[PATCH v24 08/12] landlock: Add syscall implementations

[Jann Horn]

On Thu, Nov 12, 2020 at 9:52 PM Mickaël Salaün <mic at digikod.net> wrote:
> These 3 system calls are designed to be used by unprivileged processes
> to sandbox themselves:
> * landlock_create_ruleset(2): Creates a ruleset and returns its file
>   descriptor.
> * landlock_add_rule(2): Adds a rule (e.g. file hierarchy access) to a
>   ruleset, identified by the dedicated file descriptor.
> * landlock_enforce_ruleset_current(2): Enforces a ruleset on the current
>   thread and its future children (similar to seccomp).  This syscall has
>   the same usage restrictions as seccomp(2): the caller must have the
>   no_new_privs attribute set or have CAP_SYS_ADMIN in the current user
>   namespace.
>
> All these syscalls have a "flags" argument (not currently used) to
> enable extensibility.
>
> Here are the motivations for these new syscalls:
> * A sandboxed process may not have access to file systems, including
>   /dev, /sys or /proc, but it should still be able to add more
>   restrictions to itself.
> * Neither prctl(2) nor seccomp(2) (which was used in a previous version)
>   fit well with the current definition of a Landlock security policy.
>
> All passed structs (attributes) are checked at build time to ensure that
> they don't contain holes and that they are aligned the same way for each
> architecture.
>
> See the user and kernel documentation for more details (provided by a
> following commit):
> * Documentation/userspace-api/landlock.rst
> * Documentation/security/landlock.rst
>
> Cc: Arnd Bergmann <arnd at arndb.de>
> Cc: James Morris <jmorris at namei.org>
> Cc: Jann Horn <jannh at google.com>
> Cc: Kees Cook <keescook at chromium.org>
> Cc: Serge E. Hallyn <serge at hallyn.com>
> Signed-off-by: Mickaël Salaün <mic at linux.microsoft.com>

Reviewed-by: Jann Horn <jannh at google.com>