Re: sys_chroot+sys_fchdir Fix

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To: David Newall <david@...>
Cc: Phillip Susi <psusi@...>, Alan Cox <alan@...>, Bill Davidsen <davidsen@...>, majkls <majkls@...>, <bunk@...>, <linux-kernel@...>
Date: Wednesday, September 26, 2007 - 2:40 pm

On Wed, Sep 26, 2007 at 08:04:14PM +0930, David Newall wrote:

OK, the possibilities are
	* you've discovered a bug in all Unices (BTW, even FreeBSD *does*
allow to break out of some chroots in that fashion; RTFS and you'll see -
just pay attention to setting fdp->fd_jdir logics in kern/vfs_syscalls.c:
change_root(); it sets jail boundary on _first_ chroot and if you've got
nested chroots, you can leave them just fine by use of SCM_RIGHTS to hold
directory descriptor).  All hail David, nevermind that this behaviour had
been described in Unix FAQs since _way_ back.
	* you've misunderstood the purpose of chroot(), the fact that
behaviour in question is at the very least extremely common on Unix and
the fact that any code relying on root-proof chroot(2) is broken and needs
to be fixed, simply because chroot is _not_ root-proof on (at least) almost
all systems.

Note that the last statement applies in both cases; it's simply reality.
Insisting that behaviour known for decades is a bug since it contradicts
your rather convoluted reading of the standards...  Looks rather silly,
IMO, but that has zero practical consequences anyway.  Userland code can't
rely on root-proof chroot(2), period.
-
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Messages in current thread:
sys_chroot+sys_fchdir Fix, majkls, (Wed Sep 19, 3:19 am)
Re: sys_chroot+sys_fchdir Fix, Alan Cox, (Wed Sep 19, 5:40 am)
Re: sys_chroot+sys_fchdir Fix, Bill Davidsen, (Wed Sep 19, 2:27 pm)
Re: sys_chroot+sys_fchdir Fix, Alan Cox, (Wed Sep 19, 2:45 pm)
Re: sys_chroot+sys_fchdir Fix, David Newall, (Wed Sep 19, 6:24 pm)
Re: sys_chroot+sys_fchdir Fix, Phillip Susi, (Fri Sep 21, 1:39 pm)
Re: sys_chroot+sys_fchdir Fix, Alan Cox, (Fri Sep 21, 2:10 pm)
Re: sys_chroot+sys_fchdir Fix, Phillip Susi, (Tue Sep 25, 4:53 pm)
Re: sys_chroot+sys_fchdir Fix, Al Viro, (Tue Sep 25, 8:23 pm)
Re: sys_chroot+sys_fchdir Fix, David Newall, (Wed Sep 26, 6:34 am)
Re: sys_chroot+sys_fchdir Fix, Christer Weinigel, (Wed Sep 26, 3:24 pm)
Re: sys_chroot+sys_fchdir Fix, David Newall, (Wed Sep 26, 5:19 pm)
Re: sys_chroot+sys_fchdir Fix, Christer Weinigel, (Thu Sep 27, 3:28 am)
Re: sys_chroot+sys_fchdir Fix, Theodore Tso, (Thu Sep 27, 7:23 am)
Re: sys_chroot+sys_fchdir Fix, Bill Davidsen, (Thu Sep 27, 10:36 am)
Re: sys_chroot+sys_fchdir Fix, David Newall, (Thu Sep 27, 9:06 pm)
Re: sys_chroot+sys_fchdir Fix, Adrian Bunk, (Wed Sep 26, 5:55 pm)
Re: sys_chroot+sys_fchdir Fix, David Newall, (Wed Sep 26, 7:35 pm)
Re: sys_chroot+sys_fchdir Fix, Adrian Bunk, (Wed Sep 26, 8:01 pm)
Re: sys_chroot+sys_fchdir Fix, David Newall, (Thu Sep 27, 2:42 am)
Re: sys_chroot+sys_fchdir Fix, Adrian Bunk, (Thu Sep 27, 2:53 am)
Re: sys_chroot+sys_fchdir Fix, Al Viro, (Wed Sep 26, 11:59 pm)
Re: sys_chroot+sys_fchdir Fix, Al Viro, (Wed Sep 26, 2:40 pm)
Re: sys_chroot+sys_fchdir Fix, Alan Cox, (Wed Sep 26, 7:21 am)
Re: sys_chroot+sys_fchdir Fix, David Newall, (Wed Sep 26, 7:22 am)
Re: sys_chroot+sys_fchdir Fix, Alan Cox, (Wed Sep 26, 7:38 am)
Re: sys_chroot+sys_fchdir Fix, David Newall, (Wed Sep 26, 7:56 am)
Re: sys_chroot+sys_fchdir Fix, Alan Cox, (Wed Sep 26, 10:10 am)
Re: sys_chroot+sys_fchdir Fix, David Newall, (Wed Sep 26, 12:54 pm)
Re: sys_chroot+sys_fchdir Fix, Alan Cox, (Wed Sep 26, 1:04 pm)
Re: sys_chroot+sys_fchdir Fix, David Newall, (Wed Sep 26, 1:18 pm)
Re: sys_chroot+sys_fchdir Fix, Alan Cox, (Wed Sep 26, 1:29 pm)
Re: sys_chroot+sys_fchdir Fix, David Newall, (Wed Sep 26, 1:28 pm)
Re: sys_chroot+sys_fchdir Fix, Chris Adams, (Wed Sep 26, 11:03 am)