linux-hardening - Re: [PATCH] mm/vmalloc: randomize vmalloc() allocations

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Message-ID: <20201203065801.GH751215@kernel.org>
Date:   Thu, 3 Dec 2020 08:58:01 +0200
From:   Mike Rapoport <rppt@...nel.org>
To:     Topi Miettinen <toiwoton@...il.com>
Cc:     linux-hardening@...r.kernel.org, akpm@...ux-foundation.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Andy Lutomirski <luto@...nel.org>,
        Jann Horn <jannh@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Linux API <linux-api@...r.kernel.org>,
        Matthew Wilcox <willy@...radead.org>
Subject: Re: [PATCH] mm/vmalloc: randomize vmalloc() allocations

On Wed, Dec 02, 2020 at 08:49:06PM +0200, Topi Miettinen wrote:
> On 1.12.2020 23.45, Topi Miettinen wrote:
> > Memory mappings inside kernel allocated with vmalloc() are in
> > predictable order and packed tightly toward the low addresses. With
> > new kernel boot parameter 'randomize_vmalloc=1', the entire area is
> > used randomly to make the allocations less predictable and harder to
> > guess for attackers.
> > 
> 
> This also seems to randomize module addresses. I was going to check that
> next, so nice surprise!

Heh, that's because module_alloc() uses vmalloc() in that way or another :)

> -Topi
> 
> >   	spin_unlock(&free_vmap_area_lock);
> >   	if (unlikely(addr == vend))
> > 
> 

-- 
Sincerely yours,
Mike.