Commit 06425c30 authored Feb 01, 2017 by Eric Dumazet Committed by David S. Miller Feb 01, 2017

tcp: fix 0 divide in __tcp_select_window()



syszkaller fuzzer was able to trigger a divide by zero, when
TCP window scaling is not enabled.

SO_RCVBUF can be used not only to increase sk_rcvbuf, also
to decrease it below current receive buffers utilization.

If mss is negative or 0, just return a zero TCP window.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 63117f09

net/ipv4/tcp_output.c

+4 −2

Original line number	Diff line number	Diff line
		@@ -2518,9 +2518,11 @@ u32 __tcp_select_window(struct sock *sk)
		int full_space = min_t(int, tp->window_clamp, allowed_space);
		int window;

		if (mss > full_space)
		if (unlikely(mss > full_space)) {
		mss = full_space;

		if (mss <= 0)
		return 0;
		}
		if (free_space < (full_space >> 1)) {
		icsk->icsk_ack.quick = 0;

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