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.
