On Wed, Jun 21, 2017 at 12:33 PM, Oleg Nesterov <o...@redhat.com> wrote:
> - if (unlikely(address + 65536 + 32 * sizeof(unsigned long) <
> regs->sp)) {
> +if (0) if (unlikely(address + 65536 + 32 * sizeof(unsigned long) <
> regs->sp)) {
This smells bad.
That test is not about grow-down or even the guard page. That test is
that it's always wrong to grow down the stack below %esp.
Except we allow some slop, because certain instructions take the page
fault before actually updating %rsp.
So that patch is not correct. We want a page fault (and *not* expand
the stack) if somebody accesses below the stack pointer.
If we had a regression, it's due to something else.
Linus
