CVE-2024-26874 Information

Apr 18, 2024 cve

Description

In the Linux kernel the following vulnerability has been resolved:

drm/mediatek: Fix a null pointer crash in mtk_drm_crtc_finish_page_flip

It’s possible that mtk_crtc->event is NULL in mtk_drm_crtc_finish_page_flip().

pending_needs_vblank value is set by mtk_crtc->event but in mtk_drm_crtc_atomic_flush() it’s is not guarded by the same lock in mtk_drm_finish_page_flip() thus a race condition happens.

Consider the following case:

CPU1 CPU2 step 1: mtk_drm_crtc_atomic_begin() mtk_crtc->event is not null step 1: mtk_drm_crtc_atomic_flush: mtk_drm_crtc_update_config( !!mtk_crtc->event) step 2: mtk_crtc_ddp_irq -> mtk_drm_finish_page_flip: lock mtk_crtc->event set to null pending_needs_vblank set to false unlock pending_needs_vblank set to true

                              step 2:
                              mtk_crtc_ddp_irq ->
                              mtk_drm_finish_page_flip called again
                              pending_needs_vblank is still true
                              //null pointer

Instead of guarding the entire mtk_drm_crtc_atomic_flush() it’s more efficient to just check if mtk_crtc->event is null before use.

Reference

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