---
id: "CVE-2026-98509"
kind: "vulnerability"
aliases: ["CVE-2026-98509"]
title: "Linux kernel: virtio-gpu leaks a fence event on failed execbuffer calls"
severity: "low"
cvss: null
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["linux-kernel", "runtime", "virtio-gpu", "virtual-machines"]
not_affected_if: ["no-virtio-gpu-driver"]
published_at: "2026-10-18T16:17:02+00:00"
first_seen_at: "2026-10-23T21:57:15+00:00"
updated_at: "2026-10-25T05:25:26+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98509", "first_seen_at": "2026-10-23T21:57:15+00:00"}]
---

# Linux kernel: virtio-gpu leaks a fence event on failed execbuffer calls

When a virtio-gpu execbuffer ioctl fails argument validation after a poll event was reserved, the kernel never frees that event, so memory leaks permanently. The sources describe a memory leak found by fuzzing, not an attacker gaining code execution or data.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- `uname -r` and compare against the fixed kernel builds in the upstream stable commit for drm/virtio
- `lsmod | grep virtio_gpu` to see whether the virtio-gpu driver is loaded at all

## Fix

- Update the Linux kernel to a stable release that includes the drm/virtio fence event fix (exact version unknown from the sources)
- Hosts without virtio-gpu loaded are not affected by this driver path

## Timeline

- 2026-10-23T21:57:15+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-98509

## From the sources

In the Linux kernel, the following vulnerability has been resolved:

drm/virtio: fix memory leak of fence event on execbuffer failure

virtio_gpu_execbuffer_ioctl() reserves a DRM event with
drm_event_reserve_init() when VIRTGPU_EXECBUF_RING_IDX selects a ring that
userspace has enabled polling for. virtio_gpu_init_submit() does this
before the BO handles, the command buffer, the syncobj arrays and the
in-fence are processed, so every later error path runs with the event
already pending, including plain argument validation failures such as an
invalid bo_handle or an in-syncobj that carries no fence.

On those paths, virtio_gpu_cleanup_submit() drops the out-fence without
cancelling the event. The fence is freed without ever having been emitted,
taking the only driver-side pointer to the event with it. Closing the DRM
file does not help. drm_events_release() unlinks pending events but
deliberately leaves the freeing to the driver's later drm_send_event(),
which never runs for an orphaned event, so the allocation is leaked
permanently.

Found when fuzzing the virtio driver with Syzkaller:

	BUG: memory leak
	unreferenced object 0xffff88802c176e80 (size 96):
	comm "syz.1.367", pid 10561, jiffies 4294960122
	hex dump (first 32 bytes):
		00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
		c8 6e 17 2c 80 88 ff ff 00 00 00 00 00 00 00 00  .n.,............
	backtrace (crc e1973c6b):
		kmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline]
		slab_post_alloc_hook mm/slub.c:4597 [inline]
		slab_alloc_node mm/slub.c:4917 [inline]
		__kmalloc_cache_noprof+0x49d/0x6f0 mm/slub.c:5485
		_kmalloc_noprof include/linux/slab.h:988 [inline]
		_kzalloc_noprof include/linux/slab.h:1309 [inline]
		virtio_gpu_fence_event_create drivers/gpu/drm/virtio/virtgpu_submit.c:282 [inline]
		virtio_gpu_init_submit drivers/gpu/drm/virtio/virtgpu_submit.c:398 [inline]
		virtio_gpu_execbuffer_ioctl+0xbbf/0x1aa0 drivers/gpu/drm/virtio/virtgpu_submit.c:505
		drm_ioctl_kernel+0x1f4/0x3e0 drivers/gpu/drm/drm_ioctl.c:817
		drm_ioctl+0x5f4/0xc70 drivers/gpu/drm/drm_ioctl.c:914
		vfs_ioctl fs/ioctl.c:51 [inline]
		__do_sys_ioctl fs/ioctl.c:597 [inline]
		__se_sys_ioctl fs/ioctl.c:583 [inline]
		__x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583
		do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
		do_syscall_64+0x116/0x800 arch/x86/entry/syscall_64.c:94
		entry_SYSCALL_64_after_hwframe+0x77/0x7f

Fix by cancelling and freeing the DRM event on the execbuffer error path
before dropping the fence. Clear the fence's event pointer after
cancellation so it does not retain a dangling pointer.

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