From: "Robert T. Johnson" <rtjohnso@eecs.berkeley.edu>

Since arg is a user pointer, so are uioc_mimd and uiocp, and hence umc is a
user pointer.  Thus reading umc->xferaddr requires dereferencing a user
pointer, which isn't safe.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>