[syzbot] [kernfs?] possible deadlock in lookup_one_unlocked

From: syzbot
Date: Mon Apr 08 2024 - 07:49:40 EST

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Hello,

syzbot found the following issue on:

HEAD commit: fe46a7dd189e Merge tag 'sound-6.9-rc1' of git://git.kernel..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17adb6d3180000
kernel config: https://syzkaller.appspot.com/x/.config?x=4d90a36f0cab495a
dashboard link: https://syzkaller.appspot.com/bug?extid=ac3c5eb32b9d409dc11d
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/72ab73815344/disk-fe46a7dd.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/2d6d6b0d7071/vmlinux-fe46a7dd.xz
kernel image: https://storage.googleapis.com/syzbot-assets/48e275e5478b/bzImage-fe46a7dd.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ac3c5eb32b9d409dc11d@xxxxxxxxxxxxxxxxxxxxxxxxx

======================================================
WARNING: possible circular locking dependency detected
6.8.0-syzkaller-08951-gfe46a7dd189e #0 Not tainted
------------------------------------------------------
syz-executor.1/9023 is trying to acquire lock:
ffff88805d610740 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}, at: inode_lock_shared include/linux/fs.h:803 [inline]
ffff88805d610740 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}, at: lookup_slow fs/namei.c:1708 [inline]
ffff88805d610740 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}, at: lookup_one_unlocked+0x197/0x290 fs/namei.c:2817

but task is already holding lock:
ffff88805d612450 (&ovl_i_mutex_dir_key[depth]#3){.+.+}-{3:3}, at: inode_lock_shared include/linux/fs.h:803 [inline]
ffff88805d612450 (&ovl_i_mutex_dir_key[depth]#3){.+.+}-{3:3}, at: lookup_slow+0x45/0x70 fs/namei.c:1708

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #5 (&ovl_i_mutex_dir_key[depth]#3){.+.+}-{3:3}:
lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
down_read+0xb1/0xa40 kernel/locking/rwsem.c:1526
inode_lock_shared include/linux/fs.h:803 [inline]
lookup_slow+0x45/0x70 fs/namei.c:1708
walk_component+0x2e1/0x410 fs/namei.c:2004
lookup_last fs/namei.c:2461 [inline]
path_lookupat+0x16f/0x450 fs/namei.c:2485
filename_lookup+0x256/0x610 fs/namei.c:2514
kern_path+0x35/0x50 fs/namei.c:2622
lookup_bdev+0xc5/0x290 block/bdev.c:1072
resume_store+0x1a0/0x710 kernel/power/hibernate.c:1235
kernfs_fop_write_iter+0x3a4/0x500 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+0xa84/0xcb0 fs/read_write.c:590
ksys_write+0x1a0/0x2c0 fs/read_write.c:643
do_syscall_64+0xfb/0x240
entry_SYSCALL_64_after_hwframe+0x6d/0x75

-> #4 (&of->mutex){+.+.}-{3:3}:
lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
__mutex_lock_common kernel/locking/mutex.c:608 [inline]
__mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
kernfs_seq_start+0x53/0x3b0 fs/kernfs/file.c:154
seq_read_iter+0x3d0/0xd60 fs/seq_file.c:225
call_read_iter include/linux/fs.h:2102 [inline]
new_sync_read fs/read_write.c:395 [inline]
vfs_read+0x97b/0xb70 fs/read_write.c:476
ksys_read+0x1a0/0x2c0 fs/read_write.c:619
do_syscall_64+0xfb/0x240
entry_SYSCALL_64_after_hwframe+0x6d/0x75

-> #3 (&p->lock){+.+.}-{3:3}:
lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
__mutex_lock_common kernel/locking/mutex.c:608 [inline]
__mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
seq_read_iter+0xb7/0xd60 fs/seq_file.c:182
call_read_iter include/linux/fs.h:2102 [inline]
copy_splice_read+0x662/0xb60 fs/splice.c:365
do_splice_read fs/splice.c:985 [inline]
splice_file_to_pipe+0x299/0x500 fs/splice.c:1295
do_sendfile+0x515/0xdc0 fs/read_write.c:1301
__do_sys_sendfile64 fs/read_write.c:1362 [inline]
__se_sys_sendfile64+0x17c/0x1e0 fs/read_write.c:1348
do_syscall_64+0xfb/0x240
entry_SYSCALL_64_after_hwframe+0x6d/0x75

-> #2 (&pipe->mutex){+.+.}-{3:3}:
lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
__mutex_lock_common kernel/locking/mutex.c:608 [inline]
__mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
iter_file_splice_write+0x335/0x14e0 fs/splice.c:687
do_splice_from fs/splice.c:941 [inline]
do_splice+0xd77/0x1880 fs/splice.c:1354
__do_splice fs/splice.c:1436 [inline]
__do_sys_splice fs/splice.c:1652 [inline]
__se_sys_splice+0x331/0x4a0 fs/splice.c:1634
do_syscall_64+0xfb/0x240
entry_SYSCALL_64_after_hwframe+0x6d/0x75

-> #1 (sb_writers#4){.+.+}-{0:0}:
lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
__sb_start_write include/linux/fs.h:1662 [inline]
sb_start_write+0x4d/0x1c0 include/linux/fs.h:1798
mnt_want_write+0x3f/0x90 fs/namespace.c:409
ovl_create_object+0x13b/0x370 fs/overlayfs/dir.c:629
lookup_open fs/namei.c:3497 [inline]
open_last_lookups fs/namei.c:3566 [inline]
path_openat+0x1425/0x3240 fs/namei.c:3796
do_filp_open+0x235/0x490 fs/namei.c:3826
do_sys_openat2+0x13e/0x1d0 fs/open.c:1406
do_sys_open fs/open.c:1421 [inline]
__do_sys_open fs/open.c:1429 [inline]
__se_sys_open fs/open.c:1425 [inline]
__x64_sys_open+0x225/0x270 fs/open.c:1425
do_syscall_64+0xfb/0x240
entry_SYSCALL_64_after_hwframe+0x6d/0x75

-> #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+0x18cb/0x58e0 kernel/locking/lockdep.c:3869
__lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137
lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
down_read+0xb1/0xa40 kernel/locking/rwsem.c:1526
inode_lock_shared include/linux/fs.h:803 [inline]
lookup_slow fs/namei.c:1708 [inline]
lookup_one_unlocked+0x197/0x290 fs/namei.c:2817
ovl_lookup_positive_unlocked fs/overlayfs/namei.c:210 [inline]
ovl_lookup_single+0x200/0xbd0 fs/overlayfs/namei.c:240
ovl_lookup_layer+0x417/0x510 fs/overlayfs/namei.c:333
ovl_lookup+0xcf7/0x2a60 fs/overlayfs/namei.c:1124
__lookup_slow+0x28c/0x3f0 fs/namei.c:1692
lookup_slow+0x53/0x70 fs/namei.c:1709
walk_component+0x2e1/0x410 fs/namei.c:2004
lookup_last fs/namei.c:2461 [inline]
path_lookupat+0x16f/0x450 fs/namei.c:2485
filename_lookup+0x256/0x610 fs/namei.c:2514
kern_path+0x35/0x50 fs/namei.c:2622
lookup_bdev+0xc5/0x290 block/bdev.c:1072
resume_store+0x1a0/0x710 kernel/power/hibernate.c:1235
kernfs_fop_write_iter+0x3a4/0x500 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+0xa84/0xcb0 fs/read_write.c:590
ksys_write+0x1a0/0x2c0 fs/read_write.c:643
do_syscall_64+0xfb/0x240
entry_SYSCALL_64_after_hwframe+0x6d/0x75

other info that might help us debug this:

Chain exists of:
&ovl_i_mutex_dir_key[depth] --> &of->mutex --> &ovl_i_mutex_dir_key[depth]#3

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
rlock(&ovl_i_mutex_dir_key[depth]#3);
lock(&of->mutex);
lock(&ovl_i_mutex_dir_key[depth]#3);
rlock(&ovl_i_mutex_dir_key[depth]);

*** DEADLOCK ***

5 locks held by syz-executor.1/9023:
#0: ffff888059ebf248 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x259/0x320 fs/file.c:1191
#1: ffff88802f972420 (sb_writers#8){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2853 [inline]
#1: ffff88802f972420 (sb_writers#8){.+.+}-{0:0}, at: vfs_write+0x233/0xcb0 fs/read_write.c:586
#2: ffff88801edfd088 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1eb/0x500 fs/kernfs/file.c:325
#3: ffff888019281918 (kn->active#59){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x20f/0x500 fs/kernfs/file.c:326
#4: ffff88805d612450 (&ovl_i_mutex_dir_key[depth]#3){.+.+}-{3:3}, at: inode_lock_shared include/linux/fs.h:803 [inline]
#4: ffff88805d612450 (&ovl_i_mutex_dir_key[depth]#3){.+.+}-{3:3}, at: lookup_slow+0x45/0x70 fs/namei.c:1708

stack backtrace:
CPU: 1 PID: 9023 Comm: syz-executor.1 Not tainted 6.8.0-syzkaller-08951-gfe46a7dd189e #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
check_noncircular+0x36a/0x4a0 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+0x18cb/0x58e0 kernel/locking/lockdep.c:3869
__lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137
lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
down_read+0xb1/0xa40 kernel/locking/rwsem.c:1526
inode_lock_shared include/linux/fs.h:803 [inline]
lookup_slow fs/namei.c:1708 [inline]
lookup_one_unlocked+0x197/0x290 fs/namei.c:2817
ovl_lookup_positive_unlocked fs/overlayfs/namei.c:210 [inline]
ovl_lookup_single+0x200/0xbd0 fs/overlayfs/namei.c:240
ovl_lookup_layer+0x417/0x510 fs/overlayfs/namei.c:333
ovl_lookup+0xcf7/0x2a60 fs/overlayfs/namei.c:1124
__lookup_slow+0x28c/0x3f0 fs/namei.c:1692
lookup_slow+0x53/0x70 fs/namei.c:1709
walk_component+0x2e1/0x410 fs/namei.c:2004
lookup_last fs/namei.c:2461 [inline]
path_lookupat+0x16f/0x450 fs/namei.c:2485
filename_lookup+0x256/0x610 fs/namei.c:2514
kern_path+0x35/0x50 fs/namei.c:2622
lookup_bdev+0xc5/0x290 block/bdev.c:1072
resume_store+0x1a0/0x710 kernel/power/hibernate.c:1235
kernfs_fop_write_iter+0x3a4/0x500 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+0xa84/0xcb0 fs/read_write.c:590
ksys_write+0x1a0/0x2c0 fs/read_write.c:643
do_syscall_64+0xfb/0x240
entry_SYSCALL_64_after_hwframe+0x6d/0x75
RIP: 0033:0x7f389687de69
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:00007f38963ff0c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f38969abf80 RCX: 00007f389687de69
RDX: 0000000000000012 RSI: 0000000020000000 RDI: 0000000000000006
RBP: 00007f38968ca47a R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007f38969abf80 R15: 00007ffca27d9338
</TASK>
PM: Image not found (code -6)

---
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Next message: Guenter Roeck: "Re: [PATCH 00/31] Remove use of i2c_match_id in HWMON"
Previous message: Fabio Estevam: "Re: [PATCH] arm64: dts: imx8mp-msc-sm2s: Add i2c{1,6} sda-/scl-gpios"
Next in thread: Miklos Szeredi: "Re: [syzbot] [kernfs?] possible deadlock in lookup_one_unlocked"
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