linux-kernel - Re: [PATCH 23/26] media: staging: imgu: use array

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Message-ID: <ZJ00CUwiH6DBtape@kekkonen.localdomain>
Date:   Thu, 29 Jun 2023 07:34:33 +0000
From:   Sakari Ailus <sakari.ailus@...ux.intel.com>
To:     Julia Lawall <julia.lawall@...ia.fr>
Cc:     keescook@...omium.org, kernel-janitors@...r.kernel.org,
        Bingbu Cao <bingbu.cao@...el.com>,
        Tianshu Qiu <tian.shu.qiu@...el.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-media@...r.kernel.org, linux-staging@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 23/26] media: staging: imgu: use array_size

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@...ia.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