{"id":"CVE-2026-98715","state":"PUBLISHED","title":"KVM: SVM: Preserve TLB control (i.e. pending TLB flush) on failed VMRUN","description":"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 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.","publishedAt":"2026-10-18T15:46:47.988Z","updatedAt":"2026-10-19T09:24:26.247Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"38e5e92fe8c02a8766459d505423b855caf9af1f","status":"affected","lessThan":"fd873c3d1b5240e80365f09e758e8c96b88a7cdb","versionType":"git"},{"version":"38e5e92fe8c02a8766459d505423b855caf9af1f","status":"affected","lessThan":"60d93c27859fb3ec5b5a689e24de303f166477d0","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/x86/kvm/svm/svm.c","arch/x86/kvm/svm/svm.h"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"2.6.38","status":"affected"},{"version":"0","status":"unaffected","lessThan":"2.6.38","versionType":"semver"},{"version":"7.2.10","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/x86/kvm/svm/svm.c","arch/x86/kvm/svm/svm.h"]}],"references":["https://git.kernel.org/stable/c/fd873c3d1b5240e80365f09e758e8c96b88a7cdb","https://git.kernel.org/stable/c/60d93c27859fb3ec5b5a689e24de303f166477d0"],"weaknesses":[],"ingestedAt":"2026-10-29T20:13:43.249Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/98xxx/CVE-2026-98715.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-98715","state":"PUBLISHED","datePublished":"2026-10-18T15:46:47.988Z","dateUpdated":"2026-10-19T09:24:26.247Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-25T10:25:14.366Z"},"containers":{"cna":{"title":"KVM: SVM: Preserve TLB control (i.e. pending TLB flush) on failed VMRUN","descriptions":[{"lang":"en","value":"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 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."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"38e5e92fe8c02a8766459d505423b855caf9af1f","status":"affected","lessThan":"fd873c3d1b5240e80365f09e758e8c96b88a7cdb","versionType":"git"},{"version":"38e5e92fe8c02a8766459d505423b855caf9af1f","status":"affected","lessThan":"60d93c27859fb3ec5b5a689e24de303f166477d0","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/x86/kvm/svm/svm.c","arch/x86/kvm/svm/svm.h"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"2.6.38","status":"affected"},{"version":"0","status":"unaffected","lessThan":"2.6.38","versionType":"semver"},{"version":"7.2.10","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/x86/kvm/svm/svm.c","arch/x86/kvm/svm/svm.h"]}],"references":[{"url":"https://git.kernel.org/stable/c/fd873c3d1b5240e80365f09e758e8c96b88a7cdb"},{"url":"https://git.kernel.org/stable/c/60d93c27859fb3ec5b5a689e24de303f166477d0"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-19T09:24:26.247Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.38","versionEndExcluding":"7.2.10"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.38","versionEndExcluding":"7.3"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}