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=-13.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable 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 3C2E9C433DF for ; Mon, 3 Aug 2020 12:43:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1776F2054F for ; Mon, 3 Aug 2020 12:43:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1596458587; bh=lh5kN0aZNa2kwrAZq9484r/FQcxSPMX2RaU2x6rT4S8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=uwZu2T8dkOiA2DZmxbk92jNRDKkCYrhVmzZuTw5HxJ6D8jEqTlSTRnE7kYsZtrWTQ ZPW0ihPKWT73qjOzlhKUHzfsrJ7nMcd3Xe1kx3QZW0h1/5i42EidhhimIpCoh43m1U /kfAWAaxehKPvmqDAs68UVtrafj4YnBEGa1j5arw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727902AbgHCMnD (ORCPT ); Mon, 3 Aug 2020 08:43:03 -0400 Received: from mail.kernel.org ([198.145.29.99]:57300 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729024AbgHCMaT (ORCPT ); Mon, 3 Aug 2020 08:30:19 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (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 91E0C20775; Mon, 3 Aug 2020 12:30:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1596457818; bh=lh5kN0aZNa2kwrAZq9484r/FQcxSPMX2RaU2x6rT4S8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=TuZEJcgFfIbqH2kvYywOtnqiquxXTYxUOFnrpBmnHnzzAQCT8xGf8ZT+LLaRwHXKH Kc/tbvmYeeeVbSG8LqrARJnkg/pR3s0j7ucv8rz5GmdFiEE3/wRorX19c0TjlwqMMy ejbUSMfowKkGzqkTOso1AOjnYSj1g2ToRrCodpe4= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Eric Dumazet , Martin Schiller , Xie He , "David S. Miller" , Sasha Levin Subject: [PATCH 5.4 84/90] drivers/net/wan: lapb: Corrected the usage of skb_cow Date: Mon, 3 Aug 2020 14:19:46 +0200 Message-Id: <20200803121901.666059663@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200803121857.546052424@linuxfoundation.org> References: <20200803121857.546052424@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Xie He [ Upstream commit 8754e1379e7089516a449821f88e1fe1ebbae5e1 ] This patch fixed 2 issues with the usage of skb_cow in LAPB drivers "lapbether" and "hdlc_x25": 1) After skb_cow fails, kfree_skb should be called to drop a reference to the skb. But in both drivers, kfree_skb is not called. 2) skb_cow should be called before skb_push so that is can ensure the safety of skb_push. But in "lapbether", it is incorrectly called after skb_push. More details about these 2 issues: 1) The behavior of calling kfree_skb on failure is also the behavior of netif_rx, which is called by this function with "return netif_rx(skb);". So this function should follow this behavior, too. 2) In "lapbether", skb_cow is called after skb_push. This results in 2 logical issues: a) skb_push is not protected by skb_cow; b) An extra headroom of 1 byte is ensured after skb_push. This extra headroom has no use in this function. It also has no use in the upper-layer function that this function passes the skb to (x25_lapb_receive_frame in net/x25/x25_dev.c). So logically skb_cow should instead be called before skb_push. Cc: Eric Dumazet Cc: Martin Schiller Signed-off-by: Xie He Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- drivers/net/wan/hdlc_x25.c | 4 +++- drivers/net/wan/lapbether.c | 8 +++++--- 2 files changed, 8 insertions(+), 4 deletions(-) diff --git a/drivers/net/wan/hdlc_x25.c b/drivers/net/wan/hdlc_x25.c index bf78073ee7fd9..e2a83f4cd3bb6 100644 --- a/drivers/net/wan/hdlc_x25.c +++ b/drivers/net/wan/hdlc_x25.c @@ -62,8 +62,10 @@ static int x25_data_indication(struct net_device *dev, struct sk_buff *skb) { unsigned char *ptr; - if (skb_cow(skb, 1)) + if (skb_cow(skb, 1)) { + kfree_skb(skb); return NET_RX_DROP; + } skb_push(skb, 1); skb_reset_network_header(skb); diff --git a/drivers/net/wan/lapbether.c b/drivers/net/wan/lapbether.c index 5a6f27298b90f..134e4dd916c1a 100644 --- a/drivers/net/wan/lapbether.c +++ b/drivers/net/wan/lapbether.c @@ -128,10 +128,12 @@ static int lapbeth_data_indication(struct net_device *dev, struct sk_buff *skb) { unsigned char *ptr; - skb_push(skb, 1); - - if (skb_cow(skb, 1)) + if (skb_cow(skb, 1)) { + kfree_skb(skb); return NET_RX_DROP; + } + + skb_push(skb, 1); ptr = skb->data; *ptr = X25_IFACE_DATA; -- 2.25.1