[RFC][PATCH 1/5] pid: Implement ns_of_pid

Sukadev Bhattiprolu
2008-11-26T03:45:08Z

>From f3dd53544a8a7a1c43009f686cbadec561e5a489 Mon Sep 17 00:00:00 2001
From: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Date: Mon, 10 Nov 2008 19:03:56 -0800
Subject: [PATCH 1/5] 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>
---
include/linux/pid.h | 11 +++++++++++
1 files changed, 11 insertions(+), 0 deletions(-)

diff --git a/include/linux/pid.h b/include/linux/pid.h
index d7e98ff..e9aec85 100644
--- a/include/linux/pid.h
+++ b/include/linux/pid.h
@@ -122,6 +122,17 @@ 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.
+ */
+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
*
--
1.5.2.5