From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sukadev Bhattiprolu Subject: [PATCH 1/2][v2] pid: Implement ns_of_pid Date: Tue, 16 Dec 2008 16:02:57 -0800 Message-ID: <20081217000257.GA810@us.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org To: Andrew Morton Cc: "Eric W. Biederman" , Oleg Nesterov , bastian@waldi.eu.org, Pavel Emelyanov , roland@redhat.com, Containers , linux-kernel@vger.kernel.org List-Id: containers.vger.kernel.org Resending patch with correct "From", "Signed-off-by" and a note in function header of ns_of_pid(). --- From: Eric Biederman 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 Signed-off-by: Sukadev Bhattiprolu --- 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