GHSA-Q6JW-34CJ-733V

Vulnerability from github – Published: 2022-05-24 17:41 – Updated: 2022-05-24 17:41
VLAI?
Details

Overlayfs did not properly perform permission checking when copying up files in an overlayfs and could be exploited from within a user namespace, if, for example, unprivileged user namespaces were allowed. It was possible to have a file not readable by an unprivileged user to be copied to a mountpoint controlled by the user, like a removable device. This was introduced in kernel version 4.19 by commit d1d04ef ("ovl: stack file ops"). This was fixed in kernel version 5.8 by commits 56230d9 ("ovl: verify permissions in ovl_path_open()"), 48bd024 ("ovl: switch to mounter creds in readdir") and 05acefb ("ovl: check permission to open real file"). Additionally, commits 130fdbc ("ovl: pass correct flags for opening real directory") and 292f902 ("ovl: call secutiry hook in ovl_real_ioctl()") in kernel 5.8 might also be desired or necessary. These additional commits introduced a regression in overlay mounts within user namespaces which prevented access to files with ownership outside of the user namespace. This regression was mitigated by subsequent commit b6650da ("ovl: do not fail because of O_NOATIMEi") in kernel 5.11.

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{
  "affected": [],
  "aliases": [
    "CVE-2020-16120"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-269"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2021-02-10T20:15:00Z",
    "severity": "MODERATE"
  },
  "details": "Overlayfs did not properly perform permission checking when copying up files in an overlayfs and could be exploited from within a user namespace, if, for example, unprivileged user namespaces were allowed. It was possible to have a file not readable by an unprivileged user to be copied to a mountpoint controlled by the user, like a removable device. This was introduced in kernel version 4.19 by commit d1d04ef (\"ovl: stack file ops\"). This was fixed in kernel version 5.8 by commits 56230d9 (\"ovl: verify permissions in ovl_path_open()\"), 48bd024 (\"ovl: switch to mounter creds in readdir\") and 05acefb (\"ovl: check permission to open real file\"). Additionally, commits 130fdbc (\"ovl: pass correct flags for opening real directory\") and 292f902 (\"ovl: call secutiry hook in ovl_real_ioctl()\") in kernel 5.8 might also be desired or necessary. These additional commits introduced a regression in overlay mounts within user namespaces which prevented access to files with ownership outside of the user namespace. This regression was mitigated by subsequent commit b6650da (\"ovl: do not fail because of O_NOATIMEi\") in kernel 5.11.",
  "id": "GHSA-q6jw-34cj-733v",
  "modified": "2022-05-24T17:41:41Z",
  "published": "2022-05-24T17:41:41Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2020-16120"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/linus/05acefb4872dae89e772729efb194af754c877e8"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/linus/48bd024b8a40d73ad6b086de2615738da0c7004f"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/linus/56230d956739b9cb1cbde439d76227d77979a04d"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/linus/b6650dab404c701d7fe08a108b746542a934da84"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/linus/d1d04ef8572bc8c22265057bd3d5a79f223f8f52"
    },
    {
      "type": "WEB",
      "url": "https://launchpad.net/bugs/1894980"
    },
    {
      "type": "WEB",
      "url": "https://launchpad.net/bugs/1900141"
    },
    {
      "type": "WEB",
      "url": "https://ubuntu.com/USN-4576-1"
    },
    {
      "type": "WEB",
      "url": "https://ubuntu.com/USN-4577-1"
    },
    {
      "type": "WEB",
      "url": "https://ubuntu.com/USN-4578-1"
    },
    {
      "type": "WEB",
      "url": "https://www.openwall.com/lists/oss-security/2020/10/14/2"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}


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