From: Christian Borntraeger <borntraeger@de.ibm.com>
To: Qian Cai <cai@lca.pw>, Grzegorz Halat <ghalat@redhat.com>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>,
linux-fsdevel@vger.kernel.org, linux-doc@vger.kernel.org,
ssaner@redhat.com, atomlin@redhat.com, oleksandr@redhat.com,
vbendel@redhat.com, kirill@shutemov.name,
khlebnikov@yandex-team.ru,
Andrew Morton <akpm@linux-foundation.org>,
Iurii Zaikin <yzaikin@google.com>,
Kees Cook <keescook@chromium.org>,
Luis Chamberlain <mcgrof@kernel.org>,
Jonathan Corbet <corbet@lwn.net>,
Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Subject: Re: [PATCH 1/1] mm: sysctl: add panic_on_inconsistent_mm sysctl
Date: Mon, 3 Feb 2020 15:08:30 +0100 [thread overview]
Message-ID: <34467005-1742-47a0-cd2b-05567584b91e@de.ibm.com> (raw)
In-Reply-To: <84C253EB-B348-4B62-B863-F192FBA8C202@lca.pw>
On 29.01.20 19:39, Qian Cai wrote:
>
>
>> On Jan 29, 2020, at 1:08 PM, Grzegorz Halat <ghalat@redhat.com> wrote:
>>
>> Memory management subsystem performs various checks at runtime,
>> if an inconsistency is detected then such event is being logged and kernel
>> continues to run. While debugging such problems it is helpful to collect
>> memory dump as early as possible. Currently, there is no easy way to panic
>> kernel when such error is detected.
>>
>> It was proposed[1] to panic the kernel if panic_on_oops is set but this
>> approach was not accepted. One of alternative proposals was introduction of
>> a new sysctl.
>>
>> Add a new sysctl - panic_on_inconsistent_mm. If the sysctl is set then the
>> kernel will be crashed when an inconsistency is detected by memory
>> management. This currently means panic when bad page or bad PTE
>> is detected(this may be extended to other places in MM).
>>
>> Another use case of this sysctl may be in security-wise environments,
>> it may be more desired to crash machine than continue to run with
>> potentially damaged data structures.
>
> It is annoying that I have to repeat my feedback, but I don’t know why
> admins want to enable this by allowing normal users to crash the systems
> more easily through recoverable MM bugs where I am sure we have plenty.
> How does that improve the security?
There are cases where data corruption is a no-go, while "one node going down"
is acceptable.
And then there is also the case for payed service providers that often need
a dump at the time of the problem to understand rare issues.
So I DO see value in such a thing. We should just piggy-back on panic_on_warn
I guess.
next prev parent reply other threads:[~2020-02-03 14:08 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-29 18:08 [PATCH 1/1] mm: sysctl: add panic_on_inconsistent_mm sysctl Grzegorz Halat
2020-01-29 18:39 ` Qian Cai
2020-02-03 14:08 ` Christian Borntraeger [this message]
2020-02-03 15:06 ` Qian Cai
2020-02-05 22:23 ` Kees Cook
2020-01-29 19:06 ` Qian Cai
2020-01-30 14:44 ` Vlastimil Babka
2020-01-30 19:28 ` Kees Cook
2020-02-03 12:19 ` Vlastimil Babka
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