linux-hardening - Re: [PATCH] drivers/soc: Remove all strcpy() uses in favor of strscpy()

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Date:   Sat, 31 Jul 2021 15:59:57 +0200
From:   Len Baker <len.baker@....com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        Kees Cook <keescook@...omium.org>
Cc:     Len Baker <len.baker@....com>,
        David Laight <David.Laight@...LAB.COM>,
        Robin Murphy <robin.murphy@....com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Magnus Damm <magnus.damm@...il.com>,
        Santosh Shilimkar <ssantosh@...nel.org>,
        linux-hardening@...r.kernel.org,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] drivers/soc: Remove all strcpy() uses in favor of
 strscpy()

Hi,

On Mon, Jul 26, 2021 at 10:03:18AM +0200, Geert Uytterhoeven wrote:
> Hi Len,
>
> On Sun, Jul 25, 2021 at 5:15 PM Len Baker <len.baker@....com> wrote:
> > strcpy() performs no bounds checking on the destination buffer. This
> > could result in linear overflows beyond the end of the buffer, leading
> > to all kinds of misbehaviors. The safe replacement is strscpy().
> >
> > Signed-off-by: Len Baker <len.baker@....com>
>
> Thanks for your patch!
>
> > ---
> > This is a task of the KSPP [1]
> >
> > [1] https://github.com/KSPP/linux/issues/88
>
> Any chance the almost one year old question in that ticket can be
> answered?

I'm a kernel newbie and I have chosen this task as a starting point. So,
I think that someone with more experience could answer this question.

Kees: Any comments?

>
> >  drivers/soc/renesas/rcar-sysc.c     |  6 ++++--
>
> Reviewed-by: Geert Uytterhoeven <geert+renesas@...der.be>
>
> But please see my comments below...
>
> > --- a/drivers/soc/renesas/r8a779a0-sysc.c
> > +++ b/drivers/soc/renesas/r8a779a0-sysc.c
> > @@ -404,19 +404,21 @@ static int __init r8a779a0_sysc_pd_init(void)
> >         for (i = 0; i < info->num_areas; i++) {
> >                 const struct r8a779a0_sysc_area *area = &info->areas[i];
> >                 struct r8a779a0_sysc_pd *pd;
> > +               size_t area_name_size;
>
> I wouldn't mind a shorter name, like "n".

Ok, I will change this for the next version.

> >
> >                 if (!area->name) {
> >                         /* Skip NULLified area */
> >                         continue;
> >                 }
> >
> > -               pd = kzalloc(sizeof(*pd) + strlen(area->name) + 1, GFP_KERNEL);
> > +               area_name_size = strlen(area->name) + 1;
> > +               pd = kzalloc(sizeof(*pd) + area_name_size, GFP_KERNEL);
> >                 if (!pd) {
> >                         error = -ENOMEM;
> >                         goto out_put;
> >                 }
> >
> > -               strcpy(pd->name, area->name);
> > +               strscpy(pd->name, area->name, area_name_size);
> >                 pd->genpd.name = pd->name;
> >                 pd->pdr = area->pdr;
> >                 pd->flags = area->flags;
> > diff --git a/drivers/soc/renesas/rcar-sysc.c b/drivers/soc/renesas/rcar-sysc.c
> > index 53387a72ca00..0eae5ce0eeb0 100644
> > --- a/drivers/soc/renesas/rcar-sysc.c
> > +++ b/drivers/soc/renesas/rcar-sysc.c
> > @@ -396,19 +396,21 @@ static int __init rcar_sysc_pd_init(void)
> >         for (i = 0; i < info->num_areas; i++) {
> >                 const struct rcar_sysc_area *area = &info->areas[i];
> >                 struct rcar_sysc_pd *pd;
> > +               size_t area_name_size;
>
> Likewise.

Ok, understood.

Regards,
Len