On Mon, Jun 8, 2020 at 6:05 AM Christoph Hellwig <hch@xxxxxx> wrote:
>
> On Mon, Jun 08, 2020 at 09:45:49AM +0200, Vegard Nossum wrote:
> > Just a test case.
> >
> > Allowing the kernel to allocate an unbounded amount of memory on behalf
> > of userspace is an easy DOS.
> >
> > All the length checks were already in there, e.g.
> >
> > static int cmm_timeout_handler(struct ctl_table *ctl, int write,
> > void __user *buffer, size_t *lenp, loff_t
> > *ppos)
> > {
> > char buf[64], *p;
> > [...]
> > len = min(*lenp, sizeof(buf));
> > if (copy_from_user(buf, buffer, len))
> > return -EFAULT;
>
> Doesn't help if we don't know the exact limit yet. But we can put
> some arbitrary but reasonable limit like KMALLOC_MAX_SIZE on the
> sysctls and see if this sticks.
adding Stanislav. I think he's looking into this already.
