Patch "net: ipv4: fix multipath RTM_GETROUTE behavior when iif is given" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

net: ipv4: fix multipath RTM_GETROUTE behavior when iif is given

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
net-ipv4-fix-multipath-rtm_getroute-behavior-when-iif-is-given.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Florian Larysch <[email protected]>
Date: Mon, 3 Apr 2017 16:46:09 +0200
Subject: net: ipv4: fix multipath RTM_GETROUTE behavior when iif is given

From: Florian Larysch <[email protected]>

[ Upstream commit a8801799c6975601fd58ae62f48964caec2eb83f ]

inet_rtm_getroute synthesizes a skeletal ICMP skb, which is passed to ip_route_input when iif is given. If a multipath route is present for the designated destination, ip_multipath_icmp_hash ends up being called, which uses the source/destination addresses within the skb to calculate a hash. However, those are not set in the synthetic skb, causing it to return an arbitrary and incorrect result.

Instead, use UDP, which gets no such special treatment.

---
 net/ipv4/route.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

@@ -2569,7 +2569,7 @@ static int inet_rtm_getroute(struct sk_b
 	skb_reset_network_header(skb);
 
 	/* Bugfix: need to give ip_route_input enough of an IP header to not gag. */
-	ip_hdr(skb)->protocol = IPPROTO_ICMP;
+	ip_hdr(skb)->protocol = IPPROTO_UDP;
 	skb_reserve(skb, MAX_HEADER + sizeof(struct iphdr));
 
 	src = tb[RTA_SRC] ? nla_get_in_addr(tb[RTA_SRC]) : 0;

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/net-ipv4-fix-multipath-rtm_getroute-behavior-when-iif-is-given.patch