My personal opinion is that even looking at esp/rsp is asking for
trouble. The only reliable information is VM_STACK or another VM flag
that makes the area expand in response to stack growth.
Besides, userspace could always play funky trampoline games with the
stack pointer, or even dynamically expand the stack by doing a malloc
if a stack overflow draws near, which would put the stack in the data
section temporarily.
As long as esp is in the bounds of a valid VMA, my vote is that we
should consider it undefined how the task uses it.
On Mon, Oct 3, 2016 at 4:17 PM, Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
On Mon, Oct 3, 2016 at 4:08 PM, Andy Lutomirski <luto@xxxxxxxxxxxxxx>
wrote:
Ping!
We need to decide fairly soon whether to apply these (or perhaps
just
patch 1 or just patches 2 and 3) for 4.9. For any parts that aren't
applied, I'll send quick fixups to pin the stack in the offending
code.
I think we should apply it. Hopefully nothing uses it, and nobody will
notice. And if somebody *does* notice, the sooner we find out, the
better.
Linus
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