From: Borislav Petkov <bp@alien8.de>
To: Andy Lutomirski <luto@kernel.org>
Cc: Dave Hansen <dave.hansen@intel.com>,
Sean Christopherson <sean.j.christopherson@intel.com>,
"Yu, Yu-cheng" <yu-cheng.yu@intel.com>,
LKML <linux-kernel@vger.kernel.org>, X86 ML <x86@kernel.org>,
Rik van Riel <riel@surriel.com>,
Andrew Cooper <andrew.cooper3@citrix.com>
Subject: Re: How should we handle illegal task FPU state?
Date: Mon, 2 Nov 2020 19:39:38 +0100 [thread overview]
Message-ID: <20201102183938.GA10749@zn.tnic> (raw)
In-Reply-To: <CALCETrWswWdgXO2J6nRjXW_4JRsK1TzzVZ62EDsF+d_79O+6Sw@mail.gmail.com>
On Thu, Oct 01, 2020 at 03:04:48PM -0700, Andy Lutomirski wrote:
> On Thu, Oct 1, 2020 at 2:50 PM Dave Hansen <dave.hansen@intel.com> wrote:
> > I'm not sure we should ever keep running userspace after an XRSTOR*
> > failure. For MPX, this might have provided a nice, additional vector
> > for an attacker to turn off MPX. Same for pkeys if we didn't correctly
> > differentiate between the hardware init state versus the "software init"
> > state that we keep in init_task.
> >
> > What's the advantage of letting userspace keep running after we init its
> > state? That it _might_ be able to recover?
>
> I suppose we can kill userspace and change that behavior only if
> someone complains. I still think it would be polite to try to dump
> core, but that could be tricky with the current code structure. I'll
> try to whip up a patch. Maybe I'll add a debugfs file to trash MXCSR
> for testing.
Just for the record, I like this: safe and simple. We can always do
smarter shenanigans later, if at all needed, that is.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
next prev parent reply other threads:[~2020-11-02 18:39 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-01 17:43 How should we handle illegal task FPU state? Andy Lutomirski
2020-10-01 20:32 ` Yu, Yu-cheng
2020-10-01 20:58 ` Sean Christopherson
2020-10-01 21:42 ` Andrew Cooper
2020-10-01 21:50 ` Dave Hansen
2020-10-01 22:04 ` Andy Lutomirski
2020-10-08 18:08 ` Yu, Yu-cheng
2020-10-09 0:08 ` Andy Lutomirski
2020-11-02 18:39 ` Borislav Petkov [this message]
2020-10-01 21:26 ` Andrew Cooper
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