[PATCH net] ipv6: rt6_check should return NULL if 'from' is NULL

[David Ahern <dsahern@kernel.org>]

From: David Ahern <dsahern@gmail.com>

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>
---
 net/ipv6/route.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 4d2e6b31a8d6..6fe3097b9ab7 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -2563,7 +2563,7 @@ 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;
 
-- 
2.11.0