ghsa-q6jw-34cj-733v
Vulnerability from github
Published
2022-05-24 17:41
Modified
2022-05-24 17:41
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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