FKIE_CVE-2026-63827

Vulnerability from fkie_nvd - Published: 2026-07-19 12:16 - Updated: 2026-07-20 15:16
Severity
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: apparmor: fix use-after-free in rawdata dedup loop aa_replace_profiles() walks ns->rawdata_list to dedup the incoming policy blob against entries already attached to existing profiles. Per the kernel-doc on struct aa_loaddata, list membership does not hold a reference: profiles hold pcount, and when the last pcount drops, do_ploaddata_rmfs() is queued on a workqueue that takes ns->lock and removes the entry. Between dropping the last pcount and the workqueue running, an entry remains on the list with pcount == 0. aa_get_profile_loaddata() is an unconditional kref_get() on pcount, so when the dedup loop hits such an entry, refcount hardening reports refcount_t: addition on 0; use-after-free. inside aa_replace_profiles(), and the poisoned counter then trips "saturated" and "underflow" warnings on the subsequent uses of the same loaddata. Before commit a0b7091c4de4 ("apparmor: fix race on rawdata dereference") the dedup path used a get_unless_zero-style helper on a single counter, so the existing "if (tmp)" guard was meaningful. The split-refcount refactor introduced aa_get_profile_loaddata(), which has plain kref_get() semantics, and the guard quietly became a no-op. Introduce aa_get_profile_loaddata_not0(), matching the existing _not0 convention used by aa_get_profile_not0(), and use it for the rawdata_list dedup lookup so dying entries are skipped. Reproduced on x86_64 with v7.1-rc5 in QEMU+KVM running Ubuntu 24.04 + stress-ng 0.17.06: stress-ng --apparmor 1 --klog-check --timeout 60s Without this patch the three refcount_t warnings fire within a few seconds. With it the same 60 s run is clean. Coverage is a smoke-test only; a longer soak with CONFIG_KASAN, CONFIG_KCSAN and CONFIG_PROVE_LOCKING would be welcome from anyone with the cycles.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/15fd83a1e42ede15070968806bb6c8b1a5170688
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/5e34fa9f6f7cd688ae153fff13139a5cf2d42339
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/6f060496d03e4dc560a40f73770bd08335cb7a27
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/a7a2890028f16e5b0af0bb005d80fcb32559cca3
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/c3ca2631073b2cef06824fd2bfc452ff7a1023de
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/ce261a20b41db522e320a41bbf1292bf85af66df
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "security/apparmor/include/policy_unpack.h",
            "security/apparmor/policy.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "a7a2890028f16e5b0af0bb005d80fcb32559cca3",
              "status": "affected",
              "version": "6b6ba87579c7e7c669e0bec91823e7fb693bc5df",
              "versionType": "git"
            },
            {
              "lessThan": "15fd83a1e42ede15070968806bb6c8b1a5170688",
              "status": "affected",
              "version": "6ef1f2926c41ab96952d9696d55a052f1b3a9418",
              "versionType": "git"
            },
            {
              "lessThan": "ce261a20b41db522e320a41bbf1292bf85af66df",
              "status": "affected",
              "version": "f9761add6d100962a23996cb68f3d6abdd4d1815",
              "versionType": "git"
            },
            {
              "lessThan": "c3ca2631073b2cef06824fd2bfc452ff7a1023de",
              "status": "affected",
              "version": "af782cc8871e3683ddd5a3cd2f7df526599863a9",
              "versionType": "git"
            },
            {
              "lessThan": "5e34fa9f6f7cd688ae153fff13139a5cf2d42339",
              "status": "affected",
              "version": "a0b7091c4de45a7325c8780e6934a894f92ac86b",
              "versionType": "git"
            },
            {
              "lessThan": "6f060496d03e4dc560a40f73770bd08335cb7a27",
              "status": "affected",
              "version": "a0b7091c4de45a7325c8780e6934a894f92ac86b",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "3b8e77c7abab40e6de9ad9de730d77984a498840",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "d9d8560b9b7932f8cffc4c068c14289220900f79",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "763e838adc3c7ec5a7df2990ce84cad951e42721",
              "versionType": "git"
            },
            {
              "lessThan": "6.1.177",
              "status": "affected",
              "version": "6.1.169",
              "versionType": "semver"
            },
            {
              "lessThan": "6.6.144",
              "status": "affected",
              "version": "6.6.130",
              "versionType": "semver"
            },
            {
              "lessThan": "6.12.95",
              "status": "affected",
              "version": "6.12.77",
              "versionType": "semver"
            },
            {
              "lessThan": "6.18.38",
              "status": "affected",
              "version": "6.18.18",
              "versionType": "semver"
            },
            {
              "lessThan": "5.11",
              "status": "affected",
              "version": "5.10.253",
              "versionType": "semver"
            },
            {
              "lessThan": "5.16",
              "status": "affected",
              "version": "5.15.203",
              "versionType": "semver"
            },
            {
              "lessThan": "6.20",
              "status": "affected",
              "version": "6.19.8",
              "versionType": "semver"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "security/apparmor/include/policy_unpack.h",
            "security/apparmor/policy.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "7.0"
            },
            {
              "lessThan": "7.0",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.177",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.144",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.95",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.38",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.3",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2-rc1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\napparmor: fix use-after-free in rawdata dedup loop\n\naa_replace_profiles() walks ns-\u003erawdata_list to dedup the incoming\npolicy blob against entries already attached to existing profiles.\nPer the kernel-doc on struct aa_loaddata, list membership does not\nhold a reference: profiles hold pcount, and when the last pcount\ndrops, do_ploaddata_rmfs() is queued on a workqueue that takes\nns-\u003elock and removes the entry. Between dropping the last pcount\nand the workqueue running, an entry remains on the list with\npcount == 0.\n\naa_get_profile_loaddata() is an unconditional kref_get() on\npcount, so when the dedup loop hits such an entry, refcount\nhardening reports\n\n  refcount_t: addition on 0; use-after-free.\n\ninside aa_replace_profiles(), and the poisoned counter then\ntrips \"saturated\" and \"underflow\" warnings on the subsequent\nuses of the same loaddata.\n\nBefore commit a0b7091c4de4 (\"apparmor: fix race on rawdata\ndereference\") the dedup path used a get_unless_zero-style helper\non a single counter, so the existing \"if (tmp)\" guard was\nmeaningful. The split-refcount refactor introduced\naa_get_profile_loaddata(), which has plain kref_get() semantics,\nand the guard quietly became a no-op.\n\nIntroduce aa_get_profile_loaddata_not0(), matching the existing\n_not0 convention used by aa_get_profile_not0(), and use it for\nthe rawdata_list dedup lookup so dying entries are skipped.\n\nReproduced on x86_64 with v7.1-rc5 in QEMU+KVM running Ubuntu\n24.04 + stress-ng 0.17.06:\n\n  stress-ng --apparmor 1 --klog-check --timeout 60s\n\nWithout this patch the three refcount_t warnings fire within a\nfew seconds. With it the same 60 s run is clean. Coverage is a\nsmoke-test only; a longer soak with CONFIG_KASAN, CONFIG_KCSAN\nand CONFIG_PROVE_LOCKING would be welcome from anyone with the\ncycles."
    }
  ],
  "id": "CVE-2026-63827",
  "lastModified": "2026-07-20T15:16:49.310",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "LOCAL",
          "availabilityImpact": "HIGH",
          "baseScore": 7.8,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 1.8,
        "impactScore": 5.9,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-07-19T12:16:55.960",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/15fd83a1e42ede15070968806bb6c8b1a5170688"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/5e34fa9f6f7cd688ae153fff13139a5cf2d42339"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/6f060496d03e4dc560a40f73770bd08335cb7a27"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/a7a2890028f16e5b0af0bb005d80fcb32559cca3"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/c3ca2631073b2cef06824fd2bfc452ff7a1023de"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/ce261a20b41db522e320a41bbf1292bf85af66df"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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