linux-kernel - Re: [PATCH v10 1/3] mm: Shuffle initial free memory to improve memory-side-cache utilization

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Fri, 31 May 2019 09:33:36 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Dan Williams <dan.j.williams@...el.com>, akpm@...ux-foundation.org
Cc:     Dave Hansen <dave.hansen@...ux.intel.com>,
        Michal Hocko <mhocko@...e.com>,
        Kees Cook <keescook@...omium.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, keith.busch@...el.com
Subject: Re: [PATCH v10 1/3] mm: Shuffle initial free memory to improve
 memory-side-cache utilization

On 2/1/19 6:15 AM, Dan Williams wrote:
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -1714,6 +1714,29 @@ config SLAB_FREELIST_HARDENED
>  	  sacrifies to harden the kernel slab allocator against common
>  	  freelist exploit methods.
>  
> +config SHUFFLE_PAGE_ALLOCATOR
> +	bool "Page allocator randomization"
> +	default SLAB_FREELIST_RANDOM && ACPI_NUMA
> +	help
> +	  Randomization of the page allocator improves the average
> +	  utilization of a direct-mapped memory-side-cache. See section
> +	  5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI
> +	  6.2a specification for an example of how a platform advertises
> +	  the presence of a memory-side-cache. There are also incidental
> +	  security benefits as it reduces the predictability of page
> +	  allocations to compliment SLAB_FREELIST_RANDOM, but the
> +	  default granularity of shuffling on 4MB (MAX_ORDER) pages is
> +	  selected based on cache utilization benefits.
> +
> +	  While the randomization improves cache utilization it may
> +	  negatively impact workloads on platforms without a cache. For
> +	  this reason, by default, the randomization is enabled only
> +	  after runtime detection of a direct-mapped memory-side-cache.
> +	  Otherwise, the randomization may be force enabled with the
> +	  'page_alloc.shuffle' kernel command line parameter.
> +
> +	  Say Y if unsure.

It says "Say Y if unsure", yet if I run make oldconfig, the default is
N. Does that make sense?

> Page allocator randomization (SHUFFLE_PAGE_ALLOCATOR) [N/y/?] (NEW)