tcp: avoid possible arithmetic overflows

icsk_rto is a 32bit field, and icsk_backoff can reach 15 by default,
or more if some sysctl (eg tcp_retries2) are changed.

Better use 64bit to perform icsk_rto << icsk_backoff operations

As Joe Perches suggested, add a helper for this.

Yuchung spotted the tcp_v4_err() case.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 14 insertions, 14 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 02fb66d4a018..13f3da4762e3 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3208,9 +3208,10 @@ static void tcp_ack_probe(struct sock *sk)
                  * This function is not for random using!
                  */
         } else {
+                unsigned long when = inet_csk_rto_backoff(icsk, TCP_RTO_MAX);
+
                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
-                                          min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX),
-                                          TCP_RTO_MAX);
+                                          when, TCP_RTO_MAX);
         }
 }
 
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 006b045716d8..3b2e49cb2b61 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -430,9 +430,9 @@ void tcp_v4_err(struct sk_buff *icmp_skb, u32 info)
                         break;
 
                 icsk->icsk_backoff--;
-                inet_csk(sk)->icsk_rto = (tp->srtt_us ? __tcp_set_rto(tp) :
-                        TCP_TIMEOUT_INIT) << icsk->icsk_backoff;
-                tcp_bound_rto(sk);
+                icsk->icsk_rto = tp->srtt_us ? __tcp_set_rto(tp) :
+                                               TCP_TIMEOUT_INIT;
+                icsk->icsk_rto = inet_csk_rto_backoff(icsk, TCP_RTO_MAX);
 
                 skb = tcp_write_queue_head(sk);
                 BUG_ON(!skb);
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 7f1280dcad57..8c61a7c0c889 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -3279,6 +3279,7 @@ void tcp_send_probe0(struct sock *sk)
 {
         struct inet_connection_sock *icsk = inet_csk(sk);
         struct tcp_sock *tp = tcp_sk(sk);
+        unsigned long probe_max;
         int err;
 
         err = tcp_write_wakeup(sk);
@@ -3294,9 +3295,7 @@ void tcp_send_probe0(struct sock *sk)
                 if (icsk->icsk_backoff < sysctl_tcp_retries2)
                         icsk->icsk_backoff++;
                 icsk->icsk_probes_out++;
-                inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
-                                          min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX),
-                                          TCP_RTO_MAX);
+                probe_max = TCP_RTO_MAX;
         } else {
                 /* If packet was not sent due to local congestion,
                  * do not backoff and do not remember icsk_probes_out.
@@ -3306,11 +3305,11 @@ void tcp_send_probe0(struct sock *sk)
                  */
                 if (!icsk->icsk_probes_out)
                         icsk->icsk_probes_out = 1;
-                inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
-                                          min(icsk->icsk_rto << icsk->icsk_backoff,
-                                              TCP_RESOURCE_PROBE_INTERVAL),
-                                          TCP_RTO_MAX);
+                probe_max = TCP_RESOURCE_PROBE_INTERVAL;
         }
+        inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
+                                  inet_csk_rto_backoff(icsk, probe_max),
+                                  TCP_RTO_MAX);
 }
 
 int tcp_rtx_synack(struct sock *sk, struct request_sock *req)
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index a339e7ba05a4..b24360f6e293 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -180,7 +180,7 @@ static int tcp_write_timeout(struct sock *sk)
 
                 retry_until = sysctl_tcp_retries2;
                 if (sock_flag(sk, SOCK_DEAD)) {
-                        const int alive = (icsk->icsk_rto < TCP_RTO_MAX);
+                        const int alive = icsk->icsk_rto < TCP_RTO_MAX;
 
                         retry_until = tcp_orphan_retries(sk, alive);
                         do_reset = alive ||
@@ -294,7 +294,7 @@ static void tcp_probe_timer(struct sock *sk)
         max_probes = sysctl_tcp_retries2;
 
         if (sock_flag(sk, SOCK_DEAD)) {
-                const int alive = ((icsk->icsk_rto << icsk->icsk_backoff) < TCP_RTO_MAX);
+                const int alive = inet_csk_rto_backoff(icsk, TCP_RTO_MAX) < TCP_RTO_MAX;
 
                 max_probes = tcp_orphan_retries(sk, alive);