linux-ext4 - Re: [PATCH v5 37/42] xfs: support idmapped mounts

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Date:   Fri, 15 Jan 2021 07:51:54 +1100
From:   Dave Chinner <david@...morbit.com>
To:     Christian Brauner <christian.brauner@...ntu.com>
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        Christoph Hellwig <hch@...radead.org>,
        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,
        Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v5 37/42] xfs: support idmapped mounts

On Tue, Jan 12, 2021 at 11:01:19PM +0100, Christian Brauner wrote:
> From: Christoph Hellwig <hch@....de>
> 
> Enable idmapped mounts for xfs. This basically just means passing down
> the user_namespace argument from the VFS methods down to where it is
> passed to helper.
> 
> Signed-off-by: Christoph Hellwig <hch@....de>
....
> @@ -654,6 +658,7 @@ xfs_vn_change_ok(
>   */
>  static int
>  xfs_setattr_nonsize(
> +	struct user_namespace	*mnt_userns,
>  	struct xfs_inode	*ip,
>  	struct iattr		*iattr)
>  {
> @@ -813,7 +818,7 @@ xfs_setattr_nonsize(
>  	 * 	     Posix ACL code seems to care about this issue either.
>  	 */
>  	if (mask & ATTR_MODE) {
> -		error = posix_acl_chmod(&init_user_ns, inode, inode->i_mode);
> +		error = posix_acl_chmod(mnt_userns, inode, inode->i_mode);
>  		if (error)
>  			return error;
>  	}
> @@ -868,7 +873,7 @@ xfs_setattr_size(
>  		 * Use the regular setattr path to update the timestamps.
>  		 */
>  		iattr->ia_valid &= ~ATTR_SIZE;
> -		return xfs_setattr_nonsize(ip, iattr);
> +		return xfs_setattr_nonsize(&init_user_ns, ip, iattr);

Shouldn't that be passing mnt_userns?

>  	}
>  
>  	/*
> @@ -1037,6 +1042,7 @@ xfs_setattr_size(
>  
>  int
>  xfs_vn_setattr_size(
> +	struct user_namespace	*mnt_userns,
>  	struct dentry		*dentry,
>  	struct iattr		*iattr)
>  {
> @@ -1045,7 +1051,7 @@ xfs_vn_setattr_size(
>  
>  	trace_xfs_setattr(ip);
>  
> -	error = xfs_vn_change_ok(dentry, iattr);
> +	error = xfs_vn_change_ok(mnt_userns, dentry, iattr);
>  	if (error)
>  		return error;
>  	return xfs_setattr_size(ip, iattr);

And this passing mnt_userns down into xfs_setattr_size()?  Seems
like a bit of a landmine...

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com