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([2620:15c:2c1:200:55c7:81e6:c7d8:94b]) by smtp.gmail.com with ESMTPSA id p21sm3459080pfn.129.2019.05.30.10.17.05 (version=TLS1_3 cipher=AEAD-AES128-GCM-SHA256 bits=128/128); Thu, 30 May 2019 10:17:05 -0700 (PDT) Subject: Re: [PATCH] ipv6: Prevent overrun when parsing v6 header options To: Young Xiao <92siuyang@gmail.com>, davem@davemloft.net, kuznet@ms2.inr.ac.ru, yoshfuji@linux-ipv6.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Steffen Klassert , Herbert Xu References: <1559230098-1543-1-git-send-email-92siuyang@gmail.com> From: Eric Dumazet Message-ID: Date: Thu, 30 May 2019 10:17:04 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <1559230098-1543-1-git-send-email-92siuyang@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/30/19 8:28 AM, Young Xiao wrote: > The fragmentation code tries to parse the header options in order > to figure out where to insert the fragment option. Since nexthdr points > to an invalid option, the calculation of the size of the network header > can made to be much larger than the linear section of the skb and data > is read outside of it. > > This vulnerability is similar to CVE-2017-9074. > > Signed-off-by: Young Xiao <92siuyang@gmail.com> > --- > net/ipv6/mip6.c | 24 ++++++++++++++---------- > 1 file changed, 14 insertions(+), 10 deletions(-) > > diff --git a/net/ipv6/mip6.c b/net/ipv6/mip6.c > index 64f0f7b..30ed1c5 100644 > --- a/net/ipv6/mip6.c > +++ b/net/ipv6/mip6.c > @@ -263,8 +263,6 @@ static int mip6_destopt_offset(struct xfrm_state *x, struct sk_buff *skb, > u8 **nexthdr) > { > u16 offset = sizeof(struct ipv6hdr); > - struct ipv6_opt_hdr *exthdr = > - (struct ipv6_opt_hdr *)(ipv6_hdr(skb) + 1); > const unsigned char *nh = skb_network_header(skb); > unsigned int packet_len = skb_tail_pointer(skb) - > skb_network_header(skb); > @@ -272,7 +270,8 @@ static int mip6_destopt_offset(struct xfrm_state *x, struct sk_buff *skb, > > *nexthdr = &ipv6_hdr(skb)->nexthdr; > > - while (offset + 1 <= packet_len) { > + while (offset <= packet_len) { > + struct ipv6_opt_hdr *exthdr; > > switch (**nexthdr) { > case NEXTHDR_HOP: > @@ -299,12 +298,15 @@ static int mip6_destopt_offset(struct xfrm_state *x, struct sk_buff *skb, > return offset; > } > > + if (offset + sizeof(struct ipv6_opt_hdr) > packet_len) > + return -EINVAL; > + > + exthdr = (struct ipv6_opt_hdr *)(nh + offset); > offset += ipv6_optlen(exthdr); > *nexthdr = &exthdr->nexthdr; > - exthdr = (struct ipv6_opt_hdr *)(nh + offset); > } > > - return offset; > + return -EINVAL; > } > Ok, but have you checked that callers have been fixed ? xfrm6_transport_output() seems buggy as well, unless the skbs are linearized before entering these functions ? Thanks.