On Sat, 23 Sep 2023 20:15:09 -0700
Kees Cook <keescook@xxxxxxxxxxxx> wrote:
> On Thu, Sep 21, 2023 at 04:54:00AM +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.
> >
> > We expect adc->chan_name[val] to be NUL-terminated based on ch_name's
> > use within functions that expect NUL-terminated strings like strncmp and
> > printf-likes:
> > | if (!strncmp(stm32_adc_ic[i].name, ch_name, STM32_ADC_CH_SZ)) {
> > | /* Check internal channel availability */
> > | switch (i) {
> > | case STM32_ADC_INT_CH_VDDCORE:
> > | if (!adc->cfg->regs->or_vddcore.reg)
> > | dev_warn(&indio_dev->dev,
> > | "%s channel not available\n", ch_name);
> > ...
> >
> > There is no evidence that NUL-padding is needed either.
>
> Agreed -- it's used as a C string everywhere I can see.
>
> >
> > Considering the above, a suitable replacement is `strscpy` [2] due to
> > the fact that it guarantees NUL-termination on the destination buffer
> > without unnecessarily NUL-padding. If, for any reason, NUL-padding _is_
> > required we should go for `strscpy_pad`.
> >
> > 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: build-tested
> > ---
> > drivers/iio/adc/stm32-adc.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/iio/adc/stm32-adc.c b/drivers/iio/adc/stm32-adc.c
> > index f7613efb870d..9cdcf396d901 100644
> > --- a/drivers/iio/adc/stm32-adc.c
> > +++ b/drivers/iio/adc/stm32-adc.c
> > @@ -2209,7 +2209,7 @@ static int stm32_adc_generic_chan_init(struct iio_dev *indio_dev,
> > ret = -EINVAL;
> > goto err;
> > }
> > - strncpy(adc->chan_name[val], name, STM32_ADC_CH_SZ);
> > + strscpy(adc->chan_name[val], name, STM32_ADC_CH_SZ);
>
> I still prefer sizeof($dst), but yes, these are the same:
>
> char chan_name[STM32_ADC_CH_MAX][STM32_ADC_CH_SZ];
>
> If this needs a v2, please improve the Subject, but it is technically
> correct, so:
Hi Kees,
I can tweak the subject whilst applying. What did you have in mind
as a better one?
Jonathan
>
> Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
>
> :)
>
> -Kees
>
