======================================================
WARNING: possible circular locking dependency detected
5.14.0-syzkaller #0 Not tainted
------------------------------------------------------
iou-sqp-18455/18458 is trying to acquire lock:
ffff8880170be0a8 (&ctx->uring_lock){+.+.}-{3:3}, at: __io_sq_thread fs/io_uring.c:7291 [inline]
ffff8880170be0a8 (&ctx->uring_lock){+.+.}-{3:3}, at: io_sq_thread+0x65a/0x1370 fs/io_uring.c:7368

but task is already holding lock:
ffff88807d207c70 (&sqd->lock){+.+.}-{3:3}, at: io_sq_thread+0x1131/0x1370 fs/io_uring.c:7404

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&sqd->lock){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:596 [inline]
       __mutex_lock+0x131/0x12f0 kernel/locking/mutex.c:729
       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+0x10aa/0x2e70 fs/io_uring.c:10792
       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

-> #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 kernel/locking/lockdep.c:3789 [inline]
       __lock_acquire+0x2a07/0x54a0 kernel/locking/lockdep.c:5015
       lock_acquire kernel/locking/lockdep.c:5625 [inline]
       lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5590
       __mutex_lock_common kernel/locking/mutex.c:596 [inline]
       __mutex_lock+0x131/0x12f0 kernel/locking/mutex.c:729
       __io_sq_thread fs/io_uring.c:7291 [inline]
       io_sq_thread+0x65a/0x1370 fs/io_uring.c:7368
       ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

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-18455/18458:
 #0: ffff88807d207c70 (&sqd->lock){+.+.}-{3:3}, at: io_sq_thread+0x1131/0x1370 fs/io_uring.c:7404

stack backtrace:
CPU: 1 PID: 18458 Comm: iou-sqp-18455 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+0xcd/0x134 lib/dump_stack.c:105
 check_noncircular+0x25f/0x2e0 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 kernel/locking/lockdep.c:3789 [inline]
 __lock_acquire+0x2a07/0x54a0 kernel/locking/lockdep.c:5015
 lock_acquire kernel/locking/lockdep.c:5625 [inline]
 lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5590
 __mutex_lock_common kernel/locking/mutex.c:596 [inline]
 __mutex_lock+0x131/0x12f0 kernel/locking/mutex.c:729
 __io_sq_thread fs/io_uring.c:7291 [inline]
 io_sq_thread+0x65a/0x1370 fs/io_uring.c:7368
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295