On 10/02/2021 20:36, Serge E. Hallyn wrote:
On Tue, Feb 02, 2021 at 05:27:05PM +0100, Mickaël Salaün wrote:
From: Mickaël Salaün mic@linux.microsoft.com
Thanks to the Landlock objects and ruleset, it is possible to identify inodes according to a process's domain. To enable an unprivileged
This throws me off a bit. "identify inodes according to a process's domain". What exactly does it mean? "identify" how ?
A domain is a set of rules (i.e. layers of rulesets) enforced on a set of threads. Inodes are tagged per domain (i.e. not system-wide) and actions are restricted thanks to these tags, which form rules. It means that the created access-controls are scoped to a set of threads.
process to express a file hierarchy, it first needs to open a directory (or a file) and pass this file descriptor to the kernel through landlock_add_rule(2). When checking if a file access request is allowed, we walk from the requested dentry to the real root, following the different mount layers. The access to each "tagged" inodes are collected according to their rule layer level, and ANDed to create access to the requested file hierarchy. This makes possible to identify a lot of files without tagging every inodes nor modifying the filesystem, while still following the view and understanding the user has from the filesystem.
Add a new ARCH_EPHEMERAL_INODES for UML because it currently does not keep the same struct inodes for the same inodes whereas these inodes are in use.
-serge