From: David Hildenbrand <david@redhat.com>
To: Topi Miettinen <toiwoton@gmail.com>, Michal Hocko <mhocko@suse.com>
Cc: akpm@linux-foundation.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm: optionally disable brk()
Date: Mon, 5 Oct 2020 11:55:21 +0200 [thread overview]
Message-ID: <9dc586f4-38f0-7956-0ab6-bd7921491606@redhat.com> (raw)
In-Reply-To: <4d325e3e-3139-eded-6781-435fb04fb915@gmail.com>
On 05.10.20 11:47, Topi Miettinen wrote:
> On 5.10.2020 12.13, David Hildenbrand wrote:
>> On 05.10.20 08:12, Michal Hocko wrote:
>>> On Sat 03-10-20 00:44:09, Topi Miettinen wrote:
>>>> On 2.10.2020 20.52, David Hildenbrand wrote:
>>>>> On 02.10.20 19:19, Topi Miettinen wrote:
>>>>>> The brk() system call allows to change data segment size (heap). This
>>>>>> is mainly used by glibc for memory allocation, but it can use mmap()
>>>>>> and that results in more randomized memory mappings since the heap is
>>>>>> always located at fixed offset to program while mmap()ed memory is
>>>>>> randomized.
>>>>>
>>>>> Want to take more Unix out of Linux?
>>>>>
>>>>> Honestly, why care about disabling? User space can happily use mmap() if
>>>>> it prefers.
>>>>
>>>> brk() interface doesn't seem to be used much and glibc is happy to switch to
>>>> mmap() if brk() fails, so why not allow disabling it optionally? If you
>>>> don't care to disable, don't do it and this is even the default.
>>>
>>> I do not think we want to have config per syscall, do we?
>>
>> I do wonder if grouping would be a better option then (finding a proper
>> level of abstraction ...).
>
> If hardening and compatibility are seen as tradeoffs, perhaps there
> could be a top level config choice (CONFIG_HARDENING_TRADEOFF) for this.
> It would have options
> - "compatibility" (default) to gear questions for maximum compatibility,
> deselecting any hardening options which reduce compatibility
> - "hardening" to gear questions for maximum hardening, deselecting any
> compatibility options which reduce hardening
> - "none/manual": ask all questions like before
I think the general direction is to avoid an exploding set of config
options. So if there isn't a *real* demand, I guess gluing this to a
single option ("CONFIG_SECURITY_HARDENING") might be good enough.
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2020-10-05 9:55 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-02 17:19 [PATCH] mm: optionally disable brk() Topi Miettinen
2020-10-02 17:52 ` David Hildenbrand
2020-10-02 21:19 ` David Laight
2020-10-02 21:44 ` Topi Miettinen
2020-10-05 6:12 ` Michal Hocko
2020-10-05 8:11 ` Topi Miettinen
2020-10-05 8:22 ` Michal Hocko
2020-10-05 9:03 ` Topi Miettinen
2020-10-05 14:12 ` Jonathan Corbet
2020-10-05 16:14 ` Topi Miettinen
2020-10-05 9:13 ` David Hildenbrand
2020-10-05 9:20 ` Michal Hocko
2020-10-05 9:47 ` Topi Miettinen
2020-10-05 9:55 ` David Hildenbrand [this message]
2020-10-05 11:21 ` David Laight
2020-10-05 12:18 ` David Hildenbrand
2020-10-05 12:25 ` David Laight
2020-10-07 9:43 ` Topi Miettinen
2020-11-01 11:41 ` Topi Miettinen
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