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authorEric Dumazet <edumazet@google.com>2019-06-15 17:47:27 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-06-17 19:52:45 +0200
commitf2aa4f1a05e0987e812809dbc489bd294fdae5ae (patch)
treec1be08c0b6af94c31a9b6fff448a881461d28e0f
parentcd6f35b8421ff20365ff711c0ac7647fd70e9af7 (diff)
tcp: enforce tcp_min_snd_mss in tcp_mtu_probing()
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@google.com> Reported-by: Jonathan Lemon <jonathan.lemon@gmail.com> Cc: Jonathan Looney <jtl@netflix.com> Acked-by: Neal Cardwell <ncardwell@google.com> Cc: Yuchung Cheng <ycheng@google.com> Cc: Tyler Hicks <tyhicks@canonical.com> Cc: Bruce Curtis <brucec@netflix.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--net/ipv4/tcp_timer.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index a845b7692c1b..592d6e9967a9 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -141,6 +141,7 @@ static void tcp_mtu_probing(struct inet_connection_sock *icsk, struct sock *sk)
mss = tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low) >> 1;
mss = min(net->ipv4.sysctl_tcp_base_mss, mss);
mss = max(mss, 68 - tp->tcp_header_len);
+ mss = max(mss, net->ipv4.sysctl_tcp_min_snd_mss);
icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss);
tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
}