[PATCH] drm: Fix drm_pending_vblank_event in error path for out_fence_ptr

[Thadeu Lima de Souza Cascardo]

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().

Reported-by: sashiko-bot@xxxxxxxxxx
Closes: https://sashiko.dev/#/patchset/20260727-drm_crtc_atomic_commit_leak-v1-1-23d9948a9d7c@xxxxxxxxxx?part=1
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@xxxxxxxxxx>
---
 drivers/gpu/drm/drm_atomic_uapi.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic_uapi.c b/drivers/gpu/drm/drm_atomic_uapi.c
index 1050dddadb17..aca35fb4b1f9 100644
--- a/drivers/gpu/drm/drm_atomic_uapi.c
+++ b/drivers/gpu/drm/drm_atomic_uapi.c
@@ -1464,11 +1464,15 @@ static int prepare_signaling(struct drm_device *dev,
 		if (fence_ptr) {
 			struct dma_fence *fence;
 			struct drm_out_fence_state *f;
+			struct drm_pending_vblank_event *e = crtc_state->event;
 
 			f = krealloc(*fence_state, sizeof(**fence_state) *
 				     (*num_fences + 1), GFP_KERNEL);
-			if (!f)
+			if (!f) {
+				kfree(e);
+				crtc_state->event = NULL;
 				return -ENOMEM;
+			}
 
 			memset(&f[*num_fences], 0, sizeof(*f));
 
@@ -1476,12 +1480,17 @@ static int prepare_signaling(struct drm_device *dev,
 			*fence_state = f;
 
 			fence = drm_crtc_create_fence(crtc);
-			if (!fence)
+			if (!fence) {
+				kfree(e);
+				crtc_state->event = NULL;
 				return -ENOMEM;
+			}
 
 			ret = setup_out_fence(&f[(*num_fences)++], fence);
 			if (ret) {
 				dma_fence_put(fence);
+				kfree(e);
+				crtc_state->event = NULL;
 				return ret;
 			}
 

---
base-commit: df0311845915442ab75d03ee89fb443b444c1370
change-id: 20260728-drm_pending_vblank_event_leak-a36cedb296ba

Best regards,
--  
Thadeu Lima de Souza Cascardo <cascardo@xxxxxxxxxx>