linux-kernel - Re: [PATCH 1/1] mm: sysctl: add panic_on_mm

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Message-Id: <F352EA1C-7E7C-4C0C-8F23-EC33080EBB9E@lca.pw>
Date:   Mon, 27 Jan 2020 07:26:21 -0500
From:   Qian Cai <cai@....pw>
To:     Grzegorz Halat <ghalat@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org, linux-doc@...r.kernel.org,
        ssaner@...hat.com, atomlin@...hat.com, oleksandr@...hat.com,
        vbendel@...hat.com, kirill@...temov.name,
        khlebnikov@...dex-team.ru, borntraeger@...ibm.com,
        Andrew Morton <akpm@...ux-foundation.org>,
        Iurii Zaikin <yzaikin@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Jonathan Corbet <corbet@....net>
Subject: Re: [PATCH 1/1] mm: sysctl: add panic_on_mm_error sysctl



> On Jan 27, 2020, at 5:11 AM, Grzegorz Halat <ghalat@...hat.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.
> 
> The patch adds panic_on_mm_error sysctl. 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.

Well, on the other hand, this will allow a normal user to more easily crash the system due to a recoverable bug which could result in local DoS.