Merge branch 'for-4.7-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj...

Pull more cgroup updates from Tejun Heo:
 "I forgot to include the patches which got applied to for-4.7-fixes
  late during last cycle.

  Eric's three patches fix bugs introduced with the namespace support"

* 'for-4.7-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  cgroupns: Only allow creation of hierarchies in the initial cgroup namespace
  cgroupns: Close race between cgroup_post_fork and copy_cgroup_ns
  cgroupns: Fix the locking in copy_cgroup_ns

diff --combined kernel/cgroup.c
index 9624db80dc4e485c9c3c3f3911141b343bcd0526,e0be49fc382fc339269b9be29fda59d4ad619962..d1c51b7f5221fbfbb85ed3d12e4918a970713829
--- 1/kernel/cgroup.c
--- 2/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@@ -61,7 -61,7 +61,7 @@@
  #include <linux/cpuset.h>
  #include <linux/proc_ns.h>
  #include <linux/nsproxy.h>
 -#include <linux/proc_ns.h>
 +#include <linux/file.h>
  #include <net/sock.h>
  
  /*
@@@ -1160,12 -1160,18 +1160,12 @@@ static void cgroup_exit_root_id(struct 
  {
        lockdep_assert_held(&cgroup_mutex);
  
 -      if (root->hierarchy_id) {
 -              idr_remove(&cgroup_hierarchy_idr, root->hierarchy_id);
 -              root->hierarchy_id = 0;
 -      }
 +      idr_remove(&cgroup_hierarchy_idr, root->hierarchy_id);
  }
  
  static void cgroup_free_root(struct cgroup_root *root)
  {
        if (root) {
 -              /* hierarchy ID should already have been released */
 -              WARN_ON_ONCE(root->hierarchy_id);
 -
                idr_destroy(&root->cgroup_idr);
                kfree(root);
        }
@@@ -2209,12 -2215,8 +2209,8 @@@ static struct dentry *cgroup_mount(stru
                goto out_unlock;
        }
  
-       /*
-        * We know this subsystem has not yet been bound.  Users in a non-init
-        * user namespace may only mount hierarchies with no bound subsystems,
-        * i.e. 'none,name=user1'
-        */
-       if (!opts.none && !capable(CAP_SYS_ADMIN)) {
+       /* Hierarchies may only be created in the initial cgroup namespace. */
+       if (ns != &init_cgroup_ns) {
                ret = -EPERM;
                goto out_unlock;
        }
@@@ -2956,6 -2958,7 +2952,7 @@@ int cgroup_attach_task_all(struct task_
        int retval = 0;
  
        mutex_lock(&cgroup_mutex);
+       percpu_down_write(&cgroup_threadgroup_rwsem);
        for_each_root(root) {
                struct cgroup *from_cgrp;
  
@@@ -2970,6 -2973,7 +2967,7 @@@
                if (retval)
                        break;
        }
+       percpu_up_write(&cgroup_threadgroup_rwsem);
        mutex_unlock(&cgroup_mutex);
  
        return retval;
@@@ -4337,6 -4341,8 +4335,8 @@@ int cgroup_transfer_tasks(struct cgrou
  
        mutex_lock(&cgroup_mutex);
  
+       percpu_down_write(&cgroup_threadgroup_rwsem);
+ 
        /* all tasks in @from are being moved, all csets are source */
        spin_lock_irq(&css_set_lock);
        list_for_each_entry(link, &from->cset_links, cset_link)
@@@ -4365,6 -4371,7 +4365,7 @@@
        } while (task && !ret);
  out_err:
        cgroup_migrate_finish(&preloaded_csets);
+       percpu_up_write(&cgroup_threadgroup_rwsem);
        mutex_unlock(&cgroup_mutex);
        return ret;
  }
@@@ -5140,8 -5147,6 +5141,8 @@@ static struct cgroup_subsys_state *css_
        lockdep_assert_held(&cgroup_mutex);
  
        css = ss->css_alloc(parent_css);
 +      if (!css)
 +              css = ERR_PTR(-ENOMEM);
        if (IS_ERR(css))
                return css;
  
@@@ -6168,7 -6173,7 +6169,7 @@@ struct cgroup_subsys_state *css_tryget_
  struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss)
  {
        WARN_ON_ONCE(!rcu_read_lock_held());
 -      return id > 0 ? idr_find(&ss->css_idr, id) : NULL;
 +      return idr_find(&ss->css_idr, id);
  }
  
  /**
@@@ -6205,40 -6210,6 +6206,40 @@@ struct cgroup *cgroup_get_from_path(con
  }
  EXPORT_SYMBOL_GPL(cgroup_get_from_path);
  
 +/**
 + * cgroup_get_from_fd - get a cgroup pointer from a fd
 + * @fd: fd obtained by open(cgroup2_dir)
 + *
 + * Find the cgroup from a fd which should be obtained
 + * by opening a cgroup directory.  Returns a pointer to the
 + * cgroup on success. ERR_PTR is returned if the cgroup
 + * cannot be found.
 + */
 +struct cgroup *cgroup_get_from_fd(int fd)
 +{
 +      struct cgroup_subsys_state *css;
 +      struct cgroup *cgrp;
 +      struct file *f;
 +
 +      f = fget_raw(fd);
 +      if (!f)
 +              return ERR_PTR(-EBADF);
 +
 +      css = css_tryget_online_from_dir(f->f_path.dentry, NULL);
 +      fput(f);
 +      if (IS_ERR(css))
 +              return ERR_CAST(css);
 +
 +      cgrp = css->cgroup;
 +      if (!cgroup_on_dfl(cgrp)) {
 +              cgroup_put(cgrp);
 +              return ERR_PTR(-EBADF);
 +      }
 +
 +      return cgrp;
 +}
 +EXPORT_SYMBOL_GPL(cgroup_get_from_fd);
 +
  /*
   * sock->sk_cgrp_data handling.  For more info, see sock_cgroup_data
   * definition in cgroup-defs.h.
@@@ -6339,14 -6310,11 +6340,11 @@@ struct cgroup_namespace *copy_cgroup_ns
        if (!ns_capable(user_ns, CAP_SYS_ADMIN))
                return ERR_PTR(-EPERM);
  
-       mutex_lock(&cgroup_mutex);
+       /* It is not safe to take cgroup_mutex here */
        spin_lock_irq(&css_set_lock);
- 
        cset = task_css_set(current);
        get_css_set(cset);
- 
        spin_unlock_irq(&css_set_lock);
-       mutex_unlock(&cgroup_mutex);
  
        new_ns = alloc_cgroup_ns();
        if (IS_ERR(new_ns)) {