From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: [PATCH net] ipv4: fix use-after-free in ip_cmsg_recv_dstaddr() Date: Sun, 30 Sep 2018 11:33:39 -0700 Message-ID: <20180930183339.153681-1-edumazet@google.com> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Cc: netdev , Eric Dumazet , Eric Dumazet , Willem de Bruijn To: "David S . Miller" Return-path: Received: from mail-pg1-f193.google.com ([209.85.215.193]:34218 "EHLO mail-pg1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728192AbeJABHt (ORCPT ); Sun, 30 Sep 2018 21:07:49 -0400 Received: by mail-pg1-f193.google.com with SMTP id g12-v6so2180991pgs.1 for ; Sun, 30 Sep 2018 11:33:43 -0700 (PDT) Sender: netdev-owner@vger.kernel.org List-ID: Caching ip_hdr(skb) before a call to pskb_may_pull() is buggy, do not do it. Fixes: 2efd4fca703a ("ip: in cmsg IP(V6)_ORIGDSTADDR call pskb_may_pull") Signed-off-by: Eric Dumazet Cc: Willem de Bruijn Reported-by: syzbot --- net/ipv4/ip_sockglue.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c index c0fe5ad996f238091f5b9585adb586a571f653f0..26c36cccabdc2c8cc95cfd609672d412c493fc42 100644 --- a/net/ipv4/ip_sockglue.c +++ b/net/ipv4/ip_sockglue.c @@ -149,7 +149,6 @@ static void ip_cmsg_recv_security(struct msghdr *msg, struct sk_buff *skb) static void ip_cmsg_recv_dstaddr(struct msghdr *msg, struct sk_buff *skb) { struct sockaddr_in sin; - const struct iphdr *iph = ip_hdr(skb); __be16 *ports; int end; @@ -164,7 +163,7 @@ static void ip_cmsg_recv_dstaddr(struct msghdr *msg, struct sk_buff *skb) ports = (__be16 *)skb_transport_header(skb); sin.sin_family = AF_INET; - sin.sin_addr.s_addr = iph->daddr; + sin.sin_addr.s_addr = ip_hdr(skb)->daddr; sin.sin_port = ports[1]; memset(sin.sin_zero, 0, sizeof(sin.sin_zero)); -- 2.19.0.605.g01d371f741-goog