On Sat, 30 Sep 2023 10:57:03 -0700
Kees Cook <keescook@xxxxxxxxxxxx> wrote:
> On Sat, Sep 30, 2023 at 06:41:18PM +0100, Jonathan Cameron wrote:
> > 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?
>
> I would use "iio: adc: stm32-adc: Replace deprecated strncpy() with strscpy()"
Makes sense. I also used the () approach to identify functions in the
text of the patch description instead of `funcname`
Applied with those tweaks to the togreg branch of iio.git but initially
just pushed out as testing to let 0-day take a look at it.
Thanks,
Jonathan
>
> Thanks!
>
> -Kees
>
