linux-kernel - Re: [PATCH] x86/asm/entry/32: Restore %ss before SYSRETL if necessary

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Message-ID: <20150423161138.GO28327@pd.tnic>
Date:	Thu, 23 Apr 2015 18:11:38 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Andy Lutomirski <luto@...capital.net>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Ingo Molnar <mingo@...nel.org>,
	Brian Gerst <brgerst@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	"H. Peter Anvin" <hpa@...or.com>, 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/asm/entry/32: Restore %ss before SYSRETL if necessary

On Thu, Apr 23, 2015 at 09:05:07AM -0700, Linus Torvalds wrote:
> So it sounds very much like an AMD bug/misfeature. Because sysret
> *should* reset the descriptor cache. Do we know whether this affects
> *all* AMD CPU's or just a subset?

I am being told that this might appear to be the case with at least one
uarch. I could run code on the boxes I have here to check if Andy comes
up with some nice little "exploit".

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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