lkml.org 
[lkml]   [2008]   [Dec]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[PATCH 1/2][v2] pid: Implement ns_of_pid
Resending patch with correct "From", "Signed-off-by" and a note
in function header of ns_of_pid().

---
From: Eric Biederman <ebiederm@xmission.com>
Subject: [PATCH] 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.

Changelog[v2]:
- Add a note in function header of ns_of_pid() re: NULL pid.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
---
include/linux/pid.h | 18 ++++++++++++++++++
1 files changed, 18 insertions(+), 0 deletions(-)

diff --git a/include/linux/pid.h b/include/linux/pid.h
index d7e98ff..da6f174 100644
--- a/include/linux/pid.h
+++ b/include/linux/pid.h
@@ -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
*
--
1.5.2.5


\
 
 \ /
  Last update: 2008-12-17 01:07    [W:0.040 / U:0.200 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site