tcp: Fix data-races around sysctl_tcp_reflect_tos.

While reading sysctl_tcp_reflect_tos, it can be changed concurrently.
Thus, we need to add READ_ONCE() to its readers.

Fixes: 6553988b8db0 ("tcp: reflect tos value received in SYN to the socket")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Acked-by: Wei Wang <weiwan@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index d16e6e40f47ba4aee2b1a412c42d2f9791698e27..586c102ce152d01430e89d400d70f2573483b423 100644 (file)
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1006,7 +1006,7 @@ static int tcp_v4_send_synack(const struct sock *sk, struct dst_entry *dst,
        if (skb) {
                __tcp_v4_send_check(skb, ireq->ir_loc_addr, ireq->ir_rmt_addr);
 
-               tos = sock_net(sk)->ipv4.sysctl_tcp_reflect_tos ?
+               tos = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_reflect_tos) ?
                                (tcp_rsk(req)->syn_tos & ~INET_ECN_MASK) |
                                (inet_sk(sk)->tos & INET_ECN_MASK) :
                                inet_sk(sk)->tos;
@@ -1526,7 +1526,7 @@ struct sock *tcp_v4_syn_recv_sock(const struct sock *sk, struct sk_buff *skb,
        /* Set ToS of the new socket based upon the value of incoming SYN.
         * ECT bits are set later in tcp_init_transfer().
         */
-       if (sock_net(sk)->ipv4.sysctl_tcp_reflect_tos)
+       if (READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_reflect_tos))
                newinet->tos = tcp_rsk(req)->syn_tos & ~INET_ECN_MASK;
 
        if (!dst) {

diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 9d3ede2932582e716d9fa15dd2fad7795ea1b993..be09941fe6d9a84029c02464406f4d7bd78968da 100644 (file)
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -546,7 +546,7 @@ static int tcp_v6_send_synack(const struct sock *sk, struct dst_entry *dst,
                if (np->repflow && ireq->pktopts)
                        fl6->flowlabel = ip6_flowlabel(ipv6_hdr(ireq->pktopts));
 
-               tclass = sock_net(sk)->ipv4.sysctl_tcp_reflect_tos ?
+               tclass = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_reflect_tos) ?
                                (tcp_rsk(req)->syn_tos & ~INET_ECN_MASK) |
                                (np->tclass & INET_ECN_MASK) :
                                np->tclass;
@@ -1314,7 +1314,7 @@ static struct sock *tcp_v6_syn_recv_sock(const struct sock *sk, struct sk_buff *
        /* Set ToS of the new socket based upon the value of incoming SYN.
         * ECT bits are set later in tcp_init_transfer().
         */
-       if (sock_net(sk)->ipv4.sysctl_tcp_reflect_tos)
+       if (READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_reflect_tos))
                newnp->tclass = tcp_rsk(req)->syn_tos & ~INET_ECN_MASK;
 
        /* Clone native IPv6 options from listening socket (if any)