[PATCH 4/4] usbip: synchronize event handler with sysfs code paths

[Shuah Khan]

Fuzzing uncovered race condition between sysfs code paths in usbip
drivers. Device connect/disconnect code paths initiated through
sysfs interface are prone to races if disconnect happens during
connect and vice versa.

Use sysfs_lock to synchronize event handler with sysfs paths
in usbip drivers.

Reported-and-tested-by: syzbot+a93fba6d384346a76...@syzkaller.appspotmail.com
Cc: sta...@vger.kernel.org
Signed-off-by: Shuah Khan <sk...@linuxfoundation.org>
---
 drivers/usb/usbip/usbip_event.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/usb/usbip/usbip_event.c b/drivers/usb/usbip/usbip_event.c
index 5d88917c9631..086ca76dd053 100644
--- a/drivers/usb/usbip/usbip_event.c
+++ b/drivers/usb/usbip/usbip_event.c
@@ -70,6 +70,7 @@ static void event_handler(struct work_struct *work)
        while ((ud = get_event()) != NULL) {
                usbip_dbg_eh("pending event %lx\n", ud->event);
 
+               mutex_lock(&ud->sysfs_lock);
                /*
                 * NOTE: shutdown must come first.
                 * Shutdown the device.
@@ -90,6 +91,7 @@ static void event_handler(struct work_struct *work)
                        ud->eh_ops.unusable(ud);
                        unset_event(ud, USBIP_EH_UNUSABLE);
                }
+               mutex_unlock(&ud->sysfs_lock);
 
                wake_up(&ud->eh_waitq);
        }
-- 
2.27.0