[v5.15] possible deadlock in chmod_common (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 0c935c049b5c Linux 5.15.179
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=15d7319b980000
kernel config: https://syzkaller.appspot.com/x/.config?x=bcb6af887426ce59
dashboard link: https://syzkaller.appspot.com/bug?extid=354bc843b127db2f5dde
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/75b060834e1e/disk-0c935c04.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/d42b06ae465d/vmlinux-0c935c04.xz
kernel image: https://storage.googleapis.com/syzbot-assets/d5217676cd35/bzImage-0c935c04.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+354bc8...@syzkaller.appspotmail.com

REISERFS warning: green-16003 errcatch_is_left_mergeable: Invalid item type observed, run fsck ASAP
REISERFS warning: green-16003 errcatch_is_left_mergeable: Invalid item type observed, run fsck ASAP
REISERFS (device loop2): Created .reiserfs_priv - reserved for xattr storage.
======================================================
WARNING: possible circular locking dependency detected
5.15.179-syzkaller #0 Not tainted
------------------------------------------------------
syz.2.682/6589 is trying to acquire lock:
ffff8880602c8980 (&type->i_mutex_dir_key#17){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:787 [inline]
ffff8880602c8980 (&type->i_mutex_dir_key#17){+.+.}-{3:3}, at: chmod_common+0x1b7/0x4b0 fs/open.c:576

but task is already holding lock:
ffff88807b272460 (sb_writers#20){.+.+}-{0:0}, at: mnt_want_write+0x3b/0x80 fs/namespace.c:377

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (sb_writers#20){.+.+}-{0:0}:
lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5623
percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
__sb_start_write include/linux/fs.h:1811 [inline]
sb_start_write+0x4f/0x1c0 include/linux/fs.h:1881
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+0x3b/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #1 (&sbi->lock){+.+.}-{3:3}:
lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5623
__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_slow+0x275/0x3d0 fs/namei.c:1663
lookup_one_len+0x187/0x2d0 fs/namei.c:2718
reiserfs_lookup_privroot+0x85/0x1e0 fs/reiserfs/xattr.c:980
reiserfs_fill_super+0x191e/0x2690 fs/reiserfs/super.c:2196
mount_bdev+0x2c9/0x3f0 fs/super.c:1400
legacy_get_tree+0xeb/0x180 fs/fs_context.c:611
vfs_get_tree+0x88/0x270 fs/super.c:1530
do_new_mount+0x2ba/0xb40 fs/namespace.c:3012
do_mount fs/namespace.c:3355 [inline]
__do_sys_mount fs/namespace.c:3563 [inline]
__se_sys_mount+0x2d5/0x3c0 fs/namespace.c:3540
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #0 (&type->i_mutex_dir_key#17){+.+.}-{3:3}:
check_prev_add kernel/locking/lockdep.c:3053 [inline]
check_prevs_add kernel/locking/lockdep.c:3172 [inline]
validate_chain+0x1649/0x5930 kernel/locking/lockdep.c:3788
__lock_acquire+0x1295/0x1ff0 kernel/locking/lockdep.c:5012
lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5623
down_write+0x38/0x60 kernel/locking/rwsem.c:1551
inode_lock include/linux/fs.h:787 [inline]
chmod_common+0x1b7/0x4b0 fs/open.c:576
do_fchmodat fs/open.c:621 [inline]
__do_sys_fchmodat fs/open.c:634 [inline]
__se_sys_fchmodat fs/open.c:631 [inline]
__x64_sys_fchmodat+0x117/0x1a0 fs/open.c:631
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

other info that might help us debug this:

Chain exists of:
&type->i_mutex_dir_key#17 --> &sbi->lock --> sb_writers#20

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(sb_writers#20);
lock(&sbi->lock);
lock(sb_writers#20);
lock(&type->i_mutex_dir_key#17);

*** DEADLOCK ***

1 lock held by syz.2.682/6589:
#0: ffff88807b272460 (sb_writers#20){.+.+}-{0:0}, at: mnt_want_write+0x3b/0x80 fs/namespace.c:377

stack backtrace:
CPU: 1 PID: 6589 Comm: syz.2.682 Not tainted 5.15.179-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1e3/0x2d0 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+0x1649/0x5930 kernel/locking/lockdep.c:3788
__lock_acquire+0x1295/0x1ff0 kernel/locking/lockdep.c:5012
lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5623
down_write+0x38/0x60 kernel/locking/rwsem.c:1551
inode_lock include/linux/fs.h:787 [inline]
chmod_common+0x1b7/0x4b0 fs/open.c:576
do_fchmodat fs/open.c:621 [inline]
__do_sys_fchmodat fs/open.c:634 [inline]
__se_sys_fchmodat fs/open.c:631 [inline]
__x64_sys_fchmodat+0x117/0x1a0 fs/open.c:631
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f68f7a77169
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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f68f58e0038 EFLAGS: 00000246 ORIG_RAX: 000000000000010c
RAX: ffffffffffffffda RBX: 00007f68f7c8ffa0 RCX: 00007f68f7a77169
RDX: 00000000ffffffd3 RSI: 0000400000000300 RDI: ffffffffffffff9c
RBP: 00007f68f7af82a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f68f7c8ffa0 R15: 00007ffd8c082978
</TASK>


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.