Nouveau - Oct 2023 - [PATCH] drm/nouveau/dispnv04: fix a possible null pointer dereference

In nv17_tv_get_hd_modes(), the return value of drm_mode_duplicate()
is assigned to mode, which will lead to a NULL pointer dereference on
failure of drm_mode_duplicate(). The same applies to drm_cvt_mode().
Add a check to avoid null pointer dereference.

Signed-off-by: Ma Ke <make_ruc2021 at 163.com>
---
 drivers/gpu/drm/nouveau/dispnv04/tvnv17.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/nouveau/dispnv04/tvnv17.c
b/drivers/gpu/drm/nouveau/dispnv04/tvnv17.c
index 670c9739e5e1..9c3dc9a5bb46 100644
--- a/drivers/gpu/drm/nouveau/dispnv04/tvnv17.c
+++ b/drivers/gpu/drm/nouveau/dispnv04/tvnv17.c
@@ -258,6 +258,8 @@ static int nv17_tv_get_hd_modes(struct drm_encoder *encoder,
 		if (modes[i].hdisplay == output_mode->hdisplay &&
 		    modes[i].vdisplay == output_mode->vdisplay) {
 			mode = drm_mode_duplicate(encoder->dev, output_mode);
+			if (!mode)
+				continue;
 			mode->type |= DRM_MODE_TYPE_PREFERRED;
 
 		} else {
@@ -265,6 +267,8 @@ static int nv17_tv_get_hd_modes(struct drm_encoder *encoder,
 					    modes[i].vdisplay, 60, false,
 					    (output_mode->flags &
 					     DRM_MODE_FLAG_INTERLACE), false);
+			if (!mode)
+				continue;
 		}
 
 		/* CVT modes are sometimes unsuitable... */
-- 
2.37.2

On 10/13/23 03:18, Ma Ke wrote:
> In nv17_tv_get_hd_modes(), the return value of drm_mode_duplicate()
> is assigned to mode, which will lead to a NULL pointer dereference on
> failure of drm_mode_duplicate(). The same applies to drm_cvt_mode().
> Add a check to avoid null pointer dereference.
> 
> Signed-off-by: Ma Ke <make_ruc2021 at 163.com>
For this one and the previous patch, please add the corresponding
'Fixes:' [1] and stable [2] tags and split the commits accordingly.

[1]
https://www.kernel.org/doc/html/latest/process/submitting-patches.html#using-reported-by-tested-by-reviewed-by-suggested-by-and-fixes
[2] https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
> ---
>   drivers/gpu/drm/nouveau/dispnv04/tvnv17.c | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/gpu/drm/nouveau/dispnv04/tvnv17.c
b/drivers/gpu/drm/nouveau/dispnv04/tvnv17.c
> index 670c9739e5e1..9c3dc9a5bb46 100644
> --- a/drivers/gpu/drm/nouveau/dispnv04/tvnv17.c
> +++ b/drivers/gpu/drm/nouveau/dispnv04/tvnv17.c
> @@ -258,6 +258,8 @@ static int nv17_tv_get_hd_modes(struct drm_encoder
*encoder,
>   		if (modes[i].hdisplay == output_mode->hdisplay &&
>   		    modes[i].vdisplay == output_mode->vdisplay) {
>   			mode = drm_mode_duplicate(encoder->dev, output_mode);
> +			if (!mode)
> +				continue;
>   			mode->type |= DRM_MODE_TYPE_PREFERRED;
>   
>   		} else {
> @@ -265,6 +267,8 @@ static int nv17_tv_get_hd_modes(struct drm_encoder
*encoder,
>   					    modes[i].vdisplay, 60, false,
>   					    (output_mode->flags &
>   					     DRM_MODE_FLAG_INTERLACE), false);
> +			if (!mode)
> +				continue;
>   		}
>   
>   		/* CVT modes are sometimes unsuitable... */