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Date:   Sun, 14 May 2023 11:30:30 +0200
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Subject: Re: [PATCH RFC v2] Randomized slab caches for kmalloc()
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To:     Gong Ruiqi <gongruiqi1@huawei.com>,
        Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        linux-hardening@vger.kernel.org,
        Alexander Lobakin <aleksander.lobakin@intel.com>,
        kasan-dev@googlegroups.com, Wang Weiyang <wangweiyang2@huawei.com>,
        Xiu Jianfeng <xiujianfeng@huawei.com>,
        Christoph Lameter <cl@linux.com>,
        David Rientjes <rientjes@google.com>,
        Roman Gushchin <roman.gushchin@linux.dev>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Pekka Enberg <penberg@kernel.org>,
        Kees Cook <keescook@chromium.org>,
        Paul Moore <paul@paul-moore.com>,
        James Morris <jmorris@namei.org>,
        "Serge E. Hallyn" <serge@hallyn.com>,
        "Gustavo A. R. Silva" <gustavoars@kernel.org>
References: <20230508075507.1720950-1-gongruiqi1@huawei.com>
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 <5f5a858a-7017-5424-0fa0-db3b79e5d95e@huawei.com>
From:   Vlastimil Babka <vbabka@suse.cz>
In-Reply-To: <5f5a858a-7017-5424-0fa0-db3b79e5d95e@huawei.com>
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On 5/12/23 12:11, Gong Ruiqi wrote:
> 
> 
> On 2023/05/11 2:43, Hyeonggon Yoo wrote:
>> On Mon, May 8, 2023 at 12:53 AM GONG, Ruiqi <gongruiqi1@huawei.com> wrote:
>>>
> 
> [...]
> 
>>>
>>> The overhead of performance has been tested on a 40-core x86 server by
>>> comparing the results of `perf bench all` between the kernels with and
>>> without this patch based on the latest linux-next kernel, which shows
>>> minor difference. A subset of benchmarks are listed below:
>>>
>>
>> Please Cc maintainers/reviewers of corresponding subsystem in MAINTAINERS file.
> 
> Okay, I've appended maintainers/reviewers of linux-hardening and
> security subsystem to the Cc list.

I think they were CC'd on v1 but didn't respond yet. I thought maybe if
I run into Kees at OSS, I will ask him about it, but didn't happen.

As a slab maintainer I don't mind adding such things if they don't
complicate the code excessively, and have no overhead when configured
out. This one would seem to be acceptable at first glance, although
maybe the CONFIG space is too wide, and the amount of #defines in
slab_common.c is also large (maybe there's a way to make it more
concise, maybe not).

But I don't have enough insight into hardening to decide if it's a
useful mitigation that people would enable, so I'd hope for hardening
folks to advise on that. Similar situation with freelist hardening in
the past, which was even actively pushed by Kees, IIRC.