drm/i915: Fix NULL ptr deref by checking new_crtc_state

BugLink: https://bugs.launchpad.net/bugs/2028808
[ Upstream commit a41d985902c153c31c616fe183cf2ee331e95ecb ]

intel_atomic_get_new_crtc_state can return NULL, unless crtc state wasn't
obtained previously with intel_atomic_get_crtc_state, so we must check it
for NULLness here, just as in many other places, where we can't guarantee
that intel_atomic_get_crtc_state was called.
We are currently getting NULL ptr deref because of that, so this fix was
confirmed to help.

Fixes: 74a75dc90869 ("drm/i915/display: move plane prepare/cleanup to intel_atomic_plane.c")
Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230505082212.27089-1-stanislav.lisovskiy@intel.com
(cherry picked from commit 1d5b09f8daf859247a1ea65b0d732a24d88980d8)
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/drivers/gpu/drm/i915/display/intel_atomic_plane.c b/drivers/gpu/drm/i915/display/intel_atomic_plane.c
index 10e1fc9d069827c7a34fad44bea0e4c3deaf2972..5fc5c2f0ccae441e0b84f0c71d14be3361ad69a3 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_atomic_plane.c
+++ b/drivers/gpu/drm/i915/display/intel_atomic_plane.c
@@ -1025,7 +1025,7 @@ intel_prepare_plane_fb(struct drm_plane *_plane,
        int ret;
 
        if (old_obj) {
-               const struct intel_crtc_state *crtc_state =
+               const struct intel_crtc_state *new_crtc_state =
                        intel_atomic_get_new_crtc_state(state,
                                                        to_intel_crtc(old_plane_state->hw.crtc));
 
@@ -1040,7 +1040,7 @@ intel_prepare_plane_fb(struct drm_plane *_plane,
                 * This should only fail upon a hung GPU, in which case we
                 * can safely continue.
                 */
-               if (intel_crtc_needs_modeset(crtc_state)) {
+               if (new_crtc_state && intel_crtc_needs_modeset(new_crtc_state)) {
                        ret = i915_sw_fence_await_reservation(&state->commit_ready,
                                                              old_obj->base.resv,
                                                              false, 0,