Messages in this thread | | | Date | Sat, 05 Oct 2013 19:18:13 -0500 | From | Rob Landley <> | Subject | Re: [RFC][PATCH 0/3] vfs: Detach mounts on unlink. |
| |
On 10/05/2013 06:22:15 PM, Linus Torvalds wrote: > On Sat, Oct 5, 2013 at 4:17 PM, Linus Torvalds > <torvalds@linux-foundation.org> wrote: > > > > So learn this pattern: every time you use chroot, add a simple > > > > chdir("/"); > > > > immediately after the chroot call. > > .. btw, also make sure that you close all non-essential file > descriptors. Having any open directory file descriptors pointing to > outside the chroot is also a classic escape. > > Even then, escaping chroot is usually fairly easy. Making a > escape-proof chroot is really quite hard. Basically impossible if you > allow root.
Which is why containers have all sorts of extra plumbing. But that extra plumbing is currently built on pivot_root(), not on chroot(). And I'd dismissed pivot_root() as residue from initramfs with all that kernel thread reparenting, so it seemed like the wrong tool for the job, but obviously I'll take your and Al's word it's not...
Rob
| |