[PATCH] md: raid10: Use struct_size() in kmalloc()

From: Gustavo A. R. Silva
Date: Tue Jun 04 2019 - 18:48:22 EST

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;
struct boo entry[];

instance = kmalloc(size, GFP_KERNEL);

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

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

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@xxxxxxxxxxxxxx>
drivers/md/raid10.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index aea11476fee6..3caafd433163 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -4780,8 +4780,7 @@ static int handle_reshape_read_error(struct mddev *mddev,
int idx = 0;
struct page **pages;

- r10b = kmalloc(sizeof(*r10b) +
- sizeof(struct r10dev) * conf->copies, GFP_NOIO);
+ r10b = kmalloc(struct_size(r10b, devs, conf->copies), GFP_NOIO);
if (!r10b) {
set_bit(MD_RECOVERY_INTR, &mddev->recovery);
return -ENOMEM;