loop8: detected capacity change from 0 to 128 EXT4-fs (loop8): mounted filesystem 76b65be2-f6da-4727-8c75-0525a5b65a09 r/w without journal. Quota mode: none. ext4 filesystem being mounted at /160/mnt supports timestamps until 2038-01-19 (0x7fffffff) ====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.8.2004/14203 is trying to acquire lock: ffff888024ca20e0 (&type->s_umount_key#32){++++}-{3:3}, at: __super_lock fs/super.c:58 [inline] ffff888024ca20e0 (&type->s_umount_key#32){++++}-{3:3}, at: super_lock+0x167/0x360 fs/super.c:117 but task is already holding lock: ffff88801fec0108 (&bdev->bd_holder_lock){+.+.}-{3:3}, at: blkdev_flushbuf block/ioctl.c:379 [inline] ffff88801fec0108 (&bdev->bd_holder_lock){+.+.}-{3:3}, at: blkdev_common_ioctl+0x815/0x2460 block/ioctl.c:511 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 bdev_release+0x57/0x70 block/bdev.c:968 ext4_kill_sb+0x68/0xa0 fs/ext4/super.c:7391 deactivate_locked_super+0x97/0x100 fs/super.c:481 cleanup_mnt+0x429/0x4c0 fs/namespace.c:1259 task_work_run+0x1ce/0x250 kernel/task_work.c:239 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+0xf6/0x180 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+0x61/0xb0 arch/x86/entry/common.c:87 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#32){++++}-{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_sync+0xa4/0x170 fs/super.c:1477 blkdev_flushbuf block/ioctl.c:381 [inline] blkdev_common_ioctl+0x881/0x2460 block/ioctl.c:511 blkdev_ioctl+0x4eb/0x6f0 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: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#32 --> &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#32); *** DEADLOCK *** 1 lock held by syz.8.2004/14203: #0: ffff88801fec0108 (&bdev->bd_holder_lock){+.+.}-{3:3}, at: blkdev_flushbuf block/ioctl.c:379 [inline] #0: ffff88801fec0108 (&bdev->bd_holder_lock){+.+.}-{3:3}, at: blkdev_common_ioctl+0x815/0x2460 block/ioctl.c:511 stack backtrace: CPU: 0 PID: 14203 Comm: syz.8.2004 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 Call Trace: 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_sync+0xa4/0x170 fs/super.c:1477 blkdev_flushbuf block/ioctl.c:381 [inline] blkdev_common_ioctl+0x881/0x2460 block/ioctl.c:511 blkdev_ioctl+0x4eb/0x6f0 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:51 [inline] do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81 entry_SYSCALL_64_after_hwframe+0x68/0xd2 RIP: 0033:0x7fdad2d8f749 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fdad0ff6038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007fdad2fe6090 RCX: 00007fdad2d8f749 RDX: 0000000000000000 RSI: 0000000000001261 RDI: 0000000000000008 RBP: 00007fdad2e13f91 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fdad2fe6128 R14: 00007fdad2fe6090 R15: 00007ffdaebee748