linux-kernel - Re: [PATCH v2 1/1] OverlayFS: Fix checking permissions during lookup.

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Message-Id: <419661456569602@web21g.yandex.ru>
Date:	Sat, 27 Feb 2016 13:40:02 +0300
From:	Nazarov Sergey <s-nazarov@...dex.ru>
To:	Vivek Goyal <vgoyal@...hat.com>,
	Ignacy Gawędzki 
	<ignacy.gawedzki@...en-communications.fr>,
	"linux-unionfs@...r.kernel.org" <linux-unionfs@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc:	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH v2 1/1] OverlayFS: Fix checking permissions during lookup.

26.02.2016, 22:41, "Vivek Goyal" <vgoyal@...hat.com>:
>
> So what's the problem we are trying to solve. Why should we able to
> override the DAC checks of lower layer if same directory in upper
> is searchable for user but it is not searchable in lower layer.
>

If I right, this is a one of the main feature of overlayfs - upper layer has priority over lower ones.
Override AC checks necessary for lookup operation only. Lower layer files access AC checks
remain, so this should not be a security problem.
Sergey.