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

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Message-ID: <63da08b7-7aa3-3fad-55e6-9fc3928a49de@gentwo.org>
Date: Mon, 10 Jun 2024 10:07:06 -0700 (PDT)
From: "Christoph Lameter (Ampere)" <cl@...two.org>
To: Chengming Zhou <chengming.zhou@...ux.dev>
cc: Pekka Enberg <penberg@...nel.org>, David Rientjes <rientjes@...gle.com>, 
    Joonsoo Kim <iamjoonsoo.kim@....com>, 
    Andrew Morton <akpm@...ux-foundation.org>, 
    Vlastimil Babka <vbabka@...e.cz>, 
    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 Fri, 7 Jun 2024, Chengming Zhou wrote:

> There are two inconsistencies in check_object(), which are alignment
> padding checking and object padding checking. We only print the error
> messages but don't return 0 to tell callers that something is wrong
> and needs to be handled. Please see alloc_debug_processing() and
> free_debug_processing() for details.

If the error is in the padding and the redzones are ok then its likely 
that the objects are ok. So we can actually continue with this slab page 
instead of isolating it.

We isolate it in the case that the redzones have been violated because 
that suggests someone overwrote the end of the object f.e. In that case 
objects may be corrupted. Its best to isolate the slab and hope for the 
best.

If it was just the padding then the assumption is that this may be a 
scribble. So clean it up and continue.