linux-kernel - Re: [PATCH] x86: entry_32.S: change ESPFIX test to not touch PT

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]

Date:	Mon, 9 Mar 2015 19:32:53 +0100
From:	Denys Vlasenko <vda.linux@...glemail.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Andy Lutomirski <luto@...capital.net>,
	"H. Peter Anvin" <hpa@...or.com>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>,
	Oleg Nesterov <oleg@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Alexei Starovoitov <ast@...mgrid.com>,
	Will Drewry <wad@...omium.org>,
	Kees Cook <keescook@...omium.org>,
	"the arch/x86 maintainers" <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86: entry_32.S: change ESPFIX test to not touch PT_OLDSS(%esp)

On Mon, Mar 9, 2015 at 7:16 PM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
> On Mon, Mar 9, 2015 at 11:04 AM, Andy Lutomirski <luto@...capital.net> wrote:
>>
>> One option would be to change the NMI entry code to move itself down 8
>> bytes if this happens (came from kernel mode or sp == sp0 - 12,
>> perhaps).
>
> Hmm. That whole code currently depends on the stack setup being just a
> single instruction (the move to esp). And that simplifies things, I'd
> like to keep it that way.
>
> I'd *much* rather just keep the 8-byte padding. What was so
> problematic with that? It worked. It's been around forever. Removing
> it is the bug.

Unfortunately, looks like keeping the gap is the safest thing to do.

Hopes that tss.sp0 was true top of the stack, sans "a few little problems",
died so quickly :/
(and we didn't even touch vm86 yet).

We probably better off to give that 8 a name. Now it's just another
magic constant in the entry.S maze.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/