linux-kernel - Re: [PATCH v3 1/3] slab: make check

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Date: Wed, 12 Jun 2024 11:39:19 -0700
From: Kees Cook <kees@...nel.org>
To: "Christoph Lameter (Ampere)" <cl@...ux.com>
Cc: Vlastimil Babka <vbabka@...e.cz>,
	Chengming Zhou <chengming.zhou@...ux.dev>,
	Pekka Enberg <penberg@...nel.org>,
	David Rientjes <rientjes@...gle.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Roman Gushchin <roman.gushchin@...ux.dev>,
	Hyeonggon Yoo <42.hyeyoo@...il.com>,
	Feng Tang <feng.tang@...el.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, zhouchengming@...edance.com
Subject: Re: [PATCH v3 1/3] slab: make check_object() more consistent

On Tue, Jun 11, 2024 at 03:52:49PM -0700, Christoph Lameter (Ampere) wrote:
> On Mon, 10 Jun 2024, Vlastimil Babka wrote:
> 
> > Even if some security people enable parts of slub debugging for security
> > people it is my impression they would rather panic/reboot or have memory
> > leaked than trying to salvage the slab page? (CC Kees)
> 
> In the past these resilience features have been used to allow the continued
> operation of a broken kernel.
> 
> So first the Kernel crashed with some obscure oops in the allocator due to
> metadata corruption.
> 
> One can then put a slub_debug option on the kernel command line which will
> result in detailed error reports on what caused the corruption. It will also
> activate resilience measures that will often allow the continued operation
> until a fix becomes available.

Sure, as long as it's up to the deployment. I just don't want padding
errors unilaterally ignored. If it's useful, there's the
CHECK_DATA_CORRUPTION() macro. That'll let a deployment escalate the
issue from WARN to BUG, etc.

-- 
Kees Cook