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From:   Bartosz Golaszewski <bgolaszewski@baylibre.com>
Date:   Thu, 12 Mar 2020 14:54:12 +0100
Message-ID: <CAMpxmJUUth5w8tvZp8mFV-FDz0YivmRWAqsOQSTdze1xagMX8A@mail.gmail.com>
Subject: Re: [PATCH] gpio-hammer: Avoid potential overflow in main
To:     Gabriel Ravier <gabravier@gmail.com>
Cc:     Linus Walleij <linus.walleij@linaro.org>,
        linux-gpio <linux-gpio@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
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czw., 12 mar 2020 o 10:40 Gabriel Ravier <gabravier@gmail.com> napisa=C5=82=
(a):
>
> If '-o' was used more than 64 times in a single invocation of gpio-hammer=
,
> this could lead to an overflow of the 'lines' array. This commit fixes
> this by avoiding the overflow and giving a proper diagnostic back to the
> user
>
> Signed-off-by: Gabriel Ravier <gabravier@gmail.com>
> ---
>  tools/gpio/gpio-hammer.c | 19 +++++++++++++++++--
>  1 file changed, 17 insertions(+), 2 deletions(-)
>
> diff --git a/tools/gpio/gpio-hammer.c b/tools/gpio/gpio-hammer.c
> index 0e0060a6e..273d33847 100644
> --- a/tools/gpio/gpio-hammer.c
> +++ b/tools/gpio/gpio-hammer.c
> @@ -77,7 +77,7 @@ int hammer_device(const char *device_name, unsigned int=
 *lines, int nlines,
>
>                 fprintf(stdout, "[%c] ", swirr[j]);
>                 j++;
> -               if (j =3D=3D sizeof(swirr)-1)
> +               if (j =3D=3D sizeof(swirr) - 1)

Please don't try to sneak in unrelated changes into commits. This is
of course correct coding-style-wise but send it in a separate patch.

>                         j =3D 0;
>
>                 fprintf(stdout, "[");
> @@ -135,7 +135,14 @@ int main(int argc, char **argv)
>                         device_name =3D optarg;
>                         break;
>                 case 'o':
> -                       lines[i] =3D strtoul(optarg, NULL, 10);
> +                       /*
> +                        * Avoid overflow. Do not immediately error, we w=
ant to
> +                        * be able to accurately report on the amount of =
times
> +                        *'-o' was given to give an accurate error messag=
e
> +                        */
> +                       if (i < GPIOHANDLES_MAX)
> +                               lines[i] =3D strtoul(optarg, NULL, 10);
> +
>                         i++;
>                         break;
>                 case '?':
> @@ -143,6 +150,14 @@ int main(int argc, char **argv)
>                         return -1;
>                 }
>         }
> +
> +       if (i >=3D GPIOHANDLES_MAX) {
> +               fprintf(stderr,
> +                       "Only %d occurences of '-o' are allowed, %d were =
found\n",
> +                       GPIOHANDLES_MAX, i + 1);
> +               return -1;
> +       }
> +
>         nlines =3D i;
>
>         if (!device_name || !nlines) {
> --
> 2.24.1
>

Other than that, looks good.

Bartosz