From: Miklos Szeredi <miklos@szeredi.hu>
Subject: Re: [PATCH v27 02/21] vfs: Add MAY_CREATE_FILE and MAY_CREATE_DIR
 permission flags
Date: Fri, 2 Dec 2016 10:22:58 +0100
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Cc: Alexander Viro <viro@zeniv.linux.org.uk>,
        Christoph Hellwig <hch@infradead.org>,
        "Theodore Ts'o" <tytso@mit.edu>,
        Andreas Dilger <adilger.kernel@dilger.ca>,
        "J. Bruce Fields" <bfields@fieldses.org>,
        Jeff Layton <jlayton@poochiereds.net>,
        Trond Myklebust <trond.myklebust@primarydata.com>,
        Anna Schumaker <anna.schumaker@netapp.com>,
        Dave Chinner <david@fromorbit.com>, linux-ext4@vger.kernel.org,
        xfs@oss.sgi.com, LKML <linux-kernel@vger.kernel.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        linux-nfs@vger.kernel.org, linux-cifs@vger.kernel.org,
        linux-api@vger.kernel.org
To: Andreas Gruenbacher <agruenba@redhat.com>
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On Tue, Oct 11, 2016 at 2:50 PM, Andreas Gruenbacher
<agruenba@redhat.com> wrote:
> Richacls distinguish between creating non-directories and directories. To
> support that, add an isdir parameter to may_create(). When checking
> inode_permission() for create permission, pass in an additional
> MAY_CREATE_FILE or MAY_CREATE_DIR mask flag.
>
> Add may_replace() to allow checking for delete and create access when
> replacing an existing file in vfs_rename().

That works for plain rename, but not for RENAME_EXCHANGE: is_dir and
new_is_dir may be different, which means we can be deleting a
non-directory *and* creating a directory in one dir and vice versa in
the other.

Thanks,
Miklos