compat: sync compat_stats with statfs.

This was found by inspection while tracking a similar
bug in compat_statfs64, that has been fixed in mainline
since decemeber.

- This fixes a bug where not all of the f_spare fields
  were cleared on mips and s390.
- Add the f_flags field to struct compat_statfs
- Copy f_flags to userspace in case someone cares.
- Use __clear_user to copy the f_spare field to userspace
  to ensure that all of the elements of f_spare are cleared.
  On some architectures f_spare is has 5 ints and on some
  architectures f_spare only has 4 ints.  Which makes
  the previous technique of clearing each int individually
  broken.

I don't expect anyone actually uses the old statfs system
call anymore but if they do let them benefit from having
the compat and the native version working the same.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

1 files changed, 2 insertions, 5 deletions

diff --git a/fs/compat.c b/fs/compat.c
index 58b1da45989..0f1ab468fa2 100644
--- a/fs/compat.c
+++ b/fs/compat.c
@@ -247,11 +247,8 @@ static int put_compat_statfs(struct compat_statfs __user *ubuf, struct kstatfs *
 	    __put_user(kbuf->f_fsid.val[0], &ubuf->f_fsid.val[0]) ||
 	    __put_user(kbuf->f_fsid.val[1], &ubuf->f_fsid.val[1]) ||
 	    __put_user(kbuf->f_frsize, &ubuf->f_frsize) ||
-	    __put_user(0, &ubuf->f_spare[0]) || 
-	    __put_user(0, &ubuf->f_spare[1]) || 
-	    __put_user(0, &ubuf->f_spare[2]) || 
-	    __put_user(0, &ubuf->f_spare[3]) || 
-	    __put_user(0, &ubuf->f_spare[4]))
+	    __put_user(kbuf->f_flags, &ubuf->f_flags) ||
+	    __clear_user(ubuf->f_spare, sizeof(ubuf->f_spare)))
 		return -EFAULT;
 	return 0;
 }