thunderbolt: Use kzalloc_flex() for struct tb_path allocation

Simplifies allocation of struct tb_path by using a flexible array
member. Also added __counted_by for extra runtime analysis.

Signed-off-by: Rosen Penev <rosenp@gmail.com>
Reviewed-by: Kees Cook <kees@kernel.org>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>

Author: neheb

drivers/thunderbolt/path.c

@@ -150,22 +150,17 @@ struct tb_path *tb_path_discover(struct tb_port *src, int src_hopid,
 		num_hops++;
 	}
 
-	path = kzalloc_obj(*path);
+	path = kzalloc_flex(*path, hops, num_hops);
 	if (!path)
 		return NULL;
 
+	path->path_length = num_hops;
+
 	path->name = name;
 	path->tb = src->sw->tb;
-	path->path_length = num_hops;
 	path->activated = true;
 	path->alloc_hopid = alloc_hopid;
 
-	path->hops = kzalloc_objs(*path->hops, num_hops);
-	if (!path->hops) {
-		kfree(path);
-		return NULL;
-	}
-
 	tb_dbg(path->tb, "discovering %s path starting from %llx:%u\n",
 	       path->name, tb_route(src->sw), src->port);
 
@@ -245,10 +240,6 @@ struct tb_path *tb_path_alloc(struct tb *tb, struct tb_port *src, int src_hopid,
 	size_t num_hops;
 	int i, ret;
 
-	path = kzalloc_obj(*path);
-	if (!path)
-		return NULL;
-
 	first_port = last_port = NULL;
 	i = 0;
 	tb_for_each_port_on_path(src, dst, in_port) {
@@ -259,20 +250,17 @@ struct tb_path *tb_path_alloc(struct tb *tb, struct tb_port *src, int src_hopid,
 	}
 
 	/* Check that src and dst are reachable */
-	if (first_port != src || last_port != dst) {
-		kfree(path);
+	if (first_port != src || last_port != dst)
 		return NULL;
-	}
 
 	/* Each hop takes two ports */
 	num_hops = i / 2;
 
-	path->hops = kzalloc_objs(*path->hops, num_hops);
-	if (!path->hops) {
-		kfree(path);
+	path = kzalloc_flex(*path, hops, num_hops);
+	if (!path)
 		return NULL;
-	}
 
+	path->path_length = num_hops;
 	path->alloc_hopid = true;
 
 	in_hopid = src_hopid;
@@ -339,7 +327,6 @@ struct tb_path *tb_path_alloc(struct tb *tb, struct tb_port *src, int src_hopid,
 	}
 
 	path->tb = tb;
-	path->path_length = num_hops;
 	path->name = name;
 
 	return path;
@@ -372,7 +359,6 @@ void tb_path_free(struct tb_path *path)
 		}
 	}
 
-	kfree(path->hops);
 	kfree(path);
 }
 

drivers/thunderbolt/tb.h

@@ -419,9 +419,9 @@ enum tb_path_port {
  * @activated: Is the path active
  * @clear_fc: Clear all flow control from the path config space entries
  *	      when deactivating this path
- * @hops: Path hops
  * @path_length: How many hops the path uses
  * @alloc_hopid: Does this path consume port HopID
+ * @hops: Path hops
  *
  * A path consists of a number of hops (see &struct tb_path_hop). To
  * establish a PCIe tunnel two paths have to be created between the two
@@ -440,9 +440,10 @@ struct tb_path {
 	bool drop_packages;
 	bool activated;
 	bool clear_fc;
-	struct tb_path_hop *hops;
 	int path_length;
 	bool alloc_hopid;
+
+	struct tb_path_hop hops[] __counted_by(path_length);
 };
 
 /* HopIDs 0-7 are reserved by the Thunderbolt protocol */