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Date:   Sun, 15 Aug 2021 18:36:39 +0200
From:   Len Baker <len.baker@gmx.com>
To:     Joe Perches <joe@perches.com>
Cc:     Andy Shevchenko <andy.shevchenko@gmail.com>,
        Len Baker <len.baker@gmx.com>,
        Jonathan Cameron <jic23@kernel.org>,
        Lars-Peter Clausen <lars@metafoo.de>,
        David Laight <David.Laight@aculab.com>,
        Kees Cook <keescook@chromium.org>,
        linux-hardening@vger.kernel.org,
        linux-iio <linux-iio@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v4] drivers/iio: Remove all strcpy() uses
Message-ID: <20210815163639.GA97260@titan>
References: <20210814135509.4500-1-len.baker@gmx.com>
 <CAHp75VdBuQTzCbz1CJciSA1+UOw0ZmJKAh8u2cbr5eDLSsRJEw@mail.gmail.com>
 <c08cfa8b6bbf07e1860d7dc93739e71ff5f4c0c4.camel@perches.com>
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Hi Joe,

On Sun, Aug 15, 2021 at 08:06:45AM -0700, Joe Perches wrote:
> On Sat, 2021-08-14 at 22:36 +0300, Andy Shevchenko wrote:
> > On Sat, Aug 14, 2021 at 4:55 PM Len Baker <len.baker@gmx.com> 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, remove all the uses and add
> > > devm_kstrdup() or devm_kasprintf() instead.
> > >
> > > This patch is an effort to clean up the proliferation of str*()
> > > functions in the kernel and a previous step in the path to remove
> > > the strcpy function from the kernel entirely [1].
> > >
> > > [1] https://github.com/KSPP/linux/issues/88
> >
> > Thank you very much for doing this!
> > Now I like the result,
> > Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
> []
> > > diff --git a/drivers/iio/imu/inv_mpu6050/inv_mpu_magn.c b/drivers/ii=
o/imu/inv_mpu6050/inv_mpu_magn.c
> []
> > > @@ -261,6 +261,7 @@ int inv_mpu_magn_set_rate(const struct inv_mpu60=
50_state *st, int fifo_rate)
> > > =A0=A0*/
> > > =A0int inv_mpu_magn_set_orient(struct inv_mpu6050_state *st)
> > > =A0{
> > > +       struct device *dev =3D regmap_get_device(st->map);
> > > =A0=A0=A0=A0=A0=A0=A0=A0const char *orient;
> > > =A0=A0=A0=A0=A0=A0=A0=A0char *str;
> > > =A0=A0=A0=A0=A0=A0=A0=A0int i;
> > > @@ -281,19 +282,24 @@ int inv_mpu_magn_set_orient(struct inv_mpu6050=
_state *st)
> > > =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0/* z <- -z */
> > > =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0for (i =3D 0; i < 3;=
 ++i) {
> > > =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=
=A0=A0orient =3D st->orientation.rotation[6 + i];
> > > -                       /* use length + 2 for adding minus sign if n=
eeded */
> > > -                       str =3D devm_kzalloc(regmap_get_device(st->m=
ap),
> > > -                                          strlen(orient) + 2, GFP_K=
ERNEL);
> > > -                       if (str =3D=3D NULL)
> > > +
> > > +                       /*
> > > +                        * The value is negated according to one of =
the following
> > > +                        * rules:
> > > +                        *
> > > +                        * 1) Drop leading minus.
> > > +                        * 2) Leave 0 as is.
> > > +                        * 3) Add leading minus.
> > > +                        */
> > > +                       if (orient[0] =3D=3D '-')
> > > +                               str =3D devm_kstrdup(dev, orient + 1=
, GFP_KERNEL);
> > > +                       else if (orient[0] =3D=3D '0' && orient[1] =
=3D=3D '\0')
>
> bikeshed:
>
> I think this change is less intelligible than the original strcmp.

So, if I understand correctly you suggest to change the above line for:
                              else if (strcmp(orient, "0") =3D=3D 0)

And yes, this line will be more readable ;)

>
> And separately, perhaps for loop would be more readable as
>
> 	for (i =3D 6; i < 9; i++)
>
> converting the 6 + i uses to just i.

Ok, no problem. If there are no objections I will send a new version with
these 2 changes.

Regards,
Len

>
> > > +                               str =3D devm_kstrdup(dev, orient, GF=
P_KERNEL);
> > > +                       else
> > > +                               str =3D devm_kasprintf(dev, GFP_KERN=
EL, "-%s", orient);
> > > +                       if (!str)
> > > =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=
=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0return -ENOMEM;
> > > -                       if (strcmp(orient, "0") =3D=3D 0) {
> > > -                               strcpy(str, orient);
> > > -                       } else if (orient[0] =3D=3D '-') {
> > > -                               strcpy(str, &orient[1]);
> > > -                       } else {
> > > -                               str[0] =3D '-';
> > > -                               strcpy(&str[1], orient);
> > > -                       }
> > > +
> > > =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=
=A0=A0st->magn_orient.rotation[6 + i] =3D str;
> > > =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0}
> > > =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0break;
>
>