syzbot

EXT4-fs (loop3): external journal device major/minor numbers have changed
block device autoloading is deprecated and will be removed.
EXT4-fs (loop3): external journal has bad superblock
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.3.2058/13227 is trying to acquire lock:
ffff88801fb004c8 (&disk->open_mutex){+.+.}-{3:3}, at: blkdev_put+0xff/0x760 block/bdev.c:944

but task is already holding lock:
ffff88802fd380e0 (&type->s_umount_key#31){++++}-{3:3}, at: ext4_get_journal_blkdev fs/ext4/super.c:5902 [inline]
ffff88802fd380e0 (&type->s_umount_key#31){++++}-{3:3}, at: ext4_open_dev_journal fs/ext4/super.c:5974 [inline]
ffff88802fd380e0 (&type->s_umount_key#31){++++}-{3:3}, at: ext4_load_journal fs/ext4/super.c:6037 [inline]
ffff88802fd380e0 (&type->s_umount_key#31){++++}-{3:3}, at: ext4_load_and_init_journal+0x280/0x2100 fs/ext4/super.c:4923

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&type->s_umount_key#31){++++}-{3:3}:
       down_read+0x46/0x2e0 kernel/locking/rwsem.c:1520
       __super_lock fs/super.c:58 [inline]
       super_lock+0x17f/0x3a0 fs/super.c:117
       super_lock_shared fs/super.c:146 [inline]
       super_lock_shared_active fs/super.c:1442 [inline]
       fs_bdev_sync+0xa4/0x170 fs/super.c:1477
       blkdev_flushbuf block/ioctl.c:381 [inline]
       blkdev_common_ioctl+0x8a6/0x2570 block/ioctl.c:511
       blkdev_ioctl+0x512/0x730 block/ioctl.c:633
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:871 [inline]
       __se_sys_ioctl+0xfd/0x170 fs/ioctl.c:857
       do_syscall_x64 arch/x86/entry/common.c:46 [inline]
       do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #1 (&bdev->bd_holder_lock){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:603 [inline]
       __mutex_lock+0x136/0xcc0 kernel/locking/mutex.c:747
       bdev_mark_dead+0x31/0x1a0 block/bdev.c:1028
       disk_force_media_change+0x14e/0x1d0 block/disk-events.c:302
       __loop_clr_fd+0x396/0x660 drivers/block/loop.c:1170
       blkdev_put+0x5bd/0x760 block/bdev.c:-1
       bdev_release+0x57/0x70 block/bdev.c:968
       deactivate_locked_super+0x97/0x100 fs/super.c:481
       cleanup_mnt+0x43b/0x4d0 fs/namespace.c:1259
       task_work_run+0x1d4/0x260 kernel/task_work.c:245
       resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
       exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177
       exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
       __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
       syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
       do_syscall_64+0x61/0xa0 arch/x86/entry/common.c:82
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #0 (&disk->open_mutex){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3134 [inline]
       check_prevs_add kernel/locking/lockdep.c:3253 [inline]
       validate_chain kernel/locking/lockdep.c:3869 [inline]
       __lock_acquire+0x2df1/0x7d40 kernel/locking/lockdep.c:5137
       lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5754
       __mutex_lock_common kernel/locking/mutex.c:603 [inline]
       __mutex_lock+0x136/0xcc0 kernel/locking/mutex.c:747
       blkdev_put+0xff/0x760 block/bdev.c:944
       ext4_get_journal_blkdev fs/ext4/super.c:5961 [inline]
       ext4_open_dev_journal fs/ext4/super.c:5974 [inline]
       ext4_load_journal fs/ext4/super.c:6037 [inline]
       ext4_load_and_init_journal+0xcef/0x2100 fs/ext4/super.c:4923
       __ext4_fill_super fs/ext4/super.c:5411 [inline]
       ext4_fill_super+0x430a/0x67b0 fs/ext4/super.c:5744
       get_tree_bdev+0x3f3/0x520 fs/super.c:1591
       vfs_get_tree+0x8c/0x280 fs/super.c:1764
       do_new_mount+0x24b/0xa40 fs/namespace.c:3386
       do_mount fs/namespace.c:3726 [inline]
       __do_sys_mount fs/namespace.c:3935 [inline]
       __se_sys_mount+0x2e7/0x3d0 fs/namespace.c:3912
       do_syscall_x64 arch/x86/entry/common.c:46 [inline]
       do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

other info that might help us debug this:

Chain exists of:
  &disk->open_mutex --> &bdev->bd_holder_lock --> &type->s_umount_key#31

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&type->s_umount_key#31);
                               lock(&bdev->bd_holder_lock);
                               lock(&type->s_umount_key#31);
  lock(&disk->open_mutex);

 *** DEADLOCK ***

1 lock held by syz.3.2058/13227:
 #0: ffff88802fd380e0 (&type->s_umount_key#31){++++}-{3:3}, at: ext4_get_journal_blkdev fs/ext4/super.c:5902 [inline]
 #0: ffff88802fd380e0 (&type->s_umount_key#31){++++}-{3:3}, at: ext4_open_dev_journal fs/ext4/super.c:5974 [inline]
 #0: ffff88802fd380e0 (&type->s_umount_key#31){++++}-{3:3}, at: ext4_load_journal fs/ext4/super.c:6037 [inline]
 #0: ffff88802fd380e0 (&type->s_umount_key#31){++++}-{3:3}, at: ext4_load_and_init_journal+0x280/0x2100 fs/ext4/super.c:4923

stack backtrace:
CPU: 1 PID: 13227 Comm: syz.3.2058 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
 check_noncircular+0x2fc/0x400 kernel/locking/lockdep.c:2187
 check_prev_add kernel/locking/lockdep.c:3134 [inline]
 check_prevs_add kernel/locking/lockdep.c:3253 [inline]
 validate_chain kernel/locking/lockdep.c:3869 [inline]
 __lock_acquire+0x2df1/0x7d40 kernel/locking/lockdep.c:5137
 lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5754
 __mutex_lock_common kernel/locking/mutex.c:603 [inline]
 __mutex_lock+0x136/0xcc0 kernel/locking/mutex.c:747
 blkdev_put+0xff/0x760 block/bdev.c:944
 ext4_get_journal_blkdev fs/ext4/super.c:5961 [inline]
 ext4_open_dev_journal fs/ext4/super.c:5974 [inline]
 ext4_load_journal fs/ext4/super.c:6037 [inline]
 ext4_load_and_init_journal+0xcef/0x2100 fs/ext4/super.c:4923
 __ext4_fill_super fs/ext4/super.c:5411 [inline]
 ext4_fill_super+0x430a/0x67b0 fs/ext4/super.c:5744
 get_tree_bdev+0x3f3/0x520 fs/super.c:1591
 vfs_get_tree+0x8c/0x280 fs/super.c:1764
 do_new_mount+0x24b/0xa40 fs/namespace.c:3386
 do_mount fs/namespace.c:3726 [inline]
 __do_sys_mount fs/namespace.c:3935 [inline]
 __se_sys_mount+0x2e7/0x3d0 fs/namespace.c:3912
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f4ed339da8a
Code: 48 c7 c2 e8 ff ff ff f7 d8 64 89 02 b8 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f4ed4328e58 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f4ed4328ee0 RCX: 00007f4ed339da8a
RDX: 0000200000000180 RSI: 0000200000000480 RDI: 00007f4ed4328ea0
RBP: 0000200000000180 R08: 00007f4ed4328ee0 R09: 00000000c0ed4040
R10: 00000000c0ed4040 R11: 0000000000000246 R12: 0000200000000480
R13: 00007f4ed4328ea0 R14: 000000000000047a R15: 00002000000004c0
 </TASK>
netlink: 12 bytes leftover after parsing attributes in process `syz.3.2058'.
ipvlan2: entered allmulticast mode
syz_tun: entered allmulticast mode