linux-kernel - Re: [PATCH -mm 5/7] add user namespace

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Message-Id: <1152902522.314.47.camel@localhost.localdomain>
Date:	Fri, 14 Jul 2006 11:42:02 -0700
From:	Dave Hansen <haveblue@...ibm.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	"Serge E. Hallyn" <serue@...ibm.com>,
	Cedric Le Goater <clg@...ibm.com>,
	linux-kernel@...r.kernel.org, Andrew Morton <akpm@...l.org>,
	Kirill Korotaev <dev@...nvz.org>, Andrey Savochkin <saw@...ru>,
	Herbert Poetzl <herbert@...hfloor.at>,
	Sam Vilain <sam.vilain@...alyst.net.nz>
Subject: Re: [PATCH -mm 5/7] add user namespace

On Fri, 2006-07-14 at 12:06 -0600, Eric W. Biederman wrote:
> > On Fri, 2006-07-14 at 11:18 -0600, Eric W. Biederman wrote:
> >> /proc/<pid>/fd/...
> >> /proc/<pid>/exe
> >> /proc/<pid>/cwd
> >> 
> >> It isn't quite the same as you are actually opening a second
> >> copy of the file descriptor but the essence is the same. 
> >
> > Last I checked, those were symlinks and didn't work for things like
> > deleted files.  Am I wrong?
> 
> Yes.  They are not really symlinks.
> 
> Wanting to have an executable that was deleted after it was done
> executing.  I wrote it to a file. opened it, unlinked it, set close
> on exec, and the exec'd it with /proc/self/fd/N.

Well, on one hand, it makes checkpoints with deleted files easier ;)

Now that I'm actually looking at the code, isn't
proc_fd_access_allowed()'s permission just derived from ptrace
permissions?  It doesn't seem to involve uids directly at all!

-- Dave

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