syzbot

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.1.5077/22953 is trying to acquire lock:
ffff88814e10a0e0 (&type->s_umount_key#32){++++}-{3:3}, at: __super_lock fs/super.c:58 [inline]
ffff88814e10a0e0 (&type->s_umount_key#32){++++}-{3:3}, at: super_lock+0x167/0x360 fs/super.c:117

but task is already holding lock:
ffff888148ca9808 (&bdev->bd_holder_lock){+.+.}-{3:3}, at: blkdev_flushbuf block/ioctl.c:373 [inline]
ffff888148ca9808 (&bdev->bd_holder_lock){+.+.}-{3:3}, at: blkdev_common_ioctl+0x814/0x23d0 block/ioctl.c:505

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #4 (&bdev->bd_holder_lock){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:603 [inline]
       __mutex_lock+0x129/0xcc0 kernel/locking/mutex.c:747
       bd_finish_claiming+0x22f/0x3f0 block/bdev.c:568
       blkdev_get_by_dev+0x45c/0x600 block/bdev.c:801
       bdev_open_by_dev+0x77/0x100 block/bdev.c:842
       setup_bdev_super+0x59/0x660 fs/super.c:1496
       mount_bdev+0x1dd/0x2d0 fs/super.c:1640
       legacy_get_tree+0xea/0x180 fs/fs_context.c:662
       vfs_get_tree+0x8c/0x280 fs/super.c:1764
       do_new_mount+0x24b/0xa40 fs/namespace.c:3377
       init_mount+0xd2/0x120 fs/init.c:25
       do_mount_root+0x97/0x230 init/do_mounts.c:166
       mount_root_generic+0x195/0x3c0 init/do_mounts.c:205
       prepare_namespace+0xc2/0x100 init/do_mounts.c:489
       kernel_init_freeable+0x413/0x570 init/main.c:1566
       kernel_init+0x1d/0x1c0 init/main.c:1443
       ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
       ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293

-> #3 (bdev_lock){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:603 [inline]
       __mutex_lock+0x129/0xcc0 kernel/locking/mutex.c:747
       bd_prepare_to_claim+0x1ba/0x480 block/bdev.c:510
       truncate_bdev_range+0x4e/0x260 block/bdev.c:105
       blkdev_fallocate+0x3ff/0x670 block/fops.c:792
       vfs_fallocate+0x58e/0x700 fs/open.c:324
       madvise_remove mm/madvise.c:1007 [inline]
       madvise_vma_behavior mm/madvise.c:1031 [inline]
       madvise_walk_vmas mm/madvise.c:1266 [inline]
       do_madvise+0x15fe/0x3710 mm/madvise.c:1446
       __do_sys_madvise mm/madvise.c:1459 [inline]
       __se_sys_madvise mm/madvise.c:1457 [inline]
       __x64_sys_madvise+0xa6/0xc0 mm/madvise.c:1457
       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

-> #2 (mapping.invalidate_lock#2){++++}-{3:3}:
       down_read+0x46/0x2e0 kernel/locking/rwsem.c:1520
       filemap_invalidate_lock_shared include/linux/fs.h:859 [inline]
       page_cache_ra_unbounded+0xdc/0x770 mm/readahead.c:225
       page_cache_sync_readahead include/linux/pagemap.h:1325 [inline]
       ext4_readdir+0xb71/0x39d0 fs/ext4/dir.c:197
       iterate_dir+0x1c2/0x580 fs/readdir.c:106
       __do_sys_getdents64 fs/readdir.c:405 [inline]
       __se_sys_getdents64+0xe9/0x260 fs/readdir.c:390
       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 (&type->i_mutex_dir_key#3){++++}-{3:3}:
       down_read+0x46/0x2e0 kernel/locking/rwsem.c:1520
       inode_lock_shared include/linux/fs.h:814 [inline]
       lookup_slow fs/namei.c:1710 [inline]
       lookup_one_unlocked+0x171/0x290 fs/namei.c:2805
       lookup_one_positive_unlocked fs/namei.c:2834 [inline]
       lookup_positive_unlocked+0x2b/0xb0 fs/namei.c:2874
       dquot_quota_on_mount+0x57/0xe0 fs/quota/dquot.c:2574
       ext4_quota_on_mount fs/ext4/orphan.c:316 [inline]
       ext4_orphan_cleanup+0x83b/0x1400 fs/ext4/orphan.c:444
       __ext4_fill_super fs/ext4/super.c:5608 [inline]
       ext4_fill_super+0x5de7/0x66c0 fs/ext4/super.c:5731
       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:3377
       do_mount fs/namespace.c:3717 [inline]
       __do_sys_mount fs/namespace.c:3926 [inline]
       __se_sys_mount+0x2da/0x3c0 fs/namespace.c:3903
       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:375 [inline]
       blkdev_common_ioctl+0x880/0x23d0 block/ioctl.c:505
       blkdev_ioctl+0x4eb/0x6f0 block/ioctl.c:627
       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 --> bdev_lock --> &bdev->bd_holder_lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&bdev->bd_holder_lock);
                               lock(bdev_lock);
                               lock(&bdev->bd_holder_lock);
  rlock(&type->s_umount_key#32);

 *** DEADLOCK ***

1 lock held by syz.1.5077/22953:
 #0: ffff888148ca9808 (&bdev->bd_holder_lock){+.+.}-{3:3}, at: blkdev_flushbuf block/ioctl.c:373 [inline]
 #0: ffff888148ca9808 (&bdev->bd_holder_lock){+.+.}-{3:3}, at: blkdev_common_ioctl+0x814/0x23d0 block/ioctl.c:505

stack backtrace:
CPU: 1 PID: 22953 Comm: syz.1.5077 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
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_sync+0xa4/0x170 fs/super.c:1477
 blkdev_flushbuf block/ioctl.c:375 [inline]
 blkdev_common_ioctl+0x880/0x23d0 block/ioctl.c:505
 blkdev_ioctl+0x4eb/0x6f0 block/ioctl.c:627
 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: 0033:0x7fbdcab8ebe9
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:00007fbdc8db4038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fbdcadc6180 RCX: 00007fbdcab8ebe9
RDX: 0000000000000008 RSI: 0000000000001261 RDI: 0000000000000009
RBP: 00007fbdcac11e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fbdcadc6218 R14: 00007fbdcadc6180 R15: 00007ffca0a78fb8
 </TASK>