Re: [kernel-hardening] Re: vDSO maximum stack usage, stack probes, and -fstack-check

[Andy Lutomirski]

> On Nov 10, 2017, at 8:36 AM, Hector Martin 'marcan' <marcan@xxxxxxxxx> wrote:
>
>> On 2017-11-11 01:02, Hector Martin 'marcan' wrote:
>> Not entirely sure what's going on here.
>
> Actually, if you think about it, it doesn't matter that it skips the
> first page, since it's probing one page more. That just means the caller
> will have probed the previous page. So ultimately you're just probing
> ahead of where you need to, but that should be OK.
>

The whole point is to touch the stack pages in order.  Also, I see no
guarantee that the function would touch the intermediate page before
clobbering the probed page.  You're seeing exactly that behavior, in
fact.

> --
> Hector Martin "marcan" (marcan@xxxxxxxxx)
> Public Key: https://mrcn.st/pub