Bug 2546345 (CVE-2026-98309)

Summary:	CVE-2026-98309 kernel: drm/vc4: Use managed KMS polling to fix UAF on unbind
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	---
Doc Text:	A flaw was found in the Linux kernel. A use-after-free vulnerability exists in the VideoCore IV (vc4) display driver where background polling tasks are not properly finalized when the driver is unbound. A local user could exploit this flaw by unbinding the device or unloading the driver module, causing background routines to access memory after it has been freed. This issue can lead to a system crash, resulting in a Denial of Service (DoS), or potentially allow arbitrary code execution.	Story Points:	---
Clone Of:		Environment:
Last Closed:		Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-10-06 09:02:40 UTC

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

drm/vc4: Use managed KMS polling to fix UAF on unbind

vc4_kms_load() calls drm_kms_helper_poll_init() but the driver provides
no matching drm_kms_helper_poll_fini(). The output poll work stays
scheduled after unbind and runs on the freed drm_device:

  # modprobe vc4; rmmod vc4; sleep 10
  BUG: KASAN: slab-use-after-free in delayed_work_timer_fn
  BUG: KASAN: slab-use-after-free in drm_client_dev_hotplug [drm]
  Workqueue: events output_poll_execute [drm_kms_helper]
  Allocated by task 171: __devm_drm_dev_alloc
  Freed by task 262 (rmmod): drm_dev_put / component_del

Use drmm_kms_helper_poll_init() so polling is finalized with the device,
as other drivers do.

Comment 1 gkamathe 2026-10-11 05:08:31 UTC

Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-98309.mbox