Messages in this thread | | | From | (Eric W. Biederman) | Date | Tue, 07 Oct 2014 15:42:44 -0700 | Subject | Re: [PATCH] [RFC] mnt: add ability to clone mntns starting with the current root |
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Andy Lutomirski <luto@amacapital.net> writes:
> On Tue, Oct 7, 2014 at 2:42 PM, Eric W. Biederman <ebiederm@xmission.com> wrote: >> >> I am squinting and looking this way and that but while I can imagine >> someone more clever than I can think up some unique property of rootfs >> that makes it a little more exploitable than just mounting a ramfs, >> but since you have to be root to exploit those properties I think the >> game is pretty much lost. > > Yes. rootfs might not be empty, it might have totally insane > permissions, and it's globally shared, which makes it into a wonderful > channel to pass things around that shouldn't be passed around.
But if only root with proc mounted can reach it... I don't know. There might be a case for setting MNT_LOCKED when we overmount "/" as root but I don't yet see it.
> Can non-root do this? You'd need to be in a userns with a "/" that > isn't MNT_LOCKED. Can this happen on any normal setup? > > FWIW, I think we should unconditionally MNT_LOCKED the root on userns > unshare, even if it's the only mount.
To the best of my knowledge MNT_LOCKED is set uncondintially on userns unshare.
Eric
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