RE: [PATCH] net: wireless: brcm80211: brcmfmac: dhd_sdio.c: Cleaning up missing null-terminate in conjunction with strncpy

[David Laight <David.Laight@ACULAB.COM>]

From: Rickard Strandqvist
> Replacing strncpy with strlcpy to avoid strings that lacks null terminate.
> And changed from using strncpy to strlcpy to simplify code.

I think you should return an error if the strings get truncated.
Silent truncation is going to lead to issues at some point in the future
(in some places).

> Signed-off-by: Rickard Strandqvist <rickard_strandqvist@spectrumdigital.se>
> ---
>  drivers/net/wireless/brcm80211/brcmfmac/dhd_sdio.c |   25 ++++++++++----------
>  1 file changed, 12 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/net/wireless/brcm80211/brcmfmac/dhd_sdio.c
> b/drivers/net/wireless/brcm80211/brcmfmac/dhd_sdio.c
> index f55f625..d20d4e6 100644
> --- a/drivers/net/wireless/brcm80211/brcmfmac/dhd_sdio.c
> +++ b/drivers/net/wireless/brcm80211/brcmfmac/dhd_sdio.c
> @@ -670,7 +670,6 @@ static int brcmf_sdio_get_fwnames(struct brcmf_chip *ci,
>  				  struct brcmf_sdio_dev *sdiodev)
>  {
>  	int i;
> -	uint fw_len, nv_len;
>  	char end;
> 
>  	for (i = 0; i < ARRAY_SIZE(brcmf_fwname_data); i++) {
> @@ -684,25 +683,25 @@ static int brcmf_sdio_get_fwnames(struct brcmf_chip *ci,
>  		return -ENODEV;
>  	}
> 
> -	fw_len = sizeof(sdiodev->fw_name) - 1;
> -	nv_len = sizeof(sdiodev->nvram_name) - 1;
>  	/* check if firmware path is provided by module parameter */
>  	if (brcmf_firmware_path[0] != '\0') {
> -		strncpy(sdiodev->fw_name, brcmf_firmware_path, fw_len);
> -		strncpy(sdiodev->nvram_name, brcmf_firmware_path, nv_len);
> -		fw_len -= strlen(sdiodev->fw_name);
> -		nv_len -= strlen(sdiodev->nvram_name);
> +		strlcpy(sdiodev->fw_name, brcmf_firmware_path,
> +			sizeof(sdiodev->fw_name));
> +		strlcpy(sdiodev->nvram_name, brcmf_firmware_path,
> +			sizeof(sdiodev->nvram_name));
> 
>  		end = brcmf_firmware_path[strlen(brcmf_firmware_path) - 1];

If you are doing a strlen() here, you could use the length for the copy
and/or use it to avoid the strcat().

>  		if (end != '/') {
> -			strncat(sdiodev->fw_name, "/", fw_len);
> -			strncat(sdiodev->nvram_name, "/", nv_len);
> -			fw_len--;
> -			nv_len--;
> +			strlcat(sdiodev->fw_name, "/",
> +				sizeof(sdiodev->fw_name));
> +			strlcat(sdiodev->nvram_name, "/",
> +				sizeof(sdiodev->nvram_name));
>  		}
>  	}
> -	strncat(sdiodev->fw_name, brcmf_fwname_data[i].bin, fw_len);
> -	strncat(sdiodev->nvram_name, brcmf_fwname_data[i].nv, nv_len);
> +	strlcat(sdiodev->fw_name, brcmf_fwname_data[i].bin,
> +		sizeof(sdiodev->fw_name));
> +	strlcat(sdiodev->nvram_name, brcmf_fwname_data[i].nv,
> +		sizeof(sdiodev->nvram_name));

I assume something ensures that fw_name[0] == 0 here.

	David