When an out_fence_ptr is provided but DRM_MODE_PAGE_FLIP_EVENT is not set, a drm_pending_vblank_event will be allocated. If later, there is an allocation failure or another failure at setup_out_fence(), that event will not have base.fence set and it will not be released at complete_signaling().
Release the event and set crtc_state->event to NULL just like in the DRM_MODE_PAGE_FLIP_EVENT case when there is a failure at drm_event_reserve_init(). That is, prepare_signaling() releases the event and there is nothing to be done at complete_signaling(). Use drm_event_cancel_free() as that will also undo drm_event_reserve_init() in case it has been called. Reported-by: [email protected] Closes: https://sashiko.dev/#/patchset/20260727-drm_crtc_atomic_commit_leak-v1-1-23d9948a9...@igalia.com?part=1 Fixes: 92c715fca907 ("drm/atomic: Fix double free in drm_atomic_state_default_clear") Signed-off-by: Thadeu Lima de Souza Cascardo <[email protected]> --- Changes in v3: - Use a label for the common exit pattern. - Link to v2: https://patch.msgid.link/20260729-drm_pending_vblank_event_leak-v2-1-a5074aae0...@igalia.com Changes in v2: - Fix UAF when DRM_MODE_PAGE_FLIP_EVENT is used. - Link to v1: https://patch.msgid.link/20260728-drm_pending_vblank_event_leak-v1-1-08429b920...@igalia.com --- drivers/gpu/drm/drm_atomic_uapi.c | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-) diff --git a/drivers/gpu/drm/drm_atomic_uapi.c b/drivers/gpu/drm/drm_atomic_uapi.c index 1050dddadb17..0aba33824595 100644 --- a/drivers/gpu/drm/drm_atomic_uapi.c +++ b/drivers/gpu/drm/drm_atomic_uapi.c @@ -1426,6 +1426,7 @@ static int prepare_signaling(struct drm_device *dev, struct drm_crtc_state *crtc_state; struct drm_connector *conn; struct drm_connector_state *conn_state; + struct drm_pending_vblank_event *e; int i, c = 0, ret; if (arg->flags & DRM_MODE_ATOMIC_TEST_ONLY) @@ -1437,8 +1438,6 @@ static int prepare_signaling(struct drm_device *dev, fence_ptr = get_out_fence_for_crtc(crtc_state->state, crtc); if (arg->flags & DRM_MODE_PAGE_FLIP_EVENT || fence_ptr) { - struct drm_pending_vblank_event *e; - e = create_vblank_event(crtc, arg->user_data); if (!e) return -ENOMEM; @@ -1447,7 +1446,7 @@ static int prepare_signaling(struct drm_device *dev, } if (arg->flags & DRM_MODE_PAGE_FLIP_EVENT) { - struct drm_pending_vblank_event *e = crtc_state->event; + e = crtc_state->event; if (!file_priv) continue; @@ -1464,11 +1463,14 @@ static int prepare_signaling(struct drm_device *dev, if (fence_ptr) { struct dma_fence *fence; struct drm_out_fence_state *f; + e = crtc_state->event; + + ret = -ENOMEM; f = krealloc(*fence_state, sizeof(**fence_state) * (*num_fences + 1), GFP_KERNEL); if (!f) - return -ENOMEM; + goto error; memset(&f[*num_fences], 0, sizeof(*f)); @@ -1477,12 +1479,12 @@ static int prepare_signaling(struct drm_device *dev, fence = drm_crtc_create_fence(crtc); if (!fence) - return -ENOMEM; + goto error; ret = setup_out_fence(&f[(*num_fences)++], fence); if (ret) { dma_fence_put(fence); - return ret; + goto error; } crtc_state->event->base.fence = fence; @@ -1538,6 +1540,11 @@ static int prepare_signaling(struct drm_device *dev, } return 0; + +error: + drm_event_cancel_free(dev, &e->base); + crtc_state->event = NULL; + return ret; } static void complete_signaling(struct drm_device *dev, --- base-commit: 5d2584e2ffaabf2d420edcb2d120209e151f8dce change-id: 20260728-drm_pending_vblank_event_leak-a36cedb296ba Best regards, -- Thadeu Lima de Souza Cascardo <[email protected]>
