[syzbot] [overlayfs?] possible deadlock in ovl_create_object

From: syzbot
Date: Sat Feb 01 2025 - 11:12:31 EST

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Hello,

syzbot found the following issue on:

HEAD commit: 805ba04cb7cc Merge tag 'mips_6.14' of git://git.kernel.org..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=157e6364580000
kernel config: https://syzkaller.appspot.com/x/.config?x=2ae8afe424ee551e
dashboard link: https://syzkaller.appspot.com/bug?extid=93ea1efef88821c553ad
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/7feb34a89c2a/non_bootable_disk-805ba04c.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f9b9a1354470/vmlinux-805ba04c.xz
kernel image: https://storage.googleapis.com/syzbot-assets/6c77f51f864a/bzImage-805ba04c.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+93ea1efef88821c553ad@xxxxxxxxxxxxxxxxxxxxxxxxx

======================================================
WARNING: possible circular locking dependency detected
6.13.0-syzkaller-08291-g805ba04cb7cc #0 Not tainted
------------------------------------------------------
syz.4.1894/11640 is trying to acquire lock:
ffff88805ad04420 (sb_writers#6){.+.+}-{0:0}, at: ovl_create_object+0x12e/0x300 fs/overlayfs/dir.c:656

but task is already holding lock:
ffff8880362ed258 (&ovl_i_mutex_dir_key[depth]#2){++++}-{4:4}, at: inode_lock include/linux/fs.h:865 [inline]
ffff8880362ed258 (&ovl_i_mutex_dir_key[depth]#2){++++}-{4:4}, at: open_last_lookups fs/namei.c:3745 [inline]
ffff8880362ed258 (&ovl_i_mutex_dir_key[depth]#2){++++}-{4:4}, at: path_openat+0x15a4/0x2d80 fs/namei.c:3984

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #3 (&ovl_i_mutex_dir_key[depth]#2){++++}-{4:4}:
down_read+0x9a/0x330 kernel/locking/rwsem.c:1524
inode_lock_shared include/linux/fs.h:875 [inline]
lookup_slow fs/namei.c:1807 [inline]
walk_component+0x342/0x5b0 fs/namei.c:2112
lookup_last fs/namei.c:2610 [inline]
path_lookupat+0x17f/0x770 fs/namei.c:2634
filename_lookup+0x221/0x5f0 fs/namei.c:2663
kern_path+0x35/0x50 fs/namei.c:2771
lookup_bdev+0xd9/0x280 block/bdev.c:1163
resume_store+0x1d8/0x460 kernel/power/hibernate.c:1242
kobj_attr_store+0x55/0x80 lib/kobject.c:840
sysfs_kf_write+0x117/0x170 fs/sysfs/file.c:139
kernfs_fop_write_iter+0x33d/0x500 fs/kernfs/file.c:334
new_sync_write fs/read_write.c:586 [inline]
vfs_write+0x5ae/0x1150 fs/read_write.c:679
ksys_write+0x12b/0x250 fs/read_write.c:731
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (&of->mutex){+.+.}-{4:4}:
__mutex_lock_common kernel/locking/mutex.c:585 [inline]
__mutex_lock+0x19b/0xb10 kernel/locking/mutex.c:730
kernfs_fop_write_iter+0x27b/0x500 fs/kernfs/file.c:325
iter_file_splice_write+0x90f/0x10b0 fs/splice.c:743
do_splice_from fs/splice.c:941 [inline]
do_splice+0x146a/0x1f70 fs/splice.c:1354
__do_splice+0x327/0x360 fs/splice.c:1436
__do_sys_splice fs/splice.c:1639 [inline]
__se_sys_splice fs/splice.c:1621 [inline]
__x64_sys_splice+0x187/0x250 fs/splice.c:1621
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&pipe->mutex){+.+.}-{4:4}:
__mutex_lock_common kernel/locking/mutex.c:585 [inline]
__mutex_lock+0x19b/0xb10 kernel/locking/mutex.c:730
pipe_lock fs/pipe.c:92 [inline]
pipe_lock+0x64/0x80 fs/pipe.c:89
iter_file_splice_write+0x1eb/0x10b0 fs/splice.c:687
do_splice_from fs/splice.c:941 [inline]
do_splice+0x146a/0x1f70 fs/splice.c:1354
__do_splice+0x327/0x360 fs/splice.c:1436
__do_sys_splice fs/splice.c:1639 [inline]
__se_sys_splice fs/splice.c:1621 [inline]
__x64_sys_splice+0x187/0x250 fs/splice.c:1621
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (sb_writers#6){.+.+}-{0:0}:
check_prev_add kernel/locking/lockdep.c:3163 [inline]
check_prevs_add kernel/locking/lockdep.c:3282 [inline]
validate_chain kernel/locking/lockdep.c:3906 [inline]
__lock_acquire+0x249e/0x3c40 kernel/locking/lockdep.c:5228
lock_acquire.part.0+0x11b/0x380 kernel/locking/lockdep.c:5851
percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
__sb_start_write include/linux/fs.h:1773 [inline]
sb_start_write include/linux/fs.h:1909 [inline]
mnt_want_write+0x6f/0x450 fs/namespace.c:547
ovl_create_object+0x12e/0x300 fs/overlayfs/dir.c:656
lookup_open.isra.0+0x11c8/0x1580 fs/namei.c:3649
open_last_lookups fs/namei.c:3748 [inline]
path_openat+0x904/0x2d80 fs/namei.c:3984
do_filp_open+0x20c/0x470 fs/namei.c:4014
do_sys_openat2+0x17a/0x1e0 fs/open.c:1427
do_sys_open fs/open.c:1442 [inline]
__do_sys_open fs/open.c:1450 [inline]
__se_sys_open fs/open.c:1446 [inline]
__x64_sys_open+0x154/0x1e0 fs/open.c:1446
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
sb_writers#6 --> &of->mutex --> &ovl_i_mutex_dir_key[depth]#2

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&ovl_i_mutex_dir_key[depth]#2);
lock(&of->mutex);
lock(&ovl_i_mutex_dir_key[depth]#2);
rlock(sb_writers#6);

*** DEADLOCK ***

2 locks held by syz.4.1894/11640:
#0: ffff88805690c420 (sb_writers#20){.+.+}-{0:0}, at: open_last_lookups fs/namei.c:3737 [inline]
#0: ffff88805690c420 (sb_writers#20){.+.+}-{0:0}, at: path_openat+0x1fab/0x2d80 fs/namei.c:3984
#1: ffff8880362ed258 (&ovl_i_mutex_dir_key[depth]#2){++++}-{4:4}, at: inode_lock include/linux/fs.h:865 [inline]
#1: ffff8880362ed258 (&ovl_i_mutex_dir_key[depth]#2){++++}-{4:4}, at: open_last_lookups fs/namei.c:3745 [inline]
#1: ffff8880362ed258 (&ovl_i_mutex_dir_key[depth]#2){++++}-{4:4}, at: path_openat+0x15a4/0x2d80 fs/namei.c:3984

stack backtrace:
CPU: 3 UID: 0 PID: 11640 Comm: syz.4.1894 Not tainted 6.13.0-syzkaller-08291-g805ba04cb7cc #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
print_circular_bug+0x490/0x760 kernel/locking/lockdep.c:2076
check_noncircular+0x31a/0x400 kernel/locking/lockdep.c:2208
check_prev_add kernel/locking/lockdep.c:3163 [inline]
check_prevs_add kernel/locking/lockdep.c:3282 [inline]
validate_chain kernel/locking/lockdep.c:3906 [inline]
__lock_acquire+0x249e/0x3c40 kernel/locking/lockdep.c:5228
lock_acquire.part.0+0x11b/0x380 kernel/locking/lockdep.c:5851
percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
__sb_start_write include/linux/fs.h:1773 [inline]
sb_start_write include/linux/fs.h:1909 [inline]
mnt_want_write+0x6f/0x450 fs/namespace.c:547
ovl_create_object+0x12e/0x300 fs/overlayfs/dir.c:656
lookup_open.isra.0+0x11c8/0x1580 fs/namei.c:3649
open_last_lookups fs/namei.c:3748 [inline]
path_openat+0x904/0x2d80 fs/namei.c:3984
do_filp_open+0x20c/0x470 fs/namei.c:4014
do_sys_openat2+0x17a/0x1e0 fs/open.c:1427
do_sys_open fs/open.c:1442 [inline]
__do_sys_open fs/open.c:1450 [inline]
__se_sys_open fs/open.c:1446 [inline]
__x64_sys_open+0x154/0x1e0 fs/open.c:1446
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb22938cda9
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:00007fb22a1f9038 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 00007fb2295a5fa0 RCX: 00007fb22938cda9
RDX: 0000000000000000 RSI: 0000000000060142 RDI: 0000000020000000
RBP: 00007fb22940e2a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fb2295a5fa0 R15: 00007ffe95a187a8
</TASK>

---
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Next message: Ian Rogers: "Re: [PATCH] perf test: Fix perf test 11 hwmon endianess issue"
Previous message: Greg KH: "[GIT PULL] debugfs fix for 6.14-rc1"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]