[lxc-devel] [PATCH] c/r: remember to chown the cgroup path (correctly)

Tycho Andersen tycho.andersen at canonical.com
Thu Jan 14 09:10:03 UTC 2016


On Wed, Jan 13, 2016 at 09:47:50PM +0000, Serge Hallyn wrote:
> Quoting Tycho Andersen (tycho.andersen at canonical.com):
> > 1. remember to chown the cgroup path when migrating a container
> > 2. when restoring the cgroup path, try to compute the euid for root vs.
> >    using geteuid(); geteuid works for start, but it doesn't work for
> >    migration since we're still real root at that point.
> > 
> > Signed-off-by: Tycho Andersen <tycho.andersen at canonical.com>
> > ---
> >  src/lxc/cgmanager.c | 6 +++++-
> >  src/lxc/criu.c      | 5 +++++
> >  2 files changed, 10 insertions(+), 1 deletion(-)
> > 
> > diff --git a/src/lxc/cgmanager.c b/src/lxc/cgmanager.c
> > index 357182a..54e6912 100644
> > --- a/src/lxc/cgmanager.c
> > +++ b/src/lxc/cgmanager.c
> > @@ -488,7 +488,11 @@ static bool chown_cgroup(const char *cgroup_path, struct lxc_conf *conf)
> >  		return true;
> >  
> >  	data.cgroup_path = cgroup_path;
> > -	data.origuid = geteuid();
> > +	data.origuid = mapped_hostid(0, conf, ID_TYPE_UID);
> > +	if (data.origuid < 0) {
> 
> Can you confirm that this does not break
> 
> sudo lxc-create -t download -n x1 -- -d ubuntu -r trusty -a amd64
> sudo lxc-start -n x1
> 
> Because in that case I think we have no mappings, and mapped_hostid() will
> return -1.

You can't see it in the patch, but just above this is a
lxc_list_empty() test, and this whole path isn't executed if
lxc_list_empty() is true, so I think it should be ok.

Tycho

> > +		ERROR("failed to get mapped root id");
> > +		return false;
> > +	}
> >  
> >  	/* Unpriv users can't chown it themselves, so chown from
> >  	 * a child namespace mapping both our own and the target uid
> > diff --git a/src/lxc/criu.c b/src/lxc/criu.c
> > index 6ef4905..f442612 100644
> > --- a/src/lxc/criu.c
> > +++ b/src/lxc/criu.c
> > @@ -466,6 +466,11 @@ void do_restore(struct lxc_container *c, int pipe, char *directory, bool verbose
> >  		goto out_fini_handler;
> >  	}
> >  
> > +	if (!cgroup_chown(handler)) {
> > +		ERROR("failed creating groups");
> > +		goto out_fini_handler;
> > +	}
> > +
> >  	if (!restore_net_info(c)) {
> >  		ERROR("failed restoring network info");
> >  		goto out_fini_handler;
> > -- 
> > 2.6.4
> > 
> > _______________________________________________
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> > lxc-devel at lists.linuxcontainers.org
> > http://lists.linuxcontainers.org/listinfo/lxc-devel
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