Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider: - [High] drm_vblank_init() causes a NULL pointer dereference or driver probe failure due to accessing uninitialized or empty crtc_list --
--- Patch [5]: [PATCH 5/5] drm/vblank: Require all CRTCs implement vblank support in drm_vblank_init() --- commit 178bbb448a16663eaad60425c62b446801e0f387 Author: Lyude Paul <[email protected]> drm/vblank: Require all CRTCs implement vblank support in drm_vblank_init() This commit modifies drm_vblank_init() to verify that all CRTCs implement vblank support, ensuring an all-or-nothing configuration. It returns -EINVAL if support is mixed, and -ENODEV if no CRTCs support vblank. > diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c > index d57405050554f..17affae23e7a6 100644 > --- a/drivers/gpu/drm/drm_vblank.c > +++ b/drivers/gpu/drm/drm_vblank.c > @@ -542,12 +542,31 @@ static void drm_vblank_init_release(struct drm_device > *dev, void *ptr) > * drmm_add_action_or_reset(). > * > * Returns: > - * Zero on success or a negative error code on failure. > + * Zero on success or a negative error code on failure. If no CRTCs with > vblank > + * support implemented were found, -ENODEV will be returned. > */ > int drm_vblank_init(struct drm_device *dev) > { > int ret; > struct drm_crtc *crtc; > + bool found_vbl_crtc = false, found_non_vbl_crtc = false; > + > + /* Vblank hooks are per-CRTC, not per-device - which is contrary to how > + * the vblank core was written. Since hardware that only has vblank > + * support on some CRTCs but not all is non-existent and would likely > + * lead to UB, ensure that vblank support is all or nothing. > + */ > + drm_for_each_crtc(crtc, dev) { [Severity: High] Can iterating over dev->mode_config.crtc_list here cause a NULL pointer dereference or a false -ENODEV return during driver probe? Several DRM drivers call drm_vblank_init() before initializing mode_config or creating CRTCs. For example: In i915, intel_display_driver_probe_noirq() calls drm_vblank_init() before intel_mode_config_init() sets up the crtc_list, meaning the list head is uninitialized. In vkms, vkms_create() calls drm_vblank_init() before vkms_modeset_init() initializes the crtc_list. In zynqmp_kms, zynqmp_dpsub_drm_init() initializes the list but calls drm_vblank_init() before any CRTCs are created, meaning the list is empty and this function will unconditionally return -ENODEV. Does drm_vblank_init() need to support being called before CRTCs are registered? > + if (crtc->funcs->enable_vblank) > + found_vbl_crtc = true; > + else > + found_non_vbl_crtc = true; > + > + if (drm_WARN_ON(dev, found_vbl_crtc && found_non_vbl_crtc)) > + return -EINVAL; > + } > + if (!found_vbl_crtc) > + return -ENODEV; -- Sashiko AI review ยท https://sashiko.dev/#/patchset/[email protected]?part=5
