dup2: Fix return value with oldfd == newfd and invalid fd
Jeff Mahoney [Mon, 11 May 2009 18:25:34 +0000 (14:25 -0400)]
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>

fs/fcntl.c

index cc8e4de..1ad7031 100644 (file)
@@ -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);
 }