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authorEric W. Biederman <ebiederm@xmission.com>2009-01-07 18:08:46 -0800
committerGreg Kroah-Hartman <gregkh@suse.de>2009-02-20 14:40:17 -0800
commit6f3787acee70e86e1d4e497ee8ffdad2ed0bdc3f (patch)
tree15d16f1cef7fee2ec43eca7c4145921f91709024
parent8f31afa8fcc9eb76ff502f2208f4931ae2b07c66 (diff)
downloadlwn-6f3787acee70e86e1d4e497ee8ffdad2ed0bdc3f.tar.gz
lwn-6f3787acee70e86e1d4e497ee8ffdad2ed0bdc3f.zip
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 <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> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r--include/linux/pid.h18
1 files changed, 18 insertions, 0 deletions
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
@@ -123,6 +123,24 @@ 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
*
* pid_nr() : global id, i.e. the id seen from the init namespace;