From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2ACDCC3A59B for ; Fri, 30 Aug 2019 21:55:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EBE5B23431 for ; Fri, 30 Aug 2019 21:55:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728358AbfH3VzS (ORCPT ); Fri, 30 Aug 2019 17:55:18 -0400 Received: from shards.monkeyblade.net ([23.128.96.9]:42560 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728157AbfH3VzR (ORCPT ); Fri, 30 Aug 2019 17:55:17 -0400 Received: from localhost (unknown [IPv6:2601:601:9f80:35cd::d71]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) (Authenticated sender: davem-davemloft) by shards.monkeyblade.net (Postfix) with ESMTPSA id A1D85154FF691; Fri, 30 Aug 2019 14:55:16 -0700 (PDT) Date: Fri, 30 Aug 2019 14:55:16 -0700 (PDT) Message-Id: <20190830.145516.687207471361740034.davem@davemloft.net> To: dhowells@redhat.com Cc: netdev@vger.kernel.org, linux-afs@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net 0/7] rxrpc: Fix use of skb_cow_data() From: David Miller In-Reply-To: <156708405310.26102.7954021163316252673.stgit@warthog.procyon.org.uk> References: <156708405310.26102.7954021163316252673.stgit@warthog.procyon.org.uk> X-Mailer: Mew version 6.8 on Emacs 26.1 Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.5.12 (shards.monkeyblade.net [149.20.54.216]); Fri, 30 Aug 2019 14:55:16 -0700 (PDT) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: David Howells Date: Thu, 29 Aug 2019 14:07:33 +0100 > Here's a series of patches that replaces the use of skb_cow_data() in rxrpc > with skb_unshare() early on in the input process. The problem that is > being seen is that skb_cow_data() indirectly requires that the maximum > usage count on an sk_buff be 1, and it may generate an assertion failure in > pskb_expand_head() if not. > > This can occur because rxrpc_input_data() may be still holding a ref when > it has just attached the sk_buff to the rx ring and given that attachment > its own ref. If recvmsg happens fast enough, skb_cow_data() can see the > ref still held by the softirq handler. > > Further, a packet may contain multiple subpackets, each of which gets its > own attachment to the ring and its own ref - also making skb_cow_data() go > bang. > > Fix this by: ... > There are also patches to improve the rxrpc_skb tracepoint to make sure > that Tx-derived buffers are identified separately from Rx-derived buffers > in the trace. This looks great, thanks for reimplementing this using skb_unshare(). > The patches are tagged here: > > git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git > rxrpc-fixes-20190827 Pulled, thanks again.