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[198.0.35.241]) by smtp.gmail.com with ESMTPSA id x10-20020a170902820a00b001c1f161949fsm18920114pln.96.2023.09.30.10.57.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 30 Sep 2023 10:57:07 -0700 (PDT) Date: Sat, 30 Sep 2023 10:57:03 -0700 From: Kees Cook To: Jonathan Cameron Cc: Justin Stitt , Lars-Peter Clausen , Maxime Coquelin , Alexandre Torgue , linux-iio@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: Re: [PATCH] iio: adc: stm32-adc: replace deprecated strncpy Message-ID: <202309301056.5A21C37D5@keescook> References: <20230921-strncpy-drivers-iio-adc-stm32-adc-c-v1-1-c50eca098597@google.com> <202309232006.690F89A@keescook> <20230930184118.73d7465a@jic23-huawei> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230930184118.73d7465a@jic23-huawei> Precedence: bulk List-ID: X-Mailing-List: linux-iio@vger.kernel.org On Sat, Sep 30, 2023 at 06:41:18PM +0100, Jonathan Cameron wrote: > On Sat, 23 Sep 2023 20:15:09 -0700 > Kees Cook 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@vger.kernel.org > > > Signed-off-by: Justin Stitt > > > --- > > > 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()" Thanks! -Kees -- Kees Cook