====================================================== WARNING: possible circular locking dependency detected 5.13.0-rc5-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor436/8427 is trying to acquire lock: ffff88801ad25ca0 (&bdev->bd_mutex){+.+.}-{3:3}, at: del_gendisk+0x24b/0xa00 block/genhd.c:610 but task is already holding lock: ffffffff8ca6dc88 (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 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:1069 [inline] __se_sys_ioctl fs/ioctl.c:1055 [inline] __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:1055 do_syscall_64+0x3a/0xb0 arch/x86/entry/common.c:47 entry_SYSCALL_64_after_hwframe+0x44/0xae 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-executor436/8427: #0: ffffffff8ca6dc88 (loop_ctl_mutex){+.+.}-{3:3}, at: loop_control_ioctl+0x7b/0x4f0 drivers/block/loop.c:2257 stack backtrace: CPU: 0 PID: 8427 Comm: syz-executor436 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 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:1069 [inline] __se_sys_ioctl fs/ioctl.c:1055 [inline] __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:1055 do_syscall_64+0x3a/0xb0 arch/x86/entry/common.c:47 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x43fb99 Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 b1 14 00 00 90 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 c0 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fffe06b5d98 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 0000000000400488 RCX: 000000000043fb99 RDX: 0000000000000000 RSI: 0000000000004c81 RDI: 0000000000000003 RBP: 0000000000000000 R08: 00007fffe06b5f38 R09: 00007fffe06b5f38 R10: 00007fffe06b5810 R11: 0000000000000246 R12: 0000000000403420 R13: 431bde82d7b634db R14: 00000000004ad018 R15: 0000000000400488