From: Cedric Le Goater <clg@fr.ibm.com>

Signed-off-by: Cedric Le Goater <clg@fr.ibm.com>
---
 include/linux/pid_namespace.h |    2 +
 kernel/nsproxy.c              |   25 +++++++++++++++++++++--
 kernel/pid.c                  |   44 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 68 insertions(+), 3 deletions(-)

Index: 2.6.19-rc6-mm2/include/linux/pid_namespace.h
===================================================================
--- 2.6.19-rc6-mm2.orig/include/linux/pid_namespace.h
+++ 2.6.19-rc6-mm2/include/linux/pid_namespace.h
@@ -29,6 +29,8 @@ static inline void get_pid_ns(struct pid
 	kref_get(&ns->kref);
 }
 
+extern int unshare_pid_ns(unsigned long unshare_ns_flags,
+			  struct pid_namespace **new_pid);
 extern int copy_pid_ns(int flags, struct task_struct *tsk);
 extern void free_pid_ns(struct kref *kref);
 
Index: 2.6.19-rc6-mm2/kernel/pid.c
===================================================================
--- 2.6.19-rc6-mm2.orig/kernel/pid.c
+++ 2.6.19-rc6-mm2/kernel/pid.c
@@ -361,6 +361,50 @@ struct pid *find_ge_pid(int nr)
 }
 EXPORT_SYMBOL_GPL(find_get_pid);
 
+static struct pid_namespace *clone_pid_ns(struct pid_namespace *old_ns)
+{
+	struct pid_namespace *ns;
+	int i;
+
+	ns = kmalloc(sizeof(struct pid_namespace), GFP_KERNEL);
+	if (!ns)
+		return ns;
+
+	kref_init(&ns->kref);
+
+	atomic_set(&ns->pidmap[0].nr_free, BITS_PER_PAGE - 1);
+	ns->pidmap[0].page = kzalloc(PAGE_SIZE, GFP_KERNEL);
+	if (!ns->pidmap[0].page) {
+		kfree(ns);
+		return NULL;
+	}
+
+	set_bit(0, ns->pidmap[0].page);
+
+	for (i = 1; i < PIDMAP_ENTRIES; i++) {
+		atomic_set(&ns->pidmap[i].nr_free, BITS_PER_PAGE);
+		ns->pidmap[i].page = NULL;
+	}
+	ns->last_pid = 0;
+	ns->child_reaper = current;
+	return ns;
+}
+
+int unshare_pid_ns(unsigned long unshare_ns_flags,
+		   struct pid_namespace **new_pid)
+{
+	if (unshare_ns_flags & NS_PID) {
+		if (!capable(CAP_SYS_ADMIN))
+			return -EPERM;
+
+		*new_pid = clone_pid_ns(current->nsproxy->pid_ns);
+		if (!*new_pid)
+			return -ENOMEM;
+	}
+
+	return 0;
+}
+
 int copy_pid_ns(int flags, struct task_struct *tsk)
 {
 	struct pid_namespace *old_ns = tsk->nsproxy->pid_ns;
Index: 2.6.19-rc6-mm2/kernel/nsproxy.c
===================================================================
--- 2.6.19-rc6-mm2.orig/kernel/nsproxy.c
+++ 2.6.19-rc6-mm2/kernel/nsproxy.c
@@ -324,6 +324,11 @@ static int switch_ns(int id, unsigned lo
 			put_ipc_ns(new_ns->ipc_ns);
 			new_ns->ipc_ns = get_ipc_ns(ns->ipc_ns);
 		}
+		if (flags & NS_PID) {
+			get_pid_ns(ns->pid_ns);
+			put_pid_ns(new_ns->pid_ns);
+			new_ns->pid_ns = ns->pid_ns;
+		}
 	out_ns:
 		put_nsproxy(ns);
 	}
@@ -440,6 +445,7 @@ asmlinkage long sys_unshare_ns(unsigned 
  	struct mnt_namespace *mnt, *new_mnt = NULL;
  	struct uts_namespace *uts, *new_uts = NULL;
  	struct ipc_namespace *ipc, *new_ipc = NULL;
+	struct pid_namespace *pid, *new_pid = NULL;
  	unsigned long unshare_flags = 0;
 
  	/* Return -EINVAL for all unsupported flags */
@@ -467,16 +473,19 @@ asmlinkage long sys_unshare_ns(unsigned 
  	if ((err = unshare_ipcs(unshare_flags, &new_ipc)))
  		goto bad_unshare_ns_cleanup_uts;
 
- 	if (new_mnt || new_uts || new_ipc) {
+	if ((err = unshare_pid_ns(unshare_ns_flags, &new_pid)))
+		goto bad_unshare_ns_cleanup_ipc;
+
+	if (new_mnt || new_uts || new_ipc || new_pid) {
  		old_nsproxy = current->nsproxy;
  		new_nsproxy = dup_namespaces(old_nsproxy);
  		if (!new_nsproxy) {
  			err = -ENOMEM;
- 			goto bad_unshare_ns_cleanup_ipc;
+ 			goto bad_unshare_ns_cleanup_pid;
  		}
  	}
 
- 	if (new_fs || new_mnt || new_uts || new_ipc) {
+ 	if (new_fs || new_mnt || new_uts || new_ipc || new_pid) {
 
  		task_lock(current);
 
@@ -509,12 +518,22 @@ asmlinkage long sys_unshare_ns(unsigned 
  			new_ipc = ipc;
  		}
 
+		if (new_pid) {
+			pid = current->nsproxy->pid_ns;
+			current->nsproxy->pid_ns = new_pid;
+			new_pid = pid;
+		}
+
  		task_unlock(current);
  	}
 
  	if (new_nsproxy)
  		put_nsproxy(new_nsproxy);
 
+bad_unshare_ns_cleanup_pid:
+	if (new_pid)
+		put_pid_ns(new_pid);
+
 bad_unshare_ns_cleanup_ipc:
  	if (new_ipc)
  		put_ipc_ns(new_ipc);

-- 
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