linux-kernel - Re: overlayfs vs. fscrypt

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Date:   Wed, 13 Mar 2019 19:19:46 +0000
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Eric Biggers <ebiggers@...nel.org>
Cc:     Theodore Ts'o <tytso@....edu>, Amir Goldstein <amir73il@...il.com>,
        Richard Weinberger <richard@....at>,
        Miklos Szeredi <miklos@...redi.hu>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        linux-fscrypt@...r.kernel.org,
        overlayfs <linux-unionfs@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Paul Lawrence <paullawrence@...gle.com>
Subject: Re: overlayfs vs. fscrypt

On Wed, Mar 13, 2019 at 09:44:33AM -0700, Eric Biggers wrote:

> > Just to make sure - you do realize that ban on multiple dentries refering
> > to the same directory inode is *NOT* conditional upon those dentries being
> > hashed, right?
> 
> Isn't this handled by d_splice_alias() already, by moving the old dentry to the
> new name?

... which means that if somebody without the key chdirs into subdirectory
they only see by encrypted name and waits for proper owner to look it up,
they suddenly see it by _un_encrypted name.  Or does O_PATH open, for
that matter, so exec permissions on that thing are not required.