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[198.0.35.241]) by smtp.gmail.com with ESMTPSA id l21-20020a170902d35500b001c736370245sm506840plk.54.2023.10.18.16.46.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 18 Oct 2023 16:46:28 -0700 (PDT) Date: Wed, 18 Oct 2023 16:46:28 -0700 From: Kees Cook To: Justin Stitt Cc: Kalle Valo , linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: Re: [PATCH] atmel: replace deprecated strncpy/strcpy with strscpy Message-ID: <202310181643.47D7231BF5@keescook> References: <20231016-strncpy-drivers-net-wireless-atmel-atmel-c-v1-1-038d0e73c402@google.com> Precedence: bulk X-Mailing-List: linux-hardening@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231016-strncpy-drivers-net-wireless-atmel-atmel-c-v1-1-038d0e73c402@google.com> On Mon, Oct 16, 2023 at 08:22:45PM +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. strcpy() is also deprecated [2] and shouldn't be used. Since these are read-only const C strings being copied into a fixed sized buffer, I would actually prefer to just leave these as-is since they're already getting verified by FORTIFY_SOURCE. > We expect priv->firmware_id to be NUL-terminated based on its usage > with seq_printf() and strlen() in atmel.c: > 1420 | seq_printf(m, "%s loaded by host\n", priv->firmware_id); > ... > 3884 | if (strlen(priv->firmware_id) == 0) { > > NUL-padding is not required, which is evident by the usage of a plain > strcpy(): > 3891 | strcpy(priv->firmware_id, "atmel_at76c502.bin"); > > 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. > > Let's also replace hard-coded lengths to be `sizeof(...)` for buffers > that the compiler can detect the size for as this is less error prone. > > Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1] > Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strcpy [2] > Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [3] > Link: https://github.com/KSPP/linux/issues/90 > Cc: linux-hardening@vger.kernel.org > Signed-off-by: Justin Stitt > --- > Note: build-tested only. > > Found with: $ rg "strncpy\(" > --- > drivers/net/wireless/atmel/atmel.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/drivers/net/wireless/atmel/atmel.c b/drivers/net/wireless/atmel/atmel.c > index 7c2d1c588156..199b9144ef63 100644 > --- a/drivers/net/wireless/atmel/atmel.c > +++ b/drivers/net/wireless/atmel/atmel.c > @@ -2011,7 +2011,7 @@ static int atmel_get_name(struct net_device *dev, > union iwreq_data *wrqu, > char *extra) > { > - strcpy(wrqu->name, "IEEE 802.11-DS"); > + strscpy(wrqu->name, "IEEE 802.11-DS", sizeof(wrqu->name)); > return 0; > } > > @@ -2651,8 +2651,7 @@ static int atmel_ioctl(struct net_device *dev, struct ifreq *rq, int cmd) > > priv->firmware = new_firmware; > priv->firmware_length = com.len; > - strncpy(priv->firmware_id, com.id, 31); > - priv->firmware_id[31] = '\0'; > + strscpy(priv->firmware_id, com.id, sizeof(priv->firmware_id)); I wonder why this ever used strncpy -- they're both 32 byte buffer arrays. Regardless, yup, this looks correct to me. Can you respin without the strcpy() changes? -Kees > break; > > case ATMELRD: > @@ -3889,7 +3888,8 @@ static int reset_atmel_card(struct net_device *dev) > printk(KERN_INFO > "%s: if not, use the firmware= module parameter.\n", > dev->name); > - strcpy(priv->firmware_id, "atmel_at76c502.bin"); > + strscpy(priv->firmware_id, "atmel_at76c502.bin", > + sizeof(priv->firmware_id)); > } > err = request_firmware(&fw_entry, priv->firmware_id, priv->sys_dev); > if (err != 0) { > > --- > base-commit: cbf3a2cb156a2c911d8f38d8247814b4c07f49a2 > change-id: 20231016-strncpy-drivers-net-wireless-atmel-atmel-c-7ca951cf7cfa > > Best regards, > -- > Justin Stitt > -- Kees Cook