drm/gud: fix NULL fb and crtc dereferences on USB disconnect

On disconnect drm_atomic_helper_disable_all() is called which
sets both the fb and crtc for a plane to NULL before invoking a commit.

This causes a kernel oops on every display disconnect.

Add guards for those dereferences.

Cc: <stable@vger.kernel.org> # 6.18.x
Fixes: 73cfd166e045 ("drm/gud: Replace simple display pipe with DRM atomic helpers")
Signed-off-by: Shenghao Yang <me@shenghaoyang.info>
Reviewed-by: Ruben Wauters <rubenru09@aol.com>
Signed-off-by: Ruben Wauters <rubenru09@aol.com>
Link: https://patch.msgid.link/20251231055039.44266-1-me@shenghaoyang.info

diff --git a/drivers/gpu/drm/gud/gud_pipe.c b/drivers/gpu/drm/gud/gud_pipe.c
index 76d77a736d84a8e7ec77256d08133dd6826c2da0..4b77be94348d9034eeba1497d120b380737a1637 100644 (file)
--- a/drivers/gpu/drm/gud/gud_pipe.c
+++ b/drivers/gpu/drm/gud/gud_pipe.c
@@ -457,27 +457,20 @@ int gud_plane_atomic_check(struct drm_plane *plane,
        struct drm_plane_state *old_plane_state = drm_atomic_get_old_plane_state(state, plane);
        struct drm_plane_state *new_plane_state = drm_atomic_get_new_plane_state(state, plane);
        struct drm_crtc *crtc = new_plane_state->crtc;
-       struct drm_crtc_state *crtc_state;
+       struct drm_crtc_state *crtc_state = NULL;
        const struct drm_display_mode *mode;
        struct drm_framebuffer *old_fb = old_plane_state->fb;
        struct drm_connector_state *connector_state = NULL;
        struct drm_framebuffer *fb = new_plane_state->fb;
-       const struct drm_format_info *format = fb->format;
+       const struct drm_format_info *format;
        struct drm_connector *connector;
        unsigned int i, num_properties;
        struct gud_state_req *req;
        int idx, ret;
        size_t len;
 
-       if (drm_WARN_ON_ONCE(plane->dev, !fb))
-               return -EINVAL;
-
-       if (drm_WARN_ON_ONCE(plane->dev, !crtc))
-               return -EINVAL;
-
-       crtc_state = drm_atomic_get_new_crtc_state(state, crtc);
-
-       mode = &crtc_state->mode;
+       if (crtc)
+               crtc_state = drm_atomic_get_new_crtc_state(state, crtc);
 
        ret = drm_atomic_helper_check_plane_state(new_plane_state, crtc_state,
                                                  DRM_PLANE_NO_SCALING,
@@ -492,6 +485,9 @@ int gud_plane_atomic_check(struct drm_plane *plane,
        if (old_plane_state->rotation != new_plane_state->rotation)
                crtc_state->mode_changed = true;
 
+       mode = &crtc_state->mode;
+       format = fb->format;
+
        if (old_fb && old_fb->format != format)
                crtc_state->mode_changed = true;
 
@@ -598,7 +594,7 @@ void gud_plane_atomic_update(struct drm_plane *plane,
        struct drm_atomic_helper_damage_iter iter;
        int ret, idx;
 
-       if (crtc->state->mode_changed || !crtc->state->enable) {
+       if (!crtc || crtc->state->mode_changed || !crtc->state->enable) {
                cancel_work_sync(&gdrm->work);
                mutex_lock(&gdrm->damage_lock);
                if (gdrm->fb) {