linux-ext4 - Re: [PATCH v6 05/39] namei: make permission helpers idmapped mount aware

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Message-ID: <20210122222632.GB25405@fieldses.org>
Date:   Fri, 22 Jan 2021 17:26:32 -0500
From:   bfields@...ldses.org (J. Bruce Fields)
To:     Christian Brauner <christian.brauner@...ntu.com>
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        Christoph Hellwig <hch@....de>, linux-fsdevel@...r.kernel.org,
        John Johansen <john.johansen@...onical.com>,
        James Morris <jmorris@...ei.org>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        Dmitry Kasatkin <dmitry.kasatkin@...il.com>,
        Stephen Smalley <stephen.smalley.work@...il.com>,
        Casey Schaufler <casey@...aufler-ca.com>,
        Arnd Bergmann <arnd@...db.de>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>,
        Geoffrey Thomas <geofft@...reload.com>,
        Mrunal Patel <mpatel@...hat.com>,
        Josh Triplett <josh@...htriplett.org>,
        Andy Lutomirski <luto@...nel.org>,
        Theodore Tso <tytso@....edu>, Alban Crequy <alban@...volk.io>,
        Tycho Andersen <tycho@...ho.ws>,
        David Howells <dhowells@...hat.com>,
        James Bottomley <James.Bottomley@...senpartnership.com>,
        Seth Forshee <seth.forshee@...onical.com>,
        Stéphane Graber <stgraber@...ntu.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Aleksa Sarai <cyphar@...har.com>,
        Lennart Poettering <lennart@...ttering.net>,
        "Eric W. Biederman" <ebiederm@...ssion.com>, smbarber@...omium.org,
        Phil Estes <estesp@...il.com>, Serge Hallyn <serge@...lyn.com>,
        Kees Cook <keescook@...omium.org>,
        Todd Kjos <tkjos@...gle.com>, Paul Moore <paul@...l-moore.com>,
        Jonathan Corbet <corbet@....net>,
        containers@...ts.linux-foundation.org,
        linux-security-module@...r.kernel.org, linux-api@...r.kernel.org,
        linux-ext4@...r.kernel.org, linux-xfs@...r.kernel.org,
        linux-integrity@...r.kernel.org, selinux@...r.kernel.org
Subject: Re: [PATCH v6 05/39] namei: make permission helpers idmapped mount
 aware

If I NFS-exported an idmapped mount, I think I'd expect idmapped clients
to see the mapped IDs.

Looks like that means taking the user namespace from the struct
svc_export everwhere, for example:

On Thu, Jan 21, 2021 at 02:19:24PM +0100, Christian Brauner wrote:
> index 66f2ef67792a..8d90796e236a 100644
> --- a/fs/nfsd/nfsfh.c
> +++ b/fs/nfsd/nfsfh.c
> @@ -40,7 +40,8 @@ static int nfsd_acceptable(void *expv, struct dentry *dentry)
>  		/* make sure parents give x permission to user */
>  		int err;
>  		parent = dget_parent(tdentry);
> -		err = inode_permission(d_inode(parent), MAY_EXEC);
> +		err = inode_permission(&init_user_ns,
> +				       d_inode(parent), MAY_EXEC);

		err = inode_permission(exp->ex_path.mnt->mnt_userns,
				      d_inode(parent, MAY_EXEC);

?

--b.