linux-kernel - [PATCH 3.12 72/86] net: ipv4: fix multipath RTM

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Date:   Thu,  4 May 2017 11:04:37 +0200
From:   Jiri Slaby <jslaby@...e.cz>
To:     stable@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, Florian Larysch <fl@...1.de>,
        "David S . Miller" <davem@...emloft.net>
Subject: [PATCH 3.12 72/86] net: ipv4: fix multipath RTM_GETROUTE behavior when iif is given

From: Florian Larysch <fl@...1.de>

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

===============

[ 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.

Signed-off-by: Florian Larysch <fl@...1.de>
Signed-off-by: David S. Miller <davem@...emloft.net>
---
 net/ipv4/route.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 1b180691086c..778b3e9316db 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -2492,7 +2492,7 @@ static int inet_rtm_getroute(struct sk_buff *in_skb, struct nlmsghdr *nlh)
 	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_be32(tb[RTA_SRC]) : 0;
-- 
2.12.2