net: corrections for security_secid_to_secctx returns

security_secid_to_secctx() returns the size of the new context,
whereas previous versions provided that via a pointer parameter.
Correct the type of the value returned in nfqnl_get_sk_secctx()
and the check for error in netlbl_unlhsh_add(). Add an error
check.

Fixes: 2d470c778120 ("lsm: replace context+len with lsm_context")
Signed-off-by: Casey Schaufler <[e-mail]>
Signed-off-by: Paul Moore <[e-mail]>

net/netfilter/nfnetlink_queue.c

···
 	return 0;
 }
 
-static u32 nfqnl_get_sk_secctx(struct sk_buff *skb, struct lsm_context *ctx)
+static int nfqnl_get_sk_secctx(struct sk_buff *skb, struct lsm_context *ctx)
 {
-	u32 seclen = 0;
+	int seclen = 0;
 #if IS_ENABLED(CONFIG_NETWORK_SECMARK)
 
 	if (!skb || !sk_fullsock(skb->sk))
···
 	const struct nfnl_ct_hook *nfnl_ct;
 	bool csum_verify;
 	struct lsm_context ctx;
-	u32 seclen = 0;
+	int seclen = 0;
 	ktime_t tstamp;
 
 	size = nlmsg_total_size(sizeof(struct nfgenmsg))
···
 
 	if ((queue->flags & NFQA_CFG_F_SECCTX) && entskb->sk) {
 		seclen = nfqnl_get_sk_secctx(entskb, &ctx);
-		if (seclen >= 0)
+		if (seclen < 0)
+			return NULL;
+		if (seclen)
 			size += nla_total_size(seclen);
 	}
 
···
 	if (nfqnl_put_sk_classid(skb, entskb->sk) < 0)
 		goto nla_put_failure;
 
-	if (seclen && nla_put(skb, NFQA_SECCTX, ctx.len, ctx.context))
+	if (seclen > 0 && nla_put(skb, NFQA_SECCTX, ctx.len, ctx.context))
 		goto nla_put_failure;
 
 	if (ct && nfnl_ct->build(skb, ct, ctinfo, NFQA_CT, NFQA_CT_INFO) < 0)

net/netlabel/netlabel_unlabeled.c

···
 unlhsh_add_return:
 	rcu_read_unlock();
 	if (audit_buf != NULL) {
-		if (security_secid_to_secctx(secid, &ctx) == 0) {
+		if (security_secid_to_secctx(secid, &ctx) >= 0) {
 			audit_log_format(audit_buf, " sec_obj=%s", ctx.context);
 			security_release_secctx(&ctx);
 		}
···
 					  addr->s_addr, mask->s_addr);
 		dev_put(dev);
 		if (entry != NULL &&
-		    security_secid_to_secctx(entry->secid, &ctx) == 0) {
+		    security_secid_to_secctx(entry->secid, &ctx) >= 0) {
 			audit_log_format(audit_buf, " sec_obj=%s", ctx.context);
 			security_release_secctx(&ctx);
 		}
···
 					  addr, mask);
 		dev_put(dev);
 		if (entry != NULL &&
-		    security_secid_to_secctx(entry->secid, &ctx) == 0) {
+		    security_secid_to_secctx(entry->secid, &ctx) >= 0) {
 			audit_log_format(audit_buf, " sec_obj=%s", ctx.context);
 			security_release_secctx(&ctx);
 		}