On 19/03/2021 19:54, Mickaël Salaün wrote:

On 19/03/2021 19:03, Kees Cook wrote:

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On Tue, Mar 16, 2021 at 09:42:52PM +0100, Mickaël Salaün wrote:

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From: Mickaël Salaün <redacted>

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+Special filesystems
+-------------------
+
+Access to regular files and directories can be restricted by Landlock,
+according to the handled accesses of a ruleset.  However, files that do not
+come from a user-visible filesystem (e.g. pipe, socket), but can still be
+accessed through /proc/self/fd/, cannot currently be restricted.  Likewise,
+some special kernel filesystems such as nsfs, which can be accessed through
+/proc/self/ns/, cannot currently be restricted.  For now, these kind of special
+paths are then always allowed.  Future Landlock evolutions will enable to
+restrict such paths with dedicated ruleset flags.

With this series, can /proc (at the top level) be blocked? (i.e. can a
landlock user avoid the weirdness by making /proc/$pid/ unavailable?)

/proc can be blocked, but not /proc/*/ns/* because of disconnected
roots. I plan to address this.

It is important to note that access to sensitive /proc files such as
ns/* and fd/* are automatically restricted according to domain
hierarchies. I'll add this detail to the documentation. :)