---
id: CVE-2026-98464
title: 'RISC-V: KVM: Synchronize hrtimer callback during teardown'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  RISC-V: KVM: Synchronize hrtimer callback during teardown

  The non-Sstc hrtimer callback clears next_set before its final uses of
  the enclosing vCPU.  If teardown obser…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 3a9f66cb25e18a3eeca36c08d9f823a35b3ddc22 <
    9bdbae64ae0dab93041ebc57ec4e93def793fc2d
  - >-
    Linux >= 3a9f66cb25e18a3eeca36c08d9f823a35b3ddc22 <
    2af03b606aadaaeb386658ef798c79bdcdef87c1
  - >-
    Linux >= 3a9f66cb25e18a3eeca36c08d9f823a35b3ddc22 <
    e66aced74f0122380603c9910a71d77618b28f0e
  - >-
    Linux >= 3a9f66cb25e18a3eeca36c08d9f823a35b3ddc22 <
    ea91f05a55b807ead3166546a2c75f4185ca645f
  - >-
    Linux >= 3a9f66cb25e18a3eeca36c08d9f823a35b3ddc22 <
    3cc6184bd5920c9685d87f4e260568feba08650d
  - >-
    Linux >= 3a9f66cb25e18a3eeca36c08d9f823a35b3ddc22 <
    aaad136d56d91252517272b68cd533e5714698d5
  - Linux 5.16
published: '2026-10-18'
updated: '2026-10-18'
sourceUpdated: '2026-10-18T15:15:16.624Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-98464'
references:
  - url: 'https://git.kernel.org/stable/c/9bdbae64ae0dab93041ebc57ec4e93def793fc2d'
  - url: 'https://git.kernel.org/stable/c/2af03b606aadaaeb386658ef798c79bdcdef87c1'
  - url: 'https://git.kernel.org/stable/c/e66aced74f0122380603c9910a71d77618b28f0e'
  - url: 'https://git.kernel.org/stable/c/ea91f05a55b807ead3166546a2c75f4185ca645f'
  - url: 'https://git.kernel.org/stable/c/3cc6184bd5920c9685d87f4e260568feba08650d'
  - url: 'https://git.kernel.org/stable/c/aaad136d56d91252517272b68cd533e5714698d5'
tags:
  - cve.org
ingestedAt: '2026-10-18T15:45:12.300Z'
---

## Overview

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

RISC-V: KVM: Synchronize hrtimer callback during teardown

The non-Sstc hrtimer callback clears next_set before its final uses of
the enclosing vCPU.  If teardown observes next_set as false while the
callback is still running, kvm_riscv_vcpu_timer_cancel() skips
hrtimer_cancel() and kvm_destroy_vcpus() can free the vCPU before the
callback enters kvm_riscv_vcpu_set_interrupt().

A guest can arm the timer with SBI TIME and request shutdown with SBI
legacy shutdown or SRST.  A VMM that honors KVM_EXIT_SYSTEM_EVENT and
destroys the VM supplies the teardown side of the race; no post-launch
host ioctl is needed to arm or request teardown.

On upstream master 62cc90241548, generic KASAN reported:

  BUG: KASAN: slab-use-after-free in do_raw_spin_lock
  Write of size 4 at addr ff60000005e58898

  kvm_riscv_vcpu_set_interrupt
  kvm_riscv_vcpu_hrtimer_expired
  __hrtimer_run_queues
  hrtimer_interrupt

The object was allocated by KVM_CREATE_VCPU and freed concurrently by:

  kvm_destroy_vcpus
  kvm_arch_destroy_vm
  kvm_destroy_vm
  __fput

For deterministic validation, I added mdelay(1000) immediately after
the existing next_set = false assignment.  This only widens the
existing post-clear callback window.  A no-delay trace build naturally
reached the callback-after-teardown-start/before-deinit ordering in 12
of 200 runs, but 1,500 stock-kernel stress iterations did not produce a
KASAN report, so natural reproduction is timing-sensitive.

Always invoke hrtimer_cancel() for an initialized timer.  Preserve the
existing -EINVAL result when the timer is no longer set, but only after
synchronizing with a running callback.

With this patch, hrtimer_cancel() blocked for the full widened callback
window before vCPU destruction.  KASAN reported no error in 100
fixed-and-widened runs or 200 fix-only timing-sweep runs.

## Affected

- `Linux >= 3a9f66cb25e18a3eeca36c08d9f823a35b3ddc22 < 9bdbae64ae0dab93041ebc57ec4e93def793fc2d`
- `Linux >= 3a9f66cb25e18a3eeca36c08d9f823a35b3ddc22 < 2af03b606aadaaeb386658ef798c79bdcdef87c1`
- `Linux >= 3a9f66cb25e18a3eeca36c08d9f823a35b3ddc22 < e66aced74f0122380603c9910a71d77618b28f0e`
- `Linux >= 3a9f66cb25e18a3eeca36c08d9f823a35b3ddc22 < ea91f05a55b807ead3166546a2c75f4185ca645f`
- `Linux >= 3a9f66cb25e18a3eeca36c08d9f823a35b3ddc22 < 3cc6184bd5920c9685d87f4e260568feba08650d`
- `Linux >= 3a9f66cb25e18a3eeca36c08d9f823a35b3ddc22 < aaad136d56d91252517272b68cd533e5714698d5`
- `Linux 5.16`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.