Re: [PATCH] HID: prodikeys: refactor deprecated strncpy

[Kees Cook]

On Thu, Sep 14, 2023 at 10:20:55PM +0000, Justin Stitt wrote:
> `strncpy` is deprecated for use on NUL-terminated destination strings [1].
> 
> We should prefer more robust and less ambiguous string interfaces.
> 
> A suitable replacement is `strscpy` [2] due to the fact that it guarantees
> NUL-termination on the destination buffer without unnecessarily NUL-padding.
> 
> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
> Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
> Link: https://github.com/KSPP/linux/issues/90
> Cc: linux-hardening@xxxxxxxxxxxxxxx
> Signed-off-by: Justin Stitt <justinstitt@xxxxxxxxxx>
> ---
> Note: for some reason if NUL-padding is needed let's opt for `strscpy_pad()`
> ---
>  drivers/hid/hid-prodikeys.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/hid/hid-prodikeys.c b/drivers/hid/hid-prodikeys.c
> index e4e9471d0f1e..c16d2ba6ea16 100644
> --- a/drivers/hid/hid-prodikeys.c
> +++ b/drivers/hid/hid-prodikeys.c
> @@ -639,9 +639,9 @@ static int pcmidi_snd_initialise(struct pcmidi_snd *pm)
>  		goto fail;
>  	}
>  
> -	strncpy(card->driver, shortname, sizeof(card->driver));
> -	strncpy(card->shortname, shortname, sizeof(card->shortname));
> -	strncpy(card->longname, longname, sizeof(card->longname));
> +	strscpy(card->driver, shortname, sizeof(card->driver));
> +	strscpy(card->shortname, shortname, sizeof(card->shortname));
> +	strscpy(card->longname, longname, sizeof(card->longname));

"card" is already kzalloc()ed so no _pad() is needed, good.

>  
>  	/* Set up rawmidi */
>  	err = snd_rawmidi_new(card, card->shortname, 0,
> @@ -652,7 +652,7 @@ static int pcmidi_snd_initialise(struct pcmidi_snd *pm)
>  		goto fail;
>  	}
>  	pm->rwmidi = rwmidi;
> -	strncpy(rwmidi->name, card->shortname, sizeof(rwmidi->name));
> +	strscpy(rwmidi->name, card->shortname, sizeof(rwmidi->name));
>  	rwmidi->info_flags = SNDRV_RAWMIDI_INFO_INPUT;
>  	rwmidi->private_data = pm;

Same here.

Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>

-Kees

>  
> 
> ---
> base-commit: 3669558bdf354cd352be955ef2764cde6a9bf5ec
> change-id: 20230914-strncpy-drivers-hid-hid-prodikeys-c-cf42614a21d4
> 
> Best regards,
> --
> Justin Stitt <justinstitt@xxxxxxxxxx>
> 

-- 
Kees Cook