diff options
| author | Hsin-Yi Wang <hsinyi@chromium.org> | 2024-02-23 13:23:29 -0800 |
|---|---|---|
| committer | Sasha Levin <sashal@kernel.org> | 2024-03-26 18:18:41 -0400 |
| commit | 9acee29a38b4d4b70f1f583e5ef9a245db4db710 (patch) | |
| tree | fce57127a542b619471ec9e1bf85ffecea4af0d9 /drivers/gpu | |
| parent | 859a49de7b71192272371c1a5a3a68efac064e71 (diff) | |
| download | linux-stable-9acee29a38b4d4b70f1f583e5ef9a245db4db710.tar.gz linux-stable-9acee29a38b4d4b70f1f583e5ef9a245db4db710.tar.bz2 linux-stable-9acee29a38b4d4b70f1f583e5ef9a245db4db710.zip | |
drm/mediatek: Fix a null pointer crash in mtk_drm_crtc_finish_page_flip
[ Upstream commit c958e86e9cc1b48cac004a6e245154dfba8e163b ]
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.
Fixes: 119f5173628a ("drm/mediatek: Add DRM Driver for Mediatek SoC MT8173.")
Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
Reviewed-by: CK Hu <ck.hu@mediatek.com>
Link: https://patchwork.kernel.org/project/dri-devel/patch/20240223212404.3709690-1-hsinyi@chromium.org/
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'drivers/gpu')
| -rw-r--r-- | drivers/gpu/drm/mediatek/mtk_drm_crtc.c | 12 |
1 files changed, 7 insertions, 5 deletions
diff --git a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c index db43f9dff912..d645b85f9721 100644 --- a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c +++ b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c @@ -95,11 +95,13 @@ static void mtk_drm_crtc_finish_page_flip(struct mtk_drm_crtc *mtk_crtc) struct drm_crtc *crtc = &mtk_crtc->base; unsigned long flags; - spin_lock_irqsave(&crtc->dev->event_lock, flags); - drm_crtc_send_vblank_event(crtc, mtk_crtc->event); - drm_crtc_vblank_put(crtc); - mtk_crtc->event = NULL; - spin_unlock_irqrestore(&crtc->dev->event_lock, flags); + if (mtk_crtc->event) { + spin_lock_irqsave(&crtc->dev->event_lock, flags); + drm_crtc_send_vblank_event(crtc, mtk_crtc->event); + drm_crtc_vblank_put(crtc); + mtk_crtc->event = NULL; + spin_unlock_irqrestore(&crtc->dev->event_lock, flags); + } } static void mtk_drm_finish_page_flip(struct mtk_drm_crtc *mtk_crtc) |