[Devel] [patch -mm 17/17] user namespace: add unshare

[clg at fr.ibm.com]

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

Signed-off-by: Cedric Le Goater <clg at fr.ibm.com>
---
 include/linux/user_namespace.h |   11 +++++++
 kernel/nsproxy.c               |   26 ++++++++++++++++--
 kernel/user_namespace.c        |   57 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 91 insertions(+), 3 deletions(-)

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
@@ -335,6 +335,12 @@ static int switch_ns(int id, unsigned lo
 			new_ns->net_ns = ns->net_ns;
 		}
 
+		if (flags & NS_USER) {
+			get_user_ns(ns->user_ns);
+			put_user_ns(new_ns->user_ns);
+			new_ns->user_ns = ns->user_ns;
+		}
+
 	out_ns:
 		put_nsproxy(ns);
 	}
@@ -453,6 +459,7 @@ asmlinkage long sys_unshare_ns(unsigned 
  	struct ipc_namespace *ipc, *new_ipc = NULL;
 	struct pid_namespace *pid, *new_pid = NULL;
 	struct net_namespace *net, *new_net = NULL;
+	struct user_namespace *user, *new_user = NULL;
  	unsigned long unshare_flags = 0;
 
  	/* Return -EINVAL for all unsupported flags */
@@ -484,17 +491,20 @@ asmlinkage long sys_unshare_ns(unsigned 
 		goto bad_unshare_ns_cleanup_ipc;
 	if ((err = unshare_net_ns(unshare_ns_flags, &new_net)))
 		goto bad_unshare_ns_cleanup_pid;
+	if ((err = unshare_user_ns(unshare_ns_flags, &new_user)))
+		goto bad_unshare_ns_cleanup_net;
 
-	if (new_mnt || new_uts || new_ipc || new_pid || new_net) {
+	if (new_mnt || new_uts || new_ipc || new_pid || new_net || new_user) {
  		old_nsproxy = current->nsproxy;
  		new_nsproxy = dup_namespaces(old_nsproxy);
  		if (!new_nsproxy) {
  			err = -ENOMEM;
- 			goto bad_unshare_ns_cleanup_net;
+ 			goto bad_unshare_ns_cleanup_user;
  		}
  	}
 
- 	if (new_fs || new_mnt || new_uts || new_ipc || new_pid || new_net) {
+ 	if (new_fs || new_mnt || new_uts || new_ipc || new_pid || new_net ||
+	    new_user) {
 
  		task_lock(current);
 
@@ -539,12 +549,22 @@ asmlinkage long sys_unshare_ns(unsigned 
 			new_net = net;
 		}
 
+		if (new_user) {
+			user = current->nsproxy->user_ns;
+			current->nsproxy->user_ns = new_user;
+			new_user = user;
+		}
+
  		task_unlock(current);
  	}
 
  	if (new_nsproxy)
  		put_nsproxy(new_nsproxy);
 
+bad_unshare_ns_cleanup_user:
+	if (new_user)
+		put_user_ns(new_user);
+
 bad_unshare_ns_cleanup_net:
 	if (new_net)
 		put_net_ns(new_net);
Index: 2.6.19-rc6-mm2/include/linux/user_namespace.h
===================================================================
--- 2.6.19-rc6-mm2.orig/include/linux/user_namespace.h
+++ 2.6.19-rc6-mm2/include/linux/user_namespace.h
@@ -22,6 +22,8 @@ static inline void get_user_ns(struct us
 	kref_get(&ns->kref);
 }
 
+extern int unshare_user_ns(unsigned long unshare_flags,
+			   struct user_namespace **new_user);
 extern int copy_user_ns(int flags, struct task_struct *tsk);
 extern void free_user_ns(struct kref *kref);
 
@@ -36,6 +38,15 @@ static inline void get_user_ns(struct us
 {
 }
 
+static inline int unshare_user_ns(unsigned long unshare_flags,
+				  struct user_namespace **new_user)
+{
+	if (unshare_flags & NS_USER)
+		return -EINVAL;
+
+	return 0;
+}
+
 static inline int copy_user_ns(int flags, struct task_struct *tsk)
 {
 	return 0;
Index: 2.6.19-rc6-mm2/kernel/user_namespace.c
===================================================================
--- 2.6.19-rc6-mm2.orig/kernel/user_namespace.c
+++ 2.6.19-rc6-mm2/kernel/user_namespace.c
@@ -21,6 +21,63 @@ EXPORT_SYMBOL_GPL(init_user_ns);
 
 #ifdef CONFIG_USER_NS
 
+/*
+ * Clone a new ns copying an original user ns, setting refcount to 1
+ * @old_ns: namespace to clone
+ * Return NULL on error (failure to kmalloc), new ns otherwise
+ */
+static struct user_namespace *clone_user_ns(struct user_namespace *old_ns)
+{
+	struct user_namespace *ns;
+	struct user_struct *new_user;
+	int n;
+
+	ns = kmalloc(sizeof(struct user_namespace), GFP_KERNEL);
+	if (!ns)
+		return NULL;
+
+	kref_init(&ns->kref);
+
+	for(n = 0; n < UIDHASH_SZ; ++n)
+		INIT_LIST_HEAD(ns->uidhash_table + n);
+
+	/* Insert new root user.  */
+	ns->root_user = alloc_uid(ns, 0);
+	if (!ns->root_user) {
+		kfree(ns);
+		return NULL;
+	}
+
+	/* Reset current->user with a new one */
+	new_user = alloc_uid(ns, current->uid);
+	if (!new_user) {
+		free_uid(ns->root_user);
+		kfree(ns);
+		return NULL;
+	}
+
+	switch_uid(new_user);
+	return ns;
+}
+
+/*
+ * unshare the current process' user namespace.
+ */
+int unshare_user_ns(unsigned long unshare_flags,
+		    struct user_namespace **new_user)
+{
+	if (unshare_flags & NS_USER) {
+		if (!capable(CAP_SYS_ADMIN))
+			return -EPERM;
+
+		*new_user = clone_user_ns(current->nsproxy->user_ns);
+		if (!*new_user)
+			return -ENOMEM;
+	}
+
+	return 0;
+}
+
 int copy_user_ns(int flags, struct task_struct *tsk)
 {
 	struct user_namespace *old_ns = tsk->nsproxy->user_ns;

-- 
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