[syzbot] possible deadlock in vfs_fileattr_set

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: f8f60f322f06 Add linux-next specific files for 20221111
git tree: linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=16cdceae880000
kernel config: https://syzkaller.appspot.com/x/.config?x=85ba52c07cd97289
dashboard link: https://syzkaller.appspot.com/bug?extid=abe01a74653f00aabe3e
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=138b76ae880000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16ab1bfe880000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/6008df424195/disk-f8f60f32.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/394340525f66/vmlinux-f8f60f32.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b13604a3343a/bzImage-f8f60f32.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/1398dc40e272/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+abe01a...@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
6.1.0-rc4-next-20221111-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor405/5247 is trying to acquire lock:
ffff888072c302e0 (&type->i_mutex_dir_key#6){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:756 [inline]
ffff888072c302e0 (&type->i_mutex_dir_key#6){+.+.}-{3:3}, at: vfs_fileattr_set+0x148/0xbe0 fs/ioctl.c:681

but task is already holding lock:
ffff88802ac5a460 (sb_writers#9){.+.+}-{0:0}, at: ioctl_setflags fs/ioctl.c:725 [inline]
ffff88802ac5a460 (sb_writers#9){.+.+}-{0:0}, at: do_vfs_ioctl+0xe0b/0x1580 fs/ioctl.c:839

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (sb_writers#9){.+.+}-{0:0}:
percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
__sb_start_write include/linux/fs.h:1792 [inline]
sb_start_write include/linux/fs.h:1867 [inline]
mnt_want_write_file+0x8e/0x590 fs/namespace.c:552
reiserfs_ioctl+0x19e/0x320 fs/reiserfs/ioctl.c:103
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:870 [inline]
__se_sys_ioctl fs/ioctl.c:856 [inline]
__x64_sys_ioctl+0x193/0x200 fs/ioctl.c:856
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

-> #1 (&sbi->lock){+.+.}-{3:3}:
__mutex_lock_common kernel/locking/mutex.c:603 [inline]
__mutex_lock+0x12f/0x1350 kernel/locking/mutex.c:747
reiserfs_write_lock+0x75/0xf0 fs/reiserfs/lock.c:27
reiserfs_lookup+0x171/0x490 fs/reiserfs/namei.c:364
__lookup_slow+0x24c/0x460 fs/namei.c:1685
lookup_one_len+0x16a/0x1a0 fs/namei.c:2711
reiserfs_lookup_privroot+0x92/0x280 fs/reiserfs/xattr.c:973
reiserfs_fill_super+0x20e5/0x2e90 fs/reiserfs/super.c:2174
mount_bdev+0x34d/0x410 fs/super.c:1401
legacy_get_tree+0x105/0x220 fs/fs_context.c:610
vfs_get_tree+0x89/0x2f0 fs/super.c:1531
do_new_mount fs/namespace.c:3145 [inline]
path_mount+0x1326/0x1e20 fs/namespace.c:3475
do_mount fs/namespace.c:3488 [inline]
__do_sys_mount fs/namespace.c:3696 [inline]
__se_sys_mount fs/namespace.c:3673 [inline]
__x64_sys_mount+0x27f/0x300 fs/namespace.c:3673
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 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:3097 [inline]
check_prevs_add kernel/locking/lockdep.c:3216 [inline]
validate_chain kernel/locking/lockdep.c:3831 [inline]
__lock_acquire+0x2a43/0x56d0 kernel/locking/lockdep.c:5055
lock_acquire kernel/locking/lockdep.c:5668 [inline]
lock_acquire+0x1df/0x630 kernel/locking/lockdep.c:5633
down_write+0x90/0x220 kernel/locking/rwsem.c:1562
inode_lock include/linux/fs.h:756 [inline]
vfs_fileattr_set+0x148/0xbe0 fs/ioctl.c:681
ioctl_fssetxattr fs/ioctl.c:758 [inline]
do_vfs_ioctl+0xe46/0x1580 fs/ioctl.c:845
__do_sys_ioctl fs/ioctl.c:868 [inline]
__se_sys_ioctl fs/ioctl.c:856 [inline]
__x64_sys_ioctl+0x108/0x200 fs/ioctl.c:856
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 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-executor405/5247:
#0: ffff88802ac5a460 (sb_writers#9){.+.+}-{0:0}, at: ioctl_setflags fs/ioctl.c:725 [inline]
#0: ffff88802ac5a460 (sb_writers#9){.+.+}-{0:0}, at: do_vfs_ioctl+0xe0b/0x1580 fs/ioctl.c:839

stack backtrace:
CPU: 0 PID: 5247 Comm: syz-executor405 Not tainted 6.1.0-rc4-next-20221111-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
check_noncircular+0x25f/0x2e0 kernel/locking/lockdep.c:2177
check_prev_add kernel/locking/lockdep.c:3097 [inline]
check_prevs_add kernel/locking/lockdep.c:3216 [inline]
validate_chain kernel/locking/lockdep.c:3831 [inline]
__lock_acquire+0x2a43/0x56d0 kernel/locking/lockdep.c:5055
lock_acquire kernel/locking/lockdep.c:5668 [inline]
lock_acquire+0x1df/0x630 kernel/locking/lockdep.c:5633
down_write+0x90/0x220 kernel/locking/rwsem.c:1562
inode_lock include/linux/fs.h:756 [inline]
vfs_fileattr_set+0x148/0xbe0 fs/ioctl.c:681
ioctl_fssetxattr fs/ioctl.c:758 [inline]
do_vfs_ioctl+0xe46/0x1580 fs/ioctl.c:845
__do_sys_ioctl fs/ioctl.c:868 [inline]
__se_sys_ioctl fs/ioctl.c:856 [inline]
__x64_sys_ioctl+0x108/0x200 fs/ioctl.c:856
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7fceb6e16899
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:00007ffcd70f3258 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fceb6e16899
RDX: 0000000020000600 RSI: 0000000040086602 RDI: 0000000000000005
RBP: 0000000000000000 R08: 00007fceb6e84ec0 R09: 00007fceb6e84ec0
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffcd70f3280
R13: 0000000000000000 R14: 431bde82d7b634db R15: 0000000000000000
</TASK>


---
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See https://goo.gl/tpsmEJ for more information about syzbot.
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syzbot can test patches for this issue, for details see:
https://goo.gl/tpsmEJ#testing-patches

[syzbot]

syzbot has bisected this issue to:

commit 6dd6b7643e723b4779e59c8ad97bd5db6ff3bb12
Author: Thomas Zimmermann <tzimm...@suse.de>
Date: Mon Jan 18 13:14:19 2021 +0000

drm/vmwgfx: Remove reference to struct drm_device.pdev

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1418e6a5880000
start commit: f8f60f322f06 Add linux-next specific files for 20221111
git tree: linux-next
final oops: https://syzkaller.appspot.com/x/report.txt?x=1618e6a5880000
console output: https://syzkaller.appspot.com/x/log.txt?x=1218e6a5880000

kernel config: https://syzkaller.appspot.com/x/.config?x=85ba52c07cd97289
dashboard link: https://syzkaller.appspot.com/bug?extid=abe01a74653f00aabe3e

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=138b76ae880000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16ab1bfe880000

Reported-by: syzbot+abe01a...@syzkaller.appspotmail.com
Fixes: 6dd6b7643e72 ("drm/vmwgfx: Remove reference to struct drm_device.pdev")

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

[Hillf Danton]

On 13 Nov 2022 07:51:06 -0800

> syzbot found the following issue on:
>

> HEAD commit: f8f60f322f06 Add linux-next specific files for 20221111
> git tree: linux-next
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=16cdceae880000

> kernel config: https://syzkaller.appspot.com/x/.config?x=85ba52c07cd97289
> dashboard link: https://syzkaller.appspot.com/bug?extid=abe01a74653f00aabe3e

> compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=138b76ae880000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16ab1bfe880000

Reverse the order of mnt_want_write_file() and reiserfs_write_lock() in bid
to fix deadlock.

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git f8f60f322f06

--- x/fs/reiserfs/ioctl.c
+++ i/fs/reiserfs/ioctl.c
@@ -78,6 +78,9 @@ long reiserfs_ioctl(struct file *filp, u
struct inode *inode = file_inode(filp);
int err = 0;

+ err = mnt_want_write_file(filp);
+ if (err)
+ return err;
reiserfs_write_lock(inode->i_sb);

switch (cmd) {
@@ -100,23 +103,20 @@ long reiserfs_ioctl(struct file *filp, u
err = -EPERM;
break;
}
- err = mnt_want_write_file(filp);
- if (err)
- break;
if (get_user(inode->i_generation, (int __user *)arg)) {
err = -EFAULT;
- goto setversion_out;
+ break;
}
inode->i_ctime = current_time(inode);
mark_inode_dirty(inode);
-setversion_out:
- mnt_drop_write_file(filp);
break;
default:
err = -ENOTTY;
+ break;
}

reiserfs_write_unlock(inode->i_sb);
+ mnt_drop_write_file(filp);

return err;
}
--

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+abe01a...@syzkaller.appspotmail.com

Tested on:

commit: f8f60f32 Add linux-next specific files for 20221111
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
console output: https://syzkaller.appspot.com/x/log.txt?x=14a95a11880000

kernel config: https://syzkaller.appspot.com/x/.config?x=85ba52c07cd97289
dashboard link: https://syzkaller.appspot.com/bug?extid=abe01a74653f00aabe3e
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

patch: https://syzkaller.appspot.com/x/patch.diff?x=12d16985880000

Note: testing is done by a robot and is best-effort only.

[syzbot]

Auto-closing this bug as obsolete.
No recent activity, existing reproducers are no longer triggering the issue.