Commit f9fb860f authored Jan 07, 2009 by Eric W. Biederman Committed by Linus Torvalds Jan 08, 2009

pid: implement ns_of_pid



A current problem with the pid namespace is that it is easy to do pid
related work after exit_task_namespaces which drops the nsproxy pointer.

However if we are doing pid namespace related work we are always operating
on some struct pid which retains the pid_namespace pointer of the pid
namespace it was allocated in.

So provide ns_of_pid which allows us to find the pid namespace a pid was
allocated in.

Using this we have the needed infrastructure to do pid namespace related
work at anytime we have a struct pid, removing the chance of accidentally
having a NULL pointer dereference when accessing current->nsproxy.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Roland McGrath <roland@redhat.com>
Cc: Bastian Blank <bastian@waldi.eu.org>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Nadia Derbey <Nadia.Derbey@bull.net>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 6af866af

include/linux/pid.h

+18 −0

Original line number	Diff line number	Diff line
		@@ -122,6 +122,24 @@ int next_pidmap(struct pid_namespace *pid_ns, int last);
		extern struct pid alloc_pid(struct pid_namespace ns);
		extern void free_pid(struct pid *pid);

		/*
		* ns_of_pid() returns the pid namespace in which the specified pid was
		* allocated.
		*
		* NOTE:
		* ns_of_pid() is expected to be called for a process (task) that has
		* an attached 'struct pid' (see attach_pid(), detach_pid()) i.e @pid
		* is expected to be non-NULL. If @pid is NULL, caller should handle
		* the resulting NULL pid-ns.
		*/
		static inline struct pid_namespace ns_of_pid(struct pid pid)
		{
		struct pid_namespace *ns = NULL;
		if (pid)
		ns = pid->numbers[pid->level].ns;
		return ns;
		}

		/*
		* the helpers to get the pid's id seen from different namespaces
		*