usbip: synchronize event handler with sysfs code paths

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.

Cc: stable@vger.kernel.org
Reported-and-tested-by: syzbot+a93fba6d384346a761e3@syzkaller.appspotmail.com
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
Link: https://lore.kernel.org/r/c5c8723d3f29dfe3d759cfaafa7dd16b0dfe2918.1616807117.git.skhan@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/usbip/usbip_event.c b/drivers/usb/usbip/usbip_event.c
index 5d88917c963149b0ba1daa02cc4da4e84ca3c106..086ca76dd0531acfced7450ed2a321f06428bdf1 100644 (file)
--- 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);
        }