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Commit ad9f4f50 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

tcp: avoid a possible divide by zero 



sysctl_tcp_tso_win_divisor might be set to zero while one cpu runs in
tcp_tso_should_defer(). Make sure we dont allow a divide by zero by
reading sysctl_tcp_tso_win_divisor exactly once.

Signed-off-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent c7757fdb

net/ipv4/tcp_output.c

+4 −2
Original line number Diff line number Diff line
@@ -1512,6 +1512,7 @@ static int tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb) 
	struct tcp_sock *tp = tcp_sk(sk);

	const struct inet_connection_sock *icsk = inet_csk(sk);

	u32 send_win, cong_win, limit, in_flight;

	int win_divisor;



	if (TCP_SKB_CB(skb)->flags & TCPHDR_FIN)

		goto send_now;
@@ -1543,13 +1544,14 @@ static int tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb) 
	if ((skb != tcp_write_queue_tail(sk)) && (limit >= skb->len))

		goto send_now;



	if (sysctl_tcp_tso_win_divisor) {

	win_divisor = ACCESS_ONCE(sysctl_tcp_tso_win_divisor);

	if (win_divisor) {

		u32 chunk = min(tp->snd_wnd, tp->snd_cwnd * tp->mss_cache);



		/* If at least some fraction of a window is available,

		 * just use it.

		 */

		chunk /= sysctl_tcp_tso_win_divisor;

		chunk /= win_divisor;

		if (limit >= chunk)

			goto send_now;

	} else {