From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: [PATCH net-next 2/3] udp: avoid a cache miss on dequeue Date: Thu, 1 Jun 2017 09:40:55 -0700 Message-ID: References: <1496250043.27480.6.camel@edumazet-glaptop3.roam.corp.google.com> <1496313592.4872.14.camel@redhat.com> <1496332699.27480.14.camel@edumazet-glaptop3.roam.corp.google.com> <1496334113.9312.8.camel@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Cc: Eric Dumazet , netdev , "David S. Miller" To: Paolo Abeni Return-path: Received: from mail-yw0-f173.google.com ([209.85.161.173]:36723 "EHLO mail-yw0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752043AbdFAQk5 (ORCPT ); Thu, 1 Jun 2017 12:40:57 -0400 Received: by mail-yw0-f173.google.com with SMTP id b68so22520756ywe.3 for ; Thu, 01 Jun 2017 09:40:56 -0700 (PDT) In-Reply-To: <1496334113.9312.8.camel@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: On Thu, Jun 1, 2017 at 9:21 AM, Paolo Abeni wrote: > I'm sorry, I do not follow. I'm concerned about the secpath field (skb- >>sp), which is the only one that can be not NULL in > __udp_queue_rcv_skb(). > > If the secpath is not NULL, calling there secpath_reset() (or the to- > be-introduced skb_reset_head_state()), we will properly release it and > we will clear the field, too. > > Calling skb_release_head_state() in the same scenario, we release the > secpath, but we don't clear it. So if the packet is later dropped we > will get a double free, unless we add and use a specialized a > free_stateless_skb(), too. Then simply use secpath_reset() instead of secpath_put() from skb_release_head_state() Clearly having these subtle differences bring confusion, for very little gain. secpath_put() should be removed. Most of its callers simply set skb->sp back to NULL anyway.