syzbot

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.0.108/6201 is trying to acquire lock:
ffff88807f61c0e0 (&type->s_umount_key
#31){++++}-{3:3}, at: __super_lock fs/super.c:58 [inline]
#31){++++}-{3:3}, at: super_lock+0x167/0x360 fs/super.c:117

but task is already holding lock:
ffff888148c80c88
 (&bdev->bd_holder_lock){+.+.}-{3:3}, at: bdev_mark_dead+0x31/0x1a0 block/bdev.c:1028

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&bdev->bd_holder_lock){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:603 [inline]
       __mutex_lock+0x129/0xcc0 kernel/locking/mutex.c:747
       bdev_mark_dead+0x31/0x1a0 block/bdev.c:1028
       disk_force_media_change+0x132/0x1b0 block/disk-events.c:302
       __loop_clr_fd+0x396/0x660 drivers/block/loop.c:1170
       blkdev_put+0x5bd/0x760 block/bdev.c:-1
       blkdev_release+0x84/0x90 block/fops.c:604
       __fput+0x234/0x970 fs/file_table.c:384
       __do_sys_close fs/open.c:1573 [inline]
       __se_sys_close+0x15f/0x220 fs/open.c:1558
       do_syscall_x64 arch/x86/entry/common.c:51 [inline]
       do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #1 (&disk->open_mutex){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:603 [inline]
       __mutex_lock+0x129/0xcc0 kernel/locking/mutex.c:747
       blkdev_put+0xff/0x760 block/bdev.c:944
       ext4_get_journal_blkdev fs/ext4/super.c:5941 [inline]
       ext4_open_dev_journal fs/ext4/super.c:5954 [inline]
       ext4_load_journal fs/ext4/super.c:6017 [inline]
       ext4_load_and_init_journal+0xcef/0x2100 fs/ext4/super.c:4918
       __ext4_fill_super fs/ext4/super.c:5391 [inline]
       ext4_fill_super+0x419e/0x66c0 fs/ext4/super.c:5724
       get_tree_bdev+0x3e4/0x510 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+0x2da/0x3c0 fs/namespace.c:3912
       do_syscall_x64 arch/x86/entry/common.c:51 [inline]
       do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #0 (&type->s_umount_key#31){++++}-{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+0x2ddb/0x7c80 kernel/locking/lockdep.c:5137
       lock_acquire+0x197/0x410 kernel/locking/lockdep.c:5754
       down_read+0x46/0x2e0 kernel/locking/rwsem.c:1520
       __super_lock fs/super.c:58 [inline]
       super_lock+0x167/0x360 fs/super.c:117
       super_lock_shared fs/super.c:146 [inline]
       super_lock_shared_active fs/super.c:1442 [inline]
       fs_bdev_mark_dead+0xad/0x1f0 fs/super.c:1458
       bdev_mark_dead+0x83/0x1a0 block/bdev.c:1030
       disk_force_media_change+0x132/0x1b0 block/disk-events.c:302
       __loop_clr_fd+0x396/0x660 drivers/block/loop.c:1170
       loop_clr_fd drivers/block/loop.c:1253 [inline]
       lo_ioctl+0x11e8/0x19f0 drivers/block/loop.c:1578
       blkdev_ioctl+0x58b/0x6f0 block/ioctl.c:639
       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:51 [inline]
       do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

other info that might help us debug this:

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

 Possible unsafe locking scenario:

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

 *** DEADLOCK ***

1 lock held by syz.0.108/6201:
 #0: ffff888148c80c88 (&bdev->bd_holder_lock){+.+.}-{3:3}, at: bdev_mark_dead+0x31/0x1a0 block/bdev.c:1028

stack backtrace:
CPU: 0 PID: 6201 Comm: syz.0.108 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x16c/0x230 lib/dump_stack.c:106
 check_noncircular+0x2bd/0x3c0 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+0x2ddb/0x7c80 kernel/locking/lockdep.c:5137
 lock_acquire+0x197/0x410 kernel/locking/lockdep.c:5754
 down_read+0x46/0x2e0 kernel/locking/rwsem.c:1520
 __super_lock fs/super.c:58 [inline]
 super_lock+0x167/0x360 fs/super.c:117
 super_lock_shared fs/super.c:146 [inline]
 super_lock_shared_active fs/super.c:1442 [inline]
 fs_bdev_mark_dead+0xad/0x1f0 fs/super.c:1458
 bdev_mark_dead+0x83/0x1a0 block/bdev.c:1030
 disk_force_media_change+0x132/0x1b0 block/disk-events.c:302
 __loop_clr_fd+0x396/0x660 drivers/block/loop.c:1170
 loop_clr_fd drivers/block/loop.c:1253 [inline]
 lo_ioctl+0x11e8/0x19f0 drivers/block/loop.c:1578
 blkdev_ioctl+0x58b/0x6f0 block/ioctl.c:639
 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:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f787938f34b
Code: 00 48 89 44 24 18 31 c0 48 8d 44 24 60 c7 04 24 10 00 00 00 48 89 44 24 08 48 8d 44 24 20 48 89 44 24 10 b8 10 00 00 00 0f 05 <89> c2 3d 00 f0 ff ff 77 1c 48 8b 44 24 18 64 48 2b 04 25 28 00 00
RSP: 002b:00007f78789dcdc0 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000006 RCX: 00007f787938f34b
RDX: 0000000000000000 RSI: 0000000000004c01 RDI: 0000000000000006
RBP: 0000000000000010 R08: 0000000000000000 R09: 0000000000000471
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000004
R13: 00007f78789dcef0 R14: 00007f78789dd668 R15: 00007f78681bd000
 </TASK>
loop0: detected capacity change from 0 to 512
EXT4-fs (loop0): external journal device major/minor numbers have changed
EXT4-fs (loop0): external journal has bad superblock