[PATCH next] USB: chaoskey: Fix possible deadlock chaoskey_list_lock
From: Edward Adam Davis
Date: Wed Oct 09 2024 - 10:54:09 EST
[Syzbot reported two possible deadlocks]
The first possible deadlock is:
WARNING: possible recursive locking detected
6.12.0-rc1-syzkaller-00027-g4a9fe2a8ac53 #0 Not tainted
--------------------------------------------
syz-executor363/2651 is trying to acquire lock:
ffffffff89b120e8 (chaoskey_list_lock){+.+.}-{3:3}, at: chaoskey_release+0x15d/0x2c0 drivers/usb/misc/chaoskey.c:322
but task is already holding lock:
ffffffff89b120e8 (chaoskey_list_lock){+.+.}-{3:3}, at: chaoskey_release+0x7f/0x2c0 drivers/usb/misc/chaoskey.c:299
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(chaoskey_list_lock);
lock(chaoskey_list_lock);
*** DEADLOCK ***
The second possible deadlock is:
WARNING: possible circular locking dependency detected
6.12.0-rc1-syzkaller-00027-g4a9fe2a8ac53 #0 Not tainted
------------------------------------------------------
kworker/0:2/804 is trying to acquire lock:
ffffffff899dadb0 (minor_rwsem){++++}-{3:3}, at: usb_deregister_dev+0x7c/0x1e0 drivers/usb/core/file.c:186
but task is already holding lock:
ffffffff89b120e8 (chaoskey_list_lock){+.+.}-{3:3}, at: chaoskey_disconnect+0xa8/0x2a0 drivers/usb/misc/chaoskey.c:235
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (chaoskey_list_lock){+.+.}-{3:3}:
__mutex_lock_common kernel/locking/mutex.c:608 [inline]
__mutex_lock+0x175/0x9c0 kernel/locking/mutex.c:752
chaoskey_open+0xdd/0x220 drivers/usb/misc/chaoskey.c:274
usb_open+0x186/0x220 drivers/usb/core/file.c:47
chrdev_open+0x237/0x6a0 fs/char_dev.c:414
do_dentry_open+0x6cb/0x1390 fs/open.c:958
vfs_open+0x82/0x3f0 fs/open.c:1088
do_open fs/namei.c:3774 [inline]
path_openat+0x1e6a/0x2d60 fs/namei.c:3933
do_filp_open+0x1dc/0x430 fs/namei.c:3960
do_sys_openat2+0x17a/0x1e0 fs/open.c:1415
do_sys_open fs/open.c:1430 [inline]
__do_sys_openat fs/open.c:1446 [inline]
__se_sys_openat fs/open.c:1441 [inline]
__x64_sys_openat+0x175/0x210 fs/open.c:1441
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 (minor_rwsem){++++}-{3:3}:
check_prev_add kernel/locking/lockdep.c:3161 [inline]
check_prevs_add kernel/locking/lockdep.c:3280 [inline]
validate_chain kernel/locking/lockdep.c:3904 [inline]
__lock_acquire+0x250b/0x3ce0 kernel/locking/lockdep.c:5202
lock_acquire.part.0+0x11b/0x380 kernel/locking/lockdep.c:5825
down_write+0x93/0x200 kernel/locking/rwsem.c:1577
usb_deregister_dev+0x7c/0x1e0 drivers/usb/core/file.c:186
chaoskey_disconnect+0xb7/0x2a0 drivers/usb/misc/chaoskey.c:236
usb_unbind_interface+0x1e8/0x970 drivers/usb/core/driver.c:461
device_remove drivers/base/dd.c:569 [inline]
device_remove+0x122/0x170 drivers/base/dd.c:561
__device_release_driver drivers/base/dd.c:1273 [inline]
device_release_driver_internal+0x44a/0x610 drivers/base/dd.c:1296
bus_remove_device+0x22f/0x420 drivers/base/bus.c:576
device_del+0x396/0x9f0 drivers/base/core.c:3864
usb_disable_device+0x36c/0x7f0 drivers/usb/core/message.c:1418
usb_disconnect+0x2e1/0x920 drivers/usb/core/hub.c:2304
hub_port_connect drivers/usb/core/hub.c:5361 [inline]
hub_port_connect_change drivers/usb/core/hub.c:5661 [inline]
port_event drivers/usb/core/hub.c:5821 [inline]
hub_event+0x1bed/0x4f40 drivers/usb/core/hub.c:5903
process_one_work+0x9c5/0x1ba0 kernel/workqueue.c:3229
process_scheduled_works kernel/workqueue.c:3310 [inline]
worker_thread+0x6c8/0xf00 kernel/workqueue.c:3391
kthread+0x2c1/0x3a0 kernel/kthread.c:389
ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(chaoskey_list_lock);
lock(minor_rwsem);
lock(chaoskey_list_lock);
lock(minor_rwsem);
*** DEADLOCK ***
[Analysis]
The first is AA lock, it because wrong logic, it need a unlock.
The second is AB lock, it needs to rearrange the order of lock usage.
Fixes: 422dc0a4d12d ("USB: chaoskey: fail open after removal")
Reported-by: syzbot+685e14d04fe35692d3bc@xxxxxxxxxxxxxxxxxxxxxxxxx
Reported-by: syzbot+1f8ca5ee82576ec01f12@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=685e14d04fe35692d3bc
Signed-off-by: Edward Adam Davis <eadavis@xxxxxx>
---
drivers/usb/misc/chaoskey.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/usb/misc/chaoskey.c b/drivers/usb/misc/chaoskey.c
index e8b63df5f975..225863321dc4 100644
--- a/drivers/usb/misc/chaoskey.c
+++ b/drivers/usb/misc/chaoskey.c
@@ -232,10 +232,10 @@ static void chaoskey_disconnect(struct usb_interface *interface)
if (dev->hwrng_registered)
hwrng_unregister(&dev->hwrng);
- mutex_lock(&chaoskey_list_lock);
usb_deregister_dev(interface, &chaoskey_class);
usb_set_intfdata(interface, NULL);
+ mutex_lock(&chaoskey_list_lock);
mutex_lock(&dev->lock);
dev->present = false;
@@ -319,7 +319,7 @@ static int chaoskey_release(struct inode *inode, struct file *file)
bail:
mutex_unlock(&dev->lock);
destruction:
- mutex_lock(&chaoskey_list_lock);
+ mutex_unlock(&chaoskey_list_lock);
usb_dbg(interface, "release success");
return rv;
}
--
2.43.0