CVE-2026-93827 (GCVE-0-2026-93827)
Vulnerability from cvelistv5
Published
2026-09-24 16:03
Modified
2026-09-25 12:43
Severity ?
8.4 (High) - CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: virtio-fs: avoid double-free on failed queue setup virtio_fs_setup_vqs() allocates fs->vqs and fs->mq_map before calling virtio_find_vqs(). If virtio_find_vqs() fails, the error path frees both pointers and returns an error to virtio_fs_probe(). virtio_fs_probe() then drops the last kobject reference, and virtio_fs_ktype_release() frees fs->vqs and fs->mq_map again. This leaves dangling pointers in struct virtio_fs and can trigger a double-free during probe failure cleanup. Set fs->vqs and fs->mq_map to NULL immediately after kfree() in the virtio_fs_setup_vqs() error path so that the later kobject release sees an uninitialized state and kfree(NULL) becomes harmless. This can be reproduced when a broken virtio-fs device advertises more request queues than the transport actually provides. In that case virtio_find_vqs() fails while setting up the extra queue, and the probe path reaches the double-free cleanup sequence.
References
Impacted products
Vendor Product Version
Linux Linux Version: a8f62f50b4e4ea92a938fca2ec1bd108d7f210e9
Version: a8f62f50b4e4ea92a938fca2ec1bd108d7f210e9
Version: a8f62f50b4e4ea92a938fca2ec1bd108d7f210e9
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/fuse/virtio_fs.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "3fbc5ee776fefbc6ea34d2518f1f5f90aa2e1dad",
              "status": "affected",
              "version": "a8f62f50b4e4ea92a938fca2ec1bd108d7f210e9",
              "versionType": "git"
            },
            {
              "lessThan": "20ef4739b329bb09cff11dd2458795a50674658e",
              "status": "affected",
              "version": "a8f62f50b4e4ea92a938fca2ec1bd108d7f210e9",
              "versionType": "git"
            },
            {
              "lessThan": "6af3330ec5d5fb8c06c04eb520a71cf73ea5a765",
              "status": "affected",
              "version": "a8f62f50b4e4ea92a938fca2ec1bd108d7f210e9",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/fuse/virtio_fs.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.9"
            },
            {
              "lessThan": "6.9",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.111",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.53",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.111",
                  "versionStartIncluding": "6.9",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.53",
                  "versionStartIncluding": "6.9",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2",
                  "versionStartIncluding": "6.9",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nvirtio-fs: avoid double-free on failed queue setup\n\nvirtio_fs_setup_vqs() allocates fs-\u003evqs and fs-\u003emq_map before calling\nvirtio_find_vqs(). If virtio_find_vqs() fails, the error path frees both\npointers and returns an error to virtio_fs_probe().\n\nvirtio_fs_probe() then drops the last kobject reference, and\nvirtio_fs_ktype_release() frees fs-\u003evqs and fs-\u003emq_map again. This leaves\ndangling pointers in struct virtio_fs and can trigger a double-free during\nprobe failure cleanup.\n\nSet fs-\u003evqs and fs-\u003emq_map to NULL immediately after kfree() in the\nvirtio_fs_setup_vqs() error path so that the later kobject release sees an\nuninitialized state and kfree(NULL) becomes harmless.\n\nThis can be reproduced when a broken virtio-fs device advertises more\nrequest queues than the transport actually provides. In that case\nvirtio_find_vqs() fails while setting up the extra queue, and the probe\npath reaches the double-free cleanup sequence."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 8.4,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The triggering field is virtio_fs_config.num_request_queues, read by virtio_cread_le() in virtio_fs_setup_vqs() from virtio_fs_probe() via virtio_dev_probe() after virtio_pci_probe()/register_virtio_device() binds a VIRTIO_ID_FS device; those bytes come from local PCI/MMIO/vDPA config space, not a network protocol message.\nAC:L - A device that advertises more request queues than it exposes makes virtio_find_vqs()-\u003evp_setup_vq() fail (-EINVAL when index \u003e= vp_modern_get_num_queues(), or -ENOENT on queue size 0); virtio_fs_setup_vqs() then kfree\u0027s fs-\u003evqs and fs-\u003emq_map and virtio_fs_probe() always kobject_put()s into the second free, with no race.\nPR:N - virtio_fs_probe()/virtio_fs_setup_vqs() have no capable() or credential check; MODULE_DEVICE_TABLE(virtio, id_table) autoloads virtiofs and virtio_dev_probe() binds a VIRTIO_ID_FS device at enumeration or hotplug, so a malicious virtio-fs backend needs no account on the guest.\nUI:N - The double-free runs in the probe error path (virtio_fs_setup_vqs() failure, then kobject_put() into virtio_fs_ktype_release()) when the device appears; virtio_fs_add_instance() and a virtiofs mount are never reached, so no victim must mount or open anything.\nS:U - virtio_fs_ktype_release() double-frees the guest kernel kmalloc objects fs-\u003evqs and fs-\u003emq_map; that is device-to-guest heap corruption inside the same guest kernel, not a write into host virtiofsd or a KVM/IOMMU escape.\nC:H - kfree(fs-\u003evqs) and kfree(fs-\u003emq_map) in virtio_fs_setup_vqs() leave dangling pointers that virtio_fs_ktype_release() frees again; a slab double-free of that virtio_fs_vq array and per-CPU mq_map lets those objects overlap so the attacker can read adjacent kernel heap.\nI:H - The same second kfree of fs-\u003evqs and fs-\u003emq_map corrupts the SLUB freelist for those kmalloc objects and is an arbitrary-free primitive, enabling heap overwrite and control-flow hijack in the guest kernel.\nA:H - Double-free of fs-\u003evqs and fs-\u003emq_map in virtio_fs_ktype_release() after virtio_find_vqs() fails oopses or panics the guest during probe cleanup (KASAN invalid-free, SLUB poisoned-freelist BUG, or panic_on_oops)."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-25T12:43:36.887Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/3fbc5ee776fefbc6ea34d2518f1f5f90aa2e1dad"
        },
        {
          "url": "https://git.kernel.org/stable/c/20ef4739b329bb09cff11dd2458795a50674658e"
        },
        {
          "url": "https://git.kernel.org/stable/c/6af3330ec5d5fb8c06c04eb520a71cf73ea5a765"
        }
      ],
      "title": "virtio-fs: avoid double-free on failed queue setup",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-93827",
    "datePublished": "2026-09-24T16:03:05.795Z",
    "dateReserved": "2026-09-18T17:59:28.792Z",
    "dateUpdated": "2026-09-25T12:43:36.887Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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