[RFC PATCH] lsm: add the inode_free_security_rcu() LSM implementation hook

[Paul Moore]

On Tue, Jul 9, 2024 at 10:40 PM Paul Moore <paul at paul-moore.com> wrote:
>
> The LSM framework has an existing inode_free_security() hook which
> is used by LSMs that manage state associated with an inode, but
> due to the use of RCU to protect the inode, special care must be
> taken to ensure that the LSMs do not fully release the inode state
> until it is safe from a RCU perspective.
>
> This patch implements a new inode_free_security_rcu() implementation
> hook which is called when it is safe to free the LSM's internal inode
> state.  Unfortunately, this new hook does not have access to the inode
> itself as it may already be released, so the existing
> inode_free_security() hook is retained for those LSMs which require
> access to the inode.
>
> Signed-off-by: Paul Moore <paul at paul-moore.com>
> ---
>  include/linux/lsm_hook_defs.h     |  1 +
>  security/integrity/ima/ima.h      |  2 +-
>  security/integrity/ima/ima_iint.c | 20 ++++++++------------
>  security/integrity/ima/ima_main.c |  2 +-
>  security/landlock/fs.c            |  9 ++++++---
>  security/security.c               | 26 +++++++++++++-------------
>  6 files changed, 30 insertions(+), 30 deletions(-)

FYI, this has only received "light" testing, and even that is fairly
generous.  I booted up a system with IMA set to measure the TCB and
ran through the audit and SELinux test suites; IMA seemed to be
working just fine but I didn't poke at it too hard.  I didn't have an
explicit Landlock test handy, but I'm hoping that the Landlock
enablement on a modern Rawhide system hit it a little :)

-- 
paul-moore.com