selinux: Fix error return code in sel_ib_pkey_sid_slow()

Fix to return a negative error code from the error handling case
instead of 0 in function sel_ib_pkey_sid_slow(), as done elsewhere
in this function.

Cc: stable@vger.kernel.org
Fixes: 409dcf31 ("selinux: Add a cache for quicker retreival of PKey SIDs")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Chen Zhou <chenzhou10@huawei.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

security/selinux/ibpkey.c

@@ -151,8 +151,10 @@ static int sel_ib_pkey_sid_slow(u64 subnet_prefix, u16 pkey_num, u32 *sid)
 	 * is valid, it just won't be added to the cache.
 	 */
 	new = kzalloc(sizeof(*new), GFP_ATOMIC);
-	if (!new)
+	if (!new) {
+		ret = -ENOMEM;
 		goto out;
+	}
 
 	new->psec.subnet_prefix = subnet_prefix;
 	new->psec.pkey = pkey_num;