On Wed, Nov 19, 2014 at 4:49 PM, Andy Lutomirski <l...@amacapital.net> wrote:
>
> I thought so for a while, too, but now I disagree. On PGE hardware,
> it seems entirely possible that the new stack would be in the TLB even
> if it's not visible via cr3. Then, as soon as the TLB entry expires,
> we double-fault.
Ahh. Good point.
> I don't want vmalloc to avoid low-order allocations -- I want it to
> have guard pages. The fact that a user-triggerable stack overflow is
> basically root right now and doesn't reliably OOPS scares me.
Well, if you do that, you would have to make the double-fault handler
aware of the stack issue anyway, and then you could just do teh same
PGD repopulation that a page fault does and return (for the case where
you didn't overflow the stack, just had the page tables unpopulated -
obviously an actual stack overflow should do something more drastic).
Linus
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