Bug 2486976 (CVE-2026-46317)

Summary:	CVE-2026-46317 kernel: KVM: arm64: Reassign nested_mmus array behind mmu_lock
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security <prodsec-ir-bot>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	rhel-process-autobot, 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's KVM (Kernel-based Virtual Machine) for arm64 architectures. An issue in the reallocation of the `nested_mmus` array allows a process to access freed memory. This memory corruption vulnerability could enable a local attacker to escalate privileges or cause a denial of service.	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 2026-06-09 13:01:11 UTC

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

KVM: arm64: Reassign nested_mmus array behind mmu_lock

kvm->arch.nested_mmus[] is walked under kvm->mmu_lock, including from the
MMU notifier path (kvm_unmap_gfn_range() -> kvm_nested_s2_unmap()), which
can run at any time. kvm_vcpu_init_nested() reallocates the array and frees
the old buffer while holding only kvm->arch.config_lock, so such a walker
can reference the freed array.

Allocate the new array outside of mmu_lock, as the allocation can sleep.
Under the lock, copy the existing entries, fix up the back pointers and
reassign the array. Free the old buffer after dropping the lock, as
kvfree() can sleep as well.

Comment 1 Keith Grant 2026-06-09 17:06:26 UTC

Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026060938-CVE-2026-46317-e13c@gregkh/T