tcp: fix req->saved_syn race

For the reasons explained in commit ce1050089c96 ("tcp/dccp: fix
ireq->pktopts race"), we need to make sure we do not access
req->saved_syn unless we own the request sock.

This fixes races for listeners using TCP_SAVE_SYN option.

Fixes: e994b2f0fb92 ("tcp: do not lock listener to process SYN packets")
Fixes: 079096f103fa ("tcp/dccp: install syn_recv requests into ehash table")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Ying Cai <ycai@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index c906f45..b386361 100644 (file)
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -397,6 +397,13 @@ static inline void fastopen_queue_tune(struct sock *sk, int backlog)
        queue->fastopenq.max_qlen = min_t(unsigned int, backlog, somaxconn);
 }
 
+static inline void tcp_move_syn(struct tcp_sock *tp,
+                               struct request_sock *req)
+{
+       tp->saved_syn = req->saved_syn;
+       req->saved_syn = NULL;
+}
+
 static inline void tcp_saved_syn_free(struct tcp_sock *tp)
 {
        kfree(tp->saved_syn);

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 1c2648b..59aff63 100644 (file)
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1326,6 +1326,8 @@ struct sock *tcp_v4_syn_recv_sock(const struct sock *sk, struct sk_buff *skb,
        if (__inet_inherit_port(sk, newsk) < 0)
                goto put_and_exit;
        *own_req = inet_ehash_nolisten(newsk, req_to_sk(req_unhash));
+       if (*own_req)
+               tcp_move_syn(newtp, req_unhash);
 
        return newsk;
 

diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 3575dd1..ac6b196 100644 (file)
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -551,9 +551,6 @@ struct sock *tcp_create_openreq_child(const struct sock *sk,
                newtp->rack.mstamp.v64 = 0;
                newtp->rack.advanced = 0;
 
-               newtp->saved_syn = req->saved_syn;
-               req->saved_syn = NULL;
-
                TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_PASSIVEOPENS);
        }
        return newsk;

diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index ea2f4d5..c509e55 100644 (file)
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1140,14 +1140,18 @@ static struct sock *tcp_v6_syn_recv_sock(const struct sock *sk, struct sk_buff *
                goto out;
        }
        *own_req = inet_ehash_nolisten(newsk, req_to_sk(req_unhash));
-       /* Clone pktoptions received with SYN, if we own the req */
-       if (*own_req && ireq->pktopts) {
-               newnp->pktoptions = skb_clone(ireq->pktopts,
-                                             sk_gfp_atomic(sk, GFP_ATOMIC));
-               consume_skb(ireq->pktopts);
-               ireq->pktopts = NULL;
-               if (newnp->pktoptions)
-                       skb_set_owner_r(newnp->pktoptions, newsk);
+       if (*own_req) {
+               tcp_move_syn(newtp, req_unhash);
+
+               /* Clone pktoptions received with SYN, if we own the req */
+               if (ireq->pktopts) {
+                       newnp->pktoptions = skb_clone(ireq->pktopts,
+                                                     sk_gfp_atomic(sk, GFP_ATOMIC));
+                       consume_skb(ireq->pktopts);
+                       ireq->pktopts = NULL;
+                       if (newnp->pktoptions)
+                               skb_set_owner_r(newnp->pktoptions, newsk);
+               }
        }
 
        return newsk;