From: "H. Peter Anvin" <hpa@zytor.com>
To: Andi Kleen <andi@firstfloor.org>, Andy Lutomirski <luto@amacapital.net>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org,
Andi Kleen <ak@linux.intel.com>
Subject: Re: [PATCH 4/7] x86: Add support for rd/wr fs/gs base
Date: Tue, 29 Apr 2014 21:57:46 -0700 [thread overview]
Message-ID: <536082CA.40905@zytor.com> (raw)
In-Reply-To: <53608180.5070800@zytor.com>
On 04/29/2014 09:52 PM, H. Peter Anvin wrote:
>
> It matters -- greatly -- if (and only if) we can enter the kernel with
> usergs == kernelgs and then want to change usergs inside a paranoid
> routine. At that point we risk being upside down, which basically means
> we're rooted.
>
> However, I believe this patchset also means only IST entries can be
> paranoid, which in turn means we can't sleep inside them. To the very
> best of my knowledge the only times we change usergs is on context
> switch or inside a system call. We need to make sure that is actually
> the case, though.
>
> I'm at ELC for a few days, so I'll have limited decent-sized-monitor
> time, but it shouldn't be too hard to convince ourselves of... mostly a
> matter of making sure something like ptrace can't to stupid crap.
>
Just in case anyone is getting the wrong impression: this is a
discussion about details. I'm glad to see this work getting done.
-hpa
next prev parent reply other threads:[~2014-04-30 4:57 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-28 22:12 Add support for RD/WR FS/GSBASE Andi Kleen
2014-04-28 22:12 ` [PATCH 1/7] percpu: Add a DEFINE_PER_CPU_2PAGE_ALIGNED Andi Kleen
2014-05-02 15:18 ` Tejun Heo
2014-04-28 22:12 ` [PATCH 2/7] x86: Naturally align the debug IST stack Andi Kleen
2014-04-28 22:12 ` [PATCH 3/7] x86: Add C intrinsics for new rd/wr fs/gs base instructions Andi Kleen
2014-04-29 14:10 ` Konrad Rzeszutek Wilk
2014-04-28 22:12 ` [PATCH 4/7] x86: Add support for rd/wr fs/gs base Andi Kleen
2014-04-29 18:19 ` Andy Lutomirski
2014-04-29 23:39 ` Andi Kleen
2014-04-30 4:52 ` H. Peter Anvin
2014-04-30 4:57 ` H. Peter Anvin [this message]
2014-04-30 23:44 ` Andy Lutomirski
2014-04-30 23:47 ` Andy Lutomirski
2014-05-01 21:15 ` Andi Kleen
2014-05-01 21:39 ` Andy Lutomirski
2014-05-01 21:51 ` Andi Kleen
2014-05-01 21:53 ` Andy Lutomirski
2014-05-01 21:58 ` H. Peter Anvin
2014-05-01 22:06 ` Andy Lutomirski
2014-05-01 22:18 ` Andi Kleen
2014-05-01 22:45 ` H. Peter Anvin
2014-04-28 22:12 ` [PATCH 5/7] x86: Make old K8 swapgs workaround conditional Andi Kleen
2014-04-30 4:57 ` H. Peter Anvin
2014-04-28 22:12 ` [PATCH 6/7] x86: Enumerate kernel FSGS capability in AT_HWCAP2 Andi Kleen
2014-04-28 22:12 ` [PATCH 7/7] x86: Add documentation for rd/wr fs/gs base Andi Kleen
2014-04-29 2:23 ` Randy Dunlap
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