Re: [PATCH v2] hamradio: replace deprecated strncpy with strscpy_pad
From: Kees Cook
Date: Mon Oct 16 2023 - 15:42:28 EST
On Mon, Oct 16, 2023 at 06:42:42PM +0000, Justin Stitt wrote:
> strncpy() is deprecated for use on NUL-terminated destination strings
> [1] and as such we should prefer more robust and less ambiguous string
> interfaces.
>
> We expect both hi.data.modename and hi.data.drivername to be
> NUL-terminated based on its usage with sprintf:
> | sprintf(hi.data.modename, "%sclk,%smodem,fclk=%d,bps=%d%s",
> | bc->cfg.intclk ? "int" : "ext",
> | bc->cfg.extmodem ? "ext" : "int", bc->cfg.fclk, bc->cfg.bps,
> | bc->cfg.loopback ? ",loopback" : "");
>
> Note that this data is copied out to userspace with:
> | if (copy_to_user(data, &hi, sizeof(hi)))
> ... however, the data was also copied FROM the user here:
> | if (copy_from_user(&hi, data, sizeof(hi)))
>
> Considering the above, a suitable replacement is strscpy_pad() as it
> guarantees NUL-termination on the destination buffer while also
> NUL-padding (which is good+wanted behavior when copying data to
> userspace).
>
> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
> Link: https://github.com/KSPP/linux/issues/90
> Cc: linux-hardening@xxxxxxxxxxxxxxx
> Signed-off-by: Justin Stitt <justinstitt@xxxxxxxxxx>
Thanks!
Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
--
Kees Cook