[v6.1] possible deadlock in vfs_removexattr

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 909ba1f1b414 Linux 6.1.90
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=17f4b4f0980000
kernel config: https://syzkaller.appspot.com/x/.config?x=3be6d6f79b879a67
dashboard link: https://syzkaller.appspot.com/bug?extid=3a14550adf50e687c7b5
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/63178de7cba7/disk-909ba1f1.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/25dec90d8126/vmlinux-909ba1f1.xz
kernel image: https://storage.googleapis.com/syzbot-assets/25509ea1c6cd/bzImage-909ba1f1.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+3a1455...@syzkaller.appspotmail.com

REISERFS (device loop4): checking transaction log (loop4)
REISERFS (device loop4): Using tea hash to sort names
REISERFS (device loop4): Created .reiserfs_priv - reserved for xattr storage.
======================================================
WARNING: possible circular locking dependency detected
6.1.90-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.4/6537 is trying to acquire lock:
ffff8880580002e0 (&type->i_mutex_dir_key#10){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:758 [inline]
ffff8880580002e0 (&type->i_mutex_dir_key#10){+.+.}-{3:3}, at: vfs_removexattr+0xe8/0x2a0 fs/xattr.c:535

but task is already holding lock:
ffff888013aee460 (sb_writers#14){.+.+}-{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#14){.+.+}-{0:0}:
lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5662
percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
__sb_start_write include/linux/fs.h:1891 [inline]
sb_start_write+0x4d/0x1c0 include/linux/fs.h:1966
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:51 [inline]
do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #1 (&sbi->lock){+.+.}-{3:3}:
lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5662
__mutex_lock_common kernel/locking/mutex.c:603 [inline]
__mutex_lock+0x132/0xd80 kernel/locking/mutex.c:747
reiserfs_write_lock+0x76/0xd0 fs/reiserfs/lock.c:27
reiserfs_lookup+0x15c/0x4b0 fs/reiserfs/namei.c:364
__lookup_slow+0x27e/0x3d0 fs/namei.c:1690
lookup_one_len+0x187/0x2d0 fs/namei.c:2742
reiserfs_lookup_privroot+0x85/0x1e0 fs/reiserfs/xattr.c:973
reiserfs_fill_super+0x1957/0x2620 fs/reiserfs/super.c:2192
mount_bdev+0x2c9/0x3f0 fs/super.c:1432
legacy_get_tree+0xeb/0x180 fs/fs_context.c:632
vfs_get_tree+0x88/0x270 fs/super.c:1562
do_new_mount+0x2ba/0xb40 fs/namespace.c:3051
do_mount fs/namespace.c:3394 [inline]
__do_sys_mount fs/namespace.c:3602 [inline]
__se_sys_mount+0x2d5/0x3c0 fs/namespace.c:3579
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #0 (&type->i_mutex_dir_key#10){+.+.}-{3:3}:
check_prev_add kernel/locking/lockdep.c:3090 [inline]
check_prevs_add kernel/locking/lockdep.c:3209 [inline]
validate_chain+0x1661/0x5950 kernel/locking/lockdep.c:3825
__lock_acquire+0x125b/0x1f80 kernel/locking/lockdep.c:5049
lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5662
down_write+0x36/0x60 kernel/locking/rwsem.c:1573
inode_lock include/linux/fs.h:758 [inline]
vfs_removexattr+0xe8/0x2a0 fs/xattr.c:535
removexattr fs/xattr.c:878 [inline]
path_removexattr+0x22a/0x320 fs/xattr.c:892
__do_sys_removexattr fs/xattr.c:906 [inline]
__se_sys_removexattr fs/xattr.c:903 [inline]
__x64_sys_removexattr+0x5c/0x70 fs/xattr.c:903
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2

other info that might help us debug this:

Chain exists of:
&type->i_mutex_dir_key#10 --> &sbi->lock --> sb_writers#14

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(sb_writers#14);
lock(&sbi->lock);
lock(sb_writers#14);
lock(&type->i_mutex_dir_key#10);

*** DEADLOCK ***

1 lock held by syz-executor.4/6537:
#0: ffff888013aee460 (sb_writers#14){.+.+}-{0:0}, at: mnt_want_write+0x3b/0x80 fs/namespace.c:393

stack backtrace:
CPU: 0 PID: 6537 Comm: syz-executor.4 Not tainted 6.1.90-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
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:2170
check_prev_add kernel/locking/lockdep.c:3090 [inline]
check_prevs_add kernel/locking/lockdep.c:3209 [inline]
validate_chain+0x1661/0x5950 kernel/locking/lockdep.c:3825
__lock_acquire+0x125b/0x1f80 kernel/locking/lockdep.c:5049
lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5662
down_write+0x36/0x60 kernel/locking/rwsem.c:1573
inode_lock include/linux/fs.h:758 [inline]
vfs_removexattr+0xe8/0x2a0 fs/xattr.c:535
removexattr fs/xattr.c:878 [inline]
path_removexattr+0x22a/0x320 fs/xattr.c:892
__do_sys_removexattr fs/xattr.c:906 [inline]
__se_sys_removexattr fs/xattr.c:903 [inline]
__x64_sys_removexattr+0x5c/0x70 fs/xattr.c:903
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f353b87dd69
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f353a3f60c8 EFLAGS: 00000246 ORIG_RAX: 00000000000000c5
RAX: ffffffffffffffda RBX: 00007f353b9abf80 RCX: 00007f353b87dd69
RDX: 0000000000000000 RSI: 0000000020000540 RDI: 00000000200000c0
RBP: 00007f353b8ca49e R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007f353b9abf80 R15: 00007ffd85dfe038
</TASK>


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup