Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751962AbdFEQUa (ORCPT ); Mon, 5 Jun 2017 12:20:30 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:58010 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751194AbdFEQU1 (ORCPT ); Mon, 5 Jun 2017 12:20:27 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Eric Dumazet , Andrey Konovalov , idaifish@gmail.com, "David S. Miller" Subject: [PATCH 4.4 18/53] ipv6: fix out of bound writes in __ip6_append_data() Date: Mon, 5 Jun 2017 18:17:16 +0200 Message-Id: <20170605153038.214294980@linuxfoundation.org> X-Mailer: git-send-email 2.13.0 In-Reply-To: <20170605153037.105331684@linuxfoundation.org> References: <20170605153037.105331684@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2030 Lines: 67 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet [ Upstream commit 232cd35d0804cc241eb887bb8d4d9b3b9881c64a ] Andrey Konovalov and idaifish@gmail.com reported crashes caused by one skb shared_info being overwritten from __ip6_append_data() Andrey program lead to following state : copy -4200 datalen 2000 fraglen 2040 maxfraglen 2040 alloclen 2048 transhdrlen 0 offset 0 fraggap 6200 The skb_copy_and_csum_bits(skb_prev, maxfraglen, data + transhdrlen, fraggap, 0); is overwriting skb->head and skb_shared_info Since we apparently detect this rare condition too late, move the code earlier to even avoid allocating skb and risking crashes. Once again, many thanks to Andrey and syzkaller team. Signed-off-by: Eric Dumazet Reported-by: Andrey Konovalov Tested-by: Andrey Konovalov Reported-by: Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/ipv6/ip6_output.c | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-) --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c @@ -1432,6 +1432,11 @@ alloc_new_skb: */ alloclen += sizeof(struct frag_hdr); + copy = datalen - transhdrlen - fraggap; + if (copy < 0) { + err = -EINVAL; + goto error; + } if (transhdrlen) { skb = sock_alloc_send_skb(sk, alloclen + hh_len, @@ -1481,13 +1486,9 @@ alloc_new_skb: data += fraggap; pskb_trim_unique(skb_prev, maxfraglen); } - copy = datalen - transhdrlen - fraggap; - - if (copy < 0) { - err = -EINVAL; - kfree_skb(skb); - goto error; - } else if (copy > 0 && getfrag(from, data + transhdrlen, offset, copy, fraggap, skb) < 0) { + if (copy > 0 && + getfrag(from, data + transhdrlen, offset, + copy, fraggap, skb) < 0) { err = -EFAULT; kfree_skb(skb); goto error;