[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <569EF642.90302@zytor.com>
Date: Tue, 19 Jan 2016 18:51:46 -0800
From: "H. Peter Anvin" <hpa@...or.com>
To: Kees Cook <keescook@...omium.org>, Ingo Molnar <mingo@...hat.com>
Cc: Andy Lutomirski <luto@...capital.net>,
Michael Ellerman <mpe@...erman.id.au>,
Mathias Krause <minipli@...glemail.com>,
Thomas Gleixner
<tglx@...utronix.de>, x86@...nel.org,
Arnd Bergmann <arnd@...db.de>, PaX Team <pageexec@...email.hu>,
Emese Revfy <re.emese@...il.com>, kernel-hardening@...ts.openwall.com,
linux-kernel@...r.kernel.org, linux-arch <linux-arch@...r.kernel.org>
Subject: Re: [PATCH v4 8/8] x86, vdso: mark vDSO read-only after init
On 01/19/16 10:08, Kees Cook wrote:
> The vDSO does not need to be writable after __init, so mark it as
> __ro_after_init. The result kills the exploit method of writing to the
> vDSO from kernel space resulting in userspace executing the modified code,
> as shown here to bypass SMEP restrictions: http://itszn.com/blog/?p=21
>
> The memory map (with added vDSO address reporting) shows the vDSO moving
> into read-only memory:
>
> Before:
> [ 0.143067] vDSO @ ffffffff82004000
> [ 0.143551] vDSO @ ffffffff82006000
> ---[ High Kernel Mapping ]---
> 0xffffffff80000000-0xffffffff81000000 16M pmd
> 0xffffffff81000000-0xffffffff81800000 8M ro PSE GLB x pmd
> 0xffffffff81800000-0xffffffff819f3000 1996K ro GLB x pte
> 0xffffffff819f3000-0xffffffff81a00000 52K ro NX pte
> 0xffffffff81a00000-0xffffffff81e00000 4M ro PSE GLB NX pmd
> 0xffffffff81e00000-0xffffffff81e05000 20K ro GLB NX pte
> 0xffffffff81e05000-0xffffffff82000000 2028K ro NX pte
> 0xffffffff82000000-0xffffffff8214f000 1340K RW GLB NX pte
> 0xffffffff8214f000-0xffffffff82281000 1224K RW NX pte
> 0xffffffff82281000-0xffffffff82400000 1532K RW GLB NX pte
> 0xffffffff82400000-0xffffffff83200000 14M RW PSE GLB NX pmd
> 0xffffffff83200000-0xffffffffc0000000 974M pmd
>
> After:
> [ 0.145062] vDSO @ ffffffff81da1000
> [ 0.146057] vDSO @ ffffffff81da4000
> ---[ High Kernel Mapping ]---
> 0xffffffff80000000-0xffffffff81000000 16M pmd
> 0xffffffff81000000-0xffffffff81800000 8M ro PSE GLB x pmd
> 0xffffffff81800000-0xffffffff819f3000 1996K ro GLB x pte
> 0xffffffff819f3000-0xffffffff81a00000 52K ro NX pte
> 0xffffffff81a00000-0xffffffff81e00000 4M ro PSE GLB NX pmd
> 0xffffffff81e00000-0xffffffff81e0b000 44K ro GLB NX pte
> 0xffffffff81e0b000-0xffffffff82000000 2004K ro NX pte
> 0xffffffff82000000-0xffffffff8214c000 1328K RW GLB NX pte
> 0xffffffff8214c000-0xffffffff8227e000 1224K RW NX pte
> 0xffffffff8227e000-0xffffffff82400000 1544K RW GLB NX pte
> 0xffffffff82400000-0xffffffff83200000 14M RW PSE GLB NX pmd
> 0xffffffff83200000-0xffffffffc0000000 974M pmd
>
> Based on work by PaX Team and Brad Spengler.
>
> Signed-off-by: Kees Cook <keescook@...omium.org>
> Acked-by: Andy Lutomirski <luto@...nel.org>
Acked-by: H. Peter Anvin <hpa@...ux.intel.com>
Powered by blists - more mailing lists
Confused about mailing lists and their use?
Read about mailing lists on Wikipedia
and check out these
guidelines on proper formatting of your messages.
