linux-kernel - Re: [PATCH v3] vfs: new O

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Message-ID: <20091207174049.50537ddf@lxorguk.ukuu.org.uk>
Date:	Mon, 7 Dec 2009 17:40:49 +0000
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Miklos Szeredi <miklos@...redi.hu>
Cc:	miklos@...redi.hu, luto@....edu, akpm@...ux-foundation.org,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] vfs: new O_NODE open flag

> Well, yes.  That's true.  But I still don't think revoke() is the
> answer here.  For example even without the possibility of hard links
> there's still a race in udev in the following course of events:
> 
>   open("/dev/foo", O_RDWR)
>   ... open passes permission checks
>   ... driver gets unloaded
>   ... driver intended for other user gets loaded
>   ... open finds new driver

> What we really need is to revoke the *inode*, so that it cannot be
> opened any more.  Doing it with unlink() and revoke() and requiring
> that link() does not work on the filesystem is a poor and racy
> substitute for that.

Can't argue with that and going through the kernel logic I don't see
anything preventing an exploit based on that from working.

Alan
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