Re: [PATCH 1/5] security: allow finer granularity in permitting copy-up of security xattrs

From: Amir Goldstein <amir73il@gmail.com>
To: Stefan Berger <stefanb@linux.ibm.com>
Cc: linux-integrity@vger.kernel.org,
	linux-security-module@vger.kernel.org,
	 linux-unionfs@vger.kernel.org, linux-kernel@vger.kernel.org,
	 paul@paul-moore.com, jmorris@namei.org, serge@hallyn.com,
	zohar@linux.ibm.com,  roberto.sassu@huawei.com,
	miklos@szeredi.hu,  Christian Brauner <brauner@kernel.org>
Subject: Re: [PATCH 1/5] security: allow finer granularity in permitting copy-up of security xattrs
Date: Wed, 31 Jan 2024 15:25:29 +0200	[thread overview]
Message-ID: <CAOQ4uxjgdvGU0WE+92ByQE26Jp0j16AgfyCjNyEp7=86akOSsA@mail.gmail.com> (raw)
In-Reply-To: <20240130214620.3155380-2-stefanb@linux.ibm.com>

On Tue, Jan 30, 2024 at 11:46 PM Stefan Berger <stefanb@linux.ibm.com> wrote:
>
> Copying up xattrs is solely based on the security xattr name. For finer
> granularity add a dentry parameter to the security_inode_copy_up_xattr
> hook definition, allowing decisions to be based on the xattr content as
> well.
>
> Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
> ---
>  fs/overlayfs/copy_up.c            | 2 +-
>  include/linux/evm.h               | 2 +-
>  include/linux/lsm_hook_defs.h     | 3 ++-
>  include/linux/security.h          | 4 ++--
>  security/integrity/evm/evm_main.c | 2 +-
>  security/security.c               | 7 ++++---
>  security/selinux/hooks.c          | 2 +-
>  security/smack/smack_lsm.c        | 2 +-
>  8 files changed, 13 insertions(+), 11 deletions(-)
>
> diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
> index b8e25ca51016..bd9ddcefb7a7 100644
> --- a/fs/overlayfs/copy_up.c
> +++ b/fs/overlayfs/copy_up.c
> @@ -114,7 +114,7 @@ int ovl_copy_xattr(struct super_block *sb, const struct path *oldpath, struct de
>                 if (ovl_is_private_xattr(sb, name))
>                         continue;
>
> -               error = security_inode_copy_up_xattr(name);
> +               error = security_inode_copy_up_xattr(old, name);

What do you think about:

                     error = security_inode_copy_up_xattr(name, NULL, 0);

and then later...

                     error = security_inode_copy_up_xattr(name, value, size);

I am asking because overlayfs uses mnt_idmap(path->mnt) and you
have used nop_mnt_idmap inside evm hook.
this does not look right to me?

Thanks,
Amir.