diff mbox series

net: mdio: replace deprecated strncpy with strscpy

Message ID 20231012-strncpy-drivers-net-mdio-mdio-gpio-c-v1-1-ab9b06cfcdab@google.com
State New
Headers
Series net: mdio: replace deprecated strncpy with strscpy |

Commit Message

Justin Stitt Oct. 12, 2023, 9:43 p.m. UTC 
  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 new_bus->id to be NUL-terminated but not NUL-padded based on
its prior assignment through snprintf:
|       snprintf(new_bus->id, MII_BUS_ID_SIZE, "gpio-%x", bus_id);

Due to this, 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 <justinstitt@google.com>
---
Note: build-tested only.

Found with: $ rg "strncpy\("
---
 drivers/net/mdio/mdio-gpio.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)


---
base-commit: cbf3a2cb156a2c911d8f38d8247814b4c07f49a2
change-id: 20231012-strncpy-drivers-net-mdio-mdio-gpio-c-bddd9ed0c630

Best regards,
--
Justin Stitt <justinstitt@google.com>

Comments

Andrew Lunn Oct. 12, 2023, 9:55 p.m. UTC | #1 
On Thu, Oct 12, 2023 at 09:43:02PM +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 new_bus->id to be NUL-terminated but not NUL-padded based on
> its prior assignment through snprintf:
> |       snprintf(new_bus->id, MII_BUS_ID_SIZE, "gpio-%x", bus_id);
> 
> Due to this, 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 <justinstitt@google.com>

Reviewed-by: Andrew Lunn <andrew@lunn.ch>

    Andrew
Kees Cook Oct. 16, 2023, 7:40 p.m. UTC | #2 
On Thu, Oct 12, 2023 at 09:43:02PM +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 new_bus->id to be NUL-terminated but not NUL-padded based on
> its prior assignment through snprintf:
> |       snprintf(new_bus->id, MII_BUS_ID_SIZE, "gpio-%x", bus_id);
> 
> Due to this, 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 <justinstitt@google.com>
> ---
> Note: build-tested only.
> 
> Found with: $ rg "strncpy\("
> ---
>  drivers/net/mdio/mdio-gpio.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/mdio/mdio-gpio.c b/drivers/net/mdio/mdio-gpio.c
> index 0fb3c2de0845..a1718d646504 100644
> --- a/drivers/net/mdio/mdio-gpio.c
> +++ b/drivers/net/mdio/mdio-gpio.c
> @@ -125,7 +125,7 @@ static struct mii_bus *mdio_gpio_bus_init(struct device *dev,
>  	if (bus_id != -1)
>  		snprintf(new_bus->id, MII_BUS_ID_SIZE, "gpio-%x", bus_id);
>  	else
> -		strncpy(new_bus->id, "gpio", MII_BUS_ID_SIZE);
> +		strscpy(new_bus->id, "gpio", sizeof(new_bus->id));

struct mii_bus {
	...
        char id[MII_BUS_ID_SIZE];

Yup, looks good. (I wonder about changing to sizeof() in the snprintf()
above it, but for a strscpy() refactor, I think this is fine.)

Reviewed-by: Kees Cook <keescook@chromium.org>
Kees Cook Nov. 30, 2023, 10 p.m. UTC | #3 
On Thu, 12 Oct 2023 21:43:02 +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 new_bus->id to be NUL-terminated but not NUL-padded based on
> its prior assignment through snprintf:
> |       snprintf(new_bus->id, MII_BUS_ID_SIZE, "gpio-%x", bus_id);
> 
> [...]

Applied to for-next/hardening, thanks!

[1/1] net: mdio: replace deprecated strncpy with strscpy
      https://git.kernel.org/kees/c/3247bb945786

Take care,
Jakub Kicinski Dec. 1, 2023, 6:43 a.m. UTC | #4 
On Thu, 30 Nov 2023 14:00:33 -0800 Kees Cook wrote:
> Applied to for-next/hardening, thanks!
> 
> [1/1] net: mdio: replace deprecated strncpy with strscpy
>       https://git.kernel.org/kees/c/3247bb945786

newer version of this was posted...
Kees Cook Dec. 1, 2023, 6:22 p.m. UTC | #5 
On Thu, Nov 30, 2023 at 10:43:34PM -0800, Jakub Kicinski wrote:
> On Thu, 30 Nov 2023 14:00:33 -0800 Kees Cook wrote:
> > Applied to for-next/hardening, thanks!
> > 
> > [1/1] net: mdio: replace deprecated strncpy with strscpy
> >       https://git.kernel.org/kees/c/3247bb945786
> 
> newer version of this was posted...

Hm, I didn't see anything land for this for the other with the same
subject. I've dropped both from my tree now.

Justin, can you chase down the mdio patches?
diff mbox series

Patch

diff --git a/drivers/net/mdio/mdio-gpio.c b/drivers/net/mdio/mdio-gpio.c
index 0fb3c2de0845..a1718d646504 100644
--- a/drivers/net/mdio/mdio-gpio.c
+++ b/drivers/net/mdio/mdio-gpio.c
@@ -125,7 +125,7 @@  static struct mii_bus *mdio_gpio_bus_init(struct device *dev,
 	if (bus_id != -1)
 		snprintf(new_bus->id, MII_BUS_ID_SIZE, "gpio-%x", bus_id);
 	else
-		strncpy(new_bus->id, "gpio", MII_BUS_ID_SIZE);
+		strscpy(new_bus->id, "gpio", sizeof(new_bus->id));
 
 	if (pdata) {
 		new_bus->phy_mask = pdata->phy_mask;