KVM: Don't WARN if memory is dirtied without a vCPU when the VM is dying

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Summary

CVECVE-2026-53345
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-01 14:16:42 UTC
Updated2026-07-14 15:26:52 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: KVM: Don't WARN if memory is dirtied without a vCPU when the VM is dying When marking a page dirty, complain about not having a running/loaded vCPU if and only if the VM is still alive, i.e. its refcount is non-zero. This will allow fixing a memory leak for x86 SEV-ES guests without hitting what is effectively a false positive on the WARN. For some SEV-ES VM-Exits, KVM keeps a writable mapping of a guest page across an exit to userspace, and typically unmaps the page on the next KVM_RUN. But if userspace never calls KVM_RUN after such an exit, then KVM needs to unmap the page when the vCPU is destroyed, which in turn triggers the WARN about not having a running vCPU. Alternatively, SEV-ES could temporarily load the vCPU to suppress the WARN, as is done in nested_vmx_free_vcpu() (but for completely unrelated reasons; suppressing WARN from nested_put_vmcs12_pages() is pure happenstance). But loading a vCPU during destruction is gross (ideally nVMX code would be cleaned up), risks complicating the SEV-ES code (KVM would need to ensure the temporarily load()+put() only runs when the vCPU isn't already loaded), and is ultimately pointless. The motivation for the WARN is to guard against KVM dirtying guest memory without pushing the corresponding GFN to the active vCPU's dirty ring, e.g. to ensure userspace doesn't miss a dirty page. But for the VM's refcount to reach zero, there can't be _any_ userspace mappings to the dirty ring, as mapping the dirty ring requires doing mmap() on the vCPU FD. I.e. if userspace had a valid mapping for the dirty ring, then the vCPU file and thus the owning VM would still be alive. And so since userspace can't possibly reach the dirty ring, whether or not KVM technically "misses" a push to the dirty ring is irrelevant.

Risk And Classification

EPSS: 0.001560000 probability, percentile 0.051980000 (date 2026-07-14)

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 2efd61a608b0039911924d2e5d7028eb37496e85 033d39e41fc30f484f4e4f37fb4cd76b12cbb18e git Not specified
CNA Linux Linux affected 2efd61a608b0039911924d2e5d7028eb37496e85 66a8e7ddd901023c89a2733494d827eca3f9c1b0 git Not specified
CNA Linux Linux affected 2efd61a608b0039911924d2e5d7028eb37496e85 343e95c8ecc40e0738975ef4ee24c0c35e800e6b git Not specified
CNA Linux Linux affected 2efd61a608b0039911924d2e5d7028eb37496e85 99d7d43784ae3235026581e9bf892c036e04c8e6 git Not specified
CNA Linux Linux affected 2efd61a608b0039911924d2e5d7028eb37496e85 8618004d3e897c0f1b71d9a9ab860461289bb89a git Not specified
CNA Linux Linux affected 5.17 Not specified
CNA Linux Linux unaffected 5.17 semver Not specified
CNA Linux Linux unaffected 6.6.143 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.94 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.36 6.18.* semver Not specified
CNA Linux Linux unaffected 7.0.13 7.0.* semver Not specified
CNA Linux Linux unaffected 7.1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/8618004d3e897c0f1b71d9a9ab860461289bb89a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/033d39e41fc30f484f4e4f37fb4cd76b12cbb18e 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/99d7d43784ae3235026581e9bf892c036e04c8e6 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/343e95c8ecc40e0738975ef4ee24c0c35e800e6b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/66a8e7ddd901023c89a2733494d827eca3f9c1b0 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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