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block: bio: Use struct_size() in kmalloc()

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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 bio_map_data {
	...
        struct iovec iov[];
};

instance = kmalloc(sizeof(sizeof(struct bio_map_data) + sizeof(struct iovec) *
                          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, iov, count), GFP_KERNEL);

This code was detected with the help of Coccinelle.

Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Gustavo A. R. Silva 2019-06-10 10:04:12 -05:00 committed by Jens Axboe
parent 78b90a2ce8
commit f1f8f292cd
1 changed files with 1 additions and 2 deletions
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3
block/bio.c
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@ -1120,8 +1120,7 @@ static struct bio_map_data *bio_alloc_map_data(struct iov_iter *data,
if (data->nr_segs > UIO_MAXIOV)
return NULL;
bmd = kmalloc(sizeof(struct bio_map_data) +
sizeof(struct iovec) * data->nr_segs, gfp_mask);
bmd = kmalloc(struct_size(bmd, iov, data->nr_segs), gfp_mask);
if (!bmd)
return NULL;
memcpy(bmd->iov, data->iov, sizeof(struct iovec) * data->nr_segs);