From 6f3787acee70e86e1d4e497ee8ffdad2ed0bdc3f Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Wed, 7 Jan 2009 18:08:46 -0800 Subject: pid: implement ns_of_pid commit f9fb860f67b9542cd78d1558dec7058092b57d8e upstream. 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 Signed-off-by: Sukadev Bhattiprolu Cc: Oleg Nesterov Cc: Roland McGrath Cc: Bastian Blank Cc: Pavel Emelyanov Cc: Nadia Derbey Acked-by: Serge Hallyn Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- include/linux/pid.h | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/include/linux/pid.h b/include/linux/pid.h index d7e98ff8021e..93997c968ba9 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 * -- cgit v1.2.3