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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>
This commit is contained in:
Eric W. Biederman 2010-07-12 18:50:25 -07:00
parent 0a01f2cc39
commit 5e1182deb8
1 changed files with 7 additions and 1 deletions
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8
kernel/pid.c
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@ -274,8 +274,10 @@ 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);
@ -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);