[Devel] [RFC][PATCH 6/6]: Enable unsharing pid namespace.

[sukadev at us.ibm.com]

From: Cedric Le Goater <clg at fr.ibm.com>
Subject: [RFC][PATCH 6/6]: Enable unsharing pid namespace.

Enable unsharing of pid namespace - i.e allow creating and using
a new pid namespace and attaching multiple struct pid_nrs per
process, one for each namespace.

Signed-off-by: Cedric Le Goater <clg at fr.ibm.com>
Signed-off-by: Sukadev Bhattiprolu <sukadev at us.ibm.com>

---
 include/linux/sched.h |    1 +
 kernel/fork.c         |   22 ++++++++++++++++++----
 kernel/nsproxy.c      |    5 ++++-
 kernel/pid.c          |   18 ++++++++++++++++++
 4 files changed, 41 insertions(+), 5 deletions(-)

Index: lx26-20-mm2b/kernel/pid.c
===================================================================
--- lx26-20-mm2b.orig/kernel/pid.c	2007-03-09 14:56:53.000000000 -0800
+++ lx26-20-mm2b/kernel/pid.c	2007-03-09 15:03:05.000000000 -0800
@@ -546,6 +546,24 @@ void free_pid_ns(struct kref *kref)
 	struct pid_namespace *ns;
 
 	ns = container_of(kref, struct pid_namespace, kref);
+
+	if (ns != &init_pid_ns) {
+		/* BEGIN: to be removed soon */
+		int i;
+		int nr_free = atomic_read(&ns->pidmap[0].nr_free);
+
+		BUG_ON( nr_free != (BITS_PER_PAGE - 1));
+
+		if (unlikely(PIDMAP_ENTRIES != 1)) {
+			for (i = 1; i < PIDMAP_ENTRIES; i++) {
+				nr_free = atomic_read(&ns->pidmap[i].nr_free);
+				BUG_ON(nr_free != BITS_PER_PAGE);
+			}
+		}
+		/* END: to be removed soon */
+		kfree(ns->pidmap[0].page);
+	}
+
 	kfree(ns);
 }
 
Index: lx26-20-mm2b/include/linux/sched.h
===================================================================
--- lx26-20-mm2b.orig/include/linux/sched.h	2007-03-09 14:56:12.000000000 -0800
+++ lx26-20-mm2b/include/linux/sched.h	2007-03-09 14:56:53.000000000 -0800
@@ -26,6 +26,7 @@
 #define CLONE_STOPPED		0x02000000	/* Start in stopped state */
 #define CLONE_NEWUTS		0x04000000	/* New utsname group? */
 #define CLONE_NEWIPC		0x08000000	/* New ipcs */
+#define CLONE_NEWPID		0x10000000	/* New pid namespace */
 
 /*
  * Scheduling policies
Index: lx26-20-mm2b/kernel/fork.c
===================================================================
--- lx26-20-mm2b.orig/kernel/fork.c	2007-03-09 14:56:12.000000000 -0800
+++ lx26-20-mm2b/kernel/fork.c	2007-03-09 15:05:39.000000000 -0800
@@ -57,6 +57,7 @@
 #include <asm/mmu_context.h>
 #include <asm/cacheflush.h>
 #include <asm/tlbflush.h>
+#include <linux/pid_namespace.h>
 
 /*
  * Protected counters by write_lock_irq(&tasklist_lock)
@@ -1609,6 +1610,7 @@ asmlinkage long sys_unshare(unsigned lon
 	struct nsproxy *new_nsproxy = NULL, *old_nsproxy = NULL;
 	struct uts_namespace *uts, *new_uts = NULL;
 	struct ipc_namespace *ipc, *new_ipc = NULL;
+	struct pid_nr *new_pid_nr = NULL;
 
 	check_unshare_flags(&unshare_flags);
 
@@ -1616,7 +1618,7 @@ asmlinkage long sys_unshare(unsigned lon
 	err = -EINVAL;
 	if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
 				CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
-				CLONE_NEWUTS|CLONE_NEWIPC))
+				CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWPID))
 		goto bad_unshare_out;
 
 	if ((err = unshare_thread(unshare_flags)))
@@ -1637,18 +1639,20 @@ asmlinkage long sys_unshare(unsigned lon
 		goto bad_unshare_cleanup_semundo;
 	if ((err = unshare_ipcs(unshare_flags, &new_ipc)))
 		goto bad_unshare_cleanup_uts;
+	if ((err = unshare_pid_ns(unshare_flags, &new_pid_nr)))
+		goto bad_unshare_cleanup_ipc;
 
-	if (new_ns || new_uts || new_ipc) {
+	if (new_ns || new_uts || new_ipc || new_pid_nr) {
 		old_nsproxy = current->nsproxy;
 		new_nsproxy = dup_namespaces(old_nsproxy);
 		if (!new_nsproxy) {
 			err = -ENOMEM;
-			goto bad_unshare_cleanup_ipc;
+			goto bad_unshare_cleanup_pid;
 		}
 	}
 
 	if (new_fs || new_ns || new_mm || new_fd || new_ulist ||
-				new_uts || new_ipc) {
+				new_uts || new_ipc || new_pid_nr) {
 
 		task_lock(current);
 
@@ -1696,12 +1700,22 @@ asmlinkage long sys_unshare(unsigned lon
 			new_ipc = ipc;
 		}
 
+		if (new_pid_nr) {
+			pid = task_pid_ns(current);
+			set_task_pid_ns(current, new_pid_nr->pid_ns);
+			new_pid_nr = NULL;
+		}
+
 		task_unlock(current);
 	}
 
 	if (new_nsproxy)
 		put_nsproxy(new_nsproxy);
 
+bad_unshare_cleanup_pid:
+	if (new_pid_nr)
+		free_pidmap_pid_nr(new_pid_nr);
+
 bad_unshare_cleanup_ipc:
 	if (new_ipc)
 		put_ipc_ns(new_ipc);
Index: lx26-20-mm2b/kernel/nsproxy.c
===================================================================
--- lx26-20-mm2b.orig/kernel/nsproxy.c	2007-03-09 14:56:12.000000000 -0800
+++ lx26-20-mm2b/kernel/nsproxy.c	2007-03-09 15:03:05.000000000 -0800
@@ -83,13 +83,16 @@ int copy_namespaces(int flags, struct ta
 	struct nsproxy *old_ns = tsk->nsproxy;
 	struct nsproxy *new_ns;
 	int err = 0;
+	int ns_all;
 
 	if (!old_ns)
 		return 0;
 
 	get_nsproxy(old_ns);
 
-	if (!(flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC)))
+	ns_all = CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC | CLONE_NEWPID;
+
+	if (!(flags & ns_all))
 		return 0;
 
 	new_ns = clone_namespaces(old_ns);
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