From: Daniel Borkmann Date: Tue, 3 Sep 2013 17:29:12 +0000 (+0200) Subject: net: ipv6: tcp: fix potential use after free in tcp_v6_do_rcv X-Git-Tag: firefly_0821_release~6453^2~869 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=a22eb149b18ed385c72d527c42dc398c97b6387f;p=firefly-linux-kernel-4.4.55.git net: ipv6: tcp: fix potential use after free in tcp_v6_do_rcv [ 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 --- diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c index 0a17ed9eaf39..66c718854e5a 100644 --- a/net/ipv6/tcp_ipv6.c +++ b/net/ipv6/tcp_ipv6.c @@ -1426,7 +1426,7 @@ 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_get_dsfield(ipv6_hdr(skb)); + np->rcv_tclass = ipv6_get_dsfield(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);