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=-9.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 D43DDC2D0A3 for ; Mon, 9 Nov 2020 13:37:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8703D20658 for ; Mon, 9 Nov 2020 13:37:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604929059; bh=kmMfjDW4t3+wdiEPhf8tYLDHxq/71ArM7bQTrfZPWbs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=R1NSyFT+m6AnOqSDkbJ+tCENHpg7Ojqc6VJlVk0KIafxznI78uGiCYBw2idq5SMYH NePq5CPRdc1tuR18HZ5PrdxNFXbSTUT56cxh6FOtIGbzh6fBqZFqkZ/bGDV4ueC1Aj SNfE45Jyu2q8PjLOcGrPsyXDu/1xebyZSUlgXNlk= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732148AbgKINhi (ORCPT ); Mon, 9 Nov 2020 08:37:38 -0500 Received: from mail.kernel.org ([198.145.29.99]:57292 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729913AbgKINEM (ORCPT ); Mon, 9 Nov 2020 08:04:12 -0500 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2922320663; Mon, 9 Nov 2020 13:04:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604927049; bh=kmMfjDW4t3+wdiEPhf8tYLDHxq/71ArM7bQTrfZPWbs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=CS3J+rLT32sipt8DL3slSG5BBlbM/6NbHc7RuS09v1bR4cM1k9YRB3A75gMaNjIXH t7qaOC7r7gYlkCle589EUlqW4o8Bvy/vc6nj53uQJmJIrBum8smXrR2T1fl0PUHfUp eAZOI9wMRqBUpC9zG2r6ioy0+3sw5pKvGpVUe6i4= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, James Jurack , Jakub Kicinski , Claudiu Manoil Subject: [PATCH 4.9 094/117] gianfar: Replace skb_realloc_headroom with skb_cow_head for PTP Date: Mon, 9 Nov 2020 13:55:20 +0100 Message-Id: <20201109125030.160234760@linuxfoundation.org> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201109125025.630721781@linuxfoundation.org> References: <20201109125025.630721781@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Claudiu Manoil [ Upstream commit d145c9031325fed963a887851d9fa42516efd52b ] When PTP timestamping is enabled on Tx, the controller inserts the Tx timestamp at the beginning of the frame buffer, between SFD and the L2 frame header. This means that the skb provided by the stack is required to have enough headroom otherwise a new skb needs to be created by the driver to accommodate the timestamp inserted by h/w. Up until now the driver was relying on skb_realloc_headroom() to create new skbs to accommodate PTP frames. Turns out that this method is not reliable in this context at least, as skb_realloc_headroom() for PTP frames can cause random crashes, mostly in subsequent skb_*() calls, when multiple concurrent TCP streams are run at the same time with the PTP flow on the same device (as seen in James' report). I also noticed that when the system is loaded by sending multiple TCP streams, the driver receives cloned skbs in large numbers. skb_cow_head() instead proves to be stable in this scenario, and not only handles cloned skbs too but it's also more efficient and widely used in other drivers. The commit introducing skb_realloc_headroom in the driver goes back to 2009, commit 93c1285c5d92 ("gianfar: reallocate skb when headroom is not enough for fcb"). For practical purposes I'm referencing a newer commit (from 2012) that brings the code to its current structure (and fixes the PTP case). Fixes: 9c4886e5e63b ("gianfar: Fix invalid TX frames returned on error queue when time stamping") Reported-by: James Jurack Suggested-by: Jakub Kicinski Signed-off-by: Claudiu Manoil Link: https://lore.kernel.org/r/20201029081057.8506-1-claudiu.manoil@nxp.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman --- drivers/net/ethernet/freescale/gianfar.c | 12 ++---------- 1 file changed, 2 insertions(+), 10 deletions(-) --- a/drivers/net/ethernet/freescale/gianfar.c +++ b/drivers/net/ethernet/freescale/gianfar.c @@ -2367,20 +2367,12 @@ static int gfar_start_xmit(struct sk_buf fcb_len = GMAC_FCB_LEN + GMAC_TXPAL_LEN; /* make space for additional header when fcb is needed */ - if (fcb_len && unlikely(skb_headroom(skb) < fcb_len)) { - struct sk_buff *skb_new; - - skb_new = skb_realloc_headroom(skb, fcb_len); - if (!skb_new) { + if (fcb_len) { + if (unlikely(skb_cow_head(skb, fcb_len))) { dev->stats.tx_errors++; dev_kfree_skb_any(skb); return NETDEV_TX_OK; } - - if (skb->sk) - skb_set_owner_w(skb_new, skb->sk); - dev_consume_skb_any(skb); - skb = skb_new; } /* total number of fragments in the SKB */