{"id":"CVE-2026-98464","title":"RISC-V: KVM: Synchronize hrtimer callback during teardown","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nRISC-V: KVM: Synchronize hrtimer callback during teardown\n\nThe non-Sstc hrtimer callback clears next_set before its final uses of\nthe 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","slug":"CVE-2026-98464","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nRISC-V: KVM: Synchronize hrtimer callback during teardown\n\nThe non-Sstc hrtimer callback clears next_set before its final uses of\nthe enclosing vCPU.  If teardown observes next_set as false while the\ncallback is still running, kvm_riscv_vcpu_timer_cancel() skips\nhrtimer_cancel() and kvm_destroy_vcpus() can free the vCPU before the\ncallback enters kvm_riscv_vcpu_set_interrupt().\n\nA guest can arm the timer with SBI TIME and request shutdown with SBI\nlegacy shutdown or SRST.  A VMM that honors KVM_EXIT_SYSTEM_EVENT and\ndestroys the VM supplies the teardown side of the race; no post-launch\nhost ioctl is needed to arm or request teardown.\n\nOn upstream master 62cc90241548, generic KASAN reported:\n\n  BUG: KASAN: slab-use-after-free in do_raw_spin_lock\n  Write of size 4 at addr ff60000005e58898\n\n  kvm_riscv_vcpu_set_interrupt\n  kvm_riscv_vcpu_hrtimer_expired\n  __hrtimer_run_queues\n  hrtimer_interrupt\n\nThe object was allocated by KVM_CREATE_VCPU and freed concurrently by:\n\n  kvm_destroy_vcpus\n  kvm_arch_destroy_vm\n  kvm_destroy_vm\n  __fput\n\nFor deterministic validation, I added mdelay(1000) immediately after\nthe existing next_set = false assignment.  This only widens the\nexisting post-clear callback window.  A no-delay trace build naturally\nreached the callback-after-teardown-start/before-deinit ordering in 12\nof 200 runs, but 1,500 stock-kernel stress iterations did not produce a\nKASAN report, so natural reproduction is timing-sensitive.\n\nAlways invoke hrtimer_cancel() for an initialized timer.  Preserve the\nexisting -EINVAL result when the timer is no longer set, but only after\nsynchronizing with a running callback.\n\nWith this patch, hrtimer_cancel() blocked for the full widened callback\nwindow before vCPU destruction.  KASAN reported no error in 100\nfixed-and-widened runs or 200 fix-only timing-sweep runs.\n\n## Affected\n\n- `Linux >= 3a9f66cb25e18a3eeca36c08d9f823a35b3ddc22 < 9bdbae64ae0dab93041ebc57ec4e93def793fc2d`\n- `Linux >= 3a9f66cb25e18a3eeca36c08d9f823a35b3ddc22 < 2af03b606aadaaeb386658ef798c79bdcdef87c1`\n- `Linux >= 3a9f66cb25e18a3eeca36c08d9f823a35b3ddc22 < e66aced74f0122380603c9910a71d77618b28f0e`\n- `Linux >= 3a9f66cb25e18a3eeca36c08d9f823a35b3ddc22 < ea91f05a55b807ead3166546a2c75f4185ca645f`\n- `Linux >= 3a9f66cb25e18a3eeca36c08d9f823a35b3ddc22 < 3cc6184bd5920c9685d87f4e260568feba08650d`\n- `Linux >= 3a9f66cb25e18a3eeca36c08d9f823a35b3ddc22 < aaad136d56d91252517272b68cd533e5714698d5`\n- `Linux 5.16`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}