Hi
Am 15.09.25 um 13:27 schrieb Maxime Ripard:
On Tue, Sep 02, 2025 at 03:18:17PM +0200, Thomas Zimmermann wrote:
Hi
Am 02.09.25 um 10:32 schrieb Maxime Ripard:
Bridges implement their state using a drm_private_obj and an
hand-crafted reset implementation.
Since drm_private_obj doesn't have a set of reset helper like the other
states, __drm_atomic_helper_bridge_reset() was initializing both the
drm_private_state and the drm_bridge_state structures.
This initialization however was missing the drm_private_state.obj
pointer to the drm_private_obj the state was allocated for, creating a
NULL pointer dereference when trying to access it.
Fixes: 751465913f04 ("drm/bridge: Add a drm_bridge_state object")
Signed-off-by: Maxime Ripard <mrip...@kernel.org>
---
drivers/gpu/drm/drm_atomic_state_helper.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/drivers/gpu/drm/drm_atomic_state_helper.c
b/drivers/gpu/drm/drm_atomic_state_helper.c
index
7142e163e618ea0d7d9d828e1bd9ff2a6ec0dfeb..b962c342b16aabf4e3bea52a914e5deb1c2080ce
100644
--- a/drivers/gpu/drm/drm_atomic_state_helper.c
+++ b/drivers/gpu/drm/drm_atomic_state_helper.c
@@ -707,10 +707,17 @@ void drm_atomic_helper_connector_destroy_state(struct
drm_connector *connector,
__drm_atomic_helper_connector_destroy_state(state);
kfree(state);
}
EXPORT_SYMBOL(drm_atomic_helper_connector_destroy_state);
+static void __drm_atomic_helper_private_obj_reset(struct drm_private_obj *obj,
+ struct drm_private_state
*state)
+{
+ memset(state, 0, sizeof(*state));
This argument is guaranteed to be zero'd, I think. No need for a memset.
+ state->obj = obj;
+}
+
/**
* __drm_atomic_helper_private_obj_duplicate_state - copy atomic private
state
* @obj: CRTC object
* @state: new private object state
*
@@ -796,10 +803,11 @@ EXPORT_SYMBOL(drm_atomic_helper_bridge_destroy_state);
*/
void __drm_atomic_helper_bridge_reset(struct drm_bridge *bridge,
struct drm_bridge_state *state)
{
memset(state, 0, sizeof(*state));
Another unnecessary memset?
I guess the two can be seen as redundant, but I'd argue the one in
__drm_atomic_helper_private_obj_reset should still be there.
What guarantees that the pointer points to a zero'd structure?
We only call this helper after allocation AFAICT. And the DRM APIs
already assume that allocation clears to zero.
Best regards
Thomas
Maxime
--
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)
