[syzbot] [kernfs?] possible deadlock in walk_component (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 3e92c1e6cd87 Merge tag 'selinux-pr-20240402' of git://git...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16ebae03180000
kernel config: https://syzkaller.appspot.com/x/.config?x=411644804960f423
dashboard link: https://syzkaller.appspot.com/bug?extid=fa60c773a1654e2eda40
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

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

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7bc7510fe41f/non_bootable_disk-3e92c1e6.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/34cc55fbbf72/vmlinux-3e92c1e6.xz
kernel image: https://storage.googleapis.com/syzbot-assets/09668ee3251b/bzImage-3e92c1e6.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+fa60c7...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
6.9.0-rc2-syzkaller-00042-g3e92c1e6cd87 #0 Not tainted
------------------------------------------------------
syz-executor.2/22789 is trying to acquire lock:
ffff888032f275b0 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}, at: inode_lock_shared include/linux/fs.h:803 [inline]
ffff888032f275b0 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}, at: lookup_slow fs/namei.c:1708 [inline]
ffff888032f275b0 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}, at: walk_component+0x342/0x5b0 fs/namei.c:2004

but task is already holding lock:
ffff888040373488 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x281/0x500 fs/kernfs/file.c:325

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&of->mutex){+.+.}-{3:3}:
__mutex_lock_common kernel/locking/mutex.c:608 [inline]
__mutex_lock+0x175/0x9c0 kernel/locking/mutex.c:752
kernfs_fop_write_iter+0x281/0x500 fs/kernfs/file.c:325
call_write_iter include/linux/fs.h:2108 [inline]
iter_file_splice_write+0x906/0x10b0 fs/splice.c:743
do_splice_from fs/splice.c:941 [inline]
do_splice+0x12c7/0x1f10 fs/splice.c:1354
__do_splice+0x327/0x360 fs/splice.c:1436
__do_sys_splice fs/splice.c:1652 [inline]
__se_sys_splice fs/splice.c:1634 [inline]
__x64_sys_splice+0x1d2/0x260 fs/splice.c:1634
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xd2/0x260 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x72/0x7a

-> #2 (&pipe->mutex){+.+.}-{3:3}:
__mutex_lock_common kernel/locking/mutex.c:608 [inline]
__mutex_lock+0x175/0x9c0 kernel/locking/mutex.c:752
pipe_lock fs/pipe.c:92 [inline]
pipe_lock+0x64/0x80 fs/pipe.c:89
iter_file_splice_write+0x1f0/0x10b0 fs/splice.c:687
do_splice_from fs/splice.c:941 [inline]
do_splice+0x12c7/0x1f10 fs/splice.c:1354
__do_splice+0x327/0x360 fs/splice.c:1436
__do_sys_splice fs/splice.c:1652 [inline]
__se_sys_splice fs/splice.c:1634 [inline]
__x64_sys_splice+0x1d2/0x260 fs/splice.c:1634
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xd2/0x260 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x72/0x7a

-> #1 (sb_writers#5){.+.+}-{0:0}:
percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
__sb_start_write include/linux/fs.h:1662 [inline]
sb_start_write include/linux/fs.h:1798 [inline]
mnt_want_write+0x6f/0x450 fs/namespace.c:409
ovl_xattr_set+0x136/0x530 fs/overlayfs/xattrs.c:63
ovl_own_xattr_set+0x86/0xd0 fs/overlayfs/xattrs.c:213
__vfs_setxattr+0x173/0x1e0 fs/xattr.c:200
__vfs_setxattr_noperm+0x127/0x5e0 fs/xattr.c:234
__vfs_setxattr_locked+0x182/0x260 fs/xattr.c:295
vfs_setxattr+0x146/0x350 fs/xattr.c:321
do_setxattr+0x146/0x170 fs/xattr.c:629
setxattr+0x15d/0x180 fs/xattr.c:652
path_setxattr+0x179/0x1e0 fs/xattr.c:671
__do_sys_setxattr fs/xattr.c:687 [inline]
__se_sys_setxattr fs/xattr.c:683 [inline]
__x64_sys_setxattr+0xc4/0x160 fs/xattr.c:683
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xd2/0x260 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x72/0x7a

-> #0 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}:
check_prev_add kernel/locking/lockdep.c:3134 [inline]
check_prevs_add kernel/locking/lockdep.c:3253 [inline]
validate_chain kernel/locking/lockdep.c:3869 [inline]
__lock_acquire+0x2478/0x3b30 kernel/locking/lockdep.c:5137
lock_acquire kernel/locking/lockdep.c:5754 [inline]
lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5719
down_read+0x9a/0x330 kernel/locking/rwsem.c:1526
inode_lock_shared include/linux/fs.h:803 [inline]
lookup_slow fs/namei.c:1708 [inline]
walk_component+0x342/0x5b0 fs/namei.c:2004
lookup_last fs/namei.c:2461 [inline]
path_lookupat+0x17f/0x770 fs/namei.c:2485
filename_lookup+0x1e5/0x5b0 fs/namei.c:2514
kern_path+0x35/0x50 fs/namei.c:2622
lookup_bdev+0xd9/0x280 block/bdev.c:1079
resume_store+0x1d8/0x460 kernel/power/hibernate.c:1235
kobj_attr_store+0x55/0x80 lib/kobject.c:840
sysfs_kf_write+0x117/0x170 fs/sysfs/file.c:136
kernfs_fop_write_iter+0x343/0x500 fs/kernfs/file.c:334
call_write_iter include/linux/fs.h:2108 [inline]
new_sync_write fs/read_write.c:497 [inline]
vfs_write+0x6db/0x1100 fs/read_write.c:590
ksys_write+0x12f/0x260 fs/read_write.c:643
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xd2/0x260 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x72/0x7a

other info that might help us debug this:

Chain exists of:
&ovl_i_mutex_dir_key[depth] --> &pipe->mutex --> &of->mutex

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&of->mutex);
lock(&pipe->mutex);
lock(&of->mutex);
rlock(&ovl_i_mutex_dir_key[depth]);

*** DEADLOCK ***

4 locks held by syz-executor.2/22789:
#0: ffff88802cc70ac8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0xeb/0x180 fs/file.c:1191
#1: ffff88802533e420 (sb_writers#9){.+.+}-{0:0}, at: ksys_write+0x12f/0x260 fs/read_write.c:643
#2: ffff888040373488 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x281/0x500 fs/kernfs/file.c:325
#3: ffff8880196eb5a8 (kn->active#85){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x2a4/0x500 fs/kernfs/file.c:326

stack backtrace:
CPU: 0 PID: 22789 Comm: syz-executor.2 Not tainted 6.9.0-rc2-syzkaller-00042-g3e92c1e6cd87 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:114
check_noncircular+0x31a/0x400 kernel/locking/lockdep.c:2187
check_prev_add kernel/locking/lockdep.c:3134 [inline]
check_prevs_add kernel/locking/lockdep.c:3253 [inline]
validate_chain kernel/locking/lockdep.c:3869 [inline]
__lock_acquire+0x2478/0x3b30 kernel/locking/lockdep.c:5137
lock_acquire kernel/locking/lockdep.c:5754 [inline]
lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5719
down_read+0x9a/0x330 kernel/locking/rwsem.c:1526
inode_lock_shared include/linux/fs.h:803 [inline]
lookup_slow fs/namei.c:1708 [inline]
walk_component+0x342/0x5b0 fs/namei.c:2004
lookup_last fs/namei.c:2461 [inline]
path_lookupat+0x17f/0x770 fs/namei.c:2485
filename_lookup+0x1e5/0x5b0 fs/namei.c:2514
kern_path+0x35/0x50 fs/namei.c:2622
lookup_bdev+0xd9/0x280 block/bdev.c:1079
resume_store+0x1d8/0x460 kernel/power/hibernate.c:1235
kobj_attr_store+0x55/0x80 lib/kobject.c:840
sysfs_kf_write+0x117/0x170 fs/sysfs/file.c:136
kernfs_fop_write_iter+0x343/0x500 fs/kernfs/file.c:334
call_write_iter include/linux/fs.h:2108 [inline]
new_sync_write fs/read_write.c:497 [inline]
vfs_write+0x6db/0x1100 fs/read_write.c:590
ksys_write+0x12f/0x260 fs/read_write.c:643
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xd2/0x260 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x72/0x7a
RIP: 0033:0x7fb6a4e7dde9
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:00007fb6a5b2f0c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fb6a4fabf80 RCX: 00007fb6a4e7dde9
RDX: 0000000000000012 RSI: 0000000020000000 RDI: 0000000000000007
RBP: 00007fb6a4eca47a R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000004d R14: 00007fb6a4fabf80 R15: 00007ffdad03fdb8
</TASK>
PM: Image not found (code -6)


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[Miklos Szeredi]

I think this has the same underlying cause as the other
kernfs-overlayfs deadlocks.

#syz dup: possible deadlock in kernfs_fop_llseek