From: Matthew Wilcox <willy@infradead.org>
To: Topi Miettinen <toiwoton@gmail.com>
Cc: Cristiano Giuffrida <c.giuffrida@vu.nl>,
Mike Rapoport <rppt@kernel.org>,
"linux-hardening@vger.kernel.org"
<linux-hardening@vger.kernel.org>,
"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Jann Horn <jannh@google.com>, Kees Cook <keescook@chromium.org>,
Uladzislau Rezki <urezki@gmail.com>
Subject: Re: [PATCH v4] mm: Optional full ASLR for mmap() and mremap()
Date: Fri, 20 Nov 2020 15:27:16 +0000 [thread overview]
Message-ID: <20201120152716.GA4327@casper.infradead.org> (raw)
In-Reply-To: <74fd6d3b-936f-94f5-c183-a2e6bc7a9e35@gmail.com>
On Fri, Nov 20, 2020 at 10:38:21AM +0200, Topi Miettinen wrote:
> On 20.11.2020 0.20, Cristiano Giuffrida wrote:
> > Indeed it's nontrivial to get similar randomization guarantees for the
> > kernel. I mentioned TagBleed because similar combined AnC + TLB
> > attacks should also be possible in the browser. We just happened to
> > focus on the kernel with TagBleed.
>
> Perhaps kernel objects could be also compiled as relocatable shared objects,
> like shared libraries for user applications, so that a they could be
> relocated independently away from the base address of main kernel. Also
> compiling the kernel with -mcmodel=large could allow various segments (code,
> rodata, data) to be located more freely. These would make the attacker to do
> more probing. Again, pointers between the objects may make these less
> useful.
They are relocatable shared objects. They're loaded into the vmalloc
area on some architectures but x86 has a special MODULES_VADDR region.
Maybe just jumbling them into the general vmalloc address range would be
beneficial from a security point of view? I suspect it's not all
that useful because most modules are loaded early on.
We seem to have randomness mixed into the vmalloc allocations with
DEBUG_AUGMENT_LOWEST_MATCH_CHECK, but there doesn't seem to be an
ASLR option to vmalloc ... Uladzislau?
next prev parent reply other threads:[~2020-11-20 15:27 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-26 16:05 [PATCH v4] mm: Optional full ASLR for mmap() and mremap() Topi Miettinen
2020-11-17 16:54 ` Matthew Wilcox
2020-11-17 20:21 ` Topi Miettinen
2020-11-18 17:40 ` Mike Rapoport
[not found] ` <6810b874c8df456b890d1092273b354a@pexch011a.vu.local>
2020-11-18 18:49 ` Cristiano Giuffrida
2020-11-19 9:59 ` Topi Miettinen
[not found] ` <0da9cb0a4d1a494d9ec15404f8decf01@pexch011a.vu.local>
2020-11-19 22:20 ` Cristiano Giuffrida
2020-11-20 8:38 ` Topi Miettinen
2020-11-20 15:27 ` Matthew Wilcox [this message]
[not found] ` <d7e759c8ac444aa4b0ba6932563aca00@pexch011a.vu.local>
2020-11-20 14:10 ` Cristiano Giuffrida
2020-11-20 19:37 ` Topi Miettinen
2020-11-18 22:42 ` Jann Horn
2020-11-19 9:16 ` Topi Miettinen
2020-11-24 18:27 ` Vlastimil Babka
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