[patch 15/51] dup2: Fix return value with oldfd == newfd and invalid fd

[Greg KH]

2.6.29-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Jeff Mahoney <jeffm@xxxxxxxx>

commit 2b79bc4f7ebbd5af3c8b867968f9f15602d5f802 upstream.

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@xxxxxxxxxx>
Signed-off-by: Jeff Mahoney <jeffm@xxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 fs/fcntl.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -117,11 +117,13 @@ SYSCALL_DEFINE2(dup2, unsigned int, oldf
 {
 	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);
 }


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