====================================================== WARNING: possible circular locking dependency detected 5.13.0-rc2-next-20210518-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor294/8436 is trying to acquire lock: ffff888144b845a0 (&bdev->bd_mutex){+.+.}-{3:3}, at: del_gendisk+0x250/0x9e0 block/genhd.c:618 but task is already holding lock: ffffffff8c9e4c70 (bdev_lookup_sem){++++}-{3:3}, at: del_gendisk+0x222/0x9e0 block/genhd.c:616 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (bdev_lookup_sem){++++}-{3:3}: down_write+0x92/0x150 kernel/locking/rwsem.c:1406 del_gendisk+0x222/0x9e0 block/genhd.c:616 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+0x31/0xb0 arch/x86/entry/common.c:47 entry_SYSCALL_64_after_hwframe+0x44/0xae -> #1 (loop_ctl_mutex){+.+.}-{3:3}: __mutex_lock_common kernel/locking/mutex.c:949 [inline] __mutex_lock+0x139/0x1120 kernel/locking/mutex.c:1096 lo_open+0x1a/0x130 drivers/block/loop.c:1890 __blkdev_get+0x135/0xa30 fs/block_dev.c:1305 blkdev_get_by_dev fs/block_dev.c:1453 [inline] blkdev_get_by_dev+0x200/0x660 fs/block_dev.c:1425 blkdev_open+0x154/0x2b0 fs/block_dev.c:1548 do_dentry_open+0x4b9/0x11c0 fs/open.c:826 do_open fs/namei.c:3361 [inline] path_openat+0x1c09/0x27d0 fs/namei.c:3494 do_filp_open+0x190/0x3d0 fs/namei.c:3521 do_sys_openat2+0x16d/0x420 fs/open.c:1196 do_sys_open fs/open.c:1212 [inline] __do_sys_open fs/open.c:1220 [inline] __se_sys_open fs/open.c:1216 [inline] __x64_sys_open+0x119/0x1c0 fs/open.c:1216 do_syscall_64+0x31/0xb0 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:949 [inline] __mutex_lock+0x139/0x1120 kernel/locking/mutex.c:1096 del_gendisk+0x250/0x9e0 block/genhd.c:618 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+0x31/0xb0 arch/x86/entry/common.c:47 entry_SYSCALL_64_after_hwframe+0x44/0xae other info that might help us debug this: Chain exists of: &bdev->bd_mutex --> loop_ctl_mutex --> bdev_lookup_sem Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(bdev_lookup_sem); lock(loop_ctl_mutex); lock(bdev_lookup_sem); lock(&bdev->bd_mutex); *** DEADLOCK *** 2 locks held by syz-executor294/8436: #0: ffffffff8cc73448 (loop_ctl_mutex){+.+.}-{3:3}, at: loop_control_ioctl+0x7b/0x4f0 drivers/block/loop.c:2257 #1: ffffffff8c9e4c70 (bdev_lookup_sem){++++}-{3:3}, at: del_gendisk+0x222/0x9e0 block/genhd.c:616 stack backtrace: CPU: 1 PID: 8436 Comm: syz-executor294 Not tainted 5.13.0-rc2-next-20210518-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+0x13e/0x1d6 lib/dump_stack.c:129 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:949 [inline] __mutex_lock+0x139/0x1120 kernel/locking/mutex.c:1096 del_gendisk+0x250/0x9e0 block/genhd.c:618 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+0x31/0xb0 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:00007ffff14a1ea8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 0000000000400488 RCX: 000000000043ee69