[PATCH] drm/atomic: Fix potential use of state after free

[Ander Conselvan de Oliveira]

The atomic helpers rely on drm_atomic_state_clear() to reset an atomic
state if a retry is needed due to the w/w mutexes. The subsequent calls
to drm_atomic_get_{crtc,plane,...}_state() would then return the stale
pointers in state->{crtc,plane,...}_states.

Signed-off-by: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira at 
intel.com>
---
 drivers/gpu/drm/drm_atomic.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index 1b31982..9d16fa4 100644
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -134,6 +134,7 @@ void drm_atomic_state_clear(struct drm_atomic_state *state)

                connector->funcs->atomic_destroy_state(connector,
                                                       
state->connector_states[i]);
+               state->connector_states[i] = NULL;
        }

        for (i = 0; i < config->num_crtc; i++) {
@@ -144,6 +145,7 @@ void drm_atomic_state_clear(struct drm_atomic_state *state)

                crtc->funcs->atomic_destroy_state(crtc,
                                                  state->crtc_states[i]);
+               state->crtc_states[i] = NULL;
        }

        for (i = 0; i < config->num_total_plane; i++) {
@@ -154,6 +156,7 @@ void drm_atomic_state_clear(struct drm_atomic_state *state)

                plane->funcs->atomic_destroy_state(plane,
                                                   state->plane_states[i]);
+               state->plane_states[i] = NULL;
        }
 }
 EXPORT_SYMBOL(drm_atomic_state_clear);
-- 
1.9.1