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Date:   Tue, 10 Aug 2021 17:59:53 +0200
From:   Len Baker <len.baker@gmx.com>
To:     Christophe JAILLET <christophe.jaillet@wanadoo.fr>,
        Bernd Petrovitsch <bernd@petrovitsch.priv.at>
Cc:     Andy Gross <agross@kernel.org>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Geert Uytterhoeven <geert+renesas@glider.be>,
        Magnus Damm <magnus.damm@gmail.com>,
        Santosh Shilimkar <ssantosh@kernel.org>,
        Len Baker <len.baker@gmx.com>,
        Kees Cook <keescook@chromium.org>,
        David Laight <David.Laight@ACULAB.COM>,
        Robin Murphy <robin.murphy@arm.com>,
        linux-hardening@vger.kernel.org, linux-arm-msm@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-renesas-soc@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v4 2/3] drivers/soc/renesas: Prefer memcpy over strcpy
Message-ID: <20210810155953.GB2508@titan>
References: <20210808125012.4715-1-len.baker@gmx.com>
 <20210808125012.4715-3-len.baker@gmx.com>
 <39485c0e-511c-50a0-83be-f9ce6fc47e67@petrovitsch.priv.at>
 <c33adb9e-9604-3d89-5a5b-152eb03e5b54@wanadoo.fr>
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In-Reply-To: <c33adb9e-9604-3d89-5a5b-152eb03e5b54@wanadoo.fr>
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Hi,

On Sun, Aug 08, 2021 at 07:06:30PM +0200, Christophe JAILLET wrote:
> Hi,
>
> Le 08/08/2021 =E0 17:35, Bernd Petrovitsch a =E9crit=A0:
> > Hi all!
> >
> > On 08/08/2021 14:50, Len Baker wrote:
> > > strcpy() performs no bounds checking on the destination buffer. This
> > > could result in linear overflows beyond the end of the buffer, leadi=
ng
> > > to all kinds of misbehaviors. So, use memcpy() as a safe replacement=
.
> > >
> > > This is a previous step in the path to remove the strcpy() function
> > > entirely from the kernel.
> > >
> > > Signed-off-by: Len Baker <len.baker@gmx.com>
> > > ---
> > >   drivers/soc/renesas/r8a779a0-sysc.c | 6 ++++--
> > >   drivers/soc/renesas/rcar-sysc.c     | 6 ++++--
> > >   2 files changed, 8 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/drivers/soc/renesas/r8a779a0-sysc.c b/drivers/soc/renes=
as/r8a779a0-sysc.c
> > > index d464ffa1be33..7410b9fa9846 100644
> > > --- 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 =3D 0; i < info->num_areas; i++) {
> > >   		const struct r8a779a0_sysc_area *area =3D &info->areas[i];
> > >   		struct r8a779a0_sysc_pd *pd;
> > > +		size_t n;
> > >
> > >   		if (!area->name) {
> > >   			/* Skip NULLified area */
> > >   			continue;
> > >   		}
> > >
> > > -		pd =3D kzalloc(sizeof(*pd) + strlen(area->name) + 1, GFP_KERNEL);
> > > +		n =3D strlen(area->name) + 1;
> > > +		pd =3D kzalloc(sizeof(*pd) + n, GFP_KERNEL);
> > Zeroing the allocated bytes is not needed since it's completly
> > overwritten with the strcpy()/memcpy().
>
> The strcpy()/memcpy() only overwrites the pd->name field, not the whole =
pd
> structure.

You are right.

> I think that it is needed to keep the kzalloc.

Yes, I think so. The kzalloc is needed to guarantee that the whole struct =
is
initialize (all the members are initialized with zeros).

Regards,
Len

>
> Just my 2c,
> CJ
>
> > >   		if (!pd) {
> > >   			error =3D -ENOMEM;
> > >   			goto out_put;
> > >   		}
> > >
> > > -		strcpy(pd->name, area->name);
> > > +		memcpy(pd->name, area->name, n);
> > >   		pd->genpd.name =3D pd->name;
> > >   		pd->pdr =3D area->pdr;
> > >   		pd->flags =3D area->flags;
> >
> > And similar for the second hunk.
> >
> > MfG,
> > 	Bernd
> >
>