kasan: fix cache shrink race with CPU hotplug

{
  "id": "f3afb0950c16a12688fbcb92b25146a1f3488f218b9dc7c4010968f886992590",
  "url": "https://osv.dev/vulnerability/CVE-2026-93208",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "kasan: fix cache shrink race with CPU hotplug",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: kasan: fix cache shrink race with CPU hotplug kasan_quarantine_remove_cache() first invokes per_cpu_remove_cache() on all online CPUs. Each callback moves objects belonging to the cache from cpu_quarantine to the CPU's shrink_qlist, where they can later be freed from task context. kmem_cache_destroy() invokes the quarantine removal path while holding cpus_read_lock(), but kmem_cache_shrink() does not. The latter can therefore race with CPU offlining as follows: kmem_cache_shrink() CPU hotplug ------------------- ----------- on_each_cpu() CPU1 moves objects to CPU1's shrink_qlist on_each_cpu() returns CPU1 goes offline kasan_cpu_offline() drains cpu_quarantine leaves shrink_qlist untouched for_each_online_cpu() skips CPU1 The objects left on CPU1's shrink_qlist are not returned to the slab allocator. This may prevent kmem_cache_shrink() from releasing slabs that would otherwise become empty. If CPU1 remains offline, a later kmem_cache_destroy() also skips the list and can report that the cache still contains objects. An intermittent occurrence was observed with a virtio-9p filesystem. The mount and umount commands both returned 0, but the kernel logged the following during the userspace-triggered teardown: [ 2994.380134][ T111] BUG 9p-fcall-cache-1 (Tainted: G B ): Objects remaining on __kmem_cache_shutdown() [ 2994.381140][ T111] Object 0xff11000004361118 @offset=4376 [ 2994.381607][ T111] Allocated in p9_fca",
    "evidence": "osv:CVE-2026-93208",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.1.191",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.6.157",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.12.109",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.50",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.2.4",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-93208",
      "aliases": [
        "CVE-2026-93208"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "07d067e4f2ceb72b9f681995cc53828caaba9e6e"
                },
                {
                  "fixed": "eab61c0781cbe899e074c0009af304f3b337e0c9"
                },
                {
                  "fixed": "7cd164f0e1bab0f8dd125c92ed4f19bbd6b92a4a"
                },
                {
                  "fixed": "709c3646545e0a1f99a5816384c633f6552c5a98"
                },
                {
                  "fixed": "30e8cb8598aa41b1b9f8803081d2ae5e5369c0f3"
                },
                {
                  "fixed": "3119d58e4ef8719d669911d38a53fc00086ac48b"
                },
                {
                  "fixed": "8790303cbaac52a11dfed4aab261f8ea60682525"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-93208.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "5.19.0"
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                {
                  "fixed": "6.1.191"
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            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.2.0"
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                {
                  "fixed": "6.6.157"
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              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.7.0"
                },
                {
                  "fixed": "6.12.109"
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              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.13.0"
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                {
                  "fixed": "6.18.50"
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              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.19.0"
                },
                {
                  "fixed": "7.2.4"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-93208.json"
          }
        }
      ],
      "modified": "2026-11-01T02:30:28.159005962Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/30e8cb8598aa41b1b9f8803081d2ae5e5369c0f3",
        "https://git.kernel.org/stable/c/3119d58e4ef8719d669911d38a53fc00086ac48b",
        "https://git.kernel.org/stable/c/709c3646545e0a1f99a5816384c633f6552c5a98",
        "https://git.kernel.org/stable/c/7cd164f0e1bab0f8dd125c92ed4f19bbd6b92a4a",
        "https://git.kernel.org/stable/c/8790303cbaac52a11dfed4aab261f8ea60682525",
        "https://git.kernel.org/stable/c/eab61c0781cbe899e074c0009af304f3b337e0c9",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/93xxx/CVE-2026-93208.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-93208",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/93xxx/CVE-2026-93208.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-93208",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 518641,
  "published_at": "2026-09-24T15:10:31.888+00:00"
}