Re: [PATCH 23/26] media: staging: imgu: use array_size

Sakari Ailus
2023-06-29T07:36:00Z

Hi Julia, Bingbu,

On Tue, Jun 27, 2023 at 07:35:47PM +0200, Julia Lawall wrote:
>
>
> On Fri, 23 Jun 2023, Julia Lawall wrote:
>
> > Use array_size to protect against multiplication overflows.
> >
> > The changes were done using the following Coccinelle semantic patch:
> >
> > // <smpl>
> > @@
> > expression E1, E2;
> > constant C1, C2;
> > identifier alloc = {vmalloc,vzalloc};
> > @@
> >
> > (
> > alloc(C1 * C2,...)
> > |
> > alloc(
> > - (E1) * (E2)
> > + array_size(E1, E2)
> > ,...)
> > )
> > // </smpl>
> >
> > Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr>
> >
> > ---
> > drivers/staging/media/ipu3/ipu3-mmu.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/staging/media/ipu3/ipu3-mmu.c b/drivers/staging/media/ipu3/ipu3-mmu.c
> > index cb9bf5fb29a5..9c4adb815c94 100644
> > --- a/drivers/staging/media/ipu3/ipu3-mmu.c
> > +++ b/drivers/staging/media/ipu3/ipu3-mmu.c
> > @@ -464,7 +464,7 @@ struct imgu_mmu_info *imgu_mmu_init(struct device *parent, void __iomem *base)
> > * Allocate the array of L2PT CPU pointers, initialized to zero,
> > * which means the dummy L2PT allocated above.
> > */
> > - mmu->l2pts = vzalloc(IPU3_PT_PTES * sizeof(*mmu->l2pts));
> > + mmu->l2pts = vzalloc(array_size(IPU3_PT_PTES, sizeof(*mmu->l2pts)));
> > if (!mmu->l2pts)
> > goto fail_l2pt;
>
> I think that this patch can be dropped. Since it is a multiplcation of
> two constants, if there is an overflow, I guess the compiler would detect
> it?

Indeed. vcalloc() would be perhaps nicer but the original isn't wrong
either.

--
Kind regards,

Sakari Ailus