From: Michal Kubeček Date: Mon, 23 Mar 2015 14:14:00 +0000 (+0100) Subject: tcp: prevent fetching dst twice in early demux code X-Git-Url: http://git.mmlx.us/?a=commitdiff_plain;h=1b946e381d185db8700e96634074052a62a11509;p=linux-edison.git tcp: prevent fetching dst twice in early demux code [ Upstream commit d0c294c53a771ae7e84506dfbd8c18c30f078735 ] On s390x, gcc 4.8 compiles this part of tcp_v6_early_demux() struct dst_entry *dst = sk->sk_rx_dst; if (dst) dst = dst_check(dst, inet6_sk(sk)->rx_dst_cookie); to code reading sk->sk_rx_dst twice, once for the test and once for the argument of ip6_dst_check() (dst_check() is inline). This allows ip6_dst_check() to be called with null first argument, causing a crash. Protect sk->sk_rx_dst access by ACCESS_ONCE() both in IPv4 and IPv6 TCP early demux code. Fixes: 41063e9dd119 ("ipv4: Early TCP socket demux.") Fixes: c7109986db3c ("ipv6: Early TCP socket demux") Signed-off-by: Michal Kubecek Acked-by: Eric Dumazet Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index cce35e5a7ee..7c3eec386a4 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -1901,7 +1901,7 @@ void tcp_v4_early_demux(struct sk_buff *skb) skb->sk = sk; skb->destructor = sock_edemux; if (sk->sk_state != TCP_TIME_WAIT) { - struct dst_entry *dst = sk->sk_rx_dst; + struct dst_entry *dst = ACCESS_ONCE(sk->sk_rx_dst); if (dst) dst = dst_check(dst, 0); diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c index 1a87659a613..4659b8ab55d 100644 --- a/net/ipv6/tcp_ipv6.c +++ b/net/ipv6/tcp_ipv6.c @@ -1616,7 +1616,7 @@ static void tcp_v6_early_demux(struct sk_buff *skb) skb->sk = sk; skb->destructor = sock_edemux; if (sk->sk_state != TCP_TIME_WAIT) { - struct dst_entry *dst = sk->sk_rx_dst; + struct dst_entry *dst = ACCESS_ONCE(sk->sk_rx_dst); if (dst) dst = dst_check(dst, inet6_sk(sk)->rx_dst_cookie);