smb3: fix lock ordering potential deadlock in cifs_sync_mid_result

Coverity spotted that the cifs_sync_mid_result function could deadlock

"Thread deadlock (ORDER_REVERSAL) lock_order: Calling spin_lock acquires
lock TCP_Server_Info.srv_lock while holding lock TCP_Server_Info.mid_lock"

Addresses-Coverity: 1590401 ("Thread deadlock (ORDER_REVERSAL)")
Cc: [email protected]
Reviewed-by: Shyam Prasad N <[email protected]>
Signed-off-by: Steve French <[email protected]>

Author: smfrench

fs/smb/client/transport.c

@@ -909,12 +909,15 @@ cifs_sync_mid_result(struct mid_q_entry *mid, struct TCP_Server_Info *server)
 			list_del_init(&mid->qhead);
 			mid->mid_flags |= MID_DELETED;
 		}
+		spin_unlock(&server->mid_lock);
 		cifs_server_dbg(VFS, "%s: invalid mid state mid=%llu state=%d\n",
 			 __func__, mid->mid, mid->mid_state);
 		rc = -EIO;
+		goto sync_mid_done;
 	}
 	spin_unlock(&server->mid_lock);
 
+sync_mid_done:
 	release_mid(mid);
 	return rc;
 }