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

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Message-Id: <E1NH0Ub-0007oy-43@pomaz-ex.szeredi.hu>
Date:	Sat, 05 Dec 2009 20:40:33 +0100
From:	Miklos Szeredi <miklos@...redi.hu>
To:	Andy Lutomirski <luto@....edu>
CC:	miklos@...redi.hu, alan@...rguk.ukuu.org.uk,
	akpm@...ux-foundation.org, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] vfs: new O_NODE open flag

On Sat, 05 Dec 2009, Andy Lutomirski wrote:
> I don't know what that means.  Do you mean that if:
> 
> root creates /dev/foo with 0666 perms
> eviluser opens /dev/foo with O_NODE

More precisely, O_NODE | O_NOACCESS

> root chmods /dev/foo to 0000
> root unlinks /dev/foo
> 
> then eviluser can't open /proc/self/fd/whatever for O_RDRW

Yes.

Maybe alan was worried about the O_NODE | O_RDWR, etc. case?  That
simply doesn't make any sense for special files.

Current patch only allows O_NOACCESS for any file type, but other
access modes may make sense for regular files, directories, and maybe
even symlinks.

Thanks,
Miklos
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