From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Daniel Borkmann , Eric Dumazet , Eric Dumazet , Jiri Benc , "David S. Miller" Subject: [ 16/23] net: ipv6: tcp: fix potential use after free in tcp_v6_do_rcv Date: Thu, 12 Sep 2013 10:45:12 -0700 Message-Id: <20130912174453.506907365@linuxfoundation.org> In-Reply-To: <20130912174451.748805761@linuxfoundation.org> References: <20130912174451.748805761@linuxfoundation.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Daniel Borkmann [ Upstream commit 3a1c756590633c0e86df606e5c618c190926a0df ] In tcp_v6_do_rcv() code, when processing pkt options, we soley work on our skb clone opt_skb that we've created earlier before entering tcp_rcv_established() on our way. However, only in condition ... if (np->rxopt.bits.rxtclass) np->rcv_tclass = ipv6_get_dsfield(ipv6_hdr(skb)); ... we work on skb itself. As we extract every other information out of opt_skb in ipv6_pktoptions path, this seems wrong, since skb can already be released by tcp_rcv_established() earlier on. When we try to access it in ipv6_hdr(), we will dereference freed skb. [ Bug added by commit 4c507d2897bd9b ("net: implement IP_RECVTOS for IP_PKTOPTIONS") ] Signed-off-by: Daniel Borkmann Cc: Eric Dumazet Acked-by: Eric Dumazet Acked-by: Jiri Benc Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/ipv6/tcp_ipv6.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/net/ipv6/tcp_ipv6.c +++ b/net/ipv6/tcp_ipv6.c @@ -1571,7 +1571,7 @@ ipv6_pktoptions: if (np->rxopt.bits.rxhlim || np->rxopt.bits.rxohlim) np->mcast_hops = ipv6_hdr(opt_skb)->hop_limit; if (np->rxopt.bits.rxtclass) - np->rcv_tclass = ipv6_tclass(ipv6_hdr(skb)); + np->rcv_tclass = ipv6_tclass(ipv6_hdr(opt_skb)); if (ipv6_opt_accepted(sk, opt_skb)) { skb_set_owner_r(opt_skb, sk); opt_skb = xchg(&np->pktoptions, opt_skb);