[PATCH 7/7] containers (V7): Container interface to nsproxy subsystem

[menage]

When a task enters a new namespace via a clone() or unshare(), a new
container is created and the task moves into it. Developed by Serge
Hallyn <serue@xxxxxxxxxx>, adapted by Paul Menage <menage@xxxxxxxxxx>

---
 include/linux/nsproxy.h |    6 ++
 init/Kconfig            |    9 +++
 kernel/Makefile         |    1 
 kernel/fork.c           |    4 +
 kernel/ns_container.c   |  110 ++++++++++++++++++++++++++++++++++++++++++++++++
 kernel/nsproxy.c        |    6 ++
 6 files changed, 136 insertions(+)

Index: container-2.6.20/include/linux/nsproxy.h
===================================================================
--- container-2.6.20.orig/include/linux/nsproxy.h
+++ container-2.6.20/include/linux/nsproxy.h
@@ -53,4 +53,10 @@ static inline void exit_task_namespaces(
 		put_nsproxy(ns);
 	}
 }
+#ifdef CONFIG_CONTAINER_NS
+int ns_container_clone(struct task_struct *tsk);
+#else
+static inline int ns_container_clone(struct task_struct *tsk) { return 0; }
+#endif
+
 #endif
Index: container-2.6.20/init/Kconfig
===================================================================
--- container-2.6.20.orig/init/Kconfig
+++ container-2.6.20/init/Kconfig
@@ -297,6 +297,15 @@ config CONTAINER_CPUACCT
 	  Provides a simple Resource Controller for monitoring the
 	  total CPU consumed by the tasks in a container
 
+config CONTAINER_NS
+        bool "Namespace container subsystem"
+        select CONTAINERS
+        help
+          Provides a simple namespace container subsystem to
+          provide hierarchical naming of sets of namespaces,
+          for instance virtual servers and checkpoint/restart
+          jobs.
+
 config RELAY
 	bool "Kernel->user space relay support (formerly relayfs)"
 	help
Index: container-2.6.20/kernel/Makefile
===================================================================
--- container-2.6.20.orig/kernel/Makefile
+++ container-2.6.20/kernel/Makefile
@@ -39,6 +39,7 @@ obj-$(CONFIG_COMPAT) += compat.o
 obj-$(CONFIG_CONTAINERS) += container.o
 obj-$(CONFIG_CPUSETS) += cpuset.o
 obj-$(CONFIG_CONTAINER_CPUACCT) += cpu_acct.o
+obj-$(CONFIG_CONTAINER_NS) += ns_container.o
 obj-$(CONFIG_IKCONFIG) += configs.o
 obj-$(CONFIG_STOP_MACHINE) += stop_machine.o
 obj-$(CONFIG_AUDIT) += audit.o auditfilter.o
Index: container-2.6.20/kernel/fork.c
===================================================================
--- container-2.6.20.orig/kernel/fork.c
+++ container-2.6.20/kernel/fork.c
@@ -1661,6 +1661,9 @@ asmlinkage long sys_unshare(unsigned lon
 			err = -ENOMEM;
 			goto bad_unshare_cleanup_ipc;
 		}
+		err = ns_container_clone(current);
+		if (err)
+			goto bad_unshare_cleanup_dupns;
 	}
 
 	if (new_fs || new_ns || new_mm || new_fd || new_ulist ||
@@ -1715,6 +1718,7 @@ asmlinkage long sys_unshare(unsigned lon
 		task_unlock(current);
 	}
 
+ bad_unshare_cleanup_dupns:
 	if (new_nsproxy)
 		put_nsproxy(new_nsproxy);
 
Index: container-2.6.20/kernel/ns_container.c
===================================================================
--- /dev/null
+++ container-2.6.20/kernel/ns_container.c
@@ -0,0 +1,110 @@
+/*
+ * ns_container.c - namespace container subsystem
+ *
+ * Copyright IBM, 2006
+ */
+
+#include <linux/module.h>
+#include <linux/container.h>
+#include <linux/fs.h>
+
+struct nscont {
+	struct container_subsys_state css;
+	spinlock_t lock;
+};
+
+static struct container_subsys ns_subsys;
+
+static inline struct nscont *container_nscont(struct container *cont)
+{
+	return container_of(container_subsys_state(cont, &ns_subsys),
+			    struct nscont, css);
+}
+
+int ns_container_clone(struct task_struct *tsk)
+{
+	return container_clone(tsk, &ns_subsys);
+}
+
+/*
+ * Rules:
+ *   1. you can only enter a container which is a child of your current
+ *     container
+ *   2. you can only place another process into a container if
+ *     a. you have CAP_SYS_ADMIN
+ *     b. your container is an ancestor of tsk's destination container
+ *       (hence either you are in the same container as tsk, or in an
+ *        ancestor container thereof)
+ */
+int ns_can_attach(struct container_subsys *ss,
+		  struct container *cont, struct task_struct *tsk)
+{
+	struct container *c;
+
+	if (current != tsk) {
+		if (!capable(CAP_SYS_ADMIN))
+			return -EPERM;
+
+		if (!container_is_descendant(cont))
+			return -EPERM;
+	}
+
+	if (atomic_read(&cont->count) != 0)
+		return -EPERM;
+
+	c = task_container(tsk, &ns_subsys);
+	if (c && c != cont->parent)
+		return -EPERM;
+
+	return 0;
+}
+
+/*
+ * Rules: you can only create a container if
+ *     1. you are capable(CAP_SYS_ADMIN)
+ *     2. the target container is a descendant of your own container
+ */
+static int ns_create(struct container_subsys *ss, struct container *cont)
+{
+	struct nscont *ns;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+	if (!container_is_descendant(cont))
+		return -EPERM;
+
+	ns = kzalloc(sizeof(*ns), GFP_KERNEL);
+	if (!ns) return -ENOMEM;
+	spin_lock_init(&ns->lock);
+	cont->subsys[ns_subsys.subsys_id] = &ns->css;
+	return 0;
+}
+
+static void ns_destroy(struct container_subsys *ss,
+		       struct container *cont)
+{
+	struct nscont *ns = container_nscont(cont);
+	kfree(ns);
+}
+
+static struct container_subsys ns_subsys = {
+	.name = "ns",
+	.create = ns_create,
+	.destroy  = ns_destroy,
+	.can_attach = ns_can_attach,
+	//.attach = ns_attach,
+	//.post_attach = ns_post_attach,
+	//.populate = ns_populate,
+	.subsys_id = -1,
+};
+
+int __init ns_init(void)
+{
+	int ret;
+
+	ret = container_register_subsys(&ns_subsys);
+
+	return ret < 0 ? ret : 0;
+}
+
+module_init(ns_init)
Index: container-2.6.20/kernel/nsproxy.c
===================================================================
--- container-2.6.20.orig/kernel/nsproxy.c
+++ container-2.6.20/kernel/nsproxy.c
@@ -116,10 +116,16 @@ int copy_namespaces(int flags, struct ta
 	if (err)
 		goto out_pid;
 
+	err = ns_container_clone(tsk);
+	if (err)
+		goto out_container;
 out:
 	put_nsproxy(old_ns);
 	return err;
 
+ out_container:
+	if (new_ns->pid_ns)
+		put_pid_ns(new_ns->pid_ns);
 out_pid:
 	if (new_ns->ipc_ns)
 		put_ipc_ns(new_ns->ipc_ns);

--
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