Commit fcdd1cf4 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

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: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 35f7aa53

include/net/inet_connection_sock.h

+9 −0
Original line number Diff line number Diff line
@@ -242,6 +242,15 @@ static inline void inet_csk_reset_xmit_timer(struct sock *sk, const int what, 
#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,

net/ipv4/tcp_input.c

+3 −2
Original line number Diff line number Diff line
@@ -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);

	}

}

net/ipv4/tcp_ipv4.c

+3 −3
Original line number Diff line number Diff line
@@ -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);

net/ipv4/tcp_output.c

+6 −7
Original line number Diff line number Diff line
@@ -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.
@@ -3306,12 +3305,12 @@ void tcp_send_probe0(struct sock *sk) 
		 */

		if (!icsk->icsk_probes_out)

			icsk->icsk_probes_out = 1;

		probe_max = TCP_RESOURCE_PROBE_INTERVAL;

	}

	inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,

					  min(icsk->icsk_rto << icsk->icsk_backoff,

					      TCP_RESOURCE_PROBE_INTERVAL),

				  inet_csk_rto_backoff(icsk, probe_max),

				  TCP_RTO_MAX);

}

}



int tcp_rtx_synack(struct sock *sk, struct request_sock *req)

{

net/ipv4/tcp_timer.c

+2 −2
Original line number Diff line number Diff line
@@ -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);

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