CVE-2025-40209 (GCVE-0-2025-40209)
Vulnerability from cvelistv5
Published
2025-11-21 10:19
Modified
2025-11-21 10:19
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: btrfs: fix memory leak of qgroup_list in btrfs_add_qgroup_relation When btrfs_add_qgroup_relation() is called with invalid qgroup levels (src >= dst), the function returns -EINVAL directly without freeing the preallocated qgroup_list structure passed by the caller. This causes a memory leak because the caller unconditionally sets the pointer to NULL after the call, preventing any cleanup. The issue occurs because the level validation check happens before the mutex is acquired and before any error handling path that would free the prealloc pointer. On this early return, the cleanup code at the 'out' label (which includes kfree(prealloc)) is never reached. In btrfs_ioctl_qgroup_assign(), the code pattern is: prealloc = kzalloc(sizeof(*prealloc), GFP_KERNEL); ret = btrfs_add_qgroup_relation(trans, sa->src, sa->dst, prealloc); prealloc = NULL; // Always set to NULL regardless of return value ... kfree(prealloc); // This becomes kfree(NULL), does nothing When the level check fails, 'prealloc' is never freed by either the callee or the caller, resulting in a 64-byte memory leak per failed operation. This can be triggered repeatedly by an unprivileged user with access to a writable btrfs mount, potentially exhausting kernel memory. Fix this by freeing prealloc before the early return, ensuring prealloc is always freed on all error paths.
References
Impacted products
Vendor Product Version
Linux Linux Version: 4addc1ffd67ad34394674dc91379dc04cfdd2537
Version: 4addc1ffd67ad34394674dc91379dc04cfdd2537
Version: 4addc1ffd67ad34394674dc91379dc04cfdd2537
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/btrfs/qgroup.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "3412d0e973e8f8381747d69033eda809a57a2581",
              "status": "affected",
              "version": "4addc1ffd67ad34394674dc91379dc04cfdd2537",
              "versionType": "git"
            },
            {
              "lessThan": "a4d9ebe23bcb79d9d057e3c995db73b7b3aae414",
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              "version": "4addc1ffd67ad34394674dc91379dc04cfdd2537",
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            },
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              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/btrfs/qgroup.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.11"
            },
            {
              "lessThan": "6.11",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.58",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.17.*",
              "status": "unaffected",
              "version": "6.17.8",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "6.18-rc5",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.58",
                  "versionStartIncluding": "6.11",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.17.8",
                  "versionStartIncluding": "6.11",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18-rc5",
                  "versionStartIncluding": "6.11",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: fix memory leak of qgroup_list in btrfs_add_qgroup_relation\n\nWhen btrfs_add_qgroup_relation() is called with invalid qgroup levels\n(src \u003e= dst), the function returns -EINVAL directly without freeing the\npreallocated qgroup_list structure passed by the caller. This causes a\nmemory leak because the caller unconditionally sets the pointer to NULL\nafter the call, preventing any cleanup.\n\nThe issue occurs because the level validation check happens before the\nmutex is acquired and before any error handling path that would free\nthe prealloc pointer. On this early return, the cleanup code at the\n\u0027out\u0027 label (which includes kfree(prealloc)) is never reached.\n\nIn btrfs_ioctl_qgroup_assign(), the code pattern is:\n\n    prealloc = kzalloc(sizeof(*prealloc), GFP_KERNEL);\n    ret = btrfs_add_qgroup_relation(trans, sa-\u003esrc, sa-\u003edst, prealloc);\n    prealloc = NULL;  // Always set to NULL regardless of return value\n    ...\n    kfree(prealloc);  // This becomes kfree(NULL), does nothing\n\nWhen the level check fails, \u0027prealloc\u0027 is never freed by either the\ncallee or the caller, resulting in a 64-byte memory leak per failed\noperation. This can be triggered repeatedly by an unprivileged user\nwith access to a writable btrfs mount, potentially exhausting kernel\nmemory.\n\nFix this by freeing prealloc before the early return, ensuring prealloc\nis always freed on all error paths."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2025-11-21T10:19:44.757Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/3412d0e973e8f8381747d69033eda809a57a2581"
        },
        {
          "url": "https://git.kernel.org/stable/c/a4d9ebe23bcb79d9d057e3c995db73b7b3aae414"
        },
        {
          "url": "https://git.kernel.org/stable/c/f260c6aff0b8af236084012d14f9f1bf792ea883"
        }
      ],
      "title": "btrfs: fix memory leak of qgroup_list in btrfs_add_qgroup_relation",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2025-40209",
    "datePublished": "2025-11-21T10:19:44.757Z",
    "dateReserved": "2025-04-16T07:20:57.179Z",
    "dateUpdated": "2025-11-21T10:19:44.757Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "nvd": "{\"cve\":{\"id\":\"CVE-2025-40209\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2025-11-21T11:15:47.000\",\"lastModified\":\"2025-11-21T15:13:13.800\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nbtrfs: fix memory leak of qgroup_list in btrfs_add_qgroup_relation\\n\\nWhen btrfs_add_qgroup_relation() is called with invalid qgroup levels\\n(src \u003e= dst), the function returns -EINVAL directly without freeing the\\npreallocated qgroup_list structure passed by the caller. This causes a\\nmemory leak because the caller unconditionally sets the pointer to NULL\\nafter the call, preventing any cleanup.\\n\\nThe issue occurs because the level validation check happens before the\\nmutex is acquired and before any error handling path that would free\\nthe prealloc pointer. On this early return, the cleanup code at the\\n\u0027out\u0027 label (which includes kfree(prealloc)) is never reached.\\n\\nIn btrfs_ioctl_qgroup_assign(), the code pattern is:\\n\\n    prealloc = kzalloc(sizeof(*prealloc), GFP_KERNEL);\\n    ret = btrfs_add_qgroup_relation(trans, sa-\u003esrc, sa-\u003edst, prealloc);\\n    prealloc = NULL;  // Always set to NULL regardless of return value\\n    ...\\n    kfree(prealloc);  // This becomes kfree(NULL), does nothing\\n\\nWhen the level check fails, \u0027prealloc\u0027 is never freed by either the\\ncallee or the caller, resulting in a 64-byte memory leak per failed\\noperation. This can be triggered repeatedly by an unprivileged user\\nwith access to a writable btrfs mount, potentially exhausting kernel\\nmemory.\\n\\nFix this by freeing prealloc before the early return, ensuring prealloc\\nis always freed on all error paths.\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/3412d0e973e8f8381747d69033eda809a57a2581\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/a4d9ebe23bcb79d9d057e3c995db73b7b3aae414\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/f260c6aff0b8af236084012d14f9f1bf792ea883\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


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