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Commit 5e1182de authored by Eric W. Biederman's avatar Eric W. Biederman
Browse files

pidns: Don't allow new processes in a dead pid namespace. 



Set nr_hashed to -1 just before we schedule the work to cleanup proc.
Test nr_hashed just before we hash a new pid and if nr_hashed is < 0
fail.

This guaranteees that processes never enter a pid namespaces after we
have cleaned up the state to support processes in a pid namespace.

Currently sending SIGKILL to all of the process in a pid namespace as
init exists gives us this guarantee but we need something a little
stronger to support unsharing and joining a pid namespace.

Acked-by: default avatar"Serge E. Hallyn" <serge@hallyn.com>
Signed-off-by: default avatarEric W. Biederman <ebiederm@xmission.com>
parent 0a01f2cc

kernel/pid.c

+7 −1
Original line number Diff line number Diff line
@@ -274,9 +274,11 @@ void free_pid(struct pid *pid) 
	for (i = 0; i <= pid->level; i++) {

		struct upid *upid = pid->numbers + i;

		hlist_del_rcu(&upid->pid_chain);

		if (--upid->ns->nr_hashed == 0)

		if (--upid->ns->nr_hashed == 0) {

			upid->ns->nr_hashed = -1;

			schedule_work(&upid->ns->proc_work);

		}

	}

	spin_unlock_irqrestore(&pidmap_lock, flags);



	for (i = 0; i <= pid->level; i++)
@@ -321,6 +323,8 @@ struct pid *alloc_pid(struct pid_namespace *ns) 


	upid = pid->numbers + ns->level;

	spin_lock_irq(&pidmap_lock);

	if (ns->nr_hashed < 0)

		goto out_unlock;

	for ( ; upid >= pid->numbers; --upid) {

		hlist_add_head_rcu(&upid->pid_chain,

				&pid_hash[pid_hashfn(upid->nr, upid->ns)]);
@@ -331,6 +335,8 @@ struct pid *alloc_pid(struct pid_namespace *ns) 
out:

	return pid;



out_unlock:

	spin_unlock(&pidmap_lock);

out_free:

	while (++i <= ns->level)

		free_pidmap(pid->numbers + i);