{"id":"CVE-2026-98715","title":"KVM: SVM: Preserve TLB control (i.e. pending TLB flush) on failed VMRUN","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: SVM: Preserve TLB control (i.e. pending TLB flush) on failed VMRUN\n\nDon't reset the VMCB's TLB control back to \"do nothing\" on a failed VMRUN,\nas empirical testing…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= 38e5e92fe8c02a8766459d505423b855caf9af1f < fd873c3d1b5240e80365f09e758e8c96b88a7cdb","Linux >= 38e5e92fe8c02a8766459d505423b855caf9af1f < 60d93c27859fb3ec5b5a689e24de303f166477d0","Linux 2.6.38"],"published":"2026-10-18","updated":"2026-10-18","sourceUpdated":"2026-10-18T15:46:47.988Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-98715","references":[{"url":"https://git.kernel.org/stable/c/fd873c3d1b5240e80365f09e758e8c96b88a7cdb"},{"url":"https://git.kernel.org/stable/c/60d93c27859fb3ec5b5a689e24de303f166477d0"}],"tags":["cve.org"],"ingestedAt":"2026-10-18T16:47:32.511Z","slug":"CVE-2026-98715","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nKVM: SVM: Preserve TLB control (i.e. pending TLB flush) on failed VMRUN\n\nDon't reset the VMCB's TLB control back to \"do nothing\" on a failed VMRUN,\nas empirical testing shows that the CPU performs the requested TLB flush if\nand only if VMRUN is successful, i.e. clearing TLB control on a failed\nVMRUN effectively drops a TLB flush.\n\nExplicitly track the need to flush all ASIDs on a per-CPU basis, as the\nASID reuse condition is tied to the pCPU, not to the vCPU.  As a bonus,\nthis also obviates the need to avoid clobbering FLUSH_ALL_ASID with\nTLB_CONTROL_FLUSH_ASID, e.g. in svm_flush_tlb_asid().\n\nDeliberately don't bother saving/restoring the \"old\" tlb_ctl on failure,\nin quotes because it's not exactly the old tlb_ctl, it's the tlb_ctl from\nafter pre_svm_run(), but before updating tlb_ctl for flush_all_asids.  If\nVMRUN fails and TLB_CONTROL_FLUSH_ALL_ASID is forced, then the next\nsuccessful run of the VMCB *may* unnecessarily flush all ASIDs, which\nstrictly speaking could result in noisy neighbor issues.  However, the\nfact that new_asid() is already guest-triggerable, because of KVM's flawed\nbehavior of clearing the ASID on emulated INIT, means that a guest can\nalready trigger a flush of all ASIDs at roughly the same rate.  And once\nKVM stops clobbering the ASID on emulated INIT, *or* assigns a static ASID\nto each vCPU, this flaw goes away.\n\n## Affected\n\n- `Linux >= 38e5e92fe8c02a8766459d505423b855caf9af1f < fd873c3d1b5240e80365f09e758e8c96b88a7cdb`\n- `Linux >= 38e5e92fe8c02a8766459d505423b855caf9af1f < 60d93c27859fb3ec5b5a689e24de303f166477d0`\n- `Linux 2.6.38`\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":[]}