GSD-2020-16120

Vulnerability from gsd - Updated: 2023-12-13 01:21
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.
Aliases
Aliases
CVE-2020-16120
To clipboard 

{
  "GSD": {
    "alias": "CVE-2020-16120",
    "description": "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": "GSD-2020-16120",
    "references": [
      "https://www.suse.com/security/cve/CVE-2020-16120.html",
      "https://ubuntu.com/security/CVE-2020-16120",
      "https://security.archlinux.org/CVE-2020-16120",
      "https://linux.oracle.com/cve/CVE-2020-16120.html"
    ]
  },
  "gsd": {
    "metadata": {
      "exploitCode": "unknown",
      "remediation": "unknown",
      "reportConfidence": "confirmed",
      "type": "vulnerability"
    },
    "osvSchema": {
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        "CVE-2020-16120"
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      "id": "GSD-2020-16120",
      "modified": "2023-12-13T01:21:46.615179Z",
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    }
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        "STATE": "PUBLIC",
        "TITLE": "Unprivileged overlay + shiftfs read access"
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      "credit": [
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          "value": "Giuseppe Scrivano"
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            "value": "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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      "impact": {
        "baseMetricV2": {
          "acInsufInfo": false,
          "cvssV2": {
            "accessComplexity": "LOW",
            "accessVector": "LOCAL",
            "authentication": "NONE",
            "availabilityImpact": "NONE",
            "baseScore": 2.1,
            "confidentialityImpact": "PARTIAL",
            "integrityImpact": "NONE",
            "vectorString": "AV:L/AC:L/Au:N/C:P/I:N/A:N",
            "version": "2.0"
          },
          "exploitabilityScore": 3.9,
          "impactScore": 2.9,
          "obtainAllPrivilege": false,
          "obtainOtherPrivilege": false,
          "obtainUserPrivilege": false,
          "severity": "LOW",
          "userInteractionRequired": false
        },
        "baseMetricV3": {
          "cvssV3": {
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            "confidentialityImpact": "HIGH",
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            "privilegesRequired": "HIGH",
            "scope": "UNCHANGED",
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            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N",
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          "exploitabilityScore": 0.8,
          "impactScore": 3.6
        }
      },
      "lastModifiedDate": "2021-11-18T18:40Z",
      "publishedDate": "2021-02-10T20:15Z"
    }
  }
}



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