Subject: [PATCH 03/26] ipv6: Fix nexthop refcnt leak when creating ipv6 route info

From: Xiyu Yang <[email-masked]>
Date: Sat, 25 Jul 2020 16:02:18 +0800

[ Upstream commit 706ec919164622ff5ce822065472d0f30a9e9dd2 ]

ip6_route_info_create() invokes nexthop_get(), which increases the
refcount of the "nh".

When ip6_route_info_create() returns, local variable "nh" becomes
invalid, so the refcount should be decreased to keep refcount balanced.

The reference counting issue happens in one exception handling path of
ip6_route_info_create(). When nexthops can not be used with source
routing, the function forgets to decrease the refcnt increased by
nexthop_get(), causing a refcnt leak.

Fix this issue by pulling up the error source routing handling when
nexthops can not be used with source routing.

Fixes: f88d8ea67fbd ("ipv6: Plumb support for nexthop object in a fib6_info")
Signed-off-by: Xiyu Yang <[email-masked]>
Signed-off-by: Xin Tan <[email-masked]>
Reviewed-by: David Ahern <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
---
 net/ipv6/route.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index e8a184acf668..de25836e4dde 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -3677,14 +3677,14 @@ static struct fib6_info *ip6_route_info_create(struct fib6_config *cfg,
 	rt->fib6_src.plen = cfg->fc_src_len;
 #endif
 	if (nh) {
-		if (!nexthop_get(nh)) {
-			NL_SET_ERR_MSG(extack, "Nexthop has been deleted");
-			goto out;
-		}
 		if (rt->fib6_src.plen) {
 			NL_SET_ERR_MSG(extack, "Nexthops can not be used with source routing");
 			goto out;
 		}
+		if (!nexthop_get(nh)) {
+			NL_SET_ERR_MSG(extack, "Nexthop has been deleted");
+			goto out;
+		}
 		rt->nh = nh;
 		fib6_nh = nexthop_fib6_nh(rt->nh);
 	} else {
-- 
2.26.2