linux-kernel - Re: [PATCH v2 07/25] capability: provide a helper for converting vfs

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Date: Thu, 22 Feb 2024 16:22:44 +0100
From: Christian Brauner <brauner@...nel.org>
To: "Seth Forshee (DigitalOcean)" <sforshee@...nel.org>
Cc: Serge Hallyn <serge@...lyn.com>, Paul Moore <paul@...l-moore.com>, 
	Eric Paris <eparis@...hat.com>, James Morris <jmorris@...ei.org>, 
	Alexander Viro <viro@...iv.linux.org.uk>, Jan Kara <jack@...e.cz>, 
	Stephen Smalley <stephen.smalley.work@...il.com>, Ondrej Mosnacek <omosnace@...hat.com>, 
	Casey Schaufler <casey@...aufler-ca.com>, Mimi Zohar <zohar@...ux.ibm.com>, 
	Roberto Sassu <roberto.sassu@...wei.com>, Dmitry Kasatkin <dmitry.kasatkin@...il.com>, 
	Eric Snowberg <eric.snowberg@...cle.com>, "Matthew Wilcox (Oracle)" <willy@...radead.org>, 
	Jonathan Corbet <corbet@....net>, Miklos Szeredi <miklos@...redi.hu>, 
	Amir Goldstein <amir73il@...il.com>, linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org, 
	linux-security-module@...r.kernel.org, audit@...r.kernel.org, selinux@...r.kernel.org, 
	linux-integrity@...r.kernel.org, linux-doc@...r.kernel.org, linux-unionfs@...r.kernel.org
Subject: Re: [PATCH v2 07/25] capability: provide a helper for converting
 vfs_caps to xattr for userspace

On Wed, Feb 21, 2024 at 03:24:38PM -0600, Seth Forshee (DigitalOcean) wrote:
> cap_inode_getsecurity() implements a handful of policies for capability
> xattrs read by userspace:
> 
>  - It returns EINVAL if the on-disk capability is in v1 format.
> 
>  - It masks off all bits in magic_etc except for the version and
>    VFS_CAP_FLAGS_EFFECTIVE.
> 
>  - v3 capabilities are converted to v2 format if the rootid returned to
>    userspace would be 0 or if the rootid corresponds to root in an
>    ancestor user namespace.
> 
>  - It returns EOVERFLOW for a v3 capability whose rootid does not map to
>    a valid id in current_user_ns() or to root in an ancestor namespace.
> 
> These policies must be maintained when converting vfs_caps to an xattr
> for userspace. Provide a vfs_caps_to_user_xattr() helper which will
> enforce these policies.
> 
> Signed-off-by: Seth Forshee (DigitalOcean) <sforshee@...nel.org>
> ---

Looks good,
Reviewed-by: Christian Brauner <brauner@...nel.org>