linux-kernel - [PATCH] ipv6: ip6_fib: fix possible null-pointer-dereference in ipv6_route_native_seq

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Message-ID: <20241101044828.55960-1-03zouyi09.25@gmail.com>
Date: Fri,  1 Nov 2024 12:48:28 +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: ip6_fib: fix possible null-pointer-dereference in  ipv6_route_native_seq_show

In the ipv6_route_native_seq_show function, the fib6_nh variable
is assigned the value from nexthop_fib6_nh(rt->nh), which could
return NULL. This creates a risk of a null-pointer-dereference
when accessing fib6_nh->fib_nh_gw_family. This can be resolved by
checking if fib6_nh is non-NULL before accessing fib6_nh->fib_nh_gw_family
 and assign dev using dev = fib6_nh ? fib6_nh->fib_nh_dev : NULL;
to prevent null-pointer dereference errors.

Signed-off-by: Yi Zou <03zouyi09.25@...il.com>
---
 net/ipv6/ip6_fib.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
index eb111d20615c..6632ab65d206 100644
--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c
@@ -2555,14 +2555,14 @@ static int ipv6_route_native_seq_show(struct seq_file *seq, void *v)
 #else
 	seq_puts(seq, "00000000000000000000000000000000 00 ");
 #endif
-	if (fib6_nh->fib_nh_gw_family) {
+	if (fib6_nh && fib6_nh->fib_nh_gw_family) {
 		flags |= RTF_GATEWAY;
 		seq_printf(seq, "%pi6", &fib6_nh->fib_nh_gw6);
 	} else {
 		seq_puts(seq, "00000000000000000000000000000000");
 	}
 
-	dev = fib6_nh->fib_nh_dev;
+	dev = fib6_nh ? fib6_nh->fib_nh_dev : NULL;
 	seq_printf(seq, " %08x %08x %08x %08x %8s\n",
 		   rt->fib6_metric, refcount_read(&rt->fib6_ref), 0,
 		   flags, dev ? dev->name : "");
-- 
2.44.0