syzbot


possible deadlock in do_unlinkat

Status: upstream: reported C repro on 2023/05/27 20:30
Bug presence: origin:upstream
Labels: missing-backport
[Documentation on labels]
Reported-by: syzbot+6b0854d47388370d942f@syzkaller.appspotmail.com
First crash: 504d, last: 6d05h
Fix bisection: failed (error log, bisect log)
  
Bug presence (1)
Date Name Commit Repro Result
2024/10/08 upstream (ToT) 87d6aab2389e C [report] possible deadlock in do_unlinkat
Similar bugs (2)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 possible deadlock in do_unlinkat origin:upstream C error 2 171d 506d 0/3 upstream: reported C repro on 2023/05/26 03:11
upstream possible deadlock in do_unlinkat reiserfs C error done 7 278d 502d 0/28 auto-obsoleted due to no activity on 2024/05/28 17:00
Last patch testing requests (2)
Created Duration User Patch Repo Result
2024/10/07 06:35 11m retest repro linux-5.15.y report log
2024/10/07 06:35 8m retest repro linux-5.15.y report log
Fix bisection attempts (6)
Created Duration User Patch Repo Result
2024/08/13 00:29 1h24m fix candidate upstream error job log
2024/05/01 22:32 5m fix candidate upstream error job log
2024/03/28 07:35 0m fix candidate upstream error job log
2024/02/21 22:01 1m fix candidate upstream error job log
2024/01/14 22:17 1m fix candidate upstream error job log
2023/08/09 04:49 2h39m bisect fix linux-5.15.y error job log

Sample crash report:
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
5.15.117-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor416/3499 is trying to acquire lock:
ffff888140faf090 (&sbi->lock){+.+.}-{3:3}, at: reiserfs_write_lock+0x76/0xd0 fs/reiserfs/lock.c:27

but task is already holding lock:
ffff8880708b02e0 (&type->i_mutex_dir_key#6/1){+.+.}-{3:3}, at: inode_lock_nested include/linux/fs.h:822 [inline]
ffff8880708b02e0 (&type->i_mutex_dir_key#6/1){+.+.}-{3:3}, at: do_unlinkat+0x260/0x940 fs/namei.c:4260

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+0x1db/0x4f0 kernel/locking/lockdep.c:5622
       down_write_nested+0xa0/0x180 kernel/locking/rwsem.c:1657
       inode_lock_nested include/linux/fs.h:822 [inline]
       do_unlinkat+0x260/0x940 fs/namei.c:4260
       __do_sys_unlinkat fs/namei.c:4320 [inline]
       __se_sys_unlinkat fs/namei.c:4313 [inline]
       __x64_sys_unlinkat+0xca/0xf0 fs/namei.c:4313
       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+0x61/0xcb

-> #1 (sb_writers#9){.+.+}-{0:0}:
       lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5622
       percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
       __sb_start_write include/linux/fs.h:1742 [inline]
       sb_start_write+0x4f/0x1c0 include/linux/fs.h:1812
       mnt_want_write_file+0x5a/0x1f0 fs/namespace.c:421
       reiserfs_ioctl+0x170/0x340 fs/reiserfs/ioctl.c:103
       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+0x3d/0xb0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x61/0xcb

-> #0 (&sbi->lock){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3053 [inline]
       check_prevs_add kernel/locking/lockdep.c:3172 [inline]
       validate_chain+0x1646/0x58b0 kernel/locking/lockdep.c:3787
       __lock_acquire+0x1295/0x1ff0 kernel/locking/lockdep.c:5011
       lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5622
       __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
       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:1560
       do_unlinkat+0x28e/0x940 fs/namei.c:4261
       __do_sys_unlinkat fs/namei.c:4320 [inline]
       __se_sys_unlinkat fs/namei.c:4313 [inline]
       __x64_sys_unlinkat+0xca/0xf0 fs/namei.c:4313
       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+0x61/0xcb

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-executor416/3499:
 #0: ffff888015b90460 (sb_writers#9){.+.+}-{0:0}, at: mnt_want_write+0x3b/0x80 fs/namespace.c:377
 #1: ffff8880708b02e0 (&type->i_mutex_dir_key#6/1){+.+.}-{3:3}, at: inode_lock_nested include/linux/fs.h:822 [inline]
 #1: ffff8880708b02e0 (&type->i_mutex_dir_key#6/1){+.+.}-{3:3}, at: do_unlinkat+0x260/0x940 fs/namei.c:4260

stack backtrace:
CPU: 1 PID: 3499 Comm: syz-executor416 Not tainted 5.15.117-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+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+0x1646/0x58b0 kernel/locking/lockdep.c:3787
 __lock_acquire+0x1295/0x1ff0 kernel/locking/lockdep.c:5011
 lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5622
 __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
 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:1560
 do_unlinkat+0x28e/0x940 fs/namei.c:4261
 __do_sys_unlinkat fs/namei.c:4320 [inline]
 __se_sys_unlinkat fs/namei.c:4313 [inline]
 __x64_sys_unlinkat+0xca/0xf0 fs/namei.c:4313
 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+0x61/0xcb
RIP: 0033:0x7f179e177909
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:00007fff2418f508 EFLAGS: 00000246 ORIG_RAX: 0000000000000107
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f179e177909
RDX: 00000000000000

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2023/06/19 08:59 linux-5.15.y 471e639e59d1 f3921d4d .config console log report syz C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-linux-5-15-kasan possible deadlock in do_unlinkat
2023/05/27 20:30 linux-5.15.y 1fe619a7d252 cf184559 .config console log report syz C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-linux-5-15-kasan-arm64 possible deadlock in do_unlinkat
* Struck through repros no longer work on HEAD.