possible deadlock in vfs_fileattr_set (2)

Status: upstream: reported C repro on 2025/02/05 13:53
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+e6639b4641b1e23b6cec@syzkaller.appspotmail.com
First crash: 544d, last: 405d
Fix bisection: failed (error log, bisect log)
  
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2025/03/23 linux-5.15.y (ToT) 0c935c049b5c C [report] possible deadlock in vfs_fileattr_set
2025/03/23 upstream (ToT) 586de92313fc C Didn't crash
▶ ▼ Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 possible deadlock in vfs_fileattr_set 4 1 1208d 1208d 0/3 auto-obsoleted due to no activity on 2023/08/10 15:05
upstream possible deadlock in vfs_fileattr_set fs 4 syz, C done 10 1078d 1358d 0/29 auto-obsoleted due to no activity on 2023/11/29 02:28
linux-6.1 possible deadlock in vfs_fileattr_set origin:upstream missing-backport 4 syz, C done 3 575d 859d 0/3 upstream: reported C repro on 2024/03/27 09:48
▶ ▼ Last patch testing requests (10)
Created Duration User Patch Repo Result
2026/06/15 10:36 17m retest repro linux-5.15.y report log
2026/05/19 08:01 16m retest repro linux-5.15.y report log
2026/04/05 15:09 11m retest repro linux-5.15.y report log
2026/03/10 04:15 43m retest repro linux-5.15.y report log
2026/01/25 13:33 1h18m retest repro linux-5.15.y report log
2025/12/30 01:45 12m retest repro linux-5.15.y report log
2025/11/16 10:17 15m retest repro linux-5.15.y report log
2025/10/20 08:29 11m retest repro linux-5.15.y report log
2025/09/05 00:49 10m retest repro linux-5.15.y report log
2025/08/11 07:37 12m retest repro linux-5.15.y report log
▶ ▼ Fix bisection attempts (8)
Created Duration User Patch Repo Result
2026/07/21 19:08 15m fix candidate upstream error job log
2026/06/01 05:13 15m fix candidate upstream error job log
2026/03/23 16:15 1m fix candidate upstream error job log
2026/02/21 12:36 1m fix candidate upstream error job log
2026/01/22 11:26 1m fix candidate upstream error job log
2025/12/04 13:49 3m fix candidate upstream error job log
2025/06/03 14:52 1m fix candidate upstream error job log
2025/03/22 17:32 1m bisect fix linux-5.15.y error job log

Sample crash report:
REISERFS warning: green-16003 errcatch_is_left_mergeable: Invalid item type observed, run fsck ASAP
REISERFS (device loop0): Created .reiserfs_priv - reserved for xattr storage.
======================================================
WARNING: possible circular locking dependency detected
5.15.185-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor373/4024 is trying to acquire lock:
ffff0000de6e02e0 (&type->i_mutex_dir_key#6){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:787 [inline]
ffff0000de6e02e0 (&type->i_mutex_dir_key#6){+.+.}-{3:3}, at: vfs_fileattr_set+0x108/0x8fc fs/ioctl.c:685

but task is already holding lock:
ffff0000ddde4460 (sb_writers#8){.+.+}-{0:0}, at: mnt_want_write_file+0x64/0x1e8 fs/namespace.c:421

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (sb_writers#8){.+.+}-{0:0}:
       percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
       __sb_start_write include/linux/fs.h:1811 [inline]
       sb_start_write+0xec/0x358 include/linux/fs.h:1881
       mnt_want_write_file+0x64/0x1e8 fs/namespace.c:421
       reiserfs_ioctl+0x118/0x4b4 fs/reiserfs/ioctl.c:103
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:874 [inline]
       __se_sys_ioctl fs/ioctl.c:860 [inline]
       __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:860
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
       do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
       el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608
       el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
       el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

-> #1 (&sbi->lock){+.+.}-{3:3}:
       __mutex_lock_common+0x194/0x1edc kernel/locking/mutex.c:596
       __mutex_lock kernel/locking/mutex.c:729 [inline]
       mutex_lock_nested+0xac/0x11c kernel/locking/mutex.c:743
       reiserfs_write_lock+0x7c/0xe8 fs/reiserfs/lock.c:27
       reiserfs_lookup+0x11c/0x378 fs/reiserfs/namei.c:364
       __lookup_slow+0x24c/0x380 fs/namei.c:1663
       lookup_one_len+0x178/0x28c fs/namei.c:2718
       reiserfs_lookup_privroot+0x8c/0x204 fs/reiserfs/xattr.c:980
       reiserfs_fill_super+0x17b0/0x1bb4 fs/reiserfs/super.c:2178
       mount_bdev+0x264/0x358 fs/super.c:1400
       get_super_block+0x44/0x58 fs/reiserfs/super.c:2608
       legacy_get_tree+0xd4/0x16c fs/fs_context.c:611
       vfs_get_tree+0x90/0x274 fs/super.c:1530
       do_new_mount+0x228/0x810 fs/namespace.c:3010
       path_mount+0x5b4/0x1000 fs/namespace.c:3340
       do_mount fs/namespace.c:3353 [inline]
       __do_sys_mount fs/namespace.c:3561 [inline]
       __se_sys_mount fs/namespace.c:3538 [inline]
       __arm64_sys_mount+0x514/0x5e4 fs/namespace.c:3538
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
       do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
       el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608
       el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
       el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

-> #0 (&type->i_mutex_dir_key#6){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3053 [inline]
       check_prevs_add kernel/locking/lockdep.c:3172 [inline]
       validate_chain kernel/locking/lockdep.c:3788 [inline]
       __lock_acquire+0x2928/0x651c kernel/locking/lockdep.c:5012
       lock_acquire+0x1f4/0x620 kernel/locking/lockdep.c:5623
       down_write+0xbc/0x12c kernel/locking/rwsem.c:1551
       inode_lock include/linux/fs.h:787 [inline]
       vfs_fileattr_set+0x108/0x8fc fs/ioctl.c:685
       do_vfs_ioctl+0x1c18/0x2370 fs/ioctl.c:-1
       __do_sys_ioctl fs/ioctl.c:872 [inline]
       __se_sys_ioctl fs/ioctl.c:860 [inline]
       __arm64_sys_ioctl+0xe4/0x1c8 fs/ioctl.c:860
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
       do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
       el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608
       el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
       el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

other info that might help us debug this:

Chain exists of:
  &type->i_mutex_dir_key#6 --> &sbi->lock --> sb_writers#8

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(sb_writers#8);
                               lock(&sbi->lock);
                               lock(sb_writers#8);
  lock(&type->i_mutex_dir_key#6);

 *** DEADLOCK ***

1 lock held by syz-executor373/4024:
 #0: ffff0000ddde4460 (sb_writers#8){.+.+}-{0:0}, at: mnt_want_write_file+0x64/0x1e8 fs/namespace.c:421

stack backtrace:
CPU: 1 PID: 4024 Comm: syz-executor373 Not tainted 5.15.185-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call trace:
 dump_backtrace+0x0/0x43c arch/arm64/kernel/stacktrace.c:152
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:216
 __dump_stack+0x30/0x40 lib/dump_stack.c:88
 dump_stack_lvl+0xf8/0x160 lib/dump_stack.c:106
 dump_stack+0x1c/0x5c lib/dump_stack.c:113
 print_circular_bug+0x148/0x1b0 kernel/locking/lockdep.c:2011
 check_noncircular+0x240/0x2d4 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 kernel/locking/lockdep.c:3788 [inline]
 __lock_acquire+0x2928/0x651c kernel/locking/lockdep.c:5012
 lock_acquire+0x1f4/0x620 kernel/locking/lockdep.c:5623
 down_write+0xbc/0x12c kernel/locking/rwsem.c:1551
 inode_lock include/linux/fs.h:787 [inline]
 vfs_fileattr_set+0x108/0x8fc fs/ioctl.c:685
 do_vfs_ioctl+0x1c18/0x2370 fs/ioctl.c:-1
 __do_sys_ioctl fs/ioctl.c:872 [inline]
 __se_sys_ioctl fs/ioctl.c:860 [inline]
 __arm64_sys_ioctl+0xe4/0x1c8 fs/ioctl.c:860
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
 do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
 el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608
 el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/06/08 14:35 linux-5.15.y 1c700860e8bc 4826c28e .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-linux-5-15-kasan-arm64 possible deadlock in vfs_fileattr_set
2025/02/05 13:52 linux-5.15.y c16c81c81336 5896748e .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-linux-5-15-kasan-arm64 possible deadlock in vfs_fileattr_set
2025/06/08 11:35 linux-5.15.y 1c700860e8bc 4826c28e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-arm64 possible deadlock in vfs_fileattr_set
* Struck through repros no longer work on HEAD.