[PATCH] unshare system call -v5: unshare namespace

If the namespace structure is being shared, allocate a new one and copy
information from the current, shared, structure.

Signed-off-by: Janak Desai <janak@us.ibm.com>
Cc: Al Viro <viro@ftp.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Michael Kerrisk <mtk-manpages@gmx.net>
Cc: Andi Kleen <ak@muc.de>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 11 insertions, 6 deletions

diff --git a/kernel/fork.c b/kernel/fork.c
index 598e5c27242c..07dd241aa1e0 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1388,16 +1388,21 @@ static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
 }
 
 /*
- * Unsharing of namespace for tasks created without CLONE_NEWNS is not
- * supported yet
+ * Unshare the namespace structure if it is being shared
  */
-static int unshare_namespace(unsigned long unshare_flags, struct namespace **new_nsp)
+static int unshare_namespace(unsigned long unshare_flags, struct namespace **new_nsp, struct fs_struct *new_fs)
 {
         struct namespace *ns = current->namespace;
 
         if ((unshare_flags & CLONE_NEWNS) &&
-            (ns && atomic_read(&ns->count) > 1))
-                return -EINVAL;
+            (ns && atomic_read(&ns->count) > 1)) {
+                if (!capable(CAP_SYS_ADMIN))
+                        return -EPERM;
+
+                *new_nsp = dup_namespace(current, new_fs ? new_fs : current->fs);
+                if (!*new_nsp)
+                        return -ENOMEM;
+        }
 
         return 0;
 }
@@ -1482,7 +1487,7 @@ asmlinkage long sys_unshare(unsigned long unshare_flags)
                 goto bad_unshare_out;
         if ((err = unshare_fs(unshare_flags, &new_fs)))
                 goto bad_unshare_cleanup_thread;
-        if ((err = unshare_namespace(unshare_flags, &new_ns)))
+        if ((err = unshare_namespace(unshare_flags, &new_ns, new_fs)))
                 goto bad_unshare_cleanup_fs;
         if ((err = unshare_sighand(unshare_flags, &new_sigh)))
                 goto bad_unshare_cleanup_ns;