linux-kernel - [PATCH 4.9 065/148] vti6: Dont report path MTU below IPV6_MIN

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Date:   Tue, 12 Dec 2017 13:44:35 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Steffen Klassert <steffen.klassert@...unet.com>,
        Sasha Levin <alexander.levin@...izon.com>
Subject: [PATCH 4.9 065/148] vti6: Dont report path MTU below IPV6_MIN_MTU.

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Steffen Klassert <steffen.klassert@...unet.com>


[ Upstream commit e3dc847a5f85b43ee2bfc8eae407a7e383483228 ]

In vti6_xmit(), the check for IPV6_MIN_MTU before we
send a ICMPV6_PKT_TOOBIG message is missing. So we might
report a PMTU below 1280. Fix this by adding the required
check.

Fixes: ccd740cbc6e ("vti6: Add pmtu handling to vti6_xmit.")
Signed-off-by: Steffen Klassert <steffen.klassert@...unet.com>
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/ipv6/ip6_vti.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

--- a/net/ipv6/ip6_vti.c
+++ b/net/ipv6/ip6_vti.c
@@ -485,11 +485,15 @@ vti6_xmit(struct sk_buff *skb, struct ne
 	if (!skb->ignore_df && skb->len > mtu) {
 		skb_dst(skb)->ops->update_pmtu(dst, NULL, skb, mtu);
 
-		if (skb->protocol == htons(ETH_P_IPV6))
+		if (skb->protocol == htons(ETH_P_IPV6)) {
+			if (mtu < IPV6_MIN_MTU)
+				mtu = IPV6_MIN_MTU;
+
 			icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);
-		else
+		} else {
 			icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
 				  htonl(mtu));
+		}
 
 		return -EMSGSIZE;
 	}