syzbot


possible deadlock in ext4_process_orphan

Status: auto-obsoleted due to no activity on 2026/01/09 16:00
Reported-by: syzbot+30f7a3132b5a5f1e212c@syzkaller.appspotmail.com
First crash: 219d, last: 163d

Sample crash report:
Quota error (device loop2): v2_read_file_info: Free block number 1 out of range (1, 6).
EXT4-fs warning (device loop2): ext4_enable_quotas:7175: Failed to enable quota tracking (type=1, err=-117, ino=4). Please run e2fsck to fix.
EXT4-fs (loop2): Cannot turn on quotas: error -117
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.2.376/7060 is trying to acquire lock:
ffff88805fa67210 (&type->i_mutex_dir_key#3){++++}-{3:3}, at: inode_lock include/linux/fs.h:804 [inline]
ffff88805fa67210 (&type->i_mutex_dir_key#3){++++}-{3:3}, at: ext4_process_orphan+0x187/0x300 fs/ext4/orphan.c:337

but task is already holding lock:
ffff88805d6180e0 (&type->s_umount_key#32){++++}-{3:3}, at: __super_lock fs/super.c:56 [inline]
ffff88805d6180e0 (&type->s_umount_key#32){++++}-{3:3}, at: __super_lock_excl fs/super.c:71 [inline]
ffff88805d6180e0 (&type->s_umount_key#32){++++}-{3:3}, at: get_tree_bdev+0x344/0x510 fs/super.c:1589

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #4 (&type->s_umount_key#32){++++}-{3:3}:
       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

-> #3 (&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

-> #2 (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

-> #1 (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_getdents fs/readdir.c:322 [inline]
       __se_sys_getdents+0xe9/0x260 fs/readdir.c:307
       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->i_mutex_dir_key#3){++++}-{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_write+0x97/0x1f0 kernel/locking/rwsem.c:1573
       inode_lock include/linux/fs.h:804 [inline]
       ext4_process_orphan+0x187/0x300 fs/ext4/orphan.c:337
       ext4_orphan_cleanup+0xbd4/0x1400 fs/ext4/orphan.c:474
       __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

other info that might help us debug this:

Chain exists of:
  &type->i_mutex_dir_key#3 --> &bdev->bd_holder_lock --> &type->s_umount_key#32

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&type->s_umount_key#32);
                               lock(&bdev->bd_holder_lock);
                               lock(&type->s_umount_key#32);
  lock(&type->i_mutex_dir_key#3);

 *** DEADLOCK ***

1 lock held by syz.2.376/7060:
 #0: ffff88805d6180e0 (&type->s_umount_key#32){++++}-{3:3}, at: __super_lock fs/super.c:56 [inline]
 #0: ffff88805d6180e0 (&type->s_umount_key#32){++++}-{3:3}, at: __super_lock_excl fs/super.c:71 [inline]
 #0: ffff88805d6180e0 (&type->s_umount_key#32){++++}-{3:3}, at: get_tree_bdev+0x344/0x510 fs/super.c:1589

stack backtrace:
CPU: 1 PID: 7060 Comm: syz.2.376 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
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_write+0x97/0x1f0 kernel/locking/rwsem.c:1573
 inode_lock include/linux/fs.h:804 [inline]
 ext4_process_orphan+0x187/0x300 fs/ext4/orphan.c:337
 ext4_orphan_cleanup+0xbd4/0x1400 fs/ext4/orphan.c:474
 __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
RIP: 0033:0x7f2acbb9066a
Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb a6 e8 de 1a 00 00 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f2acc9c2e68 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f2acc9c2ef0 RCX: 00007f2acbb9066a
RDX: 0000200000000040 RSI: 0000200000000000 RDI: 00007f2acc9c2eb0
RBP: 0000200000000040 R08: 00007f2acc9c2ef0 R09: 000000000001c917
R10: 000000000001c917 R11: 0000000000000246 R12: 0000200000000000
R13: 00007f2acc9c2eb0 R14: 00000000000004f2 R15: 0000200000000140
 </TASK>
EXT4-fs (loop2): 1 truncate cleaned up
EXT4-fs (loop2): mounted filesystem 00000000-0000-0000-0000-000000000000 ro without journal. Quota mode: writeback.

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/10/01 15:59 linux-6.6.y 147338df3487 a1859138 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ext4_process_orphan
2025/08/06 02:50 linux-6.6.y 3a8ababb8b6a ffe1dd46 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ext4_process_orphan
* Struck through repros no longer work on HEAD.