| Message ID | 20190610150412.GA8430@embeddedor (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | block: bio: Use struct_size() in kmalloc() | expand |
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 >
On 6/10/19 9:04 AM, 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. Applied, thanks.
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);
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> --- block/bio.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)