linux-kernel - Re: [PATCH 0/6] overlay filesystem prototype

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Date:	Sun, 05 Sep 2010 19:37:10 +0900
From:	"J. R. Okajima" <hooanon05@...oo.co.jp>
To:	Miklos Szeredi <miklos@...redi.hu>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	vaurora@...hat.com, neilb@...e.de, viro@...iv.linux.org.uk
Subject: Re: [PATCH 0/6] overlay filesystem prototype


Miklos Szeredi:
> Changes since the last version:
	:::
>  - get write ref on the upper layer on mount unless the overlay
>    itself is mounted read-only

I think it a good approach.
Although it may be harmless, write-ref will not be put when a user
executes,
- mount -o ro /overlay
- umount /overlay
It will be easy to fix by implementing s_op->remount().


>  - raise capabilities for copy up, dealing with whiteouts and opaque
>    directories.  Now the overlay works for non-root users as well

Interesting approach.
But is it safe? If multi-threaded ap or a signal handler share
the credential, then they may gain incorrect capability.


J. R. Okajima
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