linux-kernel - [PATCH] ipv6: route: fix possible null-pointer-dereference in ip6_route_info

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Message-ID: <20241101035843.52230-1-03zouyi09.25@gmail.com>
Date: Fri,  1 Nov 2024 11:58:43 +0800
From: Yi Zou <03zouyi09.25@...il.com>
To: davem@...emloft.net
Cc: 21210240012@...udan.edu.cn,
	21302010073@...udan.edu.cn,
	dsahern@...nel.org,
	edumazet@...gle.com,
	pabeni@...hat.com,
	kuba@...nel.org,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Yi Zou <03zouyi09.25@...il.com>
Subject: [PATCH] ipv6: route: fix possible null-pointer-dereference in ip6_route_info_create

In the ip6_route_info_create function, the variable fib6_nh is
assigned the return value of nexthop_fib6_nh(rt->nh), which could
result in fib6_nh being NULL. Immediately after this assignment,
there is a potential dereference of fib6_nh in the following code:
if (!ipv6_addr_any(&cfg->fc_prefsrc)) {
 struct net_device *dev = fib6_nh->fib_nh_dev;
This lead to a null pointer dereference (NPD) risk if fib6_nh is
NULL. The issue can be resolved by adding a NULL check before the
deference line.

Signed-off-by: Yi Zou <03zouyi09.25@...il.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 b4251915585f..919592fa4e64 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -3821,7 +3821,7 @@ static struct fib6_info *ip6_route_info_create(struct fib6_config *cfg,
 			rt->fib6_flags = RTF_REJECT | RTF_NONEXTHOP;
 	}

-	if (!ipv6_addr_any(&cfg->fc_prefsrc)) {
+	if (!ipv6_addr_any(&cfg->fc_prefsrc) && fib6_nh) {
 		struct net_device *dev = fib6_nh->fib_nh_dev;

 		if (!ipv6_chk_addr(net, &cfg->fc_prefsrc, dev, 0)) {
-- 
2.44.0