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Date:   Thu, 6 Oct 2022 15:35:32 +0200
From:   Christian Brauner <brauner@kernel.org>
To:     Miklos Szeredi <miklos@szeredi.hu>
Cc:     Amir Goldstein <amir73il@gmail.com>,
        "Darrick J . Wong" <djwong@kernel.org>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Christoph Hellwig <hch@lst.de>,
        Seth Forshee <sforshee@kernel.org>,
        Yang Xu <xuyang2018.jy@fujitsu.com>,
        Filipe Manana <fdmanana@kernel.org>,
        linux-unionfs@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH 1/3] attr: use consistent sgid stripping checks
Message-ID: <20221006133532.umwp6gzsh3wujwng@wittgenstein>
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 <CAJfpegss=79W+BXpOH_n7ZOtci1O0njHHxZMnb8ULJBStkq7mg@mail.gmail.com>
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On Thu, Oct 06, 2022 at 03:03:23PM +0200, Miklos Szeredi wrote:
> On Wed, 5 Oct 2022 at 17:14, Christian Brauner <brauner@kernel.org> wrote:
> >
> > Currently setgid stripping in file_remove_privs()'s should_remove_suid()
> > helper is inconsistent with other parts of the vfs. Specifically, it only
> > raises ATTR_KILL_SGID if the inode is S_ISGID and S_IXGRP but not if the
> > inode isn't in the caller's groups and the caller isn't privileged over the
> > inode although we require this already in setattr_prepare() and
> > setattr_copy() and so all filesystem implement this requirement implicitly
> > because they have to use setattr_{prepare,copy}() anyway.
> 
> Could the actual code (not just the logic) be shared between
> should_remove_sgid() and setattr_copy()?
> 
> Maybe add another helper, or reformulate should_remove_sgid() so that
> it can be used for both purposes.

Yeah, thanks for pointing that out. I'm actually working on that.