[v5.15] possible deadlock in __input_unregister_device (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 68efe5a6c16a Linux 5.15.197
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=149b5b92580000
kernel config: https://syzkaller.appspot.com/x/.config?x=7e6ed99963d6ee1d
dashboard link: https://syzkaller.appspot.com/bug?extid=ad75b408141218daacdd
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/900f9b9bd850/disk-68efe5a6.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/1e089a5019a6/vmlinux-68efe5a6.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b319f477b907/bzImage-68efe5a6.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ad75b4...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.2.234/5676 is trying to acquire lock:
ffff88807b4902c0 (&dev->mutex#2){+.+.}-{3:3}, at: input_disconnect_device drivers/input/input.c:748 [inline]
ffff88807b4902c0 (&dev->mutex#2){+.+.}-{3:3}, at: __input_unregister_device+0x2e/0x320 drivers/input/input.c:2278

but task is already holding lock:
ffff888060f3dee0 (&hdev->ll_open_lock){+.+.}-{3:3}, at: hid_hw_open+0x23/0x160 drivers/hid/hid-core.c:2127

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&hdev->ll_open_lock){+.+.}-{3:3}:
__mutex_lock_common+0x1eb/0x2390 kernel/locking/mutex.c:596
__mutex_lock kernel/locking/mutex.c:729 [inline]
mutex_lock_killable_nested+0x17/0x20 kernel/locking/mutex.c:758
hid_hw_open+0x23/0x160 drivers/hid/hid-core.c:2127
input_open_device+0x16c/0x2e0 drivers/input/input.c:640
mousedev_open_device+0xc3/0x150 drivers/input/mousedev.c:430
mousedev_open+0x2e5/0x4a0 drivers/input/mousedev.c:556
chrdev_open+0x597/0x670 fs/char_dev.c:414
do_dentry_open+0x7ff/0xf80 fs/open.c:826
do_open fs/namei.c:3616 [inline]
path_openat+0x2682/0x2f30 fs/namei.c:3750
do_filp_open+0x1b3/0x3e0 fs/namei.c:3777
do_sys_openat2+0x142/0x4a0 fs/open.c:1255
do_sys_open fs/open.c:1271 [inline]
__do_sys_openat fs/open.c:1287 [inline]
__se_sys_openat fs/open.c:1282 [inline]
__x64_sys_openat+0x135/0x160 fs/open.c:1282
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #0 (&dev->mutex#2){+.+.}-{3:3}:
check_prev_add kernel/locking/lockdep.c:3053 [inline]
check_prevs_add kernel/locking/lockdep.c:3172 [inline]
validate_chain kernel/locking/lockdep.c:3788 [inline]
__lock_acquire+0x2c33/0x7c60 kernel/locking/lockdep.c:5012
lock_acquire+0x197/0x3f0 kernel/locking/lockdep.c:5623
__mutex_lock_common+0x1eb/0x2390 kernel/locking/mutex.c:596
__mutex_lock kernel/locking/mutex.c:729 [inline]
mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
input_disconnect_device drivers/input/input.c:748 [inline]
__input_unregister_device+0x2e/0x320 drivers/input/input.c:2278
input_unregister_device+0x97/0xf0 drivers/input/input.c:2473
steam_client_ll_open+0x73/0x90 drivers/hid/hid-steam.c:640
hid_hw_open+0xdd/0x160 drivers/hid/hid-core.c:2132
hidraw_open+0x28f/0x8b0 drivers/hid/hidraw.c:289
chrdev_open+0x597/0x670 fs/char_dev.c:414
do_dentry_open+0x7ff/0xf80 fs/open.c:826
do_open fs/namei.c:3616 [inline]
path_openat+0x2682/0x2f30 fs/namei.c:3750
do_filp_open+0x1b3/0x3e0 fs/namei.c:3777
do_sys_openat2+0x142/0x4a0 fs/open.c:1255
do_sys_open fs/open.c:1271 [inline]
__do_sys_openat fs/open.c:1287 [inline]
__se_sys_openat fs/open.c:1282 [inline]
__x64_sys_openat+0x135/0x160 fs/open.c:1282
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

other info that might help us debug this:

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&hdev->ll_open_lock);
lock(&dev->mutex#2);
lock(&hdev->ll_open_lock);
lock(&dev->mutex#2);

*** DEADLOCK ***

2 locks held by syz.2.234/5676:
#0: ffffffff8d0aeb08 (minors_lock){+.+.}-{3:3}, at: hidraw_open+0x91/0x8b0 drivers/hid/hidraw.c:275
#1: ffff888060f3dee0 (&hdev->ll_open_lock){+.+.}-{3:3}, at: hid_hw_open+0x23/0x160 drivers/hid/hid-core.c:2127

stack backtrace:
CPU: 0 PID: 5676 Comm: syz.2.234 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
<TASK>
dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
check_noncircular+0x274/0x310 kernel/locking/lockdep.c:2133
check_prev_add kernel/locking/lockdep.c:3053 [inline]
check_prevs_add kernel/locking/lockdep.c:3172 [inline]
validate_chain kernel/locking/lockdep.c:3788 [inline]
__lock_acquire+0x2c33/0x7c60 kernel/locking/lockdep.c:5012
lock_acquire+0x197/0x3f0 kernel/locking/lockdep.c:5623
__mutex_lock_common+0x1eb/0x2390 kernel/locking/mutex.c:596
__mutex_lock kernel/locking/mutex.c:729 [inline]
mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
input_disconnect_device drivers/input/input.c:748 [inline]
__input_unregister_device+0x2e/0x320 drivers/input/input.c:2278
input_unregister_device+0x97/0xf0 drivers/input/input.c:2473
steam_client_ll_open+0x73/0x90 drivers/hid/hid-steam.c:640
hid_hw_open+0xdd/0x160 drivers/hid/hid-core.c:2132
hidraw_open+0x28f/0x8b0 drivers/hid/hidraw.c:289
chrdev_open+0x597/0x670 fs/char_dev.c:414
do_dentry_open+0x7ff/0xf80 fs/open.c:826
do_open fs/namei.c:3616 [inline]
path_openat+0x2682/0x2f30 fs/namei.c:3750
do_filp_open+0x1b3/0x3e0 fs/namei.c:3777
do_sys_openat2+0x142/0x4a0 fs/open.c:1255
do_sys_open fs/open.c:1271 [inline]
__do_sys_openat fs/open.c:1287 [inline]
__se_sys_openat fs/open.c:1282 [inline]
__x64_sys_openat+0x135/0x160 fs/open.c:1282
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f914ec9ff90
Code: 48 89 44 24 20 75 93 44 89 54 24 0c e8 69 95 02 00 44 8b 54 24 0c 89 da 48 89 ee 41 89 c0 bf 9c ff ff ff b8 01 01 00 00 0f 05 <48> 3d 00 f0 ff ff 77 38 44 89 c7 89 44 24 0c e8 bc 95 02 00 8b 44
RSP: 002b:00007f914cec5b70 EFLAGS: 00000293 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 000000000014a002 RCX: 00007f914ec9ff90
RDX: 000000000014a002 RSI: 00007f914cec5c10 RDI: 00000000ffffff9c
RBP: 00007f914cec5c10 R08: 0000000000000000 R09: 0023776172646968
R10: 0000000000000000 R11: 0000000000000293 R12: cccccccccccccccd
R13: 00007f914eef8218 R14: 00007f914eef8180 R15: 00007ffda3f81b38
</TASK>
input: Steam Controller as /devices/platform/dummy_hcd.2/usb3/3-1/3-1:0.0/0003:28DE:1102.0006/input/input12


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