drivers/base: cacheinfo: validate device node for all the caches

On architectures that depend on DT for obtaining cache hierarcy, we need
to validate the device node for all the cache indices, failing to do so
might result in wrong information being exposed to the userspace.

This is quite possible on initial/incomplete versions of the device
trees. In such cases, it's better to bail out if all the required device
nodes are not present.

This patch adds checks for the validation of device node for all the
caches and doesn't initialise the cacheinfo if there's any error.
Reported-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Cc: stable <stable@vger.kernel.org> # 4.0
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/cacheinfo.c

@@ -62,15 +62,21 @@ static int cache_setup_of_node(unsigned int cpu)
 		return -ENOENT;
 	}
 
-	while (np && index < cache_leaves(cpu)) {
+	while (index < cache_leaves(cpu)) {
 		this_leaf = this_cpu_ci->info_list + index;
 		if (this_leaf->level != 1)
 			np = of_find_next_cache_node(np);
 		else
 			np = of_node_get(np);/* cpu node itself */
+		if (!np)
+			break;
 		this_leaf->of_node = np;
 		index++;
 	}
+
+	if (index != cache_leaves(cpu)) /* not all OF nodes populated */
+		return -ENOENT;
+
 	return 0;
 }
 
@@ -189,8 +195,11 @@ static int detect_cache_attributes(unsigned int cpu)
 	 * will be set up here only if they are not populated already
 	 */
 	ret = cache_shared_cpu_map_setup(cpu);
-	if (ret)
+	if (ret) {
+		pr_warn("Unable to detect cache hierarcy from DT for CPU %d\n",
+			cpu);
 		goto free_ci;
+	}
 	return 0;
 
 free_ci: