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tcp: enforce tcp_min_snd_mss in tcp_mtu_probing()
commit 967c05aee4
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>
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1 changed files with 1 additions and 0 deletions
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@ -141,6 +141,7 @@ static void tcp_mtu_probing(struct inet_connection_sock *icsk, struct sock *sk)
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mss = tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low) >> 1;
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mss = min(net->ipv4.sysctl_tcp_base_mss, mss);
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mss = max(mss, 68 - tp->tcp_header_len);
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mss = max(mss, net->ipv4.sysctl_tcp_min_snd_mss);
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icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss);
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tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
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}
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