tcp: Fix data-races around some timeout sysctl knobs.

While reading these sysctl knobs, they can be changed concurrently.
Thus, we need to add READ_ONCE() to their readers.

  - tcp_retries1
  - tcp_retries2
  - tcp_orphan_retries
  - tcp_fin_timeout

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 204478d5d3887959ff5ca43a5df393bcb41fa5a9..23ccaa3867462e7fc4405dda22046bd911bf8427 100644 (file)
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1523,7 +1523,8 @@ static inline u32 keepalive_time_elapsed(const struct tcp_sock *tp)
 
 static inline int tcp_fin_time(const struct sock *sk)
 {
-       int fin_timeout = tcp_sk(sk)->linger2 ? : sock_net(sk)->ipv4.sysctl_tcp_fin_timeout;
+       int fin_timeout = tcp_sk(sk)->linger2 ? :
+               READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_fin_timeout);
        const int rto = inet_csk(sk)->icsk_rto;
 
        if (fin_timeout < (rto << 2) - (rto >> 1))

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index b3632fa5df0711c461a169cd944ec5c232b0b96c..b1b1bcbc4f60977d1c271ee05e5ab8c81b79c06e 100644 (file)
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -3973,7 +3973,7 @@ static int do_tcp_getsockopt(struct sock *sk, int level,
        case TCP_LINGER2:
                val = tp->linger2;
                if (val >= 0)
-                       val = (val ? : net->ipv4.sysctl_tcp_fin_timeout) / HZ;
+                       val = (val ? : READ_ONCE(net->ipv4.sysctl_tcp_fin_timeout)) / HZ;
                break;
        case TCP_DEFER_ACCEPT:
                val = retrans_to_secs(icsk->icsk_accept_queue.rskq_defer_accept,

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 02ab3a9c665745d9aaf36aab1a08cbd5c424976c..3b3552d292a58f083a52c7a963d72de816127a30 100644 (file)
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -4090,7 +4090,7 @@ void tcp_send_probe0(struct sock *sk)
 
        icsk->icsk_probes_out++;
        if (err <= 0) {
-               if (icsk->icsk_backoff < net->ipv4.sysctl_tcp_retries2)
+               if (icsk->icsk_backoff < READ_ONCE(net->ipv4.sysctl_tcp_retries2))
                        icsk->icsk_backoff++;
                timeout = tcp_probe0_when(sk, TCP_RTO_MAX);
        } else {

diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index a234704e8163ffa653317ba1273a70a8b4dc4308..ec5277becc6a1f17223ff19c713bbefe608f1b37 100644 (file)
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -143,7 +143,7 @@ static int tcp_out_of_resources(struct sock *sk, bool do_reset)
  */
 static int tcp_orphan_retries(struct sock *sk, bool alive)
 {
-       int retries = sock_net(sk)->ipv4.sysctl_tcp_orphan_retries; /* May be zero. */
+       int retries = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_orphan_retries); /* May be zero. */
 
        /* We know from an ICMP that something is wrong. */
        if (sk->sk_err_soft && !alive)
@@ -243,14 +243,14 @@ static int tcp_write_timeout(struct sock *sk)
                        READ_ONCE(net->ipv4.sysctl_tcp_syn_retries);
                expired = icsk->icsk_retransmits >= retry_until;
        } else {
-               if (retransmits_timed_out(sk, net->ipv4.sysctl_tcp_retries1, 0)) {
+               if (retransmits_timed_out(sk, READ_ONCE(net->ipv4.sysctl_tcp_retries1), 0)) {
                        /* Black hole detection */
                        tcp_mtu_probing(icsk, sk);
 
                        __dst_negative_advice(sk);
                }
 
-               retry_until = net->ipv4.sysctl_tcp_retries2;
+               retry_until = READ_ONCE(net->ipv4.sysctl_tcp_retries2);
                if (sock_flag(sk, SOCK_DEAD)) {
                        const bool alive = icsk->icsk_rto < TCP_RTO_MAX;
 
@@ -381,7 +381,7 @@ static void tcp_probe_timer(struct sock *sk)
                 msecs_to_jiffies(icsk->icsk_user_timeout))
                goto abort;
 
-       max_probes = sock_net(sk)->ipv4.sysctl_tcp_retries2;
+       max_probes = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_retries2);
        if (sock_flag(sk, SOCK_DEAD)) {
                const bool alive = inet_csk_rto_backoff(icsk, TCP_RTO_MAX) < TCP_RTO_MAX;
 
@@ -589,7 +589,7 @@ out_reset_timer:
        }
        inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
                                  tcp_clamp_rto_to_user_timeout(sk), TCP_RTO_MAX);
-       if (retransmits_timed_out(sk, net->ipv4.sysctl_tcp_retries1 + 1, 0))
+       if (retransmits_timed_out(sk, READ_ONCE(net->ipv4.sysctl_tcp_retries1) + 1, 0))
                __sk_dst_reset(sk);
 
 out:;