[kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address limit before returning to user-mode

[Christoph Hellwig]

On Wed, May 10, 2017 at 09:08:41AM +0100, Al Viro wrote:
> On Wed, May 10, 2017 at 09:37:04AM +0200, Arnd Bergmann wrote:
> 
> > > How about trying to remove all of them?  If we could actually get rid
> > > of all of them, we could drop the arch support, and we'd get faster,
> > > simpler, shorter uaccess code throughout the kernel.
> 
> BTW, not all get_user() under KERNEL_DS are plain loads.  There is an
> exception - probe_kernel_read().

And various calls that looks like opencoded versions, e.g. drivers/dio
or the ELF loader.

But in the long run we'll just need a separate primitive for that,
but that can wait until the set_fs calls outside the core code are
gone.