From: Andy Lutomirski <luto@amacapital.net>
To: Kees Cook <keescook@chromium.org>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
Michael Ellerman <mpe@ellerman.id.au>,
Mathias Krause <minipli@googlemail.com>,
Thomas Gleixner <tglx@linutronix.de>, X86 ML <x86@kernel.org>,
Arnd Bergmann <arnd@arndb.de>, PaX Team <pageexec@freemail.hu>,
Emese Revfy <re.emese@gmail.com>,
"kernel-hardening@lists.openwall.com"
<kernel-hardening@lists.openwall.com>,
linux-arch <linux-arch@vger.kernel.org>
Subject: Re: [PATCH v3 8/8] x86, vdso: mark vDSO read-only after init
Date: Thu, 10 Dec 2015 17:33:01 -0800 [thread overview]
Message-ID: <CALCETrUiGriJ7VHnopP+TD7EhQ6PC7zfHYMVx22koFLauX9HaA@mail.gmail.com> (raw)
In-Reply-To: <CALCETrX+FzK8njwWjREaw2+CNmpVeYi8ZLYDT1OPScNx9z31iQ@mail.gmail.com>
On Wed, Dec 9, 2015 at 3:13 PM, Andy Lutomirski <luto@amacapital.net> wrote:
> On Wed, Dec 9, 2015 at 1:43 PM, Kees Cook <keescook@chromium.org> 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@chromium.org>
>
> Acked-by: Andy Lutomirski <luto@kernel.org>
>
FWIW, this has a minor conflict with some stuff in my queue. I
wouldn't worry about it for now.
--Andy
prev parent reply other threads:[~2015-12-11 1:33 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-09 21:43 [PATCH v3 0/8] introduce post-init read-only memory Kees Cook
2015-12-09 21:43 ` Kees Cook
2015-12-09 21:43 ` [PATCH v3 1/8] asm-generic: consolidate mark_rodata_ro() Kees Cook
2015-12-09 21:43 ` Kees Cook
2015-12-09 21:43 ` [PATCH v3 2/8] lib: add "on" and "off" to strtobool Kees Cook
2015-12-09 21:43 ` Kees Cook
2015-12-11 17:00 ` Andy Shevchenko
2015-12-11 18:50 ` Kees Cook
2015-12-11 21:20 ` Andy Shevchenko
2015-12-09 21:43 ` [PATCH v3 3/8] param: convert some "on"/"off" users " Kees Cook
2015-12-09 21:43 ` Kees Cook
2015-12-09 21:43 ` [PATCH v3 4/8] init: create cmdline param to disable readonly Kees Cook
2015-12-09 21:43 ` Kees Cook
2015-12-09 21:43 ` [PATCH v3 5/8] x86: make CONFIG_DEBUG_RODATA non-optional Kees Cook
2015-12-09 21:43 ` Kees Cook
2015-12-09 21:43 ` [PATCH v3 6/8] introduce post-init read-only memory Kees Cook
2015-12-09 21:43 ` Kees Cook
2015-12-09 21:43 ` [PATCH v3 7/8] lkdtm: verify that __ro_after_init works correctly Kees Cook
2015-12-09 21:43 ` Kees Cook
2015-12-09 21:43 ` [PATCH v3 8/8] x86, vdso: mark vDSO read-only after init Kees Cook
2015-12-09 21:43 ` Kees Cook
2015-12-09 23:13 ` Andy Lutomirski
2015-12-09 23:13 ` Andy Lutomirski
2015-12-11 1:33 ` Andy Lutomirski [this message]
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