3.16.69-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet <edumazet@xxxxxxxxxx> commit 967c05aee439e6e5d7d805e195b3a20ef5c433d6 upstream. If mtu probing is enabled tcp_mtu_probing() could very well end up with a too small MSS. Use the new sysctl tcp_min_snd_mss to make sure MSS search is performed in an acceptable range. CVE-2019-11479 -- tcp mss hardcoded to 48 Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx> Reported-by: Jonathan Lemon <jonathan.lemon@xxxxxxxxx> Cc: Jonathan Looney <jtl@xxxxxxxxxxx> Acked-by: Neal Cardwell <ncardwell@xxxxxxxxxx> Cc: Yuchung Cheng <ycheng@xxxxxxxxxx> Cc: Tyler Hicks <tyhicks@xxxxxxxxxxxxx> Cc: Bruce Curtis <brucec@xxxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> [Salvatore Bonaccorso: Backport for context changes in 4.9.168] [bwh: Backported to 3.16: The sysctl is global] Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx> --- net/ipv4/tcp_timer.c | 1 + 1 file changed, 1 insertion(+) --- a/net/ipv4/tcp_timer.c +++ b/net/ipv4/tcp_timer.c @@ -113,6 +113,7 @@ static void tcp_mtu_probing(struct inet_ mss = tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low) >> 1; mss = min(sysctl_tcp_base_mss, mss); mss = max(mss, 68 - tp->tcp_header_len); + mss = max(mss, sysctl_tcp_min_snd_mss); icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss); tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); }
