linux-hardening - Re: [PATCH] mm/slub: Avoid recursive loop with kmemleak

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Date: Thu, 25 Apr 2024 17:09:43 -0400
From: Kent Overstreet <kent.overstreet@...ux.dev>
To: Kees Cook <keescook@...omium.org>
Cc: Suren Baghdasaryan <surenb@...gle.com>, 
	Catalin Marinas <catalin.marinas@....com>, Andrew Morton <akpm@...ux-foundation.org>, 
	Christoph Lameter <cl@...ux.com>, Pekka Enberg <penberg@...nel.org>, 
	David Rientjes <rientjes@...gle.com>, Joonsoo Kim <iamjoonsoo.kim@....com>, 
	Vlastimil Babka <vbabka@...e.cz>, Roman Gushchin <roman.gushchin@...ux.dev>, 
	Hyeonggon Yoo <42.hyeyoo@...il.com>, linux-mm@...ck.org, linux-kernel@...r.kernel.org, 
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH] mm/slub: Avoid recursive loop with kmemleak

On Thu, Apr 25, 2024 at 01:55:23PM -0700, Kees Cook wrote:
> The system will immediate fill up stack and crash when both
> CONFIG_DEBUG_KMEMLEAK and CONFIG_MEM_ALLOC_PROFILING are enabled.
> Avoid allocation tagging of kmemleak caches, otherwise recursive
> allocation tracking occurs.
> 
> Fixes: 279bb991b4d9 ("mm/slab: add allocation accounting into slab allocation and free paths")
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
> Cc: Suren Baghdasaryan <surenb@...gle.com>
> Cc: Kent Overstreet <kent.overstreet@...ux.dev>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Christoph Lameter <cl@...ux.com>
> Cc: Pekka Enberg <penberg@...nel.org>
> Cc: David Rientjes <rientjes@...gle.com>
> Cc: Joonsoo Kim <iamjoonsoo.kim@....com>
> Cc: Vlastimil Babka <vbabka@...e.cz>
> Cc: Roman Gushchin <roman.gushchin@...ux.dev>
> Cc: Hyeonggon Yoo <42.hyeyoo@...il.com>
> Cc: linux-mm@...ck.org
> ---
>  mm/kmemleak.c | 4 ++--
>  mm/slub.c     | 2 +-
>  2 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/kmemleak.c b/mm/kmemleak.c
> index c55c2cbb6837..fdcf01f62202 100644
> --- a/mm/kmemleak.c
> +++ b/mm/kmemleak.c
> @@ -463,7 +463,7 @@ static struct kmemleak_object *mem_pool_alloc(gfp_t gfp)
>  
>  	/* try the slab allocator first */
>  	if (object_cache) {
> -		object = kmem_cache_alloc(object_cache, gfp_kmemleak_mask(gfp));
> +		object = kmem_cache_alloc_noprof(object_cache, gfp_kmemleak_mask(gfp));

What do these get accounted to, or does this now pop a warning with
CONFIG_MEM_ALLOC_PROFILING_DEBUG?

>  		if (object)
>  			return object;
>  	}
> @@ -947,7 +947,7 @@ static void add_scan_area(unsigned long ptr, size_t size, gfp_t gfp)
>  	untagged_objp = (unsigned long)kasan_reset_tag((void *)object->pointer);
>  
>  	if (scan_area_cache)
> -		area = kmem_cache_alloc(scan_area_cache, gfp_kmemleak_mask(gfp));
> +		area = kmem_cache_alloc_noprof(scan_area_cache, gfp_kmemleak_mask(gfp));
>  
>  	raw_spin_lock_irqsave(&object->lock, flags);
>  	if (!area) {
> diff --git a/mm/slub.c b/mm/slub.c
> index a94a0507e19c..9ae032ed17ed 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -2016,7 +2016,7 @@ prepare_slab_obj_exts_hook(struct kmem_cache *s, gfp_t flags, void *p)
>  	if (!p)
>  		return NULL;
>  
> -	if (s->flags & SLAB_NO_OBJ_EXT)
> +	if (s->flags & (SLAB_NO_OBJ_EXT | SLAB_NOLEAKTRACE))
>  		return NULL;
>  
>  	if (flags & __GFP_NO_OBJ_EXT)
> -- 
> 2.34.1
>