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

Ingo Molnar
2017-05-12T07:00:12Z

* Andy Lutomirski <luto@kernel.org> wrote:

> On Tue, May 9, 2017 at 1:56 AM, Christoph Hellwig <hch@infradead.org> wrote:
> > On Tue, May 09, 2017 at 08:45:22AM +0200, Ingo Molnar wrote:
> >> We only have ~115 code blocks in the kernel that set/restore KERNEL_DS, it would
> >> be a pity to add a runtime check to every system call ...
> >
> > I think we should simply strive to remove all of them that aren't
> > in core scheduler / arch code. Basically evetyytime we do the
> >
> > oldfs = get_fs();
> > set_fs(KERNEL_DS);
> > ..
> > set_fs(oldfs);
> >
> > trick we're doing something wrong, and there should always be better
> > ways to archive it. E.g. using iov_iter with a ITER_KVEC type
> > consistently would already remove most of them.
>
> 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.

I'm all for that!

Thanks,

Ingo