usblp: poison URBs upon disconnect

BugLink: https://bugs.launchpad.net/bugs/1885932

[ Upstream commit 296a193b ]

syzkaller reported an URB that should have been killed to be active.
We do not understand it, but this should fix the issue if it is real.
Signed-off-by: Oliver Neukum <oneukum@suse.com>
Reported-by: syzbot+be5b5f86a162a6c281e6@syzkaller.appspotmail.com
Link: https://lore.kernel.org/r/20200507085806.5793-1-oneukum@suse.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Kelsey Skunberg <kelsey.skunberg@canonical.com>

drivers/usb/class/usblp.c

@@ -481,7 +481,8 @@ static int usblp_release(struct inode *inode, struct file *file)
 	usb_autopm_put_interface(usblp->intf);
 
 	if (!usblp->present)		/* finish cleanup from disconnect */
-		usblp_cleanup(usblp);
+		usblp_cleanup(usblp);	/* any URBs must be dead */
+
 	mutex_unlock(&usblp_mutex);
 	return 0;
 }
@@ -1397,9 +1398,11 @@ static void usblp_disconnect(struct usb_interface *intf)
 
 	usblp_unlink_urbs(usblp);
 	mutex_unlock(&usblp->mut);
+	usb_poison_anchored_urbs(&usblp->urbs);
 
 	if (!usblp->used)
 		usblp_cleanup(usblp);
+
 	mutex_unlock(&usblp_mutex);
 }