From: Topi Miettinen <toiwoton@gmail.com>
To: Mike Rapoport <rppt@kernel.org>
Cc: linux-hardening@vger.kernel.org, akpm@linux-foundation.org,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Andy Lutomirski <luto@kernel.org>, Jann Horn <jannh@google.com>,
Kees Cook <keescook@chromium.org>,
Linux API <linux-api@vger.kernel.org>,
Matthew Wilcox <willy@infradead.org>
Subject: Re: [PATCH] mm/vmalloc: randomize vmalloc() allocations
Date: Wed, 9 Dec 2020 21:08:23 +0200 [thread overview]
Message-ID: <26f0c73a-3a81-4ba6-2b6f-c5ca73ea866b@gmail.com> (raw)
In-Reply-To: <20201203065801.GH751215@kernel.org>
On 3.12.2020 8.58, Mike Rapoport wrote:
> 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 :)
The modules are still allocated from their small (1.5GB) separate area
instead of the much larger (32TB/12.5PB) vmalloc area, which would
greatly improve ASLR for the modules. To fix that, I tried to to #define
MODULES_VADDR to VMALLOC_START etc. like x86_32 does, but then kernel
dies very early without even any output.
-Topi
next prev parent reply other threads:[~2020-12-09 19:08 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-01 21:45 [PATCH] mm/vmalloc: randomize vmalloc() allocations Topi Miettinen
2020-12-02 18:49 ` Topi Miettinen
2020-12-03 6:58 ` Mike Rapoport
2020-12-03 23:15 ` David Laight
2020-12-04 10:58 ` Topi Miettinen
2020-12-04 13:33 ` David Laight
2020-12-04 16:53 ` Topi Miettinen
2020-12-09 19:08 ` Topi Miettinen [this message]
2020-12-10 19:58 ` Topi Miettinen
2020-12-02 18:53 ` Matthew Wilcox
2020-12-02 21:28 ` Topi Miettinen
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