linux-kernel - Re: [PATCH] mm: optionally disable brk()

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Message-ID: <2a0f5ade-d770-c36e-50bc-ff0c8e9dacbf@gmail.com>
Date:   Sat, 3 Oct 2020 00:44:09 +0300
From:   Topi Miettinen <toiwoton@...il.com>
To:     David Hildenbrand <david@...hat.com>, akpm@...ux-foundation.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: optionally disable brk()

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.

-Topi