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Test your applicationsUpgrade SLES:15.3 kernel-default-devel to version 5.3.18-150300.59.218.1 or higher.
Note: Versions mentioned in the description apply only to the upstream kernel-default-devel package and not the kernel-default-devel package as distributed by SLES.
See How to fix? for SLES:15.3 relevant fixed versions and status.
In the Linux kernel, the following vulnerability has been resolved:
clone_private_mnt(): make sure that caller has CAP_SYS_ADMIN in the right userns
What we want is to verify there is that clone won't expose something hidden by a mount we wouldn't be able to undo. "Wouldn't be able to undo" may be a result of MNT_LOCKED on a child, but it may also come from lacking admin rights in the userns of the namespace mount belongs to.
clone_private_mnt() checks the former, but not the latter.
There's a number of rather confusing CAP_SYS_ADMIN checks in various userns during the mount, especially with the new mount API; they serve different purposes and in case of clone_private_mnt() they usually, but not always end up covering the missing check mentioned above.