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

[Jeff Mahoney]

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 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>
- ---
 fs/fcntl.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

- --- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -115,13 +115,14 @@ out_unlock:
 
 SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd)
 {
+	int ret = oldfd;
 	if (unlikely(newfd == oldfd)) { /* corner case */
 		struct files_struct *files = current->files;
 		rcu_read_lock();
 		if (!fcheck_files(files, oldfd))
- -			oldfd = -EBADF;
+			ret = -EBADF;
 		rcu_read_unlock();
- -		return oldfd;
+		return ret;
 	}
 	return sys_dup3(oldfd, newfd, 0);
 }

- -- 
Jeff Mahoney
SUSE Labs
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