linux-kernel - Re: [PATCH v3] mm/slub: Avoid list corruption when removing a slab from the full list

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Message-ID: <c7b03b1e-e000-279d-f845-5808653ac3bf@gentwo.org>
Date: Fri, 11 Oct 2024 11:07:44 -0700 (PDT)
From: "Christoph Lameter (Ampere)" <cl@...two.org>
To: "yuan.gao" <yuan.gao@...oud.cn>
cc: penberg@...nel.org, rientjes@...gle.com, iamjoonsoo.kim@....com, 
    akpm@...ux-foundation.org, vbabka@...e.cz, roman.gushchin@...ux.dev, 
    42.hyeyoo@...il.com, linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] mm/slub: Avoid list corruption when removing a slab
 from the full list

On Fri, 11 Oct 2024, yuan.gao wrote:

> When an object belonging to the slab got freed later, the remove_full()
> function is called. Because the slab is neither on the partial list nor
> on the full list, it eventually lead to a list corruption.

We detect list poison....

> diff --git a/mm/slab.h b/mm/slab.h
> index 6c6fe6d630ce..7681e71d9a13 100644
> --- a/mm/slab.h
> +++ b/mm/slab.h
> @@ -73,6 +73,10 @@ struct slab {
>  						struct {
>  							unsigned inuse:16;
>  							unsigned objects:15;
> +							/*
> +							 * Reuse frozen bit for slab with debug enabled:

"If slab debugging is enabled then the frozen bit can bereused to
 indicate that the slab was corrupted"

> index 5b832512044e..b9265e9f11aa 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -1423,6 +1423,11 @@ static int check_slab(struct kmem_cache *s, struct slab *slab)
>  			slab->inuse, slab->objects);
>  		return 0;
>  	}
> +	if (slab->frozen) {
> +		slab_err(s, slab, "Corrupted slab");


"Slab folio disabled due to metadata corruption" ?


> @@ -2744,7 +2750,10 @@ static void *alloc_single_from_partial(struct kmem_cache *s,
>  	slab->inuse++;
>
>  	if (!alloc_debug_processing(s, slab, object, orig_size)) {
> -		remove_partial(n, slab);
> +		if (folio_test_slab(slab_folio(slab))) {


Does folio_test_slab test for the frozen bit??