Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S937338AbdCJNUq (ORCPT ); Fri, 10 Mar 2017 08:20:46 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:43512 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934717AbdCJLwq (ORCPT ); Fri, 10 Mar 2017 06:52:46 -0500 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Dmitry Vyukov" , "Willem de Bruijn" , "Eric Dumazet" , "David S. Miller" Date: Fri, 10 Mar 2017 11:46:23 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 354/370] ipv6: fix ip6_tnl_parse_tlv_enc_lim() In-Reply-To: X-SA-Exim-Connect-IP: 82.70.136.246 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3105 Lines: 100 3.16.42-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet [ Upstream commit fbfa743a9d2a0ffa24251764f10afc13eb21e739 ] This function suffers from multiple issues. First one is that pskb_may_pull() may reallocate skb->head, so the 'raw' pointer needs either to be reloaded or not used at all. Second issue is that NEXTHDR_DEST handling does not validate that the options are present in skb->data, so we might read garbage or access non existent memory. With help from Willem de Bruijn. Signed-off-by: Eric Dumazet Reported-by: Dmitry Vyukov Cc: Willem de Bruijn Signed-off-by: David S. Miller Signed-off-by: Ben Hutchings --- net/ipv6/ip6_tunnel.c | 34 ++++++++++++++++++++++------------ 1 file changed, 22 insertions(+), 12 deletions(-) --- a/net/ipv6/ip6_tunnel.c +++ b/net/ipv6/ip6_tunnel.c @@ -402,18 +402,19 @@ ip6_tnl_dev_uninit(struct net_device *de __u16 ip6_tnl_parse_tlv_enc_lim(struct sk_buff *skb, __u8 *raw) { - const struct ipv6hdr *ipv6h = (const struct ipv6hdr *) raw; - __u8 nexthdr = ipv6h->nexthdr; - __u16 off = sizeof (*ipv6h); + const struct ipv6hdr *ipv6h = (const struct ipv6hdr *)raw; + unsigned int nhoff = raw - skb->data; + unsigned int off = nhoff + sizeof(*ipv6h); + u8 next, nexthdr = ipv6h->nexthdr; while (ipv6_ext_hdr(nexthdr) && nexthdr != NEXTHDR_NONE) { - __u16 optlen = 0; struct ipv6_opt_hdr *hdr; - if (raw + off + sizeof (*hdr) > skb->data && - !pskb_may_pull(skb, raw - skb->data + off + sizeof (*hdr))) + u16 optlen; + + if (!pskb_may_pull(skb, off + sizeof(*hdr))) break; - hdr = (struct ipv6_opt_hdr *) (raw + off); + hdr = (struct ipv6_opt_hdr *)(skb->data + off); if (nexthdr == NEXTHDR_FRAGMENT) { struct frag_hdr *frag_hdr = (struct frag_hdr *) hdr; if (frag_hdr->frag_off) @@ -424,20 +425,29 @@ __u16 ip6_tnl_parse_tlv_enc_lim(struct s } else { optlen = ipv6_optlen(hdr); } + /* cache hdr->nexthdr, since pskb_may_pull() might + * invalidate hdr + */ + next = hdr->nexthdr; if (nexthdr == NEXTHDR_DEST) { - __u16 i = off + 2; + u16 i = 2; + + /* Remember : hdr is no longer valid at this point. */ + if (!pskb_may_pull(skb, off + optlen)) + break; + while (1) { struct ipv6_tlv_tnl_enc_lim *tel; /* No more room for encapsulation limit */ - if (i + sizeof (*tel) > off + optlen) + if (i + sizeof(*tel) > optlen) break; - tel = (struct ipv6_tlv_tnl_enc_lim *) &raw[i]; + tel = (struct ipv6_tlv_tnl_enc_lim *) skb->data + off + i; /* return index of option if found and valid */ if (tel->type == IPV6_TLV_TNL_ENCAP_LIMIT && tel->length == 1) - return i; + return i + off - nhoff; /* else jump to next option */ if (tel->type) i += tel->length + 2; @@ -445,7 +455,7 @@ __u16 ip6_tnl_parse_tlv_enc_lim(struct s i++; } } - nexthdr = hdr->nexthdr; + nexthdr = next; off += optlen; } return 0;