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Message-ID: <CA+55aFznPpS8rT_GLdAyHsr80B2FCb2Hm-4b9QTqREMCv6_s-Q@mail.gmail.com>
Date: Mon, 27 Jun 2016 10:28:12 -0700
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Andy Lutomirski <luto@...capital.net>
Cc: Brian Gerst <brgerst@...il.com>, Andy Lutomirski <luto@...nel.org>,
"the arch/x86 maintainers" <x86@...nel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
linux-arch <linux-arch@...r.kernel.org>, Borislav Petkov <bp@...en8.de>,
Nadav Amit <nadav.amit@...il.com>, Kees Cook <keescook@...omium.org>,
"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>, Josh Poimboeuf <jpoimboe@...hat.com>,
Jann Horn <jann@...jh.net>, Heiko Carstens <heiko.carstens@...ibm.com>
Subject: Re: [PATCH v4 15/29] x86/mm/64: Enable vmapped stacks
On Mon, Jun 27, 2016 at 8:54 AM, Andy Lutomirski <luto@...capital.net> wrote:
>
> How about:
>
> tsk_stack = (unsigned long)task_stack_page(tsk);
> if (regs->rsp <= tsk_stack + 7*8 && regs->rsp > tsk_stack - PAGE_SIZE) {
I'm not at all convinced that regs->rsp will be all that reliable
under a double-fault scenario either. I'd be more inclined to trusr
cr2 than the register state.
It's true that double faults can happen for *other* reasons entirely,
and as such it's not clear that %cr2 is reliable either, but since
this is all just about a printout, I'd rather go that way anyway.
Linus
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