syzbot


possible deadlock in path_openat (2)

Status: upstream: reported C repro on 2022/10/11 06:35
Reported-by: syzbot+a844a888fbc0ba4829ce@syzkaller.appspotmail.com
First crash: 53d, last: 8h33m

Cause bisection: failed (bisect log)
similar bugs (4):
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream possible deadlock in path_openat C done unreliable 349 970d 1525d 0/24 auto-obsoleted due to no activity on 2022/09/16 21:43
android-49 possible deadlock in path_openat 5 1100d 1115d 0/3 auto-closed as invalid on 2020/03/24 08:43
linux-4.14 possible deadlock in path_openat C error 324 53d 1315d 0/1 upstream: reported C repro on 2019/04/24 01:40
linux-4.19 possible deadlock in path_openat C 853 9d19h 1263d 0/1 upstream: reported C repro on 2019/06/15 07:08

Sample crash report:
REISERFS (device loop0): Created .reiserfs_priv - reserved for xattr storage.
======================================================
WARNING: possible circular locking dependency detected
6.0.0-syzkaller-05118-g833477fce7a1 #0 Not tainted
------------------------------------------------------
syz-executor874/3610 is trying to acquire lock:
ffff888073d582e0 (&type->i_mutex_dir_key#6){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:756 [inline]
ffff888073d582e0 (&type->i_mutex_dir_key#6){+.+.}-{3:3}, at: open_last_lookups fs/namei.c:3478 [inline]
ffff888073d582e0 (&type->i_mutex_dir_key#6){+.+.}-{3:3}, at: path_openat+0x7b9/0x2df0 fs/namei.c:3688

but task is already holding lock:
ffff888075052460 (sb_writers#9){.+.+}-{0:0}, at: mnt_want_write+0x3b/0x80 fs/namespace.c:393

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (sb_writers#9){.+.+}-{0:0}:
       lock_acquire+0x182/0x3c0 kernel/locking/lockdep.c:5666
       percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
       __sb_start_write include/linux/fs.h:1826 [inline]
       sb_start_write+0x4d/0x1a0 include/linux/fs.h:1901
       mnt_want_write_file+0x5a/0x1f0 fs/namespace.c:437
       reiserfs_ioctl+0x16e/0x340 fs/reiserfs/ioctl.c:103
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:870 [inline]
       __se_sys_ioctl+0xfb/0x170 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

-> #1 (&sbi->lock){+.+.}-{3:3}:
       lock_acquire+0x182/0x3c0 kernel/locking/lockdep.c:5666
       __mutex_lock_common+0x1bd/0x26e0 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+0x77/0xd0 fs/reiserfs/lock.c:27
       reiserfs_lookup+0x147/0x490 fs/reiserfs/namei.c:364
       __lookup_slow+0x266/0x3a0 fs/namei.c:1685
       lookup_one_len+0x430/0x690 fs/namei.c:2711
       reiserfs_lookup_privroot+0x85/0x1e0 fs/reiserfs/xattr.c:973
       reiserfs_fill_super+0x2071/0x24a0 fs/reiserfs/super.c:2176
       mount_bdev+0x26c/0x3a0 fs/super.c:1400
       legacy_get_tree+0xea/0x180 fs/fs_context.c:610
       vfs_get_tree+0x88/0x270 fs/super.c:1530
       do_new_mount+0x289/0xad0 fs/namespace.c:3040
       do_mount fs/namespace.c:3383 [inline]
       __do_sys_mount fs/namespace.c:3591 [inline]
       __se_sys_mount+0x2d3/0x3c0 fs/namespace.c:3568
       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 (&type->i_mutex_dir_key#6){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3095 [inline]
       check_prevs_add kernel/locking/lockdep.c:3214 [inline]
       validate_chain+0x18c1/0x6bd0 kernel/locking/lockdep.c:3829
       __lock_acquire+0x1292/0x1f60 kernel/locking/lockdep.c:5053
       lock_acquire+0x182/0x3c0 kernel/locking/lockdep.c:5666
       down_write+0x95/0x170 kernel/locking/rwsem.c:1552
       inode_lock include/linux/fs.h:756 [inline]
       open_last_lookups fs/namei.c:3478 [inline]
       path_openat+0x7b9/0x2df0 fs/namei.c:3688
       do_filp_open+0x264/0x4f0 fs/namei.c:3718
       do_sys_openat2+0x124/0x4e0 fs/open.c:1313
       do_sys_open fs/open.c:1329 [inline]
       __do_sys_creat fs/open.c:1405 [inline]
       __se_sys_creat fs/open.c:1399 [inline]
       __x64_sys_creat+0x11f/0x160 fs/open.c:1399
       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:
  &type->i_mutex_dir_key#6 --> &sbi->lock --> sb_writers#9

 Possible unsafe locking scenario:

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

 *** DEADLOCK ***

1 lock held by syz-executor874/3610:
 #0: ffff888075052460 (sb_writers#9){.+.+}-{0:0}, at: mnt_want_write+0x3b/0x80 fs/namespace.c:393

stack backtrace:
CPU: 0 PID: 3610 Comm: syz-executor874 Not tainted 6.0.0-syzkaller-05118-g833477fce7a1 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/22/2022
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1b1/0x28e lib/dump_stack.c:106
 check_noncircular+0x2cc/0x390 kernel/locking/lockdep.c:2175
 check_prev_add kernel/locking/lockdep.c:3095 [inline]
 check_prevs_add kernel/locking/lockdep.c:3214 [inline]
 validate_chain+0x18c1/0x6bd0 kernel/locking/lockdep.c:3829
 __lock_acquire+0x1292/0x1f60 kernel/locking/lockdep.c:5053
 lock_acquire+0x182/0x3c0 kernel/locking/lockdep.c:5666
 down_write+0x95/0x170 kernel/locking/rwsem.c:1552
 inode_lock include/linux/fs.h:756 [inline]
 open_last_lookups fs/namei.c:3478 [inline]
 path_openat+0x7b9/0x2df0 fs/namei.c:3688
 do_filp_open+0x264/0x4f0 fs/namei.c:3718
 do_sys_openat2+0x124/0x4e0 fs/open.c:1313
 do_sys_open fs/open.c:1329 [inline]
 __do_sys_creat fs/open.c:1405 [inline]
 __se_sys_creat fs/open.c:1399 [inline]
 __x64_sys_creat+0x11f/0x160 fs/open.c:1399
 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: 0033:0x7f4f0b64b899
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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:00007fffdc5eba48 EFLAGS: 00000246 ORIG_RAX: 0000000000000055
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f4f0b64b899
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000040
RBP: 0000000000000000 R08: 00007f4f0b6b9ec0 R09: 00007f4f0b6b9ec0
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fffdc5eba70
R13: 0000000000000000 R14: 431bde82d7b634db R15: 0000000000000000
 </TASK>

Fix bisection attempts:
Manager Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Title
ci2-upstream-fs 2022/11/07 07:02 upstream f0c4d9fc9cc9 80b58a42 .config log report syz C
* Struck through repros no longer work on HEAD.
Crashes (3):
Manager Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Title
ci2-upstream-fs 2022/10/07 06:25 upstream 833477fce7a1 80b58a42 .config log report syz C possible deadlock in path_openat
ci-qemu-upstream-386 2022/11/29 03:10 upstream b7b275e60bcd ca9683b8 .config log report info possible deadlock in path_openat
ci-qemu-upstream-386 2022/11/26 04:58 upstream 0b1dcc2cf55a f4470a7b .config log report info possible deadlock in path_openat
* Struck through repros no longer work on HEAD.