[PATCH 1/2] net: ipv4: Fix a possible null-pointer dereference in inet_csk_rebuild_route()

[Jia-Ju Bai <baijiaju1990@gmail.com>]

In inet_csk_rebuild_route(), rt is assigned to NULL on line 1071.
On line 1076, rt is used:
    return &rt->dst;
Thus, a possible null-pointer dereference may occur.

To fix this bug, rt is checked before being used.

This bug is found by a static analysis tool STCheck written by us.

Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
---
 net/ipv4/inet_connection_sock.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index f5c163d4771b..27d9d80f3401 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -1073,7 +1073,10 @@ static struct dst_entry *inet_csk_rebuild_route(struct sock *sk, struct flowi *f
 		sk_setup_caps(sk, &rt->dst);
 	rcu_read_unlock();
 
-	return &rt->dst;
+	if (rt)
+		return &rt->dst;
+	else
+		return NULL;
 }
 
 struct dst_entry *inet_csk_update_pmtu(struct sock *sk, u32 mtu)
-- 
2.17.0