syzbot


possible deadlock in do_unlinkat

Status: upstream: reported C repro on 2023/05/26 03:11
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+05875840a94b3f7a627f@syzkaller.appspotmail.com
First crash: 386d, last: 51d
Fix bisection: failed (error log, bisect log)
  
Bug presence (1)
Date Name Commit Repro Result
2023/12/16 upstream (ToT) c8e97fc6b4c0 C [report] possible deadlock in do_unlinkat
Similar bugs (2)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 possible deadlock in do_unlinkat origin:upstream missing-backport C error 2 153d 384d 0/3 upstream: reported C repro on 2023/05/27 20:30
upstream possible deadlock in do_unlinkat reiserfs C error done 7 159d 383d 0/27 auto-obsoleted due to no activity on 2024/05/28 17:00
Fix bisection attempts (9)
Created Duration User Patch Repo Result
2024/05/30 14:08 29m bisect fix linux-6.1.y error job log (0)
2024/04/24 20:35 1h13m bisect fix linux-6.1.y job log (0) log
2024/03/25 15:03 1h11m bisect fix linux-6.1.y job log (0) log
2024/02/24 12:57 59m bisect fix linux-6.1.y job log (0) log
2024/01/16 04:56 59m bisect fix linux-6.1.y job log (0) log
2023/12/16 03:53 59m bisect fix linux-6.1.y job log (0) log
2023/11/15 13:24 1h32m bisect fix linux-6.1.y job log (0) log
2023/10/14 05:24 1h32m bisect fix linux-6.1.y job log (0) log
2023/09/05 22:49 1h32m bisect fix linux-6.1.y job log (0) log

Sample crash report:
REISERFS (device loop0): journal params: device loop0, size 512, journal first block 18, max trans len 256, max batch 225, max commit age 30, max trans age 30
REISERFS (device loop0): checking transaction log (loop0)
REISERFS (device loop0): Using r5 hash to sort names
reiserfs: enabling write barrier flush mode
REISERFS (device loop0): Created .reiserfs_priv - reserved for xattr storage.
======================================================
WARNING: possible circular locking dependency detected
6.1.35-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor396/3543 is trying to acquire lock:
ffff888018f43090 (&sbi->lock){+.+.}-{3:3}, at: reiserfs_write_lock+0x76/0xd0 fs/reiserfs/lock.c:27

but task is already holding lock:
ffff888072f382e0 (&type->i_mutex_dir_key#6/1){+.+.}-{3:3}, at: inode_lock_nested include/linux/fs.h:791 [inline]
ffff888072f382e0 (&type->i_mutex_dir_key#6/1){+.+.}-{3:3}, at: do_unlinkat+0x260/0x940 fs/namei.c:4303

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&type->i_mutex_dir_key#6/1){+.+.}-{3:3}:
       lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5669
       down_write_nested+0x39/0x60 kernel/locking/rwsem.c:1689
       inode_lock_nested include/linux/fs.h:791 [inline]
       do_unlinkat+0x260/0x940 fs/namei.c:4303
       __do_sys_unlinkat fs/namei.c:4363 [inline]
       __se_sys_unlinkat fs/namei.c:4356 [inline]
       __x64_sys_unlinkat+0xca/0xf0 fs/namei.c:4356
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x63/0xcd

-> #1 (sb_writers#9){.+.+}-{0:0}:
       lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5669
       percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
       __sb_start_write include/linux/fs.h:1832 [inline]
       sb_start_write+0x4d/0x1c0 include/linux/fs.h:1907
       mnt_want_write_file+0x5a/0x1f0 fs/namespace.c:437
       reiserfs_ioctl+0x170/0x340 fs/reiserfs/ioctl.c:103
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:870 [inline]
       __se_sys_ioctl+0xf1/0x160 fs/ioctl.c:856
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x63/0xcd

-> #0 (&sbi->lock){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3098 [inline]
       check_prevs_add kernel/locking/lockdep.c:3217 [inline]
       validate_chain+0x1667/0x58e0 kernel/locking/lockdep.c:3832
       __lock_acquire+0x125b/0x1f80 kernel/locking/lockdep.c:5056
       lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5669
       __mutex_lock_common+0x1d4/0x2520 kernel/locking/mutex.c:603
       __mutex_lock kernel/locking/mutex.c:747 [inline]
       mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:799
       reiserfs_write_lock+0x76/0xd0 fs/reiserfs/lock.c:27
       reiserfs_lookup+0x15c/0x4b0 fs/reiserfs/namei.c:364
       __lookup_hash+0x117/0x240 fs/namei.c:1601
       do_unlinkat+0x28e/0x940 fs/namei.c:4304
       __do_sys_unlinkat fs/namei.c:4363 [inline]
       __se_sys_unlinkat fs/namei.c:4356 [inline]
       __x64_sys_unlinkat+0xca/0xf0 fs/namei.c:4356
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x63/0xcd

other info that might help us debug this:

Chain exists of:
  &sbi->lock --> sb_writers#9 --> &type->i_mutex_dir_key#6/1

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&type->i_mutex_dir_key#6/1);
                               lock(sb_writers#9);
                               lock(&type->i_mutex_dir_key#6/1);
  lock(&sbi->lock);

 *** DEADLOCK ***

2 locks held by syz-executor396/3543:
 #0: ffff88807aa2e460 (sb_writers#9){.+.+}-{0:0}, at: mnt_want_write+0x3b/0x80 fs/namespace.c:393
 #1: ffff888072f382e0 (&type->i_mutex_dir_key#6/1){+.+.}-{3:3}, at: inode_lock_nested include/linux/fs.h:791 [inline]
 #1: ffff888072f382e0 (&type->i_mutex_dir_key#6/1){+.+.}-{3:3}, at: do_unlinkat+0x260/0x940 fs/namei.c:4303

stack backtrace:
CPU: 0 PID: 3543 Comm: syz-executor396 Not tainted 6.1.35-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/27/2023
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e3/0x2cb lib/dump_stack.c:106
 check_noncircular+0x2fa/0x3b0 kernel/locking/lockdep.c:2178
 check_prev_add kernel/locking/lockdep.c:3098 [inline]
 check_prevs_add kernel/locking/lockdep.c:3217 [inline]
 validate_chain+0x1667/0x58e0 kernel/locking/lockdep.c:3832
 __lock_acquire+0x125b/0x1f80 kernel/locking/lockdep.c:5056
 lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5669
 __mutex_lock_common+0x1d4/0x2520 kernel/locking/mutex.c:603
 __mutex_lock kernel/locking/mutex.c:747 [inline]
 mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:799
 reiserfs_write_lock+0x76/0xd0 fs/reiserfs/lock.c:27
 reiserfs_lookup+0x15c/0x4b0 fs/reiserfs/namei.c:364
 __lookup_hash+0x117/0x240 fs/namei.c:1601
 do_unlinkat+0x28e/0x940 fs/namei.c:4304
 __do_sys_unlinkat fs/namei.c:4363 [inline]
 __se_sys_unlinkat fs/namei.c:4356 [inline]
 __x64_sys_unlinkat+0xca/0xf0 fs/namei.c:4356
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f56d2edc909
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 51 14 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 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffc2ad02e58 EFLAGS: 00000246 ORIG_RAX: 0000000000000107
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2023/06/26 07:47 linux-6.1.y e84a4e368abe 79782afc .config console log report syz C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-linux-6-1-kasan possible deadlock in do_unlinkat
2023/05/26 03:11 linux-6.1.y a343b0dd87b4 0513b3e6 .config console log report syz C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-linux-6-1-kasan-arm64 possible deadlock in do_unlinkat
* Struck through repros no longer work on HEAD.