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Subject: Re: [PATCH v2] gpio-hammer: Avoid potential overflow in main
To:     linus.walleij@linaro.org, bgolaszewski@baylibre.com
Cc:     linux-gpio@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20200312144015.1848245-1-gabravier@gmail.com>
From:   Gabriel Ravier <gabravier@gmail.com>
Message-ID: <0e3a171e-fd85-4832-d4af-15abf4c1f5fe@gmail.com>
Date:   Thu, 12 Mar 2020 15:50:09 +0100
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On 3/12/20 3:40 PM, Gabriel Ravier wrote:
> 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 | 17 ++++++++++++++++-
>   1 file changed, 16 insertions(+), 1 deletion(-)
>
> diff --git a/tools/gpio/gpio-hammer.c b/tools/gpio/gpio-hammer.c
> index 0e0060a6e..d0be21af1 100644
> --- a/tools/gpio/gpio-hammer.c
> +++ b/tools/gpio/gpio-hammer.c
> @@ -135,7 +135,14 @@ int main(int argc, char **argv)
>   			device_name = optarg;
>   			break;
>   		case 'o':
> -			lines[i] = strtoul(optarg, NULL, 10);
> +			/*
> +			 * Avoid overflow. Do not immediately error, we want to
> +			 * be able to accurately report on the amount of times
> +			 *'-o' was given to give an accurate error message
> +			 */
> +			if (i < GPIOHANDLES_MAX)
> +				lines[i] = strtoul(optarg, NULL, 10);
> +
>   			i++;
>   			break;
>   		case '?':
> @@ -143,6 +150,14 @@ int main(int argc, char **argv)
>   			return -1;
>   		}
>   	}
> +
> +	if (i >= GPIOHANDLES_MAX) {
> +		fprintf(stderr,
> +			"Only %d occurences of '-o' are allowed, %d were found\n",
> +			GPIOHANDLES_MAX, i + 1);
> +		return -1;
> +	}
> +
>   	nlines = i;
>   
>   	if (!device_name || !nlines) {

Just noticed that there isn't a space before the "'-o'" in the third 
line of the explanatory comment in the first part of the patch, will 
send a third version of the patch with a space before the "'-o'"