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SUSE: CVE-2020-16120: SUSE Linux Security Advisory

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SUSE: CVE-2020-16120: SUSE Linux Security Advisory

Severity
2
CVSS
(AV:L/AC:L/Au:N/C:P/I:N/A:N)
Published
10/14/2020
Created
11/14/2020
Added
11/12/2020
Modified
04/10/2021

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.

Solution(s)

  • suse-upgrade-kernel-default
  • suse-upgrade-kernel-docs
  • suse-upgrade-kernel-obs-build

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