Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Fri, 11 Jan 2019 14:21:29 +0000
To:     Peter Zijlstra <peterz@infradead.org>
From:   Esme <esploit@protonmail.ch>
Cc:     Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        JJiri Olsa <jolsa@redhat.com>,
        Namhyung Kim <namhyung@kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Reply-To: Esme <esploit@protonmail.ch>
Subject: Re: PROBLEM: syzkaller found / reduced C repro for non-fatal unchecked MSR access error
Message-ID: <ApiQycofBryJsrwcFgVkYUPF9sryQP9s8J2V8nbBc2m2sEhhMLrLd8HJ6nB_27Pr1z3AkoVduGvPzrHrhzRg4oryTQwXPRaYL8phr79zBAU=@protonmail.ch>
In-Reply-To: <20190111135948.GA20688@hirez.programming.kicks-ass.net>
References: <z3BgwrH88cXG8bH06po3hzY6vkYpdvZWqzSGl4lLXojvzk-33tKzdK1NWsTL1Ta-CBG7GKAWYziBAfPKsGA2CV6MVkXT93Al3SUfArOnUQE=@protonmail.ch>
 <20190111100253.GO30894@hirez.programming.kicks-ass.net>
 <kiksO_ofcRQ-2X83SaK_UGN4kwBcC8iHvgwFsGGitzaibUCc8Biv_b7AB9zfpJnM0F0a6-CIE_GxrXpabaz0duQWYcPEjhAcYHKhPsIRimk=@protonmail.ch>
 <20190111135948.GA20688@hirez.programming.kicks-ass.net>
Feedback-ID: pQGzDYT_k6dzic_kf3kwsxmTXzjnqMJxtC9J3KGyZBepPHdXRBM0BHuwPfpm1pFdJLAMwtJT5KKNaGlRVnFRQw==:Ext:ProtonMail
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: quoted-printable
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90 Original Me=
ssage =E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90
On Friday, January 11, 2019 8:59 AM, Peter Zijlstra <peterz@infradead.org> =
wrote:

> On Fri, Jan 11, 2019 at 01:37:50PM +0000, Esme wrote:
>
> > =E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90 Origina=
l Message =E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=
=90
> > On Friday, January 11, 2019 5:02 AM, Peter Zijlstra peterz@infradead.or=
g wrote:
> >
> > > On Thu, Jan 10, 2019 at 11:21:16PM +0000, Esme wrote:
> > >
> > > > Attached is a fairly small C repro I did not see any references to
> > > > this possible flaw (unchecked MSR access) in relation to
> > > > __NR_perf_event_open
> > > > Attached is the config directly extracted from proc. This is the ca=
ll
> > > > stack in relation to the MSR access error (5.0.0-rc1+), I get a ver=
y
> > > > similar stack running this test case on a stock Ubuntu
> > > > "4.18.0-11-generic" (pasted after this one).
> > >
> > > > -- Esme
> > > > [ 70.228744] unchecked MSR access error: WRMSR to 0xc0010000 (tried=
 to write 0x0000020000130076) at rIP: 0xffffffff812dde28 (native_write_msr+=
0x8/0x30)
> > >
> > > That's K7_EVNTSEL0. What kind of hardware are you running this on?
> >
> > QEMU emulator version 3.0.93 (v3.1.0-rc3-dirty)
> > [ 0.000000] DMI: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.=
0-0-ga698c8995f-prebuilt.qemu.org 04/01/2014
> > [ 0.000000] Linux version 4.18.0-11-generic (buildd@lcy01-amd64-027) (g=
cc version 8.2.0 (Ubuntu 8.2.0-7ubuntu1)) #12-Ubuntu SMP Tue Oct 23 19:22:3=
7 UTC 2018 (Ubuntu 4.18.0-11.12-generic 4.18.12)
> > [ 0.000000] Command line: BOOT_IMAGE=3D/boot/vmlinuz-4.18.0-11-generic =
root=3DUUID=3D3a43ccb9-a433-4296-8dc5-0443f2a32128 ro quiet splash vt.hando=
ff=3D1
> > [ 0.000000] KERNEL supported cpus:
> > [ 0.000000] Intel GenuineIntel
> > [ 0.000000] AMD AuthenticAMD
> > [ 0.000000] Centaur CentaurHauls
> > [ 0.000000] random: get_random_u32 called from bsp_init_amd+0x205/0x2a0=
 with crng_init=3D0
> > [ 0.000000] x86/fpu: Supporting XSAVE feature 0x001: 'x87 floating poin=
t registers'
> > [ 0.000000] x86/fpu: Supporting XSAVE feature 0x002: 'SSE registers'
> > [ 0.000000] x86/fpu: Supporting XSAVE feature 0x004: 'AVX registers'
> > [ 0.000000] x86/fpu: xstate_offset[2]: 576, xstate_sizes[2]: 256
> > [ 0.000000] x86/fpu: Enabled xstate features 0x7, context size is 832 b=
ytes, using 'standard' format.
>
> Feh, then you get to figure out how the heck it passes
> check_hw_exists().
>
> Stupid virt crap again.

I see, I'm busy most of the day, I do have some bare metal hosts I'm going =
to update with -current.

Do you have any suggested kernel flags to use for the build?

If it's specific to virt, I might just toss it into the cloud ;) and see wh=
at happens, later.
/Best Esme