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>
diff --git a/include/net/inet_connection_sock.h b/include/net/inet_connection_sock.h
index 5fbe656..848e85c 100644
--- a/include/net/inet_connection_sock.h
+++ b/include/net/inet_connection_sock.h
@@ -242,6 +242,15 @@
#endif
}
+static inline unsigned long
+inet_csk_rto_backoff(const struct inet_connection_sock *icsk,
+ unsigned long max_when)
+{
+ u64 when = (u64)icsk->icsk_rto << icsk->icsk_backoff;
+
+ return (unsigned long)min_t(u64, when, max_when);
+}
+
struct sock *inet_csk_accept(struct sock *sk, int flags, int *err);
struct request_sock *inet_csk_search_req(const struct sock *sk,
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 02fb66d..13f3da4 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3208,9 +3208,10 @@
* 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 006b045..3b2e49c 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -430,9 +430,9 @@
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 7f1280d..8c61a7c 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -3279,6 +3279,7 @@
{
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 @@
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 @@
*/
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 a339e7b..b24360f 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -180,7 +180,7 @@
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 @@
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);