CVE-2026-53345 (GCVE-0-2026-53345)

Vulnerability from cvelistv5 – Published: 2026-07-01 13:32 – Updated: 2026-07-01 13:32
VLAI
Title
KVM: Don't WARN if memory is dirtied without a vCPU when the VM is dying
Summary
In 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.
Severity
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 033d39e41fc30f484f4e4f37fb4cd76b12cbb18e (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 66a8e7ddd901023c89a2733494d827eca3f9c1b0 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 343e95c8ecc40e0738975ef4ee24c0c35e800e6b (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 99d7d43784ae3235026581e9bf892c036e04c8e6 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 8618004d3e897c0f1b71d9a9ab860461289bb89a (git)
Affected: 0 , < 6.6.143 (semver)
Affected: 0 , < 6.12.94 (semver)
Affected: 0 , < 6.18.36 (semver)
Affected: 0 , < 7.0.13 (semver)
Create a notification for this product.
Linux Linux Unaffected: 6.6.143 , ≤ 6.6.* (semver)
Unaffected: 6.12.94 , ≤ 6.12.* (semver)
Unaffected: 6.18.36 , ≤ 6.18.* (semver)
Unaffected: 7.0.13 , ≤ 7.0.* (semver)
Unaffected: 7.1 , ≤ * (original_commit_for_fix)
Create a notification for this product.
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: Don\u0027t WARN if memory is dirtied without a vCPU when the VM is dying\n\nWhen marking a page dirty, complain about not having a running/loaded vCPU\nif and only if the VM is still alive, i.e. its refcount is non-zero.  This\nwill allow fixing a memory leak for x86 SEV-ES guests without hitting what\nis effectively a false positive on the WARN.\n\nFor some SEV-ES VM-Exits, KVM keeps a writable mapping of a guest page\nacross an exit to userspace, and typically unmaps the page on the next\nKVM_RUN.  But if userspace never calls KVM_RUN after such an exit, then KVM\nneeds to unmap the page when the vCPU is destroyed, which in turn triggers\nthe WARN about not having a running vCPU.\n\nAlternatively, SEV-ES could temporarily load the vCPU to suppress the WARN,\nas is done in nested_vmx_free_vcpu() (but for completely unrelated reasons;\nsuppressing WARN from nested_put_vmcs12_pages() is pure happenstance).  But\nloading a vCPU during destruction is gross (ideally nVMX code would be\ncleaned up), risks complicating the SEV-ES code (KVM would need to ensure\nthe temporarily load()+put() only runs when the vCPU isn\u0027t already loaded),\nand is ultimately pointless.\n\nThe motivation for the WARN is to guard against KVM dirtying guest memory\nwithout pushing the corresponding GFN to the active vCPU\u0027s dirty ring, e.g.\nto ensure userspace doesn\u0027t miss a dirty page.  But for the VM\u0027s refcount\nto reach zero, there can\u0027t be _any_ userspace mappings to the dirty ring,\nas mapping the dirty ring requires doing mmap() on the vCPU FD.  I.e. if\nuserspace had a valid mapping for the dirty ring, then the vCPU file and\nthus the owning VM would still be alive.  And so since userspace can\u0027t\npossibly reach the dirty ring, whether or not KVM technically \"misses\" a\npush to the dirty ring is irrelevant."
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        "shortName": "Linux"
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But if userspace never calls KVM_RUN after such an exit, then KVM\\nneeds to unmap the page when the vCPU is destroyed, which in turn triggers\\nthe WARN about not having a running vCPU.\\n\\nAlternatively, SEV-ES could temporarily load the vCPU to suppress the WARN,\\nas is done in nested_vmx_free_vcpu() (but for completely unrelated reasons;\\nsuppressing WARN from nested_put_vmcs12_pages() is pure happenstance).  But\\nloading a vCPU during destruction is gross (ideally nVMX code would be\\ncleaned up), risks complicating the SEV-ES code (KVM would need to ensure\\nthe temporarily load()+put() only runs when the vCPU isn\u0027t already loaded),\\nand is ultimately pointless.\\n\\nThe motivation for the WARN is to guard against KVM dirtying guest memory\\nwithout pushing the corresponding GFN to the active vCPU\u0027s dirty ring, e.g.\\nto ensure userspace doesn\u0027t miss a dirty page.  But for the VM\u0027s refcount\\nto reach zero, there can\u0027t be _any_ userspace mappings to the dirty ring,\\nas mapping the dirty ring requires doing mmap() on the vCPU FD.  I.e. if\\nuserspace had a valid mapping for the dirty ring, then the vCPU file and\\nthus the owning VM would still be alive.  And so since userspace can\u0027t\\npossibly reach the dirty ring, whether or not KVM technically \\\"misses\\\" a\\npush to the dirty ring is irrelevant.\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"virt/kvm/kvm_main.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\",\"lessThan\":\"033d39e41fc30f484f4e4f37fb4cd76b12cbb18e\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\",\"lessThan\":\"66a8e7ddd901023c89a2733494d827eca3f9c1b0\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\",\"lessThan\":\"343e95c8ecc40e0738975ef4ee24c0c35e800e6b\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\",\"lessThan\":\"99d7d43784ae3235026581e9bf892c036e04c8e6\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\",\"lessThan\":\"8618004d3e897c0f1b71d9a9ab860461289bb89a\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"6.6.143\",\"versionType\":\"semver\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"6.12.94\",\"versionType\":\"semver\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"6.18.36\",\"versionType\":\"semver\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"7.0.13\",\"versionType\":\"semver\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"virt/kvm/kvm_main.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"6.6.143\",\"lessThanOrEqual\":\"6.6.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.12.94\",\"lessThanOrEqual\":\"6.12.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.18.36\",\"lessThanOrEqual\":\"6.18.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.0.13\",\"lessThanOrEqual\":\"7.0.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.1\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/033d39e41fc30f484f4e4f37fb4cd76b12cbb18e\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/343e95c8ecc40e0738975ef4ee24c0c35e800e6b\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/66a8e7ddd901023c89a2733494d827eca3f9c1b0\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/8618004d3e897c0f1b71d9a9ab860461289bb89a\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/99d7d43784ae3235026581e9bf892c036e04c8e6\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.