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

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Message-ID: <a6d03b97f74543ef8203c53b2c028fef@AcuMS.aculab.com>
Date:   Fri, 2 Oct 2020 21:19:33 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'David Hildenbrand' <david@...hat.com>,
        Topi Miettinen <toiwoton@...il.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] mm: optionally disable brk()

From: David Hildenbrand
> Sent: 02 October 2020 18:52
> 
> 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.

I bet some obscure applications rely on it.

Although hopefully nothing still does heap allocation
by just increasing the VA and calling brk() in response
to SIGSEGV.

	David

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