FAILED: patch "[PATCH] usbip: synchronize event handler with sysfs code paths" failed to apply to 4.9-stable tree

The patch below does not apply to the 4.9-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 363eaa3a450abb4e63bd6e3ad79d1f7a0f717814 Mon Sep 17 00:00:00 2001
From: Shuah Khan <[email protected]>
Date: Mon, 29 Mar 2021 19:36:51 -0600
Subject: [PATCH] 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.

index 5d88917c9631..086ca76dd053 100644
@@ -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);
 	}