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: "Serge E. Hallyn" <serge@hallyn.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
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0a01f2cc39
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5e1182deb8
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@ -274,8 +274,10 @@ void free_pid(struct pid *pid)
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for (i = 0; i <= pid->level; i++) {
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for (i = 0; i <= pid->level; i++) {
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struct upid *upid = pid->numbers + i;
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struct upid *upid = pid->numbers + i;
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hlist_del_rcu(&upid->pid_chain);
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hlist_del_rcu(&upid->pid_chain);
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if (--upid->ns->nr_hashed == 0)
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if (--upid->ns->nr_hashed == 0) {
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upid->ns->nr_hashed = -1;
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schedule_work(&upid->ns->proc_work);
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schedule_work(&upid->ns->proc_work);
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}
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}
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}
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spin_unlock_irqrestore(&pidmap_lock, flags);
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spin_unlock_irqrestore(&pidmap_lock, flags);
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@ -321,6 +323,8 @@ struct pid *alloc_pid(struct pid_namespace *ns)
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upid = pid->numbers + ns->level;
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upid = pid->numbers + ns->level;
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spin_lock_irq(&pidmap_lock);
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spin_lock_irq(&pidmap_lock);
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if (ns->nr_hashed < 0)
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goto out_unlock;
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for ( ; upid >= pid->numbers; --upid) {
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for ( ; upid >= pid->numbers; --upid) {
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hlist_add_head_rcu(&upid->pid_chain,
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hlist_add_head_rcu(&upid->pid_chain,
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&pid_hash[pid_hashfn(upid->nr, upid->ns)]);
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&pid_hash[pid_hashfn(upid->nr, upid->ns)]);
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@ -331,6 +335,8 @@ struct pid *alloc_pid(struct pid_namespace *ns)
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out:
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out:
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return pid;
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return pid;
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out_unlock:
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spin_unlock(&pidmap_lock);
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out_free:
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out_free:
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while (++i <= ns->level)
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while (++i <= ns->level)
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free_pidmap(pid->numbers + i);
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free_pidmap(pid->numbers + i);
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