dup2: Fix return value with oldfd == newfd and invalid fd

The return value of dup2 when oldfd == newfd and the fd isn't valid is
not getting properly sign extended.  We end up with 4294967287 instead
of -EBADF.

I've reproduced this on SLE11 (2.6.27.21), openSUSE Factory
(2.6.29-rc5), and Ubuntu 9.04 (2.6.28).

This patch uses a signed int for the error value so it is properly
extended.

Commit 6c5d0512a091480c9f981162227fdb1c9d70e555 introduced this
regression.

Reported-by: Jiri Dluhos <jdluhos@novell.com>
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/fs/fcntl.c b/fs/fcntl.c
index cc8e4de2fee5..1ad703150dee 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -117,11 +117,13 @@ SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd)
 {
         if (unlikely(newfd == oldfd)) { /* corner case */
                 struct files_struct *files = current->files;
+                int retval = oldfd;
+
                 rcu_read_lock();
                 if (!fcheck_files(files, oldfd))
-                        oldfd = -EBADF;
+                        retval = -EBADF;
                 rcu_read_unlock();
-                return oldfd;
+                return retval;
         }
         return sys_dup3(oldfd, newfd, 0);
 }