lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Tue, 07 Oct 2014 13:52:35 -0700
From: (Eric W. Biederman)
To:	Serge Hallyn <>
Cc:	Al Viro <>,
	Andrey Vagin <>,,,, Andrey Vagin <>,
	Andrew Morton <>,
	Cyrill Gorcunov <>,
	Pavel Emelyanov <>,
	Serge Hallyn <>,
	Rob Landley <>
Subject: Re: [PATCH] [RFC] mnt: add ability to clone mntns starting with the current root

Serge Hallyn <> writes:

> Quoting Eric W. Biederman (
>> Al Viro <> writes:
>> 2> On Tue, Oct 07, 2014 at 02:30:40PM +0100, Al Viro wrote:
>> >> On Tue, Oct 07, 2014 at 04:12:57PM +0400, Andrey Vagin wrote:
>> >> > Another problem is that rootfs can't be hidden from a container, because
>> >> > rootfs can't be moved or umounted.
>> >> 
>> >> ... which is a bug in mntns_install(), AFAICS.
>> >
>> > Ability to get to exposed rootfs, that is.
>> The container side of this argument is pretty bogus.  It only applies
>> if user namespaces are not used for the container.
> User namespaces are still far too restricted for many container use
> cases.  We can't say "we have user namespaces so now privileged
> containers can be ignored".  Yes you never should have handed the
> keys to a privileged container to an untrusted person, but we do
> still try to protect the host from accidental damage due to a
> privileged container.

What I meant is that it isn't about containers.   It is about something
root can do.  So this is not a "container" problem.

>> So it is only root (and not root in a container) who can get to the
>> exposed rootfs.
>> I have a vague memory someone actually had a real use in miminal systems
>> for being able to get back to the rootfs and being able to use rootfs as
>> the rootfs.  There was even a patch at that time that Andrew Morton was
>> carrying for a time to allow unmounting root and get at rootfs, and to
>> prevent the oops on rootfs unmount in some way.
>> So not only do I not think it is a bug to get back too rootfs, I think
>> it is a feature that some people have expressed at least half-way sane
>> uses for.
> They can still do that if they want, using chroot :)

It would take fchdir or fchroot and a directory file descriptor open on
rootfs.  Frequently there is no appropriate directory file descriptor.

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

Powered by blists - more mailing lists