syzbot


possible deadlock in io_sq_thread

Status: closed as dup on 2021/09/09 01:02
Subsystems: fs io-uring
[Documentation on labels]
Reported-by: syzbot+c9e7f2674197989e8afb@syzkaller.appspotmail.com
First crash: 932d, last: 930d
Duplicate of
Title Repro Cause bisect Fix bisect Count Last Reported
possible deadlock in io_uring_register fs 16 929d 931d
Discussions (1)
Title Replies (including bot) Last reply
[syzbot] possible deadlock in io_sq_thread 1 (2) 2021/09/09 01:02

Sample crash report:
======================================================
WARNING: possible circular locking dependency detected
5.14.0-syzkaller #0 Not tainted
------------------------------------------------------
iou-sqp-7301/7302 is trying to acquire lock:
ffff8880761080a8 (&ctx->uring_lock){+.+.}-{3:3}, at: __io_sq_thread fs/io_uring.c:7291 [inline]
ffff8880761080a8 (&ctx->uring_lock){+.+.}-{3:3}, at: io_sq_thread+0x92c/0x12a0 fs/io_uring.c:7368

but task is already holding lock:
ffff88801b509c70 (&sqd->lock){+.+.}-{3:3}, at: io_sq_thread+0x299/0x12a0 fs/io_uring.c:7356

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&sqd->lock){+.+.}-{3:3}:
       lock_acquire+0x19f/0x4d0 kernel/locking/lockdep.c:5625
       __mutex_lock_common+0x1df/0x2550 kernel/locking/mutex.c:596
       __mutex_lock kernel/locking/mutex.c:729 [inline]
       mutex_lock_nested+0x1a/0x20 kernel/locking/mutex.c:743
       io_register_iowq_max_workers fs/io_uring.c:10551 [inline]
       __io_uring_register fs/io_uring.c:10757 [inline]
       __do_sys_io_uring_register fs/io_uring.c:10792 [inline]
       __se_sys_io_uring_register+0x231e/0x3140 fs/io_uring.c:10772
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x44/0xae

-> #0 (&ctx->uring_lock){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3051 [inline]
       check_prevs_add kernel/locking/lockdep.c:3174 [inline]
       validate_chain+0x1dfb/0x8240 kernel/locking/lockdep.c:3789
       __lock_acquire+0x1382/0x2b00 kernel/locking/lockdep.c:5015
       lock_acquire+0x19f/0x4d0 kernel/locking/lockdep.c:5625
       __mutex_lock_common+0x1df/0x2550 kernel/locking/mutex.c:596
       __mutex_lock kernel/locking/mutex.c:729 [inline]
       mutex_lock_nested+0x1a/0x20 kernel/locking/mutex.c:743
       __io_sq_thread fs/io_uring.c:7291 [inline]
       io_sq_thread+0x92c/0x12a0 fs/io_uring.c:7368
       ret_from_fork+0x1f/0x30

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&sqd->lock);
                               lock(&ctx->uring_lock);
                               lock(&sqd->lock);
  lock(&ctx->uring_lock);

 *** DEADLOCK ***

1 lock held by iou-sqp-7301/7302:
 #0: ffff88801b509c70 (&sqd->lock){+.+.}-{3:3}, at: io_sq_thread+0x299/0x12a0 fs/io_uring.c:7356

stack backtrace:
CPU: 1 PID: 7302 Comm: iou-sqp-7301 Not tainted 5.14.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1dc/0x2d8 lib/dump_stack.c:106
 check_noncircular+0x2f9/0x3b0 kernel/locking/lockdep.c:2131
 check_prev_add kernel/locking/lockdep.c:3051 [inline]
 check_prevs_add kernel/locking/lockdep.c:3174 [inline]
 validate_chain+0x1dfb/0x8240 kernel/locking/lockdep.c:3789
 __lock_acquire+0x1382/0x2b00 kernel/locking/lockdep.c:5015
 lock_acquire+0x19f/0x4d0 kernel/locking/lockdep.c:5625
 __mutex_lock_common+0x1df/0x2550 kernel/locking/mutex.c:596
 __mutex_lock kernel/locking/mutex.c:729 [inline]
 mutex_lock_nested+0x1a/0x20 kernel/locking/mutex.c:743
 __io_sq_thread fs/io_uring.c:7291 [inline]
 io_sq_thread+0x92c/0x12a0 fs/io_uring.c:7368
 ret_from_fork+0x1f/0x30

Crashes (11):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2021/09/09 08:02 upstream 2d338201d531 e2776ee4 .config console log report syz C ci-upstream-kasan-gce-smack-root possible deadlock in io_sq_thread
2021/09/10 13:31 upstream bf9f243f23e6 5ae8508a .config console log report info ci-upstream-kasan-gce-root possible deadlock in io_sq_thread
2021/09/09 18:42 upstream a3fa7a101dcf e2776ee4 .config console log report info ci-upstream-kasan-gce-root possible deadlock in io_sq_thread
2021/09/09 17:47 upstream a3fa7a101dcf e2776ee4 .config console log report info ci-upstream-kasan-gce-smack-root possible deadlock in io_sq_thread
2021/09/09 07:10 upstream 0f4b9289bad3 e2776ee4 .config console log report info ci-upstream-kasan-gce possible deadlock in io_sq_thread
2021/09/09 05:10 upstream 730bf31b8fc8 e2776ee4 .config console log report info ci-upstream-kasan-gce-selinux-root possible deadlock in io_sq_thread
2021/09/08 00:50 upstream a2b28235335f 064c9eb7 .config console log report info ci-upstream-kasan-gce-selinux-root possible deadlock in io_sq_thread
2021/09/07 23:55 upstream a2b28235335f 064c9eb7 .config console log report info ci-upstream-kasan-gce possible deadlock in io_sq_thread
2021/09/07 23:50 upstream a2b28235335f 064c9eb7 .config console log report info ci-upstream-kasan-gce-selinux-root possible deadlock in io_sq_thread
2021/09/07 22:05 upstream a2b28235335f 064c9eb7 .config console log report info ci-upstream-kasan-gce possible deadlock in io_sq_thread
2021/09/10 05:29 upstream bf9f243f23e6 e2776ee4 .config console log report info ci-upstream-kasan-gce-386 possible deadlock in io_sq_thread
* Struck through repros no longer work on HEAD.