======================================================
WARNING: possible circular locking dependency detected
5.13.0-rc5-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.3/17861 is trying to acquire lock:
ffff8880115b6820 (&bdev->bd_mutex){+.+.}-{3:3}, at: del_gendisk+0x24b/0xa00 block/genhd.c:610

but task is already holding lock:
ffffffff8ca6dec8 (loop_ctl_mutex){+.+.}-{3:3}, at: loop_control_ioctl+0x7b/0x4f0 drivers/block/loop.c:2257

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (loop_ctl_mutex){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:959 [inline]
       __mutex_lock+0x139/0x10c0 kernel/locking/mutex.c:1104
       lo_open+0x1a/0x130 drivers/block/loop.c:1890
       __blkdev_get+0x182/0xa30 fs/block_dev.c:1311
       blkdev_get_by_dev fs/block_dev.c:1451 [inline]
       blkdev_get_by_dev+0x200/0x660 fs/block_dev.c:1423
       blkdev_open+0x154/0x2b0 fs/block_dev.c:1546
       do_dentry_open+0x4b9/0x11b0 fs/open.c:826
       do_open fs/namei.c:3361 [inline]
       path_openat+0x1c0e/0x27e0 fs/namei.c:3494
       do_filp_open+0x190/0x3d0 fs/namei.c:3521
       do_sys_openat2+0x16d/0x420 fs/open.c:1187
       do_sys_open fs/open.c:1203 [inline]
       __do_sys_open fs/open.c:1211 [inline]
       __se_sys_open fs/open.c:1207 [inline]
       __x64_sys_open+0x119/0x1c0 fs/open.c:1207
       do_syscall_64+0x3a/0xb0 arch/x86/entry/common.c:47
       entry_SYSCALL_64_after_hwframe+0x44/0xae

-> #0 (&bdev->bd_mutex){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:2938 [inline]
       check_prevs_add kernel/locking/lockdep.c:3061 [inline]
       validate_chain kernel/locking/lockdep.c:3676 [inline]
       __lock_acquire+0x2a17/0x5230 kernel/locking/lockdep.c:4902
       lock_acquire kernel/locking/lockdep.c:5512 [inline]
       lock_acquire+0x1ab/0x740 kernel/locking/lockdep.c:5477
       __mutex_lock_common kernel/locking/mutex.c:959 [inline]
       __mutex_lock+0x139/0x10c0 kernel/locking/mutex.c:1104
       del_gendisk+0x24b/0xa00 block/genhd.c:610
       loop_remove drivers/block/loop.c:2191 [inline]
       loop_control_ioctl drivers/block/loop.c:2291 [inline]
       loop_control_ioctl+0x40d/0x4f0 drivers/block/loop.c:2251
       __do_compat_sys_ioctl+0x1c7/0x290 fs/ioctl.c:1167
       do_syscall_32_irqs_on arch/x86/entry/common.c:78 [inline]
       __do_fast_syscall_32+0x67/0xe0 arch/x86/entry/common.c:143
       do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:168
       entry_SYSENTER_compat_after_hwframe+0x4d/0x5c

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(loop_ctl_mutex);
                               lock(&bdev->bd_mutex);
                               lock(loop_ctl_mutex);
  lock(&bdev->bd_mutex);

 *** DEADLOCK ***

1 lock held by syz-executor.3/17861:
 #0: ffffffff8ca6dec8 (loop_ctl_mutex){+.+.}-{3:3}, at: loop_control_ioctl+0x7b/0x4f0 drivers/block/loop.c:2257

stack backtrace:
CPU: 0 PID: 17861 Comm: syz-executor.3 Not tainted 5.13.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x141/0x1d7 lib/dump_stack.c:120
 check_noncircular+0x25f/0x2e0 kernel/locking/lockdep.c:2129
 check_prev_add kernel/locking/lockdep.c:2938 [inline]
 check_prevs_add kernel/locking/lockdep.c:3061 [inline]
 validate_chain kernel/locking/lockdep.c:3676 [inline]
 __lock_acquire+0x2a17/0x5230 kernel/locking/lockdep.c:4902
 lock_acquire kernel/locking/lockdep.c:5512 [inline]
 lock_acquire+0x1ab/0x740 kernel/locking/lockdep.c:5477
 __mutex_lock_common kernel/locking/mutex.c:959 [inline]
 __mutex_lock+0x139/0x10c0 kernel/locking/mutex.c:1104
 del_gendisk+0x24b/0xa00 block/genhd.c:610
 loop_remove drivers/block/loop.c:2191 [inline]
 loop_control_ioctl drivers/block/loop.c:2291 [inline]
 loop_control_ioctl+0x40d/0x4f0 drivers/block/loop.c:2251
 __do_compat_sys_ioctl+0x1c7/0x290 fs/ioctl.c:1167
 do_syscall_32_irqs_on arch/x86/entry/common.c:78 [inline]
 __do_fast_syscall_32+0x67/0xe0 arch/x86/entry/common.c:143
 do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:168
 entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
RIP: 0023:0xf7fa9549
Code: 03 74 c0 01 10 05 03 74 b8 01 10 06 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 8d b4 26 00 00 00 00 8d b4 26 00 00 00 00
RSP: 002b:00000000f55a35fc EFLAGS: 00000296 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000004c81
RDX: 0000000000000001 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000