Re: [libvirt] [PATCH v2]LXC: Helper function for checking ownership of dir when userns enabled
-----Original Message-----
From: Daniel P. Berrange [mailto:berrange@redhat.com]
Sent: Saturday, August 10, 2013 12:54 AM
To: Chen Hanxiao
Cc: libvir-list(a)redhat.com
Subject: Re: [libvirt] [PATCH v2]LXC: Helper function for checking ownership of
dir when userns enabled
On Fri, Aug 09, 2013 at 04:05:58PM +0800, Chen Hanxiao wrote:
> From: Chen Hanxiao <chenhanxiao(a)cn.fujitsu.com>
>
> If we enable userns, the ownership of dir we provided for containers
> should match the uid/gid in idmap.
> Currently, the debug log is very implicit or misleading sometimes.
> This patch will help clarify this for us when using
> debug log or virsh.
I do recall hitting some permission issue once, but can't remember
just what it was. Can you describe exactly how to reproduce the
problem ?
1) Enable user namespace in kernel
2) Add idmap for container
3) Don't change the ownership of devices/ filesystem/ source dir ( leave them to
'root' for instance)
4) Start the container
Usually I got an input/output error by virsh, which is not a good hint.
> Signed-off-by: Chen Hanxiao <chenhanxiao(a)cn.fujitsu.com>
> ---
> src/lxc/lxc_container.c | 46
++++++++++++++++++++++++++++++++++++++++++++++
> 1 files changed, 46 insertions(+), 0 deletions(-)
>
> diff --git a/src/lxc/lxc_container.c b/src/lxc/lxc_container.c
> index b910b10..2ccdc61 100644
> --- a/src/lxc/lxc_container.c
> +++ b/src/lxc/lxc_container.c
> @@ -1815,6 +1815,49 @@ lxcNeedNetworkNamespace(virDomainDefPtr
def)
> return false;
> }
>
> +/*
> + * Helper function for helping check
> + * whether we have enough privilege
> + * to operate the source dir when userns enabled
> + * @vmDef: pointer to vm definition structure
> + * Returns 0 on success or -1 in case of error
> + */
> +static int
> +lxcContainerUsernsSrcOwnershipCheck(virDomainDefPtr vmDef)
> +{
> + struct stat buf;
> + size_t i;
> + uid_t uid;
> + gid_t gid;
> +
> + VIR_DEBUG("vmDef->nfss %d", (int)vmDef->nfss);
> + for (i = 0; i < vmDef->nfss; i++) {
> + VIR_DEBUG("dst is %s, src is %s",
> + vmDef->fss[i]->dst,
> + vmDef->fss[i]->src);
> +
> + uid = vmDef->idmap.uidmap[0].target;
> + gid = vmDef->idmap.gidmap[0].target;
> +
> + if (lstat(vmDef->fss[i]->src, &buf) < 0) {
> + virReportSystemError(errno, _("Cannot access '%s'"),
> + vmDef->fss[i]->src);
> + return -1;
> + } else if (uid != buf.st_uid || gid != buf.st_gid) {
> + VIR_DEBUG("In userns uid is %d, gid is %d\n",
> + uid, gid);
> + errno = EINVAL;
> +
> + virReportSystemError(errno,
> + _("[userns] Src dir '%s' does not
belong to uid/gid: %d/%d"),
> + vmDef->fss[i]->src, uid, gid);
> + return -1;
> + }
> + }
> +
> + return 0;
> +}
> +
> /**
> * lxcContainerStart:
> * @def: pointer to virtual machine structure
> @@ -1866,6 +1909,9 @@ int lxcContainerStart(virDomainDefPtr def,
> if (userns_supported()) {
> VIR_DEBUG("Enable user namespace");
> cflags |= CLONE_NEWUSER;
> + if (lxcContainerUsernsSrcOwnershipCheck(def) < 0) {
> + return -1;
> + }
> } else {
> virReportSystemError(VIR_ERR_CONFIG_UNSUPPORTED,
"%s",
> _("Kernel doesn't support user
namespace"));
Daniel
--
|: http://berrange.com -o-
http://www.flickr.com/photos/dberrange/ :|
|: http://libvirt.org -o-
http://virt-manager.org :|
|: http://autobuild.org -o-
http://search.cpan.org/~danberr/ :|
|: http://entangle-photo.org -o-
http://live.gnome.org/gtk-vnc :|