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: v5.1.21~58
X-Git-Url: http://git.ipfire.org/?p=thirdparty%2Fkernel%2Fstable.git;a=commitdiff_plain;h=f2acb2903f1603643a7b683c04bd88a7781888dd

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 ab348489bd8a6..9fc2d803c6842 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -2183,7 +2183,7 @@ 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;