linux-kernel - Re: [PATCH v4 0/3] x86/fpu: prevent leaking FPU registers via invalid FPU state

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Message-ID: <20170923090907.kk6hgbmupkeftae2@gmail.com>
Date:   Sat, 23 Sep 2017 11:09:07 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Eric Biggers <ebiggers3@...il.com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        kernel-hardening@...ts.openwall.com,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Kevin Hao <haokexin@...il.com>,
        Oleg Nesterov <oleg@...hat.com>,
        Wanpeng Li <wanpeng.li@...mail.com>,
        Yu-cheng Yu <yu-cheng.yu@...el.com>,
        Michael Halcrow <mhalcrow@...gle.com>,
        Eric Biggers <ebiggers@...gle.com>
Subject: Re: [PATCH v4 0/3] x86/fpu: prevent leaking FPU registers via
 invalid FPU state


* Eric Biggers <ebiggers3@...il.com> wrote:

> From: Eric Biggers <ebiggers@...gle.com>
> 
> This series fixes the bug found by syzkaller where the ptrace syscall
> can be used to set invalid bits in a task's FPU state.  I also found
> that an equivalent bug was reachable using the sigreturn syscall, so the
> first patch fixes the bug in both cases.
> 
> The other two patches start validating the other parts of the
> xstate_header and make it so that invalid FPU states can no longer be
> abused to leak the FPU registers of other processes.
> 
> Changes since v3:
>     - Rebase onto tip/master
> 
> Changes since v2:
>     - Use an exception handler to handle invalid FPU states
>       (suggested by Andy Lutomirski)
>     - Check the size of xstate_header.reserved at build time
>       (suggested by Dave Hansen)
> 
> Eric Biggers (3):
>   x86/fpu: don't let userspace set bogus xcomp_bv
>   x86/fpu: tighten validation of user-supplied xstate_header
>   x86/fpu: reinitialize FPU registers if restoring FPU state fails
> 
>  arch/x86/include/asm/fpu/internal.h | 51 +++++++++++-------------------------
>  arch/x86/include/asm/fpu/xstate.h   | 25 ++++++++++++++++++
>  arch/x86/kernel/fpu/regset.c        | 17 +++++-------
>  arch/x86/kernel/fpu/signal.c        | 18 ++++++++-----
>  arch/x86/kernel/fpu/xstate.c        | 52 ++++++++++++++-----------------------
>  arch/x86/mm/extable.c               | 24 +++++++++++++++++
>  6 files changed, 102 insertions(+), 85 deletions(-)

Thank you Eric - I've applied them and will push it all out together with the 
other pending bits in WIP.x86/fpu.

	Ingo