Re: [libvirt] [PATCH 2/2] LXC: don't unmount mounts for shared root

On Tue, Nov 19, 2013 at 05:53:21PM +0800, Gao feng wrote: > Also after commit 5ff9d8a65ce80efb509ce4e8051394e9ed2cd942 > vfs: Lock in place mounts from more privileged users, > > unprivileged user has no rights to umount the mounts that > inherited from parent mountns. > > right now, I have no good idea to fix this problem, we need > to do more research. this patch just skip unmounting these > mounts for shared root. > > BTW, I think when libvirt lxc enables user namespace, the > configuation that shares root with host is very rara. > > Signed-off-by: Gao feng <gaofeng(a)cn.fujitsu.com&gt; > --- > src/lxc/lxc_container.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/src/lxc/lxc_container.c b/src/lxc/lxc_container.c > index 61283e4..8003594 100644 > --- a/src/lxc/lxc_container.c > +++ b/src/lxc/lxc_container.c > @@ -1591,7 +1591,9 @@ static int lxcContainerSetupPivotRoot(virDomainDefPtr vmDef, > if (lxcContainerPivotRoot(root) < 0) > goto cleanup; > > - if (STREQ(root->src, "/") && > + /* FIXME: we should find a way to unmount these mounts for container > + * even user namespace is enabled. */ > + if (STREQ(root->src, "/") && (!vmDef->idmap.nuidmap) && > lxcContainerUnmountForSharedRoot(stateDir, vmDef->name) < 0) > goto cleanup; If unmounting fails for these few temporary filesystems, then how is unmount succeeding for everything under /.oldroot after we do the pivot root ? Does the pivot_root() confuse the kernel into thinking stuff under /.oldroot was owned by this process & thus allowed to be unmounted ? Or is it falling back to the MNT_DETACH scenario instead ?