[syzbot] possible deadlock in chown_common

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 2bca25eaeba6 Merge tag 'spi-v6.1' of git://git.kernel.org/..
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=169d7034880000
kernel config: https://syzkaller.appspot.com/x/.config?x=9df203be43a870b5
dashboard link: https://syzkaller.appspot.com/bug?extid=3abaeed5039cc1c49c7c
compiler: Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1539e7b8880000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16c6cb32880000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/9885e6765755/disk-2bca25ea.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/6e78c91286aa/vmlinux-2bca25ea.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/a0aa130c8e62/mount_0.gz

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

REISERFS (device loop0): checking transaction log (loop0)
REISERFS (device loop0): Using rupasov hash to sort names
REISERFS (device loop0): Created .reiserfs_priv - reserved for xattr storage.
======================================================
WARNING: possible circular locking dependency detected
6.0.0-syzkaller-03015-g2bca25eaeba6 #0 Not tainted
------------------------------------------------------
syz-executor428/3608 is trying to acquire lock:
ffff8880704302e0 (&type->i_mutex_dir_key#6){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:756 [inline]
ffff8880704302e0 (&type->i_mutex_dir_key#6){+.+.}-{3:3}, at: chown_common+0x414/0x8f0 fs/open.c:729

but task is already holding lock:
ffff888020438460 (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]
chown_common+0x414/0x8f0 fs/open.c:729
do_fchownat+0x165/0x240 fs/open.c:767
__do_sys_lchown fs/open.c:792 [inline]
__se_sys_lchown fs/open.c:790 [inline]
__x64_sys_lchown+0x81/0x90 fs/open.c:790
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-executor428/3608:
#0: ffff888020438460 (sb_writers#9){.+.+}-{0:0}, at: mnt_want_write+0x3b/0x80 fs/namespace.c:393

stack backtrace:
CPU: 0 PID: 3608 Comm: syz-executor428 Not tainted 6.0.0-syzkaller-03015-g2bca25eaeba6 #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]
chown_common+0x414/0x8f0 fs/open.c:729
do_fchownat+0x165/0x240 fs/open.c:767
__do_sys_lchown fs/open.c:792 [inline]
__se_sys_lchown fs/open.c:790 [inline]
__x64_sys_lchown+0x81/0x90 fs/open.c:790
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: 0033:0x7f7b93991899
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:00007ffcd35199f8 EFLAGS: 00000246 ORIG_RAX: 000000000000005e
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f7b93991899
RDX: 0000000000000000 RSI: 000000000000ee01 RDI: 0000000020000080
RBP: 0000000000000000 R08: 00007f7b939ffec0 R09: 00007f7b939ffec0
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffcd3519a20
R13: 0000000000000000 R14: 431bde82d7b634db R15: 0000000000000000
</TASK>


---
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[syzbot]

syzbot suspects this issue was fixed by commit:

commit 6f861765464f43a71462d52026fbddfc858239a5
Author: Jan Kara <ja...@suse.cz>
Date: Wed Nov 1 17:43:10 2023 +0000

fs: Block writes to mounted block devices

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=14ecbc83e80000
start commit: 2bca25eaeba6 Merge tag 'spi-v6.1' of git://git.kernel.org/..
git tree: upstream

kernel config: https://syzkaller.appspot.com/x/.config?x=9df203be43a870b5
dashboard link: https://syzkaller.appspot.com/bug?extid=3abaeed5039cc1c49c7c

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1539e7b8880000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16c6cb32880000

If the result looks correct, please mark the issue as fixed by replying with:

#syz fix: fs: Block writes to mounted block devices

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

[Jan Kara]

On Wed 17-01-24 08:20:06, syzbot wrote:
> syzbot suspects this issue was fixed by commit:
>
> commit 6f861765464f43a71462d52026fbddfc858239a5
> Author: Jan Kara <ja...@suse.cz>
> Date: Wed Nov 1 17:43:10 2023 +0000
>
> fs: Block writes to mounted block devices
>
> bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=14ecbc83e80000
> start commit: 2bca25eaeba6 Merge tag 'spi-v6.1' of git://git.kernel.org/..
> git tree: upstream
> kernel config: https://syzkaller.appspot.com/x/.config?x=9df203be43a870b5
> dashboard link: https://syzkaller.appspot.com/bug?extid=3abaeed5039cc1c49c7c
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1539e7b8880000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16c6cb32880000
>
> If the result looks correct, please mark the issue as fixed by replying with:

Makes sense:

#syz fix: fs: Block writes to mounted block devices

Honza
--
Jan Kara <ja...@suse.com>
SUSE Labs, CR

[Christian Brauner]

I remember once trying to chase that bug down and being very confused.