Messages in this thread | | | Date | Mon, 10 Jun 2019 10:53:08 -0700 | From | Kees Cook <> | Subject | Re: [PATCH] block: bio: Use struct_size() in kmalloc() |
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On Mon, Jun 10, 2019 at 10:04:12AM -0500, Gustavo A. R. Silva wrote: > 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. > > Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
-Kees
> --- > block/bio.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/block/bio.c b/block/bio.c > index 683cbb40f051..4bcdcd3f63f4 100644 > --- a/block/bio.c > +++ b/block/bio.c > @@ -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); > -- > 2.21.0 >
-- Kees Cook
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