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From:   Nadav Amit <namit@vmware.com>
To:     Joseph Qi <joseph.qi@linux.alibaba.com>
CC:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        the arch/x86 maintainers <x86@kernel.org>,
        "Peter Zijlstra (Intel)" <peterz@infradead.org>,
        Ingo Molnar <mingo@kernel.org>,
        Greg KH <gregkh@linuxfoundation.org>,
        Caspar Zhang <caspar@linux.alibaba.com>,
        jiufei Xue <jiufei.xue@linux.alibaba.com>,
        Sasha Levin <sashal@kernel.org>
Subject: Re: [bug report][stable] kernel tried to execute NX-protected page -
 exploit attempt? (uid: 0)
Thread-Topic: [bug report][stable] kernel tried to execute NX-protected page -
 exploit attempt? (uid: 0)
Thread-Index: AQHVG4jKPNn+Vxg1aUiHBnctqPni6KaP/2uAgABocgA=
Date:   Fri, 7 Jun 2019 16:38:44 +0000
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> On Jun 7, 2019, at 3:24 AM, Joseph Qi <joseph.qi@linux.alibaba.com> wrote=
:
>=20
> Hi all,
> Any idea on this regression?=20

Sorry for the late response (I assumed, for some reason, that you also foll=
ow=20
the second thread about this issue).

Anyhow, it should be fixed by backporting some patches which were mistakenl=
y
missed.

See https://lore.kernel.org/stable/20190606131558.GJ29739@sasha-vm/

Regards,
Nadav


> Thanks,
> Joseph
>=20
> On 19/6/5 18:23, Joseph Qi wrote:
>> Hi,
>>=20
>> I have encountered a kernel BUG when running ltp ftrace-stress-test
>> on 4.19.48.
>>=20
>> [  209.704855] LTP: starting ftrace-stress-test (ftrace_stress_test.sh 9=
0)
>> [  209.739412] Scheduler tracepoints stat_sleep, stat_iowait, stat_block=
ed and stat_runtime require the kernel parameter schedstats=3Denable or ker=
nel.sched_schedstats=3D1
>> [  212.054506] kernel tried to execute NX-protected page - exploit attem=
pt? (uid: 0)
>> [  212.055595] BUG: unable to handle kernel paging request at ffffffffc0=
349000
>> [  212.056589] PGD d00c067 P4D d00c067 PUD d00e067 PMD 23673e067 PTE 800=
000023457f061
>> [  212.057759] Oops: 0011 [#1] SMP PTI
>> [  212.058303] CPU: 0 PID: 0 Comm: swapper/0 Kdump: loaded Not tainted 4=
.19.48 #112
>>=20
>> After some investigation I have found that it is introduced by commit
>> 8715ce033eb3 ("x86/modules: Avoid breaking W^X while loading modules"),
>> and then revert this commit the issue is gone.
>>=20
>> I have also tested the same case on 5.2-rc3 as well as right at
>> upstream commit f2c65fb3221a ("x86/modules: Avoid breaking W^X while
>> loading modules"), which has been merged in 5.2-rc1, it doesn't
>> happen.
>>=20
>> So I don't know why only stable has this issue while upstream doesn't.
>>=20
>> Thanks,
>> Joseph