linux — security advisory

{
  "id": "d9c568af5daecaa83b2aa62abc51d199ab6d0c040f2b1b059c7ed9767926f608",
  "url": "https://osv.dev/vulnerability/DEBIAN-CVE-2021-47465",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "DEBIAN-CVE-2021-47465",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: KVM: PPC: Book3S HV: Fix stack handling in idle_kvm_start_guest() In commit 10d91611f426 (\"powerpc/64s: Reimplement book3s idle code in C\") kvm_start_guest() became idle_kvm_start_guest(). The old code allocated a stack frame on the emergency stack, but didn't use the frame to store anything, and also didn't store anything in its caller's frame. idle_kvm_start_guest() on the other hand is written more like a normal C function, it creates a frame on entry, and also stores CR/LR into its callers frame (per the ABI). The problem is that there is no caller frame on the emergency stack. The emergency stack for a given CPU is allocated with: paca_ptrs[i]->emergency_sp = alloc_stack(limit, i) + THREAD_SIZE; So emergency_sp actually points to the first address above the emergency stack allocation for a given CPU, we must not store above it without first decrementing it to create a frame. This is different to the regular kernel stack, paca->kstack, which is initialised to point at an initial frame that is ready to use. idle_kvm_start_guest() stores the backchain, CR and LR all of which write outside the allocation for the emergency stack. It then creates a stack frame and saves the non-volatile registers. Unfortunately the frame it creates is not large enough to fit the non-volatiles, and so the saving of the non-volatile registers also writes outside the emergency stack allocation. The end result is that we corrupt w",
    "evidence": "osv:DEBIAN-CVE-2021-47465",
    "products": [
      {
        "name": {
          "value": "linux",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "5.14.16-1",
            "evidence": "/affected/0/ranges"
          }
        ],
        "affected_versions": []
      },
      {
        "name": {
          "value": "linux",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "5.14.16-1",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      },
      {
        "name": {
          "value": "linux",
          "evidence": "/affected/2/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "5.14.16-1",
            "evidence": "/affected/2/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "medium",
    "structured": {
      "id": "DEBIAN-CVE-2021-47465",
      "aliases": [
        "DEBIAN-CVE-2021-47465"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "5.14.16-1"
                }
              ]
            }
          ],
          "package": {
            "name": "linux",
            "purl": "pkg:deb/debian/linux?arch=source&distro=bookworm",
            "ecosystem": "Debian:12"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2021-47465.json"
          },
          "ecosystem_specific": {
            "urgency": "not yet assigned"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "5.14.16-1"
                }
              ]
            }
          ],
          "package": {
            "name": "linux",
            "purl": "pkg:deb/debian/linux?arch=source&distro=trixie",
            "ecosystem": "Debian:13"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2021-47465.json"
          },
          "ecosystem_specific": {
            "urgency": "not yet assigned"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "5.14.16-1"
                }
              ]
            }
          ],
          "package": {
            "name": "linux",
            "purl": "pkg:deb/debian/linux?arch=source&distro=forky",
            "ecosystem": "Debian:14"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2021-47465.json"
          },
          "ecosystem_specific": {
            "urgency": "not yet assigned"
          }
        }
      ],
      "modified": "2026-10-23T18:04:19.846709808Z",
      "provider": "osv",
      "upstream": [
        "CVE-2021-47465"
      ],
      "references": [
        "https://security-tracker.debian.org/tracker/CVE-2021-47465"
      ]
    },
    "related_cves": [
      {
        "value": "CVE-2021-47465",
        "evidence": "/upstream"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 423451,
  "published_at": "2024-05-22T07:15:11.367+00:00"
}