9534
 io_uring_release+0x42/0x46 fs/io_uring.c:9554
 __fput+0x286/0x9f0 fs/file_table.c:280
 task_work_run+0xdd/0x1a0 kernel/task_work.c:164
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:175 [inline]
 exit_to_user_mode_prepare+0x27e/0x290 kernel/entry/common.c:207
 __syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
 syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:300
 do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f087b422ae9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f0878977188 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
RAX: 0000000020ffa000 RBX: 00007f087b536020 RCX: 00007f087b422ae9
RDX: 0000000003000001 RSI: 0000000000004000 RDI: 0000000020ffa000
RBP: 00007f087b47cf6d R08: 0000000000000003 R09: 0000000010000000
R10: 0000000000000012 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffe7626bd9f R14: 00007f0878977300 R15: 0000000000022000
 </TASK>


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at [email protected].

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

^ permalink raw reply	[flat|nested] 2+ messages in thread

* Re: [syzbot] possible deadlock in __io_commit_cqring_flush
  2021-11-26 12:40 [syzbot] possible deadlock in __io_commit_cqring_flush syzbot
@ 2021-11-26 14:28 ` Pavel Begunkov
  0 siblings, 0 replies; 2+ messages in thread
From: Pavel Begunkov @ 2021-11-26 14:28 UTC (permalink / raw)
  To: syzbot, axboe, io-uring, linux-kernel, syzkaller-bugs

On 11/26/21 12:40, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:

#syz dup: possible deadlock in io_flush_timeouts

> 
> HEAD commit:    a4849f6000e2 Merge tag 'drm-fixes-2021-11-26' of git://ano..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=10d5f726b00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=75f05fb8d1a152d3
> dashboard link: https://syzkaller.appspot.com/bug?extid=ff49a3059d49b0ca0eec
> 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: [email protected]
> 
> ============================================
> WARNING: possible recursive locking detected
> 5.16.0-rc2-syzkaller #0 Not tainted
> --------------------------------------------
> syz-executor.1/8766 is trying to acquire lock:
> ffff888096b57418 (&ctx->timeout_lock){+.+.}-{2:2}, at: spin_lock_irq include/linux/spinlock.h:374 [inline]
> ffff888096b57418 (&ctx->timeout_lock){+.+.}-{2:2}, at: io_flush_timeouts fs/io_uring.c:1587 [inline]
> ffff888096b57418 (&ctx->timeout_lock){+.+.}-{2:2}, at: __io_commit_cqring_flush+0x108/0x50d fs/io_uring.c:1618
> 
> but task is already holding lock:
> ffff888096b57418 (&ctx->timeout_lock){+.+.}-{2:2}, at: spin_lock_irq include/linux/spinlock.h:374 [inline]
> ffff888096b57418 (&ctx->timeout_lock){+.+.}-{2:2}, at: io_poll_remove_all+0x50/0x235 fs/io_uring.c:5702
> 
> other info that might help us debug this:
>   Possible unsafe locking scenario:
> 
>         CPU0
>         ----
>    lock(&ctx->timeout_lock);
>    lock(&ctx->timeout_lock);
> 
>   *** DEADLOCK ***
> 
>   May be due to missing lock nesting notation
> 
> 2 locks held by syz-executor.1/8766:
>   #0: ffff888096b573d8 (&ctx->completion_lock#2){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:349 [inline]
>   #0: ffff888096b573d8 (&ctx->completion_lock#2){+.+.}-{2:2}, at: io_poll_remove_all+0x48/0x235 fs/io_uring.c:5701
>   #1: ffff888096b57418 (&ctx->timeout_lock){+.+.}-{2:2}, at: spin_lock_irq include/linux/spinlock.h:374 [inline]
>   #1: ffff888096b57418 (&ctx->timeout_lock){+.+.}-{2:2}, at: io_poll_remove_all+0x50/0x235 fs/io_uring.c:5702
> 
> stack backtrace:
> CPU: 0 PID: 8766 Comm: syz-executor.1 Not tainted 5.16.0-rc2-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
>   print_deadlock_bug kernel/locking/lockdep.c:2956 [inline]
>   check_deadlock kernel/locking/lockdep.c:2999 [inline]
>   validate_chain kernel/locking/lockdep.c:3788 [inline]
>   __lock_acquire.cold+0x149/0x3ab kernel/locking/lockdep.c:5027
>   lock_acquire kernel/locking/lockdep.c:5637 [inline]
>   lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5602
>   __raw_spin_lock_irq include/linux/spinlock_api_smp.h:119 [inline]
>   _raw_spin_lock_irq+0x32/0x50 kernel/locking/spinlock.c:170
>   spin_lock_irq include/linux/spinlock.h:374 [inline]
>   io_flush_timeouts fs/io_uring.c:1587 [inline]
>   __io_commit_cqring_flush+0x108/0x50d fs/io_uring.c:1618
>   io_commit_cqring fs/io_uring.c:1626 [inline]
>   io_poll_remove_one fs/io_uring.c:5684 [inline]
>   io_poll_remove_one.cold+0xd/0x12 fs/io_uring.c:5674
>   io_poll_remove_all+0x1af/0x235 fs/io_uring.c:5709
>   io_ring_ctx_wait_and_kill+0x1cc/0x322 fs/io_uring.c:9534
>   io_uring_release+0x42/0x46 fs/io_uring.c:9554
>   __fput+0x286/0x9f0 fs/file_table.c:280
>   task_work_run+0xdd/0x1a0 kernel/task_work.c:164
>   tracehook_notify_resume include/linux/tracehook.h:189 [inline]
>   exit_to_user_mode_loop kernel/entry/common.c:175 [inline]
>   exit_to_user_mode_prepare+0x27e/0x290 kernel/entry/common.c:207
>   __syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
>   syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:300
>   do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
>   entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x7f087b422ae9
> Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 bc ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007f0878977188 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
> RAX: 0000000020ffa000 RBX: 00007f087b536020 RCX: 00007f087b422ae9
> RDX: 0000000003000001 RSI: 0000000000004000 RDI: 0000000020ffa000
> RBP: 00007f087b47cf6d R08: 0000000000000003 R09: 0000000010000000
> R10: 0000000000000012 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007ffe7626bd9f R14: 00007f0878977300 R15: 0000000000022000
>   </TASK>
> 
> 
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at [email protected].
> 
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> 

-- 
Pavel Begunkov

^ permalink raw reply	[flat|nested] 2+ messages in thread

end of thread, other threads:[~2021-11-26 14:51 UTC | newest]

Thread overview: 2+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2021-11-26 12:40 [syzbot] possible deadlock in __io_commit_cqring_flush syzbot
2021-11-26 14:28 ` Pavel Begunkov

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox