Messages in this thread Patch in this message | | | From | Ben Hutchings <> | Date | Tue, 18 Jun 2019 15:28:02 +0100 | Subject | [PATCH 3.16 10/10] tcp: enforce tcp_min_snd_mss in tcp_mtu_probing() |
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3.16.69-rc1 review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet <edumazet@google.com>
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> [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@decadent.org.uk> --- 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); }
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