Commit bcd67654 authored Aug 05, 2019 by Gustavo A. R. Silva Committed by Mike Snitzer Aug 26, 2019

dm raid1: use struct_size() with 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 mirror_set {
	...
        struct mirror mirror[0];
};

size = sizeof(struct mirror_set) + count * sizeof(struct mirror);
instance = kzalloc(size, 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, mirror, count), GFP_KERNEL)

Notice that, in this case, variable len is not necessary, hence it
is removed.

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

parent 5229b489

drivers/md/dm-raid1.c

+2 −5

Original line number	Diff line number	Diff line
		@@ -878,12 +878,9 @@ static struct mirror_set *alloc_context(unsigned int nr_mirrors,
		struct dm_target *ti,
		struct dm_dirty_log *dl)
		{
		size_t len;
		struct mirror_set *ms = NULL;

		len = sizeof(ms) + (sizeof(ms->mirror[0]) nr_mirrors);
		struct mirror_set *ms =
		kzalloc(struct_size(ms, mirror, nr_mirrors), GFP_KERNEL);

		ms = kzalloc(len, GFP_KERNEL);
		if (!ms) {
		ti->error = "Cannot allocate mirror context";
		return NULL;