drm/radeon: use eld_mutex to protect access to connector->eld

[ Upstream commit b54c14f824 ]

Reading access to connector->eld can happen at the same time the
drm_edid_to_eld() updates the data. Take the newly added eld_mutex in
order to protect connector->eld from concurrent access.

Reviewed-by: Maxime Ripard <mripard@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20241206-drm-connector-eld-mutex-v2-8-c9bce1ee8bea@linaro.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/gpu/drm/radeon/radeon_audio.c

@@ -773,8 +773,10 @@ static int radeon_audio_component_get_eld(struct device *kdev, int port,
 		if (!dig->pin || dig->pin->id != port)
 			continue;
 		*enabled = true;
+		mutex_lock(&connector->eld_mutex);
 		ret = drm_eld_size(connector->eld);
 		memcpy(buf, connector->eld, min(max_bytes, ret));
+		mutex_unlock(&connector->eld_mutex);
 		break;
 	}