CVE-2026-98319 in Linux
Summary
by MITRE • 10/06/2026
In the Linux kernel, the following vulnerability has been resolved:
drm: Fix drm_pending_vblank_event leak in error path for out_fence_ptr
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.
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Analysis
by VulDB Data Team • 10/06/2026
The Linux kernel's Direct Rendering Manager subsystem contains a resource management flaw within its page flip handling logic, specifically concerning the interaction between fence pointers and vblank events. This vulnerability arises when an application requests a page flip with an output fence pointer but does not request a vblank event by omitting the DRM_MODE_PAGE_FLIP_EVENT flag. In this specific configuration, the kernel still allocates a drm_pending_vblank_event structure to manage potential signaling requirements. However, if subsequent operations such as setup_out_fence() fail due to allocation errors or other initialization issues, the allocated event remains in memory without its base.fence field being properly initialized. This incomplete state prevents the standard cleanup routine complete_signaling() from recognizing and releasing the resource, leading to a persistent kernel memory leak that accumulates over time with repeated failed operations.
This issue represents a classic case of improper resource deallocation during error handling paths, categorized under CWE-401 as missing release of resources after effective ownership. The root cause lies in an asymmetry between successful and failure code paths within the DRM page flip implementation. While the path for explicit vblank event requests correctly handles cleanup through prepare_signaling() which releases the event if initialization fails, the path for fence-only operations lacks this safeguard. Consequently, any driver or subsystem component that triggers a page flip with out_fence_ptr but without an accompanying event will leak kernel memory whenever setup_out_fence encounters an error condition. This can lead to gradual degradation of system performance and potential denial of service through resource exhaustion if triggered repeatedly by unprivileged userspace applications interacting with graphics drivers.
From a threat modeling perspective, this vulnerability aligns with ATT&CK technique T1496 Resource Hijacking, specifically involving environmental preparation where an attacker consumes limited kernel resources to degrade system availability. Although the immediate impact is primarily memory leakage rather than arbitrary code execution or privilege escalation, sustained exploitation can destabilize the host by exhausting available kernel memory pools. The vulnerability affects systems relying on DRM-based graphics stacks and highlights the importance of rigorous error path validation in low-level driver development. Mitigation strategies involve applying the upstream kernel patch that ensures consistent cleanup behavior across all page flip scenarios. Specifically, developers must ensure that drm_event_cancel_free() is invoked during failure paths for fence-only operations to properly undo any partial initialization performed by drm_event_reserve_init(). System administrators should prioritize updating their Linux kernels to versions where this DRM subsystem fix has been integrated, thereby restoring proper resource lifecycle management and preventing memory leaks in graphics-intensive environments.