[PATCH] namespaces: utsname: implement CLONE_NEWUTS flag

Implement a CLONE_NEWUTS flag, and use it at clone and sys_unshare.

[clg@fr.ibm.com: IPC unshare fix]
[bunk@stusta.de: cleanup]
Signed-off-by: Serge Hallyn <serue@us.ibm.com>
Cc: Kirill Korotaev <dev@openvz.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Herbert Poetzl <herbert@13thfloor.at>
Cc: Andrey Savochkin <saw@sw.ru>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Cedric Le Goater <clg@fr.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 53 insertions, 0 deletions

diff --git a/kernel/utsname.c b/kernel/utsname.c
index 1824384ecfa3..c859164a6993 100644
--- a/kernel/utsname.c
+++ b/kernel/utsname.c
@@ -15,6 +15,41 @@
 #include <linux/version.h>
 
 /*
+ * Clone a new ns copying an original utsname, setting refcount to 1
+ * @old_ns: namespace to clone
+ * Return NULL on error (failure to kmalloc), new ns otherwise
+ */
+static struct uts_namespace *clone_uts_ns(struct uts_namespace *old_ns)
+{
+        struct uts_namespace *ns;
+
+        ns = kmalloc(sizeof(struct uts_namespace), GFP_KERNEL);
+        if (ns) {
+                memcpy(&ns->name, &old_ns->name, sizeof(ns->name));
+                kref_init(&ns->kref);
+        }
+        return ns;
+}
+
+/*
+ * unshare the current process' utsname namespace.
+ * called only in sys_unshare()
+ */
+int unshare_utsname(unsigned long unshare_flags, struct uts_namespace **new_uts)
+{
+        if (unshare_flags & CLONE_NEWUTS) {
+                if (!capable(CAP_SYS_ADMIN))
+                        return -EPERM;
+
+                *new_uts = clone_uts_ns(current->nsproxy->uts_ns);
+                if (!*new_uts)
+                        return -ENOMEM;
+        }
+
+        return 0;
+}
+
+/*
  * Copy task tsk's utsname namespace, or clone it if flags
  * specifies CLONE_NEWUTS.  In latter case, changes to the
  * utsname of this process won't be seen by parent, and vice
@@ -23,6 +58,7 @@
 int copy_utsname(int flags, struct task_struct *tsk)
 {
         struct uts_namespace *old_ns = tsk->nsproxy->uts_ns;
+        struct uts_namespace *new_ns;
         int err = 0;
 
         if (!old_ns)
@@ -30,6 +66,23 @@ int copy_utsname(int flags, struct task_struct *tsk)
 
         get_uts_ns(old_ns);
 
+        if (!(flags & CLONE_NEWUTS))
+                return 0;
+
+        if (!capable(CAP_SYS_ADMIN)) {
+                err = -EPERM;
+                goto out;
+        }
+
+        new_ns = clone_uts_ns(old_ns);
+        if (!new_ns) {
+                err = -ENOMEM;
+                goto out;
+        }
+        tsk->nsproxy->uts_ns = new_ns;
+
+out:
+        put_uts_ns(old_ns);
         return err;
 }