[PATCH] drm/nouveau: fix a possible null pointer dereference

[Ma Ke]

In ch7006_encoder_get_modes(), the return value of drm_mode_duplicate() is
used directly in drm_mode_probed_add(), which will lead to a NULL pointer
dereference on failure of drm_mode_duplicate(). Add a check to avoid npd.

Cc: stable@xxxxxxxxxxxxxxx
Fixes: 6ee738610f41 ("drm/nouveau: Add DRM driver for NVIDIA GPUs")
Signed-off-by: Ma Ke <make24@xxxxxxxxxxx>
---
 drivers/gpu/drm/i2c/ch7006_drv.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i2c/ch7006_drv.c b/drivers/gpu/drm/i2c/ch7006_drv.c
index 131512a5f3bd..48bf6e4e8bdb 100644
--- a/drivers/gpu/drm/i2c/ch7006_drv.c
+++ b/drivers/gpu/drm/i2c/ch7006_drv.c
@@ -229,6 +229,7 @@ static int ch7006_encoder_get_modes(struct drm_encoder *encoder,
 {
 	struct ch7006_priv *priv = to_ch7006_priv(encoder);
 	const struct ch7006_mode *mode;
+	struct drm_display_mode *encoder_mode = NULL;
 	int n = 0;
 
 	for (mode = ch7006_modes; mode->mode.clock; mode++) {
@@ -236,8 +237,11 @@ static int ch7006_encoder_get_modes(struct drm_encoder *encoder,
 		    ~mode->valid_norms & 1<<priv->norm)
 			continue;
 
-		drm_mode_probed_add(connector,
-				drm_mode_duplicate(encoder->dev, &mode->mode));
+		encoder_mode = drm_mode_duplicate(encoder->dev, &mode->mode);
+		if (!encoder_mode)
+			return 0;
+
+		drm_mode_probed_add(connector, encoder_mode);
 
 		n++;
 	}
-- 
2.25.1