linux-kernel - Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core)

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CA+55aFzBAdM2UGpmVQjhnEtsvfPmJE1aqeoo4e65PrQvsvsFnQ@mail.gmail.com>
Date:	Tue, 21 Jun 2016 10:16:46 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Andy Lutomirski <luto@...nel.org>,
	"the arch/x86 maintainers" <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
	Borislav Petkov <bp@...en8.de>,
	Nadav Amit <nadav.amit@...il.com>,
	Kees Cook <keescook@...omium.org>,
	Brian Gerst <brgerst@...il.com>,
	"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 v3 00/13] Virtually mapped stacks with guard pages (x86, core)

On Tue, Jun 21, 2016 at 9:45 AM, Andy Lutomirski <luto@...capital.net> wrote:
>
> So I'm leaning toward fewer cache entries per cpu, maybe just one.
> I'm all for making it a bit faster, but I think we should weigh that
> against increasing memory usage too much and thus scaring away the
> embedded folks.

I don't think the embedded folks will be scared by a per-cpu cache, if
it's just one or two entries.  And I really do think that even just
one or two entries will indeed catch a lot of the cases.

And yes, fork+execve() is too damn expensive in page table build-up
and tear-down. I'm not sure why bash doesn't do vfork+exec for when it
has to wait for the process anyway, but it doesn't seem to do that.

                 Linus