Re: Why use copy_from_user/copy_to_user ?
From: Kasper Dupont (kasperd_at_daimi.au.dk)
Date: Fri, 22 Oct 2004 23:41:11 +0200
"Pete Zaitcev (OTID1)" wrote:
> On Wed, 20 Oct 2004 16:47:31 -0700, Thomas wrote:
> > Then why should
> > the system calls use copy_from_user and copy_to_user to access
> > user-space memory?
> Two reasons.
Actually there are a few more reasons. In some cases
it might be a problem if the data is changed while the
system call is using them. If it first performs some
consistency check and use the data afterwards, the
program may change the data (possible using threads or
DMA). Copying the data first prevents the user program
from providing some good data and later change it.
Another potential problem is the fact that a user mode
program can give a pointer to kernel space instead of
a pointer to user space.
-- Kasper Dupont