possible deadlock in btrfs_dirty_inode (3)

Status: upstream: reported C repro on 2024/12/09 11:33
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+30f24026dfac984b80fc@syzkaller.appspotmail.com
First crash: 614d, last: 17h34m
Fix bisection: the issue occurs on the latest tested release (bisect log)
Crash: possible deadlock in btrfs_dirty_inode (log)
Repro: C syz .config
  
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2024/12/09 linux-5.15.y (ToT) 0a51d2d4527b C [report] possible deadlock in btrfs_dirty_inode
2024/12/09 upstream (ToT) 7cb1b4663150 C Didn't crash
▶ ▼ Similar bugs (4)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream possible deadlock in btrfs_dirty_inode (2) prio:high btrfs 4 68 14d 607d 0/29 upstream: reported on 2024/12/16 02:12
linux-5.15 possible deadlock in btrfs_dirty_inode (2) 4 2 791d 854d 0/3 auto-obsoleted due to no activity on 2024/09/22 15:54
linux-5.15 possible deadlock in btrfs_dirty_inode 4 3 1151d 1170d 0/3 auto-obsoleted due to no activity on 2023/09/28 23:24
upstream possible deadlock in btrfs_dirty_inode btrfs 4 syz, C error done 48 1357d 1369d 0/29 auto-obsoleted due to no activity on 2023/05/16 05:18
▶ ▼ Last patch testing requests (8)
Created Duration User Patch Repo Result
2026/08/14 19:54 14m retest repro linux-5.15.y report job log log
2026/05/30 21:38 14m retest repro linux-5.15.y report log
2026/03/18 06:12 9m retest repro linux-5.15.y report log
2026/01/07 05:44 11m retest repro linux-5.15.y report log
2025/10/29 01:00 9m retest repro linux-5.15.y report log
2025/08/19 12:16 12m retest repro linux-5.15.y report log
2025/06/10 03:25 12m retest repro linux-5.15.y report log
2025/03/31 15:07 15m retest repro linux-5.15.y report log
▶ ▼ Fix bisection attempts (2)
Created Duration User Patch Repo Result
2025/02/11 07:02 1h36m fix candidate upstream OK (0) job log
2025/01/19 14:41 2h05m bisect fix linux-5.15.y OK (0) job log log

Sample crash report:
BTRFS info (device loop0): clearing free space tree
BTRFS info (device loop0): clearing compat-ro feature flag for FREE_SPACE_TREE (0x1)
BTRFS info (device loop0): clearing compat-ro feature flag for FREE_SPACE_TREE_VALID (0x2)
======================================================
WARNING: possible circular locking dependency detected
5.15.173-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor302/4161 is trying to acquire lock:
ffff88802a33c650 (sb_internal#2){.+.+}-{0:0}, at: btrfs_dirty_inode+0xcc/0x1c0 fs/btrfs/inode.c:6436

but task is already holding lock:
ffff888071218610 (&type->i_mutex_dir_key#6){++++}-{3:3}, at: inode_lock include/linux/fs.h:789 [inline]
ffff888071218610 (&type->i_mutex_dir_key#6){++++}-{3:3}, at: chown_common+0x499/0x890 fs/open.c:674

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&type->i_mutex_dir_key#6){++++}-{3:3}:
       lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5623
       down_read+0x45/0x2e0 kernel/locking/rwsem.c:1498
       inode_lock_shared include/linux/fs.h:799 [inline]
       lookup_slow+0x45/0x70 fs/namei.c:1679
       walk_component+0x48c/0x610 fs/namei.c:1976
       lookup_last fs/namei.c:2431 [inline]
       path_lookupat+0x16f/0x450 fs/namei.c:2455
       filename_lookup+0x230/0x5c0 fs/namei.c:2484
       kern_path+0x37/0x180 fs/namei.c:2582
       lookup_bdev+0xc1/0x280 block/bdev.c:979
       device_matched fs/btrfs/volumes.c:568 [inline]
       btrfs_free_stale_devices+0x71f/0xb00 fs/btrfs/volumes.c:608
       btrfs_forget_devices+0x52/0x80 fs/btrfs/volumes.c:1395
       btrfs_control_ioctl+0x108/0x210 fs/btrfs/super.c:2451
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:874 [inline]
       __se_sys_ioctl+0xf1/0x160 fs/ioctl.c:860
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #2 (&fs_devs->device_list_mutex){+.+.}-{3:3}:
       lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5623
       __mutex_lock_common+0x1da/0x25a0 kernel/locking/mutex.c:596
       __mutex_lock kernel/locking/mutex.c:729 [inline]
       mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
       btrfs_run_dev_stats+0xeb/0xfd0 fs/btrfs/volumes.c:7949
       commit_cowonly_roots+0x1cb/0x9d0 fs/btrfs/transaction.c:1290
       btrfs_commit_transaction+0x13af/0x3800 fs/btrfs/transaction.c:2392
       btrfs_clear_free_space_tree+0x755/0xbd0 fs/btrfs/free-space-tree.c:1264
       btrfs_start_pre_rw_mount+0x2b0/0x680 fs/btrfs/disk-io.c:3079
       open_ctree+0x2dcf/0x3500 fs/btrfs/disk-io.c:3634
       btrfs_fill_super+0x1c7/0x2d0 fs/btrfs/super.c:1387
       btrfs_mount_root+0x803/0x930 fs/btrfs/super.c:1752
       legacy_get_tree+0xeb/0x180 fs/fs_context.c:611
       vfs_get_tree+0x88/0x270 fs/super.c:1530
       fc_mount fs/namespace.c:1000 [inline]
       vfs_kern_mount+0xb8/0x150 fs/namespace.c:1030
       btrfs_mount+0x395/0xb40 fs/btrfs/super.c:1812
       legacy_get_tree+0xeb/0x180 fs/fs_context.c:611
       vfs_get_tree+0x88/0x270 fs/super.c:1530
       do_new_mount+0x2ba/0xb40 fs/namespace.c:3012
       do_mount fs/namespace.c:3355 [inline]
       __do_sys_mount fs/namespace.c:3563 [inline]
       __se_sys_mount+0x2d5/0x3c0 fs/namespace.c:3540
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #1 (&fs_info->tree_log_mutex){+.+.}-{3:3}:
       reacquire_held_locks+0x3a2/0x660 kernel/locking/lockdep.c:5150
       __lock_release kernel/locking/lockdep.c:5339 [inline]
       lock_release+0x369/0x9a0 kernel/locking/lockdep.c:5643
       __mutex_unlock_slowpath+0xde/0x750 kernel/locking/mutex.c:851
       btrfs_commit_transaction+0x1e34/0x3800 fs/btrfs/transaction.c:2439
       btrfs_clear_free_space_tree+0x755/0xbd0 fs/btrfs/free-space-tree.c:1264
       btrfs_start_pre_rw_mount+0x2b0/0x680 fs/btrfs/disk-io.c:3079
       open_ctree+0x2dcf/0x3500 fs/btrfs/disk-io.c:3634
       btrfs_fill_super+0x1c7/0x2d0 fs/btrfs/super.c:1387
       btrfs_mount_root+0x803/0x930 fs/btrfs/super.c:1752
       legacy_get_tree+0xeb/0x180 fs/fs_context.c:611
       vfs_get_tree+0x88/0x270 fs/super.c:1530
       fc_mount fs/namespace.c:1000 [inline]
       vfs_kern_mount+0xb8/0x150 fs/namespace.c:1030
       btrfs_mount+0x395/0xb40 fs/btrfs/super.c:1812
       legacy_get_tree+0xeb/0x180 fs/fs_context.c:611
       vfs_get_tree+0x88/0x270 fs/super.c:1530
       do_new_mount+0x2ba/0xb40 fs/namespace.c:3012
       do_mount fs/namespace.c:3355 [inline]
       __do_sys_mount fs/namespace.c:3563 [inline]
       __se_sys_mount+0x2d5/0x3c0 fs/namespace.c:3540
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #0 (sb_internal#2){.+.+}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3053 [inline]
       check_prevs_add kernel/locking/lockdep.c:3172 [inline]
       validate_chain+0x1649/0x5930 kernel/locking/lockdep.c:3788
       __lock_acquire+0x1295/0x1ff0 kernel/locking/lockdep.c:5012
       lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5623
       percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
       __sb_start_write include/linux/fs.h:1813 [inline]
       sb_start_intwrite include/linux/fs.h:1930 [inline]
       start_transaction+0x5a8/0x11a0 fs/btrfs/transaction.c:678
       btrfs_dirty_inode+0xcc/0x1c0 fs/btrfs/inode.c:6436
       btrfs_setattr+0x2d0/0xf70 fs/btrfs/inode.c:5495
       notify_change+0xc6d/0xf50 fs/attr.c:505
       chown_common+0x592/0x890 fs/open.c:680
       do_fchownat+0x169/0x240 fs/open.c:711
       __do_sys_lchown fs/open.c:736 [inline]
       __se_sys_lchown fs/open.c:734 [inline]
       __x64_sys_lchown+0x81/0x90 fs/open.c:734
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

other info that might help us debug this:

Chain exists of:
  sb_internal#2 --> &fs_devs->device_list_mutex --> &type->i_mutex_dir_key#6

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&type->i_mutex_dir_key#6);
                               lock(&fs_devs->device_list_mutex);
                               lock(&type->i_mutex_dir_key#6);
  lock(sb_internal#2);

 *** DEADLOCK ***

2 locks held by syz-executor302/4161:
 #0: ffff88802a33c460 (sb_writers#9){.+.+}-{0:0}, at: mnt_want_write+0x3b/0x80 fs/namespace.c:377
 #1: ffff888071218610 (&type->i_mutex_dir_key#6){++++}-{3:3}, at: inode_lock include/linux/fs.h:789 [inline]
 #1: ffff888071218610 (&type->i_mutex_dir_key#6){++++}-{3:3}, at: chown_common+0x499/0x890 fs/open.c:674

stack backtrace:
CPU: 1 PID: 4161 Comm: syz-executor302 Not tainted 5.15.173-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e3/0x2d0 lib/dump_stack.c:106
 check_noncircular+0x2f8/0x3b0 kernel/locking/lockdep.c:2133
 check_prev_add kernel/locking/lockdep.c:3053 [inline]
 check_prevs_add kernel/locking/lockdep.c:3172 [inline]
 validate_chain+0x1649/0x5930 kernel/locking/lockdep.c:3788
 __lock_acquire+0x1295/0x1ff0 kernel/locking/lockdep.c:5012
 lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5623
 percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
 __sb_start_write include/linux/fs.h:1813 [inline]
 sb_start_intwrite include/linux/fs.h:1930 [inline]
 start_transaction+0x5a8/0x11a0 fs/btrfs/transaction.c:678
 btrfs_dirty_inode+0xcc/0x1c0 fs/btrfs/inode.c:6436
 btrfs_setattr+0x2d0/0xf70 fs/btrfs/inode.c:5495
 notify_change+0xc6d/0xf50 fs/attr.c:505
 chown_common+0x592/0x890 fs/open.c:680
 do_fchownat+0x169/0x240 fs/open.c:711
 __do_sys_lchown fs/open.c:736 [inline]
 __se_sys_lchown fs/open.c:734 [inline]
 __x64_sys_lchown+0x81/0x90 fs/open.c:734
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fc70478cb39
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 61 17 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffcf58a9ee8 EFLAGS: 00000246 ORIG_RA

Crashes (5):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2024/12/09 13:19 linux-5.15.y 0a51d2d4527b 9ac0fdc6 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-linux-5-15-kasan possible deadlock in btrfs_dirty_inode
2025/12/01 14:28 linux-5.15.y cc5ec8769306 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan possible deadlock in btrfs_dirty_inode
2025/01/21 23:09 linux-5.15.y 4735586da88e da72ac06 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan possible deadlock in btrfs_dirty_inode
2024/12/09 11:35 linux-5.15.y 0a51d2d4527b 9ac0fdc6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan possible deadlock in btrfs_dirty_inode
2024/12/09 11:33 linux-5.15.y 0a51d2d4527b 9ac0fdc6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan possible deadlock in btrfs_dirty_inode
* Struck through repros no longer work on HEAD.