fkie_cve-2020-16120
Vulnerability from fkie_nvd
Published
2021-02-10 20:15
Modified
2024-11-21 05:06
Severity ?
5.1 (Medium) - CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
4.4 (Medium) - CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N
Summary
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.
References
security@ubuntu.comhttps://git.kernel.org/linus/05acefb4872dae89e772729efb194af754c877e8Patch, Third Party Advisory
security@ubuntu.comhttps://git.kernel.org/linus/48bd024b8a40d73ad6b086de2615738da0c7004fPatch, Third Party Advisory
security@ubuntu.comhttps://git.kernel.org/linus/56230d956739b9cb1cbde439d76227d77979a04dPatch, Third Party Advisory
security@ubuntu.comhttps://git.kernel.org/linus/b6650dab404c701d7fe08a108b746542a934da84Patch, Third Party Advisory
security@ubuntu.comhttps://git.kernel.org/linus/d1d04ef8572bc8c22265057bd3d5a79f223f8f52Patch, Third Party Advisory
security@ubuntu.comhttps://launchpad.net/bugs/1894980Issue Tracking, Patch, Third Party Advisory
security@ubuntu.comhttps://launchpad.net/bugs/1900141Issue Tracking, Third Party Advisory
security@ubuntu.comhttps://ubuntu.com/USN-4576-1Third Party Advisory
security@ubuntu.comhttps://ubuntu.com/USN-4577-1Third Party Advisory
security@ubuntu.comhttps://ubuntu.com/USN-4578-1Third Party Advisory
security@ubuntu.comhttps://www.openwall.com/lists/oss-security/2020/10/14/2Mailing List, Third Party Advisory
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/linus/05acefb4872dae89e772729efb194af754c877e8Patch, Third Party Advisory
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/linus/48bd024b8a40d73ad6b086de2615738da0c7004fPatch, Third Party Advisory
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/linus/56230d956739b9cb1cbde439d76227d77979a04dPatch, Third Party Advisory
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/linus/b6650dab404c701d7fe08a108b746542a934da84Patch, Third Party Advisory
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/linus/d1d04ef8572bc8c22265057bd3d5a79f223f8f52Patch, Third Party Advisory
af854a3a-2127-422b-91ae-364da2661108https://launchpad.net/bugs/1894980Issue Tracking, Patch, Third Party Advisory
af854a3a-2127-422b-91ae-364da2661108https://launchpad.net/bugs/1900141Issue Tracking, Third Party Advisory
af854a3a-2127-422b-91ae-364da2661108https://ubuntu.com/USN-4576-1Third Party Advisory
af854a3a-2127-422b-91ae-364da2661108https://ubuntu.com/USN-4577-1Third Party Advisory
af854a3a-2127-422b-91ae-364da2661108https://ubuntu.com/USN-4578-1Third Party Advisory
af854a3a-2127-422b-91ae-364da2661108https://www.openwall.com/lists/oss-security/2020/10/14/2Mailing List, Third Party Advisory
Impacted products
Vendor Product Version
linux linux_kernel *
canonical ubuntu_linux 14.04
canonical ubuntu_linux 16.04
canonical ubuntu_linux 18.04
canonical ubuntu_linux 20.04


To clipboard 

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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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