[PATCH] unshare system call -v5: unshare filesystem info

If filesystem 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, 6 insertions, 3 deletions

diff --git a/kernel/fork.c b/kernel/fork.c
index 6eb9362775f9..598e5c27242c 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1371,15 +1371,18 @@ static int unshare_thread(unsigned long unshare_flags)
 }
 
 /*
- * Unsharing of fs info for tasks created with CLONE_FS is not supported yet
+ * Unshare the filesystem structure if it is being shared
  */
 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
 {
         struct fs_struct *fs = current->fs;
 
         if ((unshare_flags & CLONE_FS) &&
-            (fs && atomic_read(&fs->count) > 1))
-                return -EINVAL;
+            (fs && atomic_read(&fs->count) > 1)) {
+                *new_fsp = __copy_fs_struct(current->fs);
+                if (!*new_fsp)
+                        return -ENOMEM;
+        }
 
         return 0;
 }