[PATCH v2] drm/gma500: refactor deprecated strncpy

[PATCH v2] drm/gma500: refactor deprecated strncpy

[Justin Stitt]

`strncpy` is deprecated for use on NUL-terminated destination strings [1].

We should prefer more robust and less ambiguous string interfaces.

Since `chan->base.name` is expected to be NUL-terminated, a suitable
replacement is `strscpy` [2] due to the fact that it guarantees
NUL-termination on the destination buffer without also unnecessarily
NUL-padding (since `chan` is kzalloc'd already).

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>
---
Changes in v2:
- use sizeof() instead of I2C_NAME_SIZE (thanks Kees, Patrik)
- Link to v1: https://lore.kernel.org/r/20230914-drivers-gpu-drm-gma500-oaktrail_lvds_i2c-c-v1-1-0a53a076ce20@google.com
---
 drivers/gpu/drm/gma500/oaktrail_lvds_i2c.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/gma500/oaktrail_lvds_i2c.c b/drivers/gpu/drm/gma500/oaktrail_lvds_i2c.c
index 06b5b2d70d48..939c53fd09e8 100644
--- a/drivers/gpu/drm/gma500/oaktrail_lvds_i2c.c
+++ b/drivers/gpu/drm/gma500/oaktrail_lvds_i2c.c
@@ -141,7 +141,7 @@ struct gma_i2c_chan *oaktrail_lvds_i2c_init(struct drm_device *dev)
 
 	chan->drm_dev = dev;
 	chan->reg = dev_priv->lpc_gpio_base;
-	strncpy(chan->base.name, "gma500 LPC",  I2C_NAME_SIZE - 1);
+	strscpy(chan->base.name, "gma500 LPC",  sizeof(chan->base.name));
 	chan->base.owner = THIS_MODULE;
 	chan->base.algo_data = &chan->algo;
 	chan->base.dev.parent = dev->dev;

---
base-commit: 3669558bdf354cd352be955ef2764cde6a9bf5ec
change-id: 20230914-drivers-gpu-drm-gma500-oaktrail_lvds_i2c-c-a53c6d8bd62f

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

Re: [PATCH v2] drm/gma500: refactor deprecated strncpy

[Kees Cook]

On Tue, Sep 19, 2023 at 04:41:16AM +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.
> 
> Since `chan->base.name` is expected to be NUL-terminated, a suitable
> replacement is `strscpy` [2] due to the fact that it guarantees
> NUL-termination on the destination buffer without also unnecessarily
> NUL-padding (since `chan` is kzalloc'd already).
> 
> 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>

Thanks, looks good. If a v3 is needed, Subject can be improved to be
"...: Replace strncpy with strscpy".

Reviewed-by: Kees Cook <keescook@chromium.org>

-- 
Kees Cook

Re: [PATCH v2] drm/gma500: refactor deprecated strncpy

[Patrik Jakobsson]

On Tue, Sep 19, 2023 at 04:41:16AM +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.
> 
> Since `chan->base.name` is expected to be NUL-terminated, a suitable
> replacement is `strscpy` [2] due to the fact that it guarantees
> NUL-termination on the destination buffer without also unnecessarily
> NUL-padding (since `chan` is kzalloc'd already).
> 
> 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>

Applied to drm-misc-next.

Thanks
Patrik

> ---
> Changes in v2:
> - use sizeof() instead of I2C_NAME_SIZE (thanks Kees, Patrik)
> - Link to v1: https://lore.kernel.org/r/20230914-drivers-gpu-drm-gma500-oaktrail_lvds_i2c-c-v1-1-0a53a076ce20@google.com
> ---
>  drivers/gpu/drm/gma500/oaktrail_lvds_i2c.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/gma500/oaktrail_lvds_i2c.c b/drivers/gpu/drm/gma500/oaktrail_lvds_i2c.c
> index 06b5b2d70d48..939c53fd09e8 100644
> --- a/drivers/gpu/drm/gma500/oaktrail_lvds_i2c.c
> +++ b/drivers/gpu/drm/gma500/oaktrail_lvds_i2c.c
> @@ -141,7 +141,7 @@ struct gma_i2c_chan *oaktrail_lvds_i2c_init(struct drm_device *dev)
>  
>  	chan->drm_dev = dev;
>  	chan->reg = dev_priv->lpc_gpio_base;
> -	strncpy(chan->base.name, "gma500 LPC",  I2C_NAME_SIZE - 1);
> +	strscpy(chan->base.name, "gma500 LPC",  sizeof(chan->base.name));
>  	chan->base.owner = THIS_MODULE;
>  	chan->base.algo_data = &chan->algo;
>  	chan->base.dev.parent = dev->dev;
> 
> ---
> base-commit: 3669558bdf354cd352be955ef2764cde6a9bf5ec
> change-id: 20230914-drivers-gpu-drm-gma500-oaktrail_lvds_i2c-c-a53c6d8bd62f
> 
> Best regards,
> --
> Justin Stitt <justinstitt@google.com>
>