From 280dc0e145b2b04fd1b414e512118ce6eb9b93e8 Mon Sep 17 00:00:00 2001 From: Jon Hunter Date: Wed, 18 May 2016 16:37:36 +0100 Subject: [PATCH] drm/tegra: Fix crash caused by reference count imbalance Commit d2307dea14a4 ("drm/atomic: use connector references (v3)") added reference counting for DRM connectors and this caused a crash when exercising system suspend on Tegra114 Dalmore. The Tegra DSI driver implements a Tegra specific function, tegra_dsi_connector_duplicate_state(), to duplicate the connector state and destroys the state using the generic helper function, drm_atomic_helper_connector_destroy_state(). Following commit d2307dea14a4 ("drm/atomic: use connector references (v3)") there is now an imbalance in the connector reference count because the Tegra function to duplicate state does not take a reference when duplicating the state information. However, the generic helper function to destroy the state information assumes a reference has been taken and during system suspend, when the connector state is destroyed, this leads to a crash because we attempt to put the reference for an object that has already been freed. Fix this by calling __drm_atomic_helper_connector_duplicate_state() from tegra_dsi_connector_duplicate_state() to ensure that we take a reference on a connector if crtc is set. Note that this will also copy the connector state a 2nd time, but this should be harmless. By fixing tegra_dsi_connector_duplicate_state() to take a reference, although a crash was no longer seen, it was then observed that after each system suspend-resume cycle, the reference would be one greater than before the suspend-resume cycle. Following commit d2307dea14a4 ("drm/atomic: use connector references (v3)"), it was found that we also need to put the reference when calling the function tegra_dsi_connector_reset() before freeing the state. Fix this by updating tegra_dsi_connector_reset() to call the function __drm_atomic_helper_connector_destroy_state() in order to put the reference for the connector. Fixes: d2307dea14a4 ("drm/atomic: use connector references (v3)") Signed-off-by: Jon Hunter Reviewed-by: Daniel Vetter Acked-by: Thierry Reding Signed-off-by: Daniel Vetter Link: http://patchwork.freedesktop.org/patch/msgid/1463585856-16606-1-git-send-email-jonathanh@nvidia.com --- drivers/gpu/drm/tegra/dsi.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/tegra/dsi.c b/drivers/gpu/drm/tegra/dsi.c index 44e102799195..d1239ebc190f 100644 --- a/drivers/gpu/drm/tegra/dsi.c +++ b/drivers/gpu/drm/tegra/dsi.c @@ -745,13 +745,17 @@ static void tegra_dsi_soft_reset(struct tegra_dsi *dsi) static void tegra_dsi_connector_reset(struct drm_connector *connector) { - struct tegra_dsi_state *state = - kzalloc(sizeof(*state), GFP_KERNEL); + struct tegra_dsi_state *state = kzalloc(sizeof(*state), GFP_KERNEL); - if (state) { + if (!state) + return; + + if (connector->state) { + __drm_atomic_helper_connector_destroy_state(connector->state); kfree(connector->state); - __drm_atomic_helper_connector_reset(connector, &state->base); } + + __drm_atomic_helper_connector_reset(connector, &state->base); } static struct drm_connector_state * @@ -764,6 +768,9 @@ tegra_dsi_connector_duplicate_state(struct drm_connector *connector) if (!copy) return NULL; + __drm_atomic_helper_connector_duplicate_state(connector, + ©->base); + return ©->base; } -- 2.20.1