Messages in this thread | | | Date | Sat, 05 Oct 2013 19:13:48 -0500 | From | Rob Landley <> | Subject | Re: [RFC][PATCH 0/3] vfs: Detach mounts on unlink. |
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On 10/05/2013 06:19:15 PM, Al Viro wrote: > On Sat, Oct 05, 2013 at 06:07:42PM -0500, Rob Landley wrote: > > A todo item I've had _forever_ is fixing chroot() to not be broken > > so that you can trivially break out of a chroot via: > > > > chdir("/"); > > mkdir("sub"); > > chroot("sub"); > > chdir("./../../../../../../../.."); > > > > (Because chroot() affects where "/" points but NOT where "." points > > to, and chdir does an == check with the dentry "/" points at to know > > when to stop, so if you move "/" under "." you can back up to the > > actual root of the tree.) > > > > The above is why lxc uses pivot_root() instead of chroot(). > > > > These days, we have multiple mount trees so there's no reason > > chroot() can't trim the process local mount tree (creating a new > > bind mount if necessary). Except my todo list runneth over and I > > haven't had a chance to dig in and see what would be involved. (Last > > time I brought this up people were wondering why chroot() didn't > > just move "." to the new "/" if it wasn't under it. I had no idea, > > still don't.) > > 1) RTFUNIXFAQ. chroot() never has been root-proof. > > 2) your "fix" isn't - it will lead to mounts done by chrooted process > not affecting other processes in the same namespace.
So if I write a lightweight container setup command, I need to use pivot_root just like lxc does?
Rob
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