kernel/gcov/gcc_3_4.c: use struct_size() in kzalloc()

One of the more common cases of allocation size calculations is finding
the size of a structure that has a zero-sized array at the end, along
with memory for some number of elements for that array. For example:

struct foo {
int stuff;
void *entry[];
};

instance = kzalloc(sizeof(struct foo) + sizeof(void *) * count, GFP_KERNEL);

Instead of leaving these open-coded and prone to type mistakes, we can
now use the new struct_size() helper:

instance = kzalloc(struct_size(instance, entry, count), GFP_KERNEL);

This code was detected with the help of Coccinelle.

Link: http://lkml.kernel.org/r/20190109172445.GA15908@embeddedor
Signed-off-by: Gustavo A. R. Silva <[e-mail]>
Reviewed-by: Peter Oberparleiter <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

kernel/gcov/gcc_3_4.c

···
 
 	/* Duplicate gcov_info. */
 	active = num_counter_active(info);
-	dup = kzalloc(sizeof(struct gcov_info) +
-		      sizeof(struct gcov_ctr_info) * active, GFP_KERNEL);
+	dup = kzalloc(struct_size(dup, counts, active), GFP_KERNEL);
 	if (!dup)
 		return NULL;
 	dup->version		= info->version;
···
 {
 	struct gcov_iterator *iter;
 
-	iter = kzalloc(sizeof(struct gcov_iterator) +
-		       num_counter_active(info) * sizeof(struct type_info),
+	iter = kzalloc(struct_size(iter, type_info, num_counter_active(info)),
 		       GFP_KERNEL);
 	if (iter)
 		iter->info = info;