{"id":"CVE-2026-98464","summary":"RISC-V: KVM: Synchronize hrtimer callback during teardown","details":"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 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.","modified":"2026-10-20T02:30:21.768850181Z","published":"2026-10-18T15:15:16.624Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98464.json"},"references":[{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"},{"type":"WEB","url":"https://git.kernel.org/stable/c/2af03b606aadaaeb386658ef798c79bdcdef87c1"},{"type":"WEB","url":"https://git.kernel.org/stable/c/3cc6184bd5920c9685d87f4e260568feba08650d"},{"type":"WEB","url":"https://git.kernel.org/stable/c/9bdbae64ae0dab93041ebc57ec4e93def793fc2d"},{"type":"WEB","url":"https://git.kernel.org/stable/c/aaad136d56d91252517272b68cd533e5714698d5"},{"type":"WEB","url":"https://git.kernel.org/stable/c/e66aced74f0122380603c9910a71d77618b28f0e"},{"type":"WEB","url":"https://git.kernel.org/stable/c/ea91f05a55b807ead3166546a2c75f4185ca645f"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98464.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98464"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"3a9f66cb25e18a3eeca36c08d9f823a35b3ddc22"},{"fixed":"9bdbae64ae0dab93041ebc57ec4e93def793fc2d"},{"fixed":"2af03b606aadaaeb386658ef798c79bdcdef87c1"},{"fixed":"e66aced74f0122380603c9910a71d77618b28f0e"},{"fixed":"ea91f05a55b807ead3166546a2c75f4185ca645f"},{"fixed":"3cc6184bd5920c9685d87f4e260568feba08650d"},{"fixed":"aaad136d56d91252517272b68cd533e5714698d5"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98464.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"5.16.0"},{"fixed":"6.1.189"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.158"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.112"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.55"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.2.9"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98464.json"}}],"schema_version":"1.9.0"}