====================================================== WARNING: possible circular locking dependency detected 5.13.0-rc5-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor002/8416 is trying to acquire lock: ffff888145783a20 (&bdev->bd_mutex){+.+.}-{3:3}, at: del_gendisk+0x2ab/0x860 block/genhd.c:610 but task is already holding lock: ffffffff8d671668 (loop_ctl_mutex){+.+.}-{3:3}, at: loop_control_ioctl+0x9b/0x770 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}: lock_acquire+0x17f/0x720 kernel/locking/lockdep.c:5512 __mutex_lock_common+0x1bf/0x3100 kernel/locking/mutex.c:959 __mutex_lock kernel/locking/mutex.c:1104 [inline] mutex_lock_killable_nested+0x1a/0x20 kernel/locking/mutex.c:1134 lo_open+0x1c/0x100 drivers/block/loop.c:1890 __blkdev_get+0x293/0xa50 fs/block_dev.c:1311 blkdev_get_by_dev+0xf9/0x640 fs/block_dev.c:1451 blkdev_open+0x132/0x2c0 fs/block_dev.c:1546 do_dentry_open+0x7cb/0x1010 fs/open.c:826 do_open fs/namei.c:3361 [inline] path_openat+0x28e6/0x39b0 fs/namei.c:3494 do_filp_open+0x221/0x460 fs/namei.c:3521 do_sys_openat2+0x124/0x460 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+0x221/0x270 fs/open.c:1207 do_syscall_64+0x3f/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+0x4f9/0x5b60 kernel/locking/lockdep.c:3061 validate_chain kernel/locking/lockdep.c:3676 [inline] __lock_acquire+0x4307/0x6040 kernel/locking/lockdep.c:4902 lock_acquire+0x17f/0x720 kernel/locking/lockdep.c:5512 __mutex_lock_common+0x1bf/0x3100 kernel/locking/mutex.c:959 __mutex_lock kernel/locking/mutex.c:1104 [inline] mutex_lock_nested+0x1a/0x20 kernel/locking/mutex.c:1119 del_gendisk+0x2ab/0x860 block/genhd.c:610 loop_remove drivers/block/loop.c:2191 [inline] loop_control_ioctl+0x647/0x770 drivers/block/loop.c:2291 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:1069 [inline] __se_sys_ioctl+0xfb/0x170 fs/ioctl.c:1055 do_syscall_64+0x3f/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-executor002/8416: #0: ffffffff8d671668 (loop_ctl_mutex){+.+.}-{3:3}, at: loop_control_ioctl+0x9b/0x770 drivers/block/loop.c:2257 stack backtrace: CPU: 0 PID: 8416 Comm: syz-executor002 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+0x202/0x31e lib/dump_stack.c:120 print_circular_bug+0xb17/0xdc0 kernel/locking/lockdep.c:2007 check_noncircular+0x2cc/0x390 kernel/locking/lockdep.c:2129 check_prev_add kernel/locking/lockdep.c:2938 [inline] check_prevs_add+0x4f9/0x5b60 kernel/locking/lockdep.c:3061 validate_chain kernel/locking/lockdep.c:3676 [inline] __lock_acquire+0x4307/0x6040 kernel/locking/lockdep.c:4902 lock_acquire+0x17f/0x720 kernel/locking/lockdep.c:5512 __mutex_lock_common+0x1bf/0x3100 kernel/locking/mutex.c:959 __mutex_lock kernel/locking/mutex.c:1104 [inline] mutex_lock_nested+0x1a/0x20 kernel/locking/mutex.c:1119 del_gendisk+0x2ab/0x860 block/genhd.c:610 loop_remove drivers/block/loop.c:2191 [inline] loop_control_ioctl+0x647/0x770 drivers/block/loop.c:2291 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:1069 [inline] __se_sys_ioctl+0xfb/0x170 fs/ioctl.c:1055 do_syscall_64+0x3f/0xb0 arch/x86/entry/common.c:47 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x43ee69 Code: 28 c3 e8 2a 14 00 00 66 2e 0f 1f 84 00 00 00 00 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 c0 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ffc24f2c378 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 0000000000400488 RCX: 000000000043ee69 RDX: 9999999999999999 RSI: 0000000000004c81 RDI: 0000000000000003 RBP: 0000000000402e50 R08: 0000000000000000 R09: 0000000000400488 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000402ee0 R13: 0000000000000000 R14: 00000000004ac018 R15: 0000000000400488