btrfs: support unprivileged destroy

Do this by calling the bdev->destroy() hook from a user namespace
configured as the container's.

Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
Acked-by: Stéphane Graber <stgraber@ubuntu.com>

diff --git a/src/lxc/lxccontainer.c b/src/lxc/lxccontainer.c
index 9e23c7b08cd1d6d946fd459fb7dfb1bae2217843..255fde5760f47b5d32e75ce402210d38fb4af148 100644 (file)
--- a/src/lxc/lxccontainer.c
+++ b/src/lxc/lxccontainer.c
@@ -1987,10 +1987,41 @@ static int lxc_rmdir_onedev_wrapper(void *data)
        return lxc_rmdir_onedev(arg);
 }
 
+static int do_bdev_destroy(struct lxc_conf *conf)
+{
+       struct bdev *r;
+       int ret = 0;
+
+       r = bdev_init(conf->rootfs.path, conf->rootfs.mount, NULL);
+       if (!r)
+               return -1;
+
+       if (r->ops->destroy(r) < 0)
+               ret = -1;
+       bdev_put(r);
+       return ret;
+}
+
+static int bdev_destroy_wrapper(void *data)
+{
+       struct lxc_conf *conf = data;
+
+       if (setgid(0) < 0) {
+               ERROR("Failed to setgid to 0");
+               return -1;
+       }
+       if (setgroups(0, NULL) < 0)
+               WARN("Failed to clear groups");
+       if (setuid(0) < 0) {
+               ERROR("Failed to setuid to 0");
+               return -1;
+       }
+       return do_bdev_destroy(conf);
+}
+
 // do we want the api to support --force, or leave that to the caller?
 static bool lxcapi_destroy(struct lxc_container *c)
 {
-       struct bdev *r = NULL;
        bool bret = false;
        int ret;
 
@@ -2011,15 +2042,14 @@ static bool lxcapi_destroy(struct lxc_container *c)
                goto out;
        }
 
-       if (!am_unpriv() && c->lxc_conf && c->lxc_conf->rootfs.path && c->lxc_conf->rootfs.mount) {
-               r = bdev_init(c->lxc_conf->rootfs.path, c->lxc_conf->rootfs.mount, NULL);
-               if (r) {
-                       if (r->ops->destroy(r) < 0) {
-                               bdev_put(r);
-                               ERROR("Error destroying rootfs for %s", c->name);
-                               goto out;
-                       }
-                       bdev_put(r);
+       if (c->lxc_conf && c->lxc_conf->rootfs.path && c->lxc_conf->rootfs.mount) {
+               if (am_unpriv())
+                       ret = userns_exec_1(c->lxc_conf, bdev_destroy_wrapper, c->lxc_conf);
+               else
+                       ret = do_bdev_destroy(c->lxc_conf);
+               if (ret < 0) {
+                       ERROR("Error destroying rootfs for %s", c->name);
+                       goto out;
                }
        }