From: Xiyu Yang <xiyuyang19@fudan.edu.cn>
Date: Sat, 25 Jul 2020 08:02:18 +0000 (+0800)
Subject: ipv6: Fix nexthop refcnt leak when creating ipv6 route info
X-Git-Tag: iomap-folio-5.17-old~3587^2~24
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=706ec919164622ff5ce822065472d0f30a9e9dd2;p=users%2Fwilly%2Flinux.git

ipv6: Fix nexthop refcnt leak when creating ipv6 route info

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 <xiyuyang19@fudan.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index f3279810d765..4c36bd0c7930 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -3685,14 +3685,14 @@ 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 {