From: Eric Dumazet <[email protected]> commit 06425c308b92eaf60767bc71d359f4cbc7a561f8 upstream.
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 <[email protected]> Reported-by: Dmitry Vyukov <[email protected]> Acked-by: Neal Cardwell <[email protected]> Signed-off-by: David S. Miller <[email protected]> Signed-off-by: Willy Tarreau <[email protected]> --- net/ipv4/tcp_output.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 1f2f6b5..8729a93 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -2154,9 +2154,11 @@ u32 __tcp_select_window(struct sock *sk) int full_space = min_t(int, tp->window_clamp, tcp_full_space(sk)); 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; -- 2.8.0.rc2.1.gbe9624a
