[U-Boot] [PATCH v1] tools: mtk_image: replace strncpy(d, s, sizeof(d)) with snprintf()

[Weijie Gao]

On Tue, 2018-12-11 at 16:41 +0200, Andy Shevchenko wrote:
> Starting from version 8 the GCC, i.e. C compiler, starts complaining about
> possible '\0' terminator loss or, as in this case, garbage copy.
> 
> In function ‘mtk_image_set_gen_header’,
>     inlined from ‘mtk_image_set_header’ at tools/mtk_image.c:733:3:
> tools/mtk_image.c:659:2: warning: ‘strncpy’ specified bound 12 equals destination size [-Wstringop-truncation]
>   strncpy(hdr->boot.name, bootname, sizeof(hdr->boot.name));
>   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> In function ‘mtk_brom_parse_imagename’,
>     inlined from ‘mtk_image_check_params’ at tools/mtk_image.c:388:9:
> tools/mtk_image.c:325:5: warning: ‘strncpy’ specified bound 32 equals destination size [-Wstringop-truncation]
>      strncpy(lk_name, val, sizeof(lk_name));
>      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> Replace it with snprintf() to tell compiler how much room we have in the
> destination buffer for source string.
> 
> Fixes: 3b975a147c3c ("tools: MediaTek: add MTK boot header generation to mkimage")
> Cc: Ryder Lee <ryder.lee at mediatek.com>
> Cc: Weijie Gao <weijie.gao at mediatek.com>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko at linux.intel.com>
> ---
>  tools/mtk_image.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/mtk_image.c b/tools/mtk_image.c
> index 2706d2de32..2ca519483d 100644
> --- a/tools/mtk_image.c
> +++ b/tools/mtk_image.c
> @@ -322,7 +322,7 @@ static int mtk_brom_parse_imagename(const char *imagename)
>  				lk = val;
>  
>  			if (!strcmp(key, "lkname"))
> -				strncpy(lk_name, val, sizeof(lk_name));
> +				snprintf(lk_name, sizeof(lk_name), "%s", val);
>  		}
>  
>  		if (next)
> @@ -656,7 +656,7 @@ static void mtk_image_set_gen_header(void *ptr, off_t filesize,
>  		bootname = SDMMC_BOOT_NAME;
>  
>  	/* Generic device header */
> -	strncpy(hdr->boot.name, bootname, sizeof(hdr->boot.name));
> +	snprintf(hdr->boot.name, sizeof(hdr->boot.name), "%s", bootname);
>  	hdr->boot.version = cpu_to_le32(1);
>  	hdr->boot.size = cpu_to_le32(sizeof(hdr->boot));
>  

Hi Andy,

The snprintf adds a NULL char at the end of the string which gives
only 31 available bytes for the lk name filed. But it's OK for this
because almost no one would like to give a name to fill the whole
field. The same applies to the device header.

Reviewed-by: Weijie Gao <weijie.gao at mediatek.com>

Best Regards,

Weijie