tcp: prevent fetching dst twice in early demux code
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 READ_ONCE() both in IPv4 and IPv6 TCP early demux code. Fixes:41063e9dd1
("ipv4: Early TCP socket demux.") Fixes:c7109986db
("ipv6: Early TCP socket demux") Signed-off-by: Michal Kubecek <mkubecek@suse.cz> Acked-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -1518,7 +1518,7 @@ void tcp_v4_early_demux(struct sk_buff *skb)
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skb->sk = sk;
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skb->sk = sk;
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skb->destructor = sock_edemux;
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skb->destructor = sock_edemux;
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if (sk->sk_state != TCP_TIME_WAIT) {
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if (sk->sk_state != TCP_TIME_WAIT) {
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struct dst_entry *dst = sk->sk_rx_dst;
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struct dst_entry *dst = READ_ONCE(sk->sk_rx_dst);
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if (dst)
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if (dst)
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dst = dst_check(dst, 0);
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dst = dst_check(dst, 0);
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@ -1585,7 +1585,7 @@ static void tcp_v6_early_demux(struct sk_buff *skb)
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skb->sk = sk;
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skb->sk = sk;
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skb->destructor = sock_edemux;
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skb->destructor = sock_edemux;
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if (sk->sk_state != TCP_TIME_WAIT) {
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if (sk->sk_state != TCP_TIME_WAIT) {
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struct dst_entry *dst = sk->sk_rx_dst;
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struct dst_entry *dst = READ_ONCE(sk->sk_rx_dst);
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if (dst)
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if (dst)
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dst = dst_check(dst, inet6_sk(sk)->rx_dst_cookie);
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dst = dst_check(dst, inet6_sk(sk)->rx_dst_cookie);
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