From: David Ahern <dsahern@gmail.com>
Date: Wed, 17 Jul 2019 22:08:43 +0000 (-0700)
Subject: ipv6: rt6_check should return NULL if 'from' is NULL
X-Git-Tag: v5.2.4~62
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=2cc82af89d1f4c47aafb16cbfbfe9bb659eaeafb;p=users%2Fdwmw2%2Flinux.git

ipv6: rt6_check should return NULL if 'from' is NULL

[ Upstream commit 49d05fe2c9d1b4a27761c9807fec39b8155bef9e ]

Paul reported that l2tp sessions were broken after the commit referenced
in the Fixes tag. Prior to this commit rt6_check returned NULL if the
rt6_info 'from' was NULL - ie., the dst_entry was disconnected from a FIB
entry. Restore that behavior.

Fixes: 93531c674315 ("net/ipv6: separate handling of FIB entries from dst based routes")
Reported-by: Paul Donohue <linux-kernel@PaulSD.com>
Tested-by: Paul Donohue <linux-kernel@PaulSD.com>
Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 97a843cf164cd..5f5a0a42ce60f 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -2215,7 +2215,7 @@ static struct dst_entry *rt6_check(struct rt6_info *rt,
 {
 	u32 rt_cookie = 0;
 
-	if ((from && !fib6_get_cookie_safe(from, &rt_cookie)) ||
+	if (!from || !fib6_get_cookie_safe(from, &rt_cookie) ||
 	    rt_cookie != cookie)
 		return NULL;