On 17/08/2026 23:36, Thadeu Lima de Souza Cascardo wrote:
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);
I think it's clearer to name the error handle as `err_free_event`, and
to use `&crtc_state->event` directly instead of `&e` here.
With this,
Reviewed-by: Melissa Wen <[email protected]>
Thanks!
+ 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]>
