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Subject: Re: [bug report][stable] kernel tried to execute NX-protected page -
 exploit attempt? (uid: 0)
From:   Joseph Qi <joseph.qi@linux.alibaba.com>
To:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        x86@kernel.org, Nadav Amit <namit@vmware.com>,
        "Peter Zijlstra (Intel)" <peterz@infradead.org>,
        Ingo Molnar <mingo@kernel.org>,
        Greg KH <gregkh@linuxfoundation.org>
Cc:     Caspar Zhang <caspar@linux.alibaba.com>,
        jiufei Xue <jiufei.xue@linux.alibaba.com>
References: <5817eaac-29cc-6331-af3b-b9d85a7c1cd7@linux.alibaba.com>
Message-ID: <bde5bf17-35d2-45d8-1d1d-59d0f027b9c0@linux.alibaba.com>
Date:   Fri, 7 Jun 2019 18:24:53 +0800
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Hi all,
Any idea on this regression? 

Thanks,
Joseph

On 19/6/5 18:23, Joseph Qi wrote:
> Hi,
> 
> I have encountered a kernel BUG when running ltp ftrace-stress-test
> on 4.19.48.
> 
> [  209.704855] LTP: starting ftrace-stress-test (ftrace_stress_test.sh 90)
> [  209.739412] Scheduler tracepoints stat_sleep, stat_iowait, stat_blocked and stat_runtime require the kernel parameter schedstats=enable or kernel.sched_schedstats=1
> [  212.054506] kernel tried to execute NX-protected page - exploit attempt? (uid: 0)
> [  212.055595] BUG: unable to handle kernel paging request at ffffffffc0349000
> [  212.056589] PGD d00c067 P4D d00c067 PUD d00e067 PMD 23673e067 PTE 800000023457f061
> [  212.057759] Oops: 0011 [#1] SMP PTI
> [  212.058303] CPU: 0 PID: 0 Comm: swapper/0 Kdump: loaded Not tainted 4.19.48 #112
> 
> 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.
> 
> 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.
> 
> So I don't know why only stable has this issue while upstream doesn't.
> 
> Thanks,
> Joseph
>