netlink: fix state reallocation in policy export

[ Upstream commit d1fb555 ]

Evidently, when I did this previously, we didn't have more than
10 policies and didn't run into the reallocation path, because
it's missing a memset() for the unused policies. Fix that.

Fixes: d07dcf9 ("netlink: add infrastructure to expose policies to userspace")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

net/netlink/policy.c

@@ -51,6 +51,9 @@ static int add_policy(struct nl_policy_dump **statep,
 	if (!state)
 		return -ENOMEM;
 
+	memset(&state->policies[state->n_alloc], 0,
+	       flex_array_size(state, policies, n_alloc - state->n_alloc));
+
 	state->policies[state->n_alloc].policy = policy;
 	state->policies[state->n_alloc].maxtype = maxtype;
 	state->n_alloc = n_alloc;