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=-6.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, 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 B1297C6786C for ; Fri, 14 Dec 2018 12:11:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 788EB214C4 for ; Fri, 14 Dec 2018 12:11:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1544789487; bh=tlGw/gKX/Z45HCNDkh1wKKQMHpLIn883WBI3UM2d9vM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=DIlgK28s+9HqRYTCkOw8V36KEVzzwobj2y4jCv+DR2cp541tcthyioxqxjDcwsN8m 6LyB7d83yF4nhAeYtVsbavyUaN9efgzvllnnZQToErt5D882pEWDyPQjZ5JU54V9xv CBMx6jISwVSuS/kNgnhrNAPKX7C8dvTF+yXGW1No= DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 788EB214C4 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731781AbeLNML0 (ORCPT ); Fri, 14 Dec 2018 07:11:26 -0500 Received: from mail.kernel.org ([198.145.29.99]:58030 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731768AbeLNMLX (ORCPT ); Fri, 14 Dec 2018 07:11:23 -0500 Received: from localhost (5356596B.cm-6-7b.dynamic.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 8ACCE2147D; Fri, 14 Dec 2018 12:11:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1544789482; bh=tlGw/gKX/Z45HCNDkh1wKKQMHpLIn883WBI3UM2d9vM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=A3m44encEcGUph48G47ElENz4EJb996ebFTpHT++aotTBmQQmvDhaawGYmSaV6FqS 0nfwZKVsyQWzTD0dS/ZbldwS+Re6ziRsIHHDF6xm+1KGTwXiCUVSojGbx8Q49oTyHE VFL6hBjQrSjyU7YBuyrauf3zWGyuGfELq+9UqzyU= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Stefano Brivio , "David S. Miller" Subject: [PATCH 4.9 10/51] neighbour: Avoid writing before skb->head in neigh_hh_output() Date: Fri, 14 Dec 2018 13:00:12 +0100 Message-Id: <20181214115714.246127730@linuxfoundation.org> X-Mailer: git-send-email 2.20.0 In-Reply-To: <20181214115713.244259772@linuxfoundation.org> References: <20181214115713.244259772@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review X-Patchwork-Hint: ignore MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Stefano Brivio [ Upstream commit e6ac64d4c4d095085d7dd71cbd05704ac99829b2 ] While skb_push() makes the kernel panic if the skb headroom is less than the unaligned hardware header size, it will proceed normally in case we copy more than that because of alignment, and we'll silently corrupt adjacent slabs. In the case fixed by the previous patch, "ipv6: Check available headroom in ip6_xmit() even without options", we end up in neigh_hh_output() with 14 bytes headroom, 14 bytes hardware header and write 16 bytes, starting 2 bytes before the allocated buffer. Always check we're not writing before skb->head and, if the headroom is not enough, warn and drop the packet. v2: - instead of panicking with BUG_ON(), WARN_ON_ONCE() and drop the packet (Eric Dumazet) - if we avoid the panic, though, we need to explicitly check the headroom before the memcpy(), otherwise we'll have corrupted slabs on a running kernel, after we warn - use __skb_push() instead of skb_push(), as the headroom check is already implemented here explicitly (Eric Dumazet) Signed-off-by: Stefano Brivio Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- include/net/neighbour.h | 28 +++++++++++++++++++++++----- 1 file changed, 23 insertions(+), 5 deletions(-) --- a/include/net/neighbour.h +++ b/include/net/neighbour.h @@ -448,6 +448,7 @@ static inline int neigh_hh_bridge(struct static inline int neigh_hh_output(const struct hh_cache *hh, struct sk_buff *skb) { + unsigned int hh_alen = 0; unsigned int seq; int hh_len; @@ -455,16 +456,33 @@ static inline int neigh_hh_output(const seq = read_seqbegin(&hh->hh_lock); hh_len = hh->hh_len; if (likely(hh_len <= HH_DATA_MOD)) { - /* this is inlined by gcc */ - memcpy(skb->data - HH_DATA_MOD, hh->hh_data, HH_DATA_MOD); + hh_alen = HH_DATA_MOD; + + /* skb_push() would proceed silently if we have room for + * the unaligned size but not for the aligned size: + * check headroom explicitly. + */ + if (likely(skb_headroom(skb) >= HH_DATA_MOD)) { + /* this is inlined by gcc */ + memcpy(skb->data - HH_DATA_MOD, hh->hh_data, + HH_DATA_MOD); + } } else { - int hh_alen = HH_DATA_ALIGN(hh_len); + hh_alen = HH_DATA_ALIGN(hh_len); - memcpy(skb->data - hh_alen, hh->hh_data, hh_alen); + if (likely(skb_headroom(skb) >= hh_alen)) { + memcpy(skb->data - hh_alen, hh->hh_data, + hh_alen); + } } } while (read_seqretry(&hh->hh_lock, seq)); - skb_push(skb, hh_len); + if (WARN_ON_ONCE(skb_headroom(skb) < hh_alen)) { + kfree_skb(skb); + return NET_XMIT_DROP; + } + + __skb_push(skb, hh_len); return dev_queue_xmit(skb); }