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

commit 95baa60a0da80a0143e3ddd4d3725758b4513825 upstream.

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: NGen Zhang <blackgod016574@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NJeffle Xu <jefflexu@linux.alibaba.com>
Acked-by: NJoseph Qi <joseph.qi@linux.alibaba.com>

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) {