[PATCH 3/4] drm: make drm_atomic_set_mode_prop_for_crtc() more reliable

[Tomi Valkeinen]

drm_atomic_set_mode_prop_for_crtc() has a few issues:

- it doesn't clear the state->mode, so old data may be left there when a
  new mode is set.
- if an error happens, state->mode is left in a partially updated state.

This patch improves the situation by:

- bail out early if blob is of wrong length.
- construct drm_display_mode first in an initialized local variable, and
  copy it to state->mode only when we know the call has succeeded.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen at ti.com>
---
 drivers/gpu/drm/drm_atomic.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index 3ff1ed7b33db..5bfecb2bbedf 100644
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -348,16 +348,24 @@ int drm_atomic_set_mode_prop_for_crtc(struct drm_crtc_state *state,
 	if (blob == state->mode_blob)
 		return 0;
 
+	if (blob && blob->length != sizeof(struct drm_mode_modeinfo))
+		return -EINVAL;
+
 	drm_property_unreference_blob(state->mode_blob);
 	state->mode_blob = NULL;
 
 	if (blob) {
-		if (blob->length != sizeof(struct drm_mode_modeinfo) ||
-		    drm_mode_convert_umode(&state->mode,
-		                           (const struct drm_mode_modeinfo *)
-		                            blob->data))
+		const struct drm_mode_modeinfo *umode =
+			(const struct drm_mode_modeinfo *)blob->data;
+		struct drm_display_mode mode;
+
+		memset(&mode, 0, sizeof(mode));
+
+		if (drm_mode_convert_umode(&mode, umode))
 			return -EINVAL;
 
+		state->mode = mode;
+
 		state->mode_blob = drm_property_reference_blob(blob);
 		state->enable = true;
 		DRM_DEBUG_ATOMIC("Set [MODE:%s] for CRTC state %p\n",
-- 
2.5.0