tcp6: don't move IP6CB before xfrm6_policy_check()

When xfrm6_policy_check() is used, _decode_session6() is called after some
intermediate functions. This function uses IP6CB(), thus TCP_SKB_CB() must be
prepared after the call of xfrm6_policy_check().

Before this patch, scenarii with IPv6 + TCP + IPsec Transport are broken.

Fixes: 971f10eca186 ("tcp: better TCP_SKB_CB layout to reduce cache line misses")
Reported-by: Huaibin Wang <huaibin.wang@6wind.com>
Suggested-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 29 insertions, 16 deletions

diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 5ff87805258e..9c0b54e87b47 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1387,6 +1387,28 @@ ipv6_pktoptions:
         return 0;
 }
 
+static void tcp_v6_fill_cb(struct sk_buff *skb, const struct ipv6hdr *hdr,
+                           const struct tcphdr *th)
+{
+        /* This is tricky: we move IP6CB at its correct location into
+         * TCP_SKB_CB(). It must be done after xfrm6_policy_check(), because
+         * _decode_session6() uses IP6CB().
+         * barrier() makes sure compiler won't play aliasing games.
+         */
+        memmove(&TCP_SKB_CB(skb)->header.h6, IP6CB(skb),
+                sizeof(struct inet6_skb_parm));
+        barrier();
+
+        TCP_SKB_CB(skb)->seq = ntohl(th->seq);
+        TCP_SKB_CB(skb)->end_seq = (TCP_SKB_CB(skb)->seq + th->syn + th->fin +
+                                    skb->len - th->doff*4);
+        TCP_SKB_CB(skb)->ack_seq = ntohl(th->ack_seq);
+        TCP_SKB_CB(skb)->tcp_flags = tcp_flag_byte(th);
+        TCP_SKB_CB(skb)->tcp_tw_isn = 0;
+        TCP_SKB_CB(skb)->ip_dsfield = ipv6_get_dsfield(hdr);
+        TCP_SKB_CB(skb)->sacked = 0;
+}
+
 static int tcp_v6_rcv(struct sk_buff *skb)
 {
         const struct tcphdr *th;
@@ -1418,24 +1440,9 @@ static int tcp_v6_rcv(struct sk_buff *skb)
 
         th = tcp_hdr(skb);
         hdr = ipv6_hdr(skb);
-        /* This is tricky : We move IPCB at its correct location into TCP_SKB_CB()
-         * barrier() makes sure compiler wont play fool^Waliasing games.
-         */
-        memmove(&TCP_SKB_CB(skb)->header.h6, IP6CB(skb),
-                sizeof(struct inet6_skb_parm));
-        barrier();
-
-        TCP_SKB_CB(skb)->seq = ntohl(th->seq);
-        TCP_SKB_CB(skb)->end_seq = (TCP_SKB_CB(skb)->seq + th->syn + th->fin +
-                                    skb->len - th->doff*4);
-        TCP_SKB_CB(skb)->ack_seq = ntohl(th->ack_seq);
-        TCP_SKB_CB(skb)->tcp_flags = tcp_flag_byte(th);
-        TCP_SKB_CB(skb)->tcp_tw_isn = 0;
-        TCP_SKB_CB(skb)->ip_dsfield = ipv6_get_dsfield(hdr);
-        TCP_SKB_CB(skb)->sacked = 0;
 
         sk = __inet6_lookup_skb(&tcp_hashinfo, skb, th->source, th->dest,
-                                tcp_v6_iif(skb));
+                                inet6_iif(skb));
         if (!sk)
                 goto no_tcp_socket;
 
@@ -1451,6 +1458,8 @@ process:
         if (!xfrm6_policy_check(sk, XFRM_POLICY_IN, skb))
                 goto discard_and_relse;
 
+        tcp_v6_fill_cb(skb, hdr, th);
+
 #ifdef CONFIG_TCP_MD5SIG
         if (tcp_v6_inbound_md5_hash(sk, skb))
                 goto discard_and_relse;
@@ -1482,6 +1491,8 @@ no_tcp_socket:
         if (!xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb))
                 goto discard_it;
 
+        tcp_v6_fill_cb(skb, hdr, th);
+
         if (skb->len < (th->doff<<2) || tcp_checksum_complete(skb)) {
 csum_error:
                 TCP_INC_STATS_BH(net, TCP_MIB_CSUMERRORS);
@@ -1505,6 +1516,8 @@ do_time_wait:
                 goto discard_it;
         }
 
+        tcp_v6_fill_cb(skb, hdr, th);
+
         if (skb->len < (th->doff<<2)) {
                 inet_twsk_put(inet_twsk(sk));
                 goto bad_packet;