[PATCH] ipv6_sockglue: Fix a missing-check bug in ip6_ra_control()

[Gen Zhang <blackgod016574@gmail.com>]

In function ip6_ra_control(), the pointer new_ra is allocated a memory 
space via kmalloc(). And it is used in the following codes. However, 
when there is a memory allocation error, kmalloc() fails. Thus null 
pointer dereference may happen. And it will cause the kernel to crash. 
Therefore, we should check the return value and handle the error.

Signed-off-by: Gen Zhang <blackgod016574@gmail.com>

---
diff --git a/net/ipv6/ipv6_sockglue.c b/net/ipv6/ipv6_sockglue.c
index 40f21fe..0a3d035 100644
--- a/net/ipv6/ipv6_sockglue.c
+++ b/net/ipv6/ipv6_sockglue.c
@@ -68,6 +68,8 @@ int ip6_ra_control(struct sock *sk, int sel)
 		return -ENOPROTOOPT;
 
 	new_ra = (sel >= 0) ? kmalloc(sizeof(*new_ra), GFP_KERNEL) : NULL;
+	if (sel >= 0 && !new_ra)
+		return -ENOMEM;
 
 	write_lock_bh(&ip6_ra_lock);
 	for (rap = &ip6_ra_chain; (ra = *rap) != NULL; rap = &ra->next) {