Nouveau - Jun 2023 - [PATCH] drm/nouveau/dp: check for NULL nv_connector->native_mode

Add checking for NULL before calling nouveau_connector_detect_depth() in
nouveau_connector_get_modes() function because nv_connector->native_mode
could be dereferenced there since connector pointer passed to
nouveau_connector_detect_depth() and the same value of
nv_connector->native_mode is used there.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: d4c2c99bdc83 ("drm/nouveau/dp: remove broken display depth function,
use the improved one")

Signed-off-by: Natalia Petrova <n.petrova at fintech.ru>
---
 drivers/gpu/drm/nouveau/nouveau_connector.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_connector.c
b/drivers/gpu/drm/nouveau/nouveau_connector.c
index 086b66b60d91..5dbf025e6873 100644
--- a/drivers/gpu/drm/nouveau/nouveau_connector.c
+++ b/drivers/gpu/drm/nouveau/nouveau_connector.c
@@ -966,7 +966,7 @@ nouveau_connector_get_modes(struct drm_connector *connector)
 	/* Determine display colour depth for everything except LVDS now,
 	 * DP requires this before mode_valid() is called.
 	 */
-	if (connector->connector_type != DRM_MODE_CONNECTOR_LVDS)
+	if (connector->connector_type != DRM_MODE_CONNECTOR_LVDS &&
nv_connector->native_mode)
 		nouveau_connector_detect_depth(connector);
 
 	/* Find the native mode if this is a digital panel, if we didn't
@@ -987,7 +987,7 @@ nouveau_connector_get_modes(struct drm_connector *connector)
 	 * "native" mode as some VBIOS tables require us to use the
 	 * pixel clock as part of the lookup...
 	 */
-	if (connector->connector_type == DRM_MODE_CONNECTOR_LVDS)
+	if (connector->connector_type == DRM_MODE_CONNECTOR_LVDS &&
nv_connector->native_mode)
 		nouveau_connector_detect_depth(connector);
 
 	if (nv_encoder->dcb->type == DCB_OUTPUT_TV)
-- 
2.34.1

Reviewed-by: Lyude Paul <lyude at redhat.com>

Will push upstream in a bit

On Fri, 2023-05-12 at 14:15 +0300, Natalia Petrova
wrote:
> Add checking for NULL before calling nouveau_connector_detect_depth() in
> nouveau_connector_get_modes() function because nv_connector->native_mode
> could be dereferenced there since connector pointer passed to
> nouveau_connector_detect_depth() and the same value of
> nv_connector->native_mode is used there.
> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Fixes: d4c2c99bdc83 ("drm/nouveau/dp: remove broken display depth
function, use the improved one")
> 
> Signed-off-by: Natalia Petrova <n.petrova at fintech.ru>
> ---
>  drivers/gpu/drm/nouveau/nouveau_connector.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/nouveau/nouveau_connector.c
b/drivers/gpu/drm/nouveau/nouveau_connector.c
> index 086b66b60d91..5dbf025e6873 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_connector.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_connector.c
> @@ -966,7 +966,7 @@ nouveau_connector_get_modes(struct drm_connector
*connector)
>  	/* Determine display colour depth for everything except LVDS now,
>  	 * DP requires this before mode_valid() is called.
>  	 */
> -	if (connector->connector_type != DRM_MODE_CONNECTOR_LVDS)
> +	if (connector->connector_type != DRM_MODE_CONNECTOR_LVDS &&
nv_connector->native_mode)
>  		nouveau_connector_detect_depth(connector);
>  
>  	/* Find the native mode if this is a digital panel, if we didn't
> @@ -987,7 +987,7 @@ nouveau_connector_get_modes(struct drm_connector
*connector)
>  	 * "native" mode as some VBIOS tables require us to use the
>  	 * pixel clock as part of the lookup...
>  	 */
> -	if (connector->connector_type == DRM_MODE_CONNECTOR_LVDS)
> +	if (connector->connector_type == DRM_MODE_CONNECTOR_LVDS &&
nv_connector->native_mode)
>  		nouveau_connector_detect_depth(connector);
>  
>  	if (nv_encoder->dcb->type == DCB_OUTPUT_TV)
-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat