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[198.0.35.241]) by smtp.gmail.com with ESMTPSA id g12-20020a170902740c00b001c62b9a51c0sm13314483pll.103.2023.10.02.11.05.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 02 Oct 2023 11:05:15 -0700 (PDT) Date: Mon, 2 Oct 2023 11:05:14 -0700 From: Kees Cook To: Justin Stitt Cc: Arnd Bergmann , Greg Kroah-Hartman , linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: Re: [PATCH] drivers: misc: ti-st: replace deprecated strncpy with strscpy Message-ID: <202310021104.30D14A206F@keescook> References: <20230927-strncpy-drivers-misc-ti-st-st_kim-c-v1-1-29bbdeed1a2c@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230927-strncpy-drivers-misc-ti-st-st_kim-c-v1-1-29bbdeed1a2c@google.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 27, 2023 at 06:17:34AM +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 `kim_data->dev_name` and `kim_gdata->dev_name` to be > NUL-terminated. > > `kim_data->dev_name` seems to not require NUL-padding. > > `kim_gdata` is already zero-allocated and as such does not require > NUL-padding: > | kim_gdata = kzalloc(sizeof(struct kim_data_s), GFP_KERNEL); > > 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. > > 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 only. > --- > drivers/misc/ti-st/st_kim.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/drivers/misc/ti-st/st_kim.c b/drivers/misc/ti-st/st_kim.c > index fe682e0553b2..a034b5d8b585 100644 > --- a/drivers/misc/ti-st/st_kim.c > +++ b/drivers/misc/ti-st/st_kim.c > @@ -590,7 +590,7 @@ static ssize_t store_dev_name(struct device *dev, > { > struct kim_data_s *kim_data = dev_get_drvdata(dev); > pr_debug("storing dev name >%s<", buf); > - strncpy(kim_data->dev_name, buf, count); > + strscpy(kim_data->dev_name, buf, count); This is again the early truncation issue. This should use sizeof(kim_data->dev_name). "buf" will be %NUL terminated already. > pr_debug("stored dev name >%s<", kim_data->dev_name); > return count; > } > @@ -751,7 +751,8 @@ static int kim_probe(struct platform_device *pdev) > } > > /* copying platform data */ > - strncpy(kim_gdata->dev_name, pdata->dev_name, UART_DEV_NAME_LEN); > + strscpy(kim_gdata->dev_name, pdata->dev_name, > + sizeof(kim_gdata->dev_name)); This looks correct. > kim_gdata->flow_cntrl = pdata->flow_cntrl; > kim_gdata->baud_rate = pdata->baud_rate; > pr_info("sysfs entries created\n"); > > --- > base-commit: 6465e260f48790807eef06b583b38ca9789b6072 > change-id: 20230927-strncpy-drivers-misc-ti-st-st_kim-c-e1663a211a0c > > Best regards, > -- > Justin Stitt > -- Kees Cook