md: raid10: Use struct_size() in kmalloc()

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@embeddedor.com>
Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 1facd015339997a8efa649448f58b78a7f78b9a5..f35e076ee47d8be2b36814ad8cf6615a56c78381 100644 (file)
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -4755,8 +4755,7 @@ 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;