CVE - CVE-2020-16120

CVE-ID
CVE-2020-16120	Learn more at National Vulnerability Database (NVD) • CVSS Severity Rating • Fix Information • Vulnerable Software Versions • SCAP Mappings • CPE Information
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.
References
Note: References are provided for the convenience of the reader to help distinguish between vulnerabilities. The list is not intended to be complete.
CONFIRM:https://git.kernel.org/linus/05acefb4872dae89e772729efb194af754c877e8 URL:https://git.kernel.org/linus/05acefb4872dae89e772729efb194af754c877e8 CONFIRM:https://git.kernel.org/linus/48bd024b8a40d73ad6b086de2615738da0c7004f URL:https://git.kernel.org/linus/48bd024b8a40d73ad6b086de2615738da0c7004f CONFIRM:https://git.kernel.org/linus/56230d956739b9cb1cbde439d76227d77979a04d URL:https://git.kernel.org/linus/56230d956739b9cb1cbde439d76227d77979a04d CONFIRM:https://git.kernel.org/linus/b6650dab404c701d7fe08a108b746542a934da84 URL:https://git.kernel.org/linus/b6650dab404c701d7fe08a108b746542a934da84 CONFIRM:https://git.kernel.org/linus/d1d04ef8572bc8c22265057bd3d5a79f223f8f52 URL:https://git.kernel.org/linus/d1d04ef8572bc8c22265057bd3d5a79f223f8f52 CONFIRM:https://www.openwall.com/lists/oss-security/2020/10/14/2 URL:https://www.openwall.com/lists/oss-security/2020/10/14/2 UBUNTU:https://launchpad.net/bugs/1894980 URL:https://launchpad.net/bugs/1894980 UBUNTU:https://launchpad.net/bugs/1900141 URL:https://launchpad.net/bugs/1900141 UBUNTU:https://ubuntu.com/USN-4576-1 URL:https://ubuntu.com/USN-4576-1 UBUNTU:https://ubuntu.com/USN-4577-1 URL:https://ubuntu.com/USN-4577-1 UBUNTU:https://ubuntu.com/USN-4578-1 URL:https://ubuntu.com/USN-4578-1
Assigning CNA
Canonical Ltd.
Date Record Created
20200729	Disclaimer: The record creation date may reflect when the CVE ID was allocated or reserved, and does not necessarily indicate when this vulnerability was discovered, shared with the affected vendor, publicly disclosed, or updated in CVE.
Phase (Legacy)
Assigned (20200729)
Votes (Legacy)

Comments (Legacy)

Proposed (Legacy)
N/A
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