Re: [igt-dev] [PATCH i-g-t] debugfs: Fix writing an extra zero out of bounds in igt_crc_to_string_extended()

[Jani Nikula <jani.nikula@linux.intel.com>]

On Mon, 28 Jan 2019, Maarten Lankhorst <maarten.lankhorst@linux.intel.com> wrote:
> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> ---
>  lib/igt_debugfs.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/lib/igt_debugfs.c b/lib/igt_debugfs.c
> index 3656c66a5674..d1fc0ff7f710 100644
> --- a/lib/igt_debugfs.c
> +++ b/lib/igt_debugfs.c
> @@ -458,17 +458,17 @@ char *igt_crc_to_string_extended(igt_crc_t *crc, char delimiter, int crc_size)
>  	int i;
>  	int len = 0;
>  	int field_width = 2 * crc_size; /* Two chars per byte. */
> -	char *buf = malloc((field_width+1) * crc->n_words * sizeof(char));
> +	char *buf = malloc((field_width+1) * crc->n_words);
>  
>  	if (!buf)
>  		return NULL;
>  
> -	for (i = 0; i < crc->n_words; i++)
> +	for (i = 0; i < crc->n_words - 1; i++)
>  		len += sprintf(buf + len, "%0*x%c", field_width,
>  			       crc->crc[i], delimiter);

Or keep the loop condition and make this:

		len += sprintf(buf + len, "%s%0*x", i ? &delimiter : "",
			       field_width, crc->crc[i]);

Additionally could make the delimiter passed here a char*.

BR,
Jani.

>  
> -	/* Eat the last delimiter */
> -	buf[len - 1] = '\0';
> +	sprintf(buf + len, "%0*x", field_width, crc->crc[i]);
> +
>  	return buf;
>  }

-- 
Jani Nikula, Intel Open Source Graphics Center
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