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SubjectRe: [syzbot] [reiserfs?] possible deadlock in open_xa_dir
From
syzbot has found a reproducer for the following issue on:

HEAD commit: 78b421b6a7c6 Merge tag 'linux-watchdog-6.4-rc1' of git://w..
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=150c42a8280000
kernel config: https://syzkaller.appspot.com/x/.config?x=73a06f6ef2d5b492
dashboard link: https://syzkaller.appspot.com/bug?extid=8fb64a61fdd96b50f3b8
compiler: Debian clang version 15.0.7, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14e2e518280000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17c03112280000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/25168a5d3be8/disk-78b421b6.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f5af9f784d9d/vmlinux-78b421b6.xz
kernel image: https://storage.googleapis.com/syzbot-assets/7781e4e3e606/bzImage-78b421b6.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/29a59b19c7a8/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+8fb64a61fdd96b50f3b8@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
6.3.0-syzkaller-13164-g78b421b6a7c6 #0 Not tainted
------------------------------------------------------
syz-executor363/4996 is trying to acquire lock:
ffff888074558980 (&type->i_mutex_dir_key#6/3){+.+.}-{3:3}, at: inode_lock_nested include/linux/fs.h:810 [inline]
ffff888074558980 (&type->i_mutex_dir_key#6/3){+.+.}-{3:3}, at: open_xa_root fs/reiserfs/xattr.c:128 [inline]
ffff888074558980 (&type->i_mutex_dir_key#6/3){+.+.}-{3:3}, at: open_xa_dir+0x136/0x610 fs/reiserfs/xattr.c:153

but task is already holding lock:
ffff8880156f2090 (&sbi->lock){+.+.}-{3:3}, at: reiserfs_write_lock_nested+0x5f/0xd0 fs/reiserfs/lock.c:78

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&sbi->lock){+.+.}-{3:3}:
lock_acquire+0x1e3/0x520 kernel/locking/lockdep.c:5691
__mutex_lock_common+0x1d8/0x2530 kernel/locking/mutex.c:603
__mutex_lock kernel/locking/mutex.c:747 [inline]
mutex_lock_nested+0x1b/0x20 kernel/locking/mutex.c:799
reiserfs_write_lock+0x7a/0xd0 fs/reiserfs/lock.c:27
reiserfs_mkdir+0x321/0x8f0 fs/reiserfs/namei.c:829
xattr_mkdir fs/reiserfs/xattr.c:77 [inline]
open_xa_root fs/reiserfs/xattr.c:137 [inline]
open_xa_dir+0x2cd/0x610 fs/reiserfs/xattr.c:153
xattr_lookup+0x24/0x280 fs/reiserfs/xattr.c:396
reiserfs_xattr_set_handle+0xfc/0xdc0 fs/reiserfs/xattr.c:534
reiserfs_security_write+0x157/0x1d0 fs/reiserfs/xattr_security.c:106
reiserfs_new_inode+0x1631/0x1d40 fs/reiserfs/inode.c:2111
reiserfs_create+0x3e7/0x6e0 fs/reiserfs/namei.c:666
lookup_open fs/namei.c:3492 [inline]
open_last_lookups fs/namei.c:3560 [inline]
path_openat+0x13df/0x3170 fs/namei.c:3788
do_filp_open+0x234/0x490 fs/namei.c:3818
do_sys_openat2+0x13f/0x500 fs/open.c:1356
do_sys_open fs/open.c:1372 [inline]
__do_sys_openat fs/open.c:1388 [inline]
__se_sys_openat fs/open.c:1383 [inline]
__x64_sys_openat+0x247/0x290 fs/open.c:1383
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

-> #0 (&type->i_mutex_dir_key#6/3){+.+.}-{3:3}:
check_prev_add kernel/locking/lockdep.c:3108 [inline]
check_prevs_add kernel/locking/lockdep.c:3227 [inline]
validate_chain+0x166b/0x58e0 kernel/locking/lockdep.c:3842
__lock_acquire+0x1295/0x2000 kernel/locking/lockdep.c:5074
lock_acquire+0x1e3/0x520 kernel/locking/lockdep.c:5691
down_write_nested+0x3d/0x50 kernel/locking/rwsem.c:1689
inode_lock_nested include/linux/fs.h:810 [inline]
open_xa_root fs/reiserfs/xattr.c:128 [inline]
open_xa_dir+0x136/0x610 fs/reiserfs/xattr.c:153
xattr_lookup+0x24/0x280 fs/reiserfs/xattr.c:396
reiserfs_xattr_get+0xfd/0x570 fs/reiserfs/xattr.c:678
__vfs_getxattr+0x436/0x470 fs/xattr.c:424
smk_fetch+0xb1/0x140 security/smack/smack_lsm.c:295
smack_d_instantiate+0x6d9/0xb40 security/smack/smack_lsm.c:3475
security_d_instantiate+0x9b/0xf0 security/security.c:3760
d_instantiate_new+0x65/0x120 fs/dcache.c:2053
reiserfs_create+0x5cf/0x6e0 fs/reiserfs/namei.c:692
lookup_open fs/namei.c:3492 [inline]
open_last_lookups fs/namei.c:3560 [inline]
path_openat+0x13df/0x3170 fs/namei.c:3788
do_filp_open+0x234/0x490 fs/namei.c:3818
do_sys_openat2+0x13f/0x500 fs/open.c:1356
do_sys_open fs/open.c:1372 [inline]
__do_sys_openat fs/open.c:1388 [inline]
__se_sys_openat fs/open.c:1383 [inline]
__x64_sys_openat+0x247/0x290 fs/open.c:1383
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

other info that might help us debug this:

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&sbi->lock);
lock(&type->i_mutex_dir_key#6/3);
lock(&sbi->lock);
lock(&type->i_mutex_dir_key#6/3);

*** DEADLOCK ***

3 locks held by syz-executor363/4996:
#0: ffff88807c6be460 (sb_writers#9){.+.+}-{0:0}, at: mnt_want_write+0x3f/0x90 fs/namespace.c:394
#1: ffff8880745582e0 (&type->i_mutex_dir_key#6){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:775 [inline]
#1: ffff8880745582e0 (&type->i_mutex_dir_key#6){+.+.}-{3:3}, at: open_last_lookups fs/namei.c:3557 [inline]
#1: ffff8880745582e0 (&type->i_mutex_dir_key#6){+.+.}-{3:3}, at: path_openat+0x7ba/0x3170 fs/namei.c:3788
#2: ffff8880156f2090 (&sbi->lock){+.+.}-{3:3}, at: reiserfs_write_lock_nested+0x5f/0xd0 fs/reiserfs/lock.c:78

stack backtrace:
CPU: 1 PID: 4996 Comm: syz-executor363 Not tainted 6.3.0-syzkaller-13164-g78b421b6a7c6 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/14/2023
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1e7/0x2d0 lib/dump_stack.c:106
check_noncircular+0x2fe/0x3b0 kernel/locking/lockdep.c:2188
check_prev_add kernel/locking/lockdep.c:3108 [inline]
check_prevs_add kernel/locking/lockdep.c:3227 [inline]
validate_chain+0x166b/0x58e0 kernel/locking/lockdep.c:3842
__lock_acquire+0x1295/0x2000 kernel/locking/lockdep.c:5074
lock_acquire+0x1e3/0x520 kernel/locking/lockdep.c:5691
down_write_nested+0x3d/0x50 kernel/locking/rwsem.c:1689
inode_lock_nested include/linux/fs.h:810 [inline]
open_xa_root fs/reiserfs/xattr.c:128 [inline]
open_xa_dir+0x136/0x610 fs/reiserfs/xattr.c:153
xattr_lookup+0x24/0x280 fs/reiserfs/xattr.c:396
reiserfs_xattr_get+0xfd/0x570 fs/reiserfs/xattr.c:678
__vfs_getxattr+0x436/0x470 fs/xattr.c:424
smk_fetch+0xb1/0x140 security/smack/smack_lsm.c:295
smack_d_instantiate+0x6d9/0xb40 security/smack/smack_lsm.c:3475
security_d_instantiate+0x9b/0xf0 security/security.c:3760
d_instantiate_new+0x65/0x120 fs/dcache.c:2053
reiserfs_create+0x5cf/0x6e0 fs/reiserfs/namei.c:692
lookup_open fs/namei.c:3492 [inline]
open_last_lookups fs/namei.c:3560 [inline]
path_openat+0x13df/0x3170 fs/namei.c:3788
do_filp_open+0x234/0x490 fs/namei.c:3818
do_sys_openat2+0x13f/0x500 fs/open.c:1356
do_sys_open fs/open.c:1372 [inline]
__do_sys_openat fs/open.c:1388 [inline]
__se_sys_openat fs/open.c:1383 [inline]
__x64_sys_openat+0x247/0x290 fs/open.c:1383
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7fdd867933d9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 b1 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fdd867402f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007fdd868196c0 RCX: 00007fdd867933d9
RDX: 000000000000275a RSI: 0000000020000080 RDI: 00000000ffffff9c


---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

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