[PATCH] bio-integrity: use struct_size() in kmalloc()

[Gustavo A. R. Silva]

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

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gust...@embeddedor.com>
---
 block/bio-integrity.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/block/bio-integrity.c b/block/bio-integrity.c
index 1b633a3526d4..ae8c68ecc0ca 100644
--- a/block/bio-integrity.c
+++ b/block/bio-integrity.c
@@ -57,8 +57,8 @@ struct bio_integrity_payload *bio_integrity_alloc(struct bio 
*bio,
        unsigned inline_vecs;
 
        if (!bs || !mempool_initialized(&bs->bio_integrity_pool)) {
-               bip = kmalloc(sizeof(struct bio_integrity_payload) +
-                             sizeof(struct bio_vec) * nr_vecs, gfp_mask);
+               bip = kmalloc(struct_size(bip, bip_inline_vecs, nr_vecs),
+                             gfp_mask);
                inline_vecs = nr_vecs;
        } else {
                bip = mempool_alloc(&bs->bio_integrity_pool, gfp_mask);
-- 
2.20.1