On 25 August 2025 16.43.06 EEST, Maxime Ripard <mripard@kernel.org> wrote:
>The drm_atomic_get_connector_state() tries to lookup if a connector
>state was already allocated in the global state to return early if it
>was the case. drm_atomic_get_plane_state() and
>drm_atomic_get_crtc_state() behave similarly.
>
>However, and unlike the other two, drm_atomic_get_connector_state() will
>do that lookup after having called drm_modeset_lock(), when the others
>will do it before.
>
>Let's move the early return before the lock to make it consistent.
>
>Signed-off-by: Maxime Ripard <mripard@kernel.org>
>---
> drivers/gpu/drm/drm_atomic.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
>diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
>index cd15cf52f0c9144711da5879da57884674aea9e4..fe21f154e0fa030f85fb3d6d35e2684adcf36e26 100644
>--- a/drivers/gpu/drm/drm_atomic.c
>+++ b/drivers/gpu/drm/drm_atomic.c
>@@ -1128,10 +1128,13 @@ drm_atomic_get_connector_state(struct drm_atomic_state *state,
> struct drm_mode_config *config = &connector->dev->mode_config;
> struct drm_connector_state *connector_state;
>
> WARN_ON(!state->acquire_ctx);
>
>+ if (state->connectors[index].state)
>+ return state->connectors[index].state;
Unlike other DRM objects, connectors are dynamic. There is no guarantee that at this point this array entry exists and it's valid. You might be tampering with the unallocated memory.
>+
> ret = drm_modeset_lock(&config->connection_mutex, state->acquire_ctx);
> if (ret)
> return ERR_PTR(ret);
>
> index = drm_connector_index(connector);
>@@ -1150,13 +1153,10 @@ drm_atomic_get_connector_state(struct drm_atomic_state *state,
> sizeof(*state->connectors) * (alloc - state->num_connector));
>
> state->num_connector = alloc;
> }
>
>- if (state->connectors[index].state)
>- return state->connectors[index].state;
>-
> connector_state = connector->funcs->atomic_duplicate_state(connector);
> if (!connector_state)
> return ERR_PTR(-ENOMEM);
>
> drm_connector_get(connector);
>
With best wishes
Dmitry