Re: [PATCH 1/1] mm: sysctl: add panic_on_inconsistent_mm sysctl

From: Kees Cook <keescook@chromium.org>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Grzegorz Halat <ghalat@redhat.com>,
	linux-kernel@vger.kernel.org, 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, borntraeger@de.ibm.com,
	Andrew Morton <akpm@linux-foundation.org>,
	Iurii Zaikin <yzaikin@google.com>,
	Luis Chamberlain <mcgrof@kernel.org>,
	Jonathan Corbet <corbet@lwn.net>,
	Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
	Qian Cai <cai@lca.pw>
Subject: Re: [PATCH 1/1] mm: sysctl: add panic_on_inconsistent_mm sysctl
Date: Thu, 30 Jan 2020 11:28:45 -0800	[thread overview]
Message-ID: <202001301128.1CBD1BA52@keescook> (raw)
In-Reply-To: <d47a5f31-5862-b0a9-660c-48105f4f049b@suse.cz>

On Thu, Jan 30, 2020 at 03:44:50PM +0100, Vlastimil Babka wrote:
> On 1/29/20 7:08 PM, Grzegorz Halat 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).
> 
> I wonder, should enabling the sysctl also effectively convert VM_WARN...
> to VM_BUG... ?

There is already panic_on_warn sysctl... wouldn't that be sufficient?

-- 
Kees Cook