======================================================
WARNING: possible circular locking dependency detected
5.13.0-rc7-syzkaller #0 Not tainted
------------------------------------------------------
systemd-udevd/8493 is trying to acquire lock:
ffffffff8ca6dca8 (loop_ctl_mutex){+.+.}-{3:3}, at: loop_probe+0xc7/0x150 drivers/block/loop.c:2234

but task is already holding lock:
ffffffff8c7e01e8 (major_names_lock){+.+.}-{3:3}, at: blk_request_module+0x25/0x1d0 block/genhd.c:680

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (major_names_lock){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:959 [inline]
       __mutex_lock+0x139/0x10c0 kernel/locking/mutex.c:1104
       __register_blkdev+0x2b/0x3e0 block/genhd.c:223
       register_mtd_blktrans+0x85/0x3c0 drivers/mtd/mtd_blkdevs.c:534
       do_one_initcall+0x103/0x650 init/main.c:1249
       do_initcall_level init/main.c:1322 [inline]
       do_initcalls init/main.c:1338 [inline]
       do_basic_setup init/main.c:1358 [inline]
       kernel_init_freeable+0x6c4/0x74d init/main.c:1560
       kernel_init+0xd/0x1b8 init/main.c:1447
       ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

-> #2 (mtd_table_mutex){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:959 [inline]
       __mutex_lock+0x139/0x10c0 kernel/locking/mutex.c:1104
       blktrans_open+0x69/0x600 drivers/mtd/mtd_blkdevs.c:212
       __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

-> #1 (&bdev->bd_mutex){+.+.}-{3:3}:
       __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:2180 [inline]
       loop_control_ioctl drivers/block/loop.c:2280 [inline]
       loop_control_ioctl+0x3e7/0x4c0 drivers/block/loop.c:2240
       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

-> #0 (loop_ctl_mutex){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:2940 [inline]
       check_prevs_add kernel/locking/lockdep.c:3063 [inline]
       validate_chain kernel/locking/lockdep.c:3678 [inline]
       __lock_acquire+0x2a17/0x5230 kernel/locking/lockdep.c:4904
       lock_acquire kernel/locking/lockdep.c:5514 [inline]
       lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5479
       __mutex_lock_common kernel/locking/mutex.c:959 [inline]
       __mutex_lock+0x139/0x10c0 kernel/locking/mutex.c:1104
       loop_probe+0xc7/0x150 drivers/block/loop.c:2234
       blk_request_module+0x111/0x1d0 block/genhd.c:683
       blkdev_get_no_open+0x1d8/0x250 fs/block_dev.c:1374
       blkdev_get_by_dev fs/block_dev.c:1437 [inline]
       blkdev_get_by_dev+0x76/0x660 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

other info that might help us debug this:

Chain exists of:
  loop_ctl_mutex --> mtd_table_mutex --> major_names_lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(major_names_lock);
                               lock(mtd_table_mutex);
                               lock(major_names_lock);
  lock(loop_ctl_mutex);

 *** DEADLOCK ***

1 lock held by systemd-udevd/8493:
 #0: ffffffff8c7e01e8 (major_names_lock){+.+.}-{3:3}, at: blk_request_module+0x25/0x1d0 block/genhd.c:680

stack backtrace:
CPU: 0 PID: 8493 Comm: systemd-udevd Not tainted 5.13.0-rc7-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:2131
 check_prev_add kernel/locking/lockdep.c:2940 [inline]
 check_prevs_add kernel/locking/lockdep.c:3063 [inline]
 validate_chain kernel/locking/lockdep.c:3678 [inline]
 __lock_acquire+0x2a17/0x5230 kernel/locking/lockdep.c:4904
 lock_acquire kernel/locking/lockdep.c:5514 [inline]
 lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5479
 __mutex_lock_common kernel/locking/mutex.c:959 [inline]
 __mutex_lock+0x139/0x10c0 kernel/locking/mutex.c:1104
 loop_probe+0xc7/0x150 drivers/block/loop.c:2234
 blk_request_module+0x111/0x1d0 block/genhd.c:683
 blkdev_get_no_open+0x1d8/0x250 fs/block_dev.c:1374
 blkdev_get_by_dev fs/block_dev.c:1437 [inline]
 blkdev_get_by_dev+0x76/0x660 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
RIP: 0033:0x7f10fd84f840
Code: 73 01 c3 48 8b 0d 68 77 20 00 f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 83 3d 89 bb 20 00 00 75 10 b8 02 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 31 c3 48 83 ec 08 e8 1e f6 ff ff 48 89 04 24
RSP: 002b:00007ffe18311028 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 000055d38ec55380 RCX: 00007f10fd84f840
RDX: 000055d38cf88fe3 RSI: 00000000000a0800 RDI: 000055d38ec56390
RBP: 00007ffe183111a0 R08: 000055d38cf88670 R09: 0000000000000010
R10: 000055d38cf88d0c R11: 0000000000000246 R12: 00007ffe183110f0
R13: 000055d38ec55090 R14: 0000000000000003 R15: 000000000000000e