From patchwork Fri May 19 21:17:48 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Dumazet X-Patchwork-Id: 764880 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 3wV19Y5pcTz9s3w for ; Sat, 20 May 2017 07:17:53 +1000 (AEST) Authentication-Results: ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=gmail.com header.i=@gmail.com header.b="H66D2hZe"; dkim-atps=neutral Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932505AbdESVRv (ORCPT ); Fri, 19 May 2017 17:17:51 -0400 Received: from mail-pg0-f67.google.com ([74.125.83.67]:32773 "EHLO mail-pg0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754357AbdESVRu (ORCPT ); Fri, 19 May 2017 17:17:50 -0400 Received: by mail-pg0-f67.google.com with SMTP id s62so10879741pgc.0 for ; Fri, 19 May 2017 14:17:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=message-id:subject:from:to:cc:date:in-reply-to:references :mime-version:content-transfer-encoding; bh=zuiDqH+RwmeKTgKglzChkSQxROvVyjxXGXtLBPaUj9s=; b=H66D2hZeta97qU0J1OY9lBpDSIicxTFQ4Sb+lZAEYUrE/yy5THjO8Gc+L/hcZWBUYy W9Id4FYXSIknszxzyzuJDqgL+n4y+belTr+MvmFeDUX8ljeY23lvPzRVaIt4VdmgLbP5 chGSlACyF1HiD6EH7F5NfV912iPvCKROzZn7VYYYHv061gdfzcrmck9xJuGIWfYz37pR wTJe7Yd00RWsI5J2GnymJNi/ikcW/Iqs5g6t1KnOGSj45TcG42oEqVQZCltu7LKFkX2A /3p1DdMj+meDEnSAtNSkPyRMEuJba+cuIo5vRd6P1UlzUg1B9hPibiHyoEuJCOCqI1Ld PbpQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:message-id:subject:from:to:cc:date:in-reply-to :references:mime-version:content-transfer-encoding; bh=zuiDqH+RwmeKTgKglzChkSQxROvVyjxXGXtLBPaUj9s=; b=G/dWABEDGJOGy5Bm+i2tOzZBhZdX8678OojCoE76Hq6NRaUSiEGH4ElShJ7lMQSb4y hLbhHEVFgobpErGH4NbU9qvEw2jx1MED7lAmU1ShdJUhfIJrKYHGhEHl2q48wtGVlQR8 jFbou4NAdCw7tCATs1YmhswZ/SJq6pHmHm0NmoNiSSuW1XSl5jDpXQYUBWY/pDHJXlJl RjmpL4IqmdVkb9elw9nsWfUi1aKMInchHrVOapIuZpjb0/UGWuLzQE3uG/BB8+Ovn5UM ojjuwqZQ81HzGMMBDl4V2piBBsoDdm04RLNODCEgLL8rRB2l2+VCMn4HRs9PItiCE0O/ kIpQ== X-Gm-Message-State: AODbwcBmwh9x49C/GP/b97V3CXCn9ULMCCiACj0CiYEK28nbPJyT7Kcf UF9FnSJKLcVipw== X-Received: by 10.99.172.84 with SMTP id z20mr8752832pgn.191.1495228670026; Fri, 19 May 2017 14:17:50 -0700 (PDT) Received: from [192.168.86.171] (c-73-231-122-98.hsd1.ca.comcast.net. [73.231.122.98]) by smtp.googlemail.com with ESMTPSA id b1sm16505965pfc.27.2017.05.19.14.17.49 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 19 May 2017 14:17:49 -0700 (PDT) Message-ID: <1495228668.6465.44.camel@edumazet-glaptop3.roam.corp.google.com> Subject: [PATCH net] ipv6: fix out of bound writes in __ip6_append_data() From: Eric Dumazet To: Andrey Konovalov Cc: Eric Dumazet , idaifish@gmail.com, "David S. Miller" , netdev Date: Fri, 19 May 2017 14:17:48 -0700 In-Reply-To: References: X-Mailer: Evolution 3.10.4-0ubuntu2 Mime-Version: 1.0 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Eric Dumazet 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: --- net/ipv6/ip6_output.c | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-) diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c index d4a31becbd25dda895d7391e1e65c2de237bf2a3..bf8a58a1c32d83a9605844075da5815be23a6bf1 100644 --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c @@ -1466,6 +1466,11 @@ static int __ip6_append_data(struct sock *sk, */ 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, @@ -1515,13 +1520,9 @@ static int __ip6_append_data(struct sock *sk, 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;