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From: Kees Cook <keescook@chromium.org>
To: Will Deacon <will.deacon@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
	Kristina Martsenko <kristina.martsenko@arm.com>,
	linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
	Mark Rutland <mark.rutland@arm.com>,
	linux-arch <linux-arch@vger.kernel.org>,
	Andrew Jones <drjones@redhat.com>,
	Jacob Bramley <jacob.bramley@arm.com>,
	Arnd Bergmann <arnd@arndb.de>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Marc Zyngier <marc.zyngier@arm.com>,
	Adam Wallis <awallis@codeaurora.org>,
	"Suzuki K . Poulose" <suzuki.poulose@arm.com>,
	Christoffer Dall <christoffer.dall@arm.com>,
	kvmarm@lists.cs.columbia.edu,
	Ramana Radhakrishnan <ramana.radhakrishnan@arm.com>,
	Amit Kachhap <Amit.Kachhap@arm.com>,
	Dave P Martin <Dave.Martin@arm.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Cyrill Gorcunov <gorcunov@openvz.org>
Subject: Re: [PATCH v5 07/17] arm64: add basic pointer authentication support
Date: Fri, 19 Oct 2018 09:05:57 -0700
Message-ID: <CAGXu5jK8OK+430FQtztwVD8B95_SCjTWoysZXBdkZaDeSiV+ow@mail.gmail.com> (raw)
In-Reply-To: <20181019154948.GD16771@arm.com>

On Fri, Oct 19, 2018 at 8:49 AM, Will Deacon <will.deacon@arm.com> wrote:
> On Fri, Oct 19, 2018 at 08:36:45AM -0700, Kees Cook wrote:
>> On Fri, Oct 19, 2018 at 4:24 AM, Will Deacon <will.deacon@arm.com> wrote:
>> > FWIW: I think we should be entertaining a prctl() interface to use a new
>> > key on a per-thread basis. Obviously, this would need to be used with care
>> > (e.g. you'd fork(); use the prctl() and then you'd better not return from
>> > the calling function!).
>> >
>> > Assuming we want this (Kees -- I was under the impression that everything in
>> > Android would end up with the same key otherwise?), then the question is
>> > do we want:
>> >
>> >   - prctl() get/set operations for the key, or
>> >   - prctl() set_random_key operation, or
>> >   - both of the above?
>> >
>> > Part of the answer to that may lie in the requirements of CRIU, where I
>> > strongly suspect they need explicit get/set operations, although these
>> > could be gated on CONFIG_CHECKPOINT_RESTORE=y.
>>
>> Oh CRIU. Yikes. I'd like the get/set to be gated by the CONFIG, yes.
>> No reason to allow explicit access to the key (and selected algo) if
>> we don't have to.
>
> Makes sense.
>
>> As for per-thread or not, having a "pick a new key now" prctl() sounds
>> good, but I'd like to have an eye toward having it just be "automatic"
>> on clone().
>
> I thought about that too, but we're out of clone() flags afaict and there's
> no arch hook in there. We could add yet another clone syscall, but yuck (and
> I reckon viro would kill us).
>
> Or are you saying that we could infer the behaviour from the existing set
> of flags?

I mean if it's starting a new thread, it should get a new key
automatically, just like the ssp canary happens in dup_task_struct().

(Or did I miss some context for why that's not possible?)

-Kees

-- 
Kees Cook
Pixel Security

  reply index

Thread overview: 62+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-05  8:47 [PATCH 00/17] ARMv8.3 " Kristina Martsenko
2018-10-05  8:47 ` [PATCH v5 01/17] arm64: add pointer authentication register bits Kristina Martsenko
2018-10-11 16:28   ` Will Deacon
2018-10-12  8:53     ` Mark Rutland
2018-10-12  8:56       ` Will Deacon
2018-10-12  9:50         ` Mark Rutland
2018-10-05  8:47 ` [PATCH v5 02/17] arm64/kvm: consistently handle host HCR_EL2 flags Kristina Martsenko
2018-10-05  8:47 ` [PATCH v5 03/17] arm64/kvm: hide ptrauth from guests Kristina Martsenko
2018-10-05  8:47 ` [PATCH v5 04/17] arm64: Don't trap host pointer auth use to EL2 Kristina Martsenko
2018-10-05  8:47 ` [PATCH v5 05/17] arm64/cpufeature: detect pointer authentication Kristina Martsenko
2018-10-05  8:47 ` [PATCH v5 06/17] asm-generic: mm_hooks: allow hooks to be overridden individually Kristina Martsenko
2018-10-05  8:47 ` [PATCH v5 07/17] arm64: add basic pointer authentication support Kristina Martsenko
2018-10-11 16:00   ` Suzuki K Poulose
2018-10-19 11:15   ` Catalin Marinas
2018-10-19 11:24     ` Will Deacon
2018-10-19 15:36       ` Kees Cook
2018-10-19 15:49         ` Will Deacon
2018-10-19 16:05           ` Kees Cook [this message]
2018-10-19 16:16             ` Will Deacon
2018-10-19 15:54         ` Mark Rutland
2018-10-19 16:49       ` Cyrill Gorcunov
2018-11-14 18:11       ` Will Deacon
2018-11-15 10:25         ` Dave Martin
2018-10-23  8:36     ` Ramana Radhakrishnan
2018-10-23 10:20       ` Will Deacon
2018-10-05  8:47 ` [PATCH v5 08/17] arm64: expose user PAC bit positions via ptrace Kristina Martsenko
2018-10-05  8:47 ` [PATCH v5 09/17] arm64: perf: strip PAC when unwinding userspace Kristina Martsenko
2018-10-05  8:47 ` [PATCH v5 10/17] arm64: enable pointer authentication Kristina Martsenko
2018-10-05  8:47 ` [PATCH v5 11/17] arm64: docs: document " Kristina Martsenko
2018-10-05  9:04   ` Ramana Radhakrishnan
2018-10-16 16:14     ` Kristina Martsenko
2018-10-19 11:35       ` Catalin Marinas
2018-10-19 11:47         ` Marc Zyngier
2018-10-19 12:22         ` Will Deacon
2018-10-19 14:42         ` Kristina Martsenko
2018-10-19 15:10           ` Catalin Marinas
2018-10-19 17:45             ` Will Deacon
2018-11-02  6:02               ` Jon Masters
2018-10-24 10:56         ` Ramana Radhakrishnan
2018-10-15 22:35   ` Kees Cook
2018-11-02  9:46     ` Ramana Radhakrishnan
2018-10-05  8:47 ` [RFC 12/17] arm64: move ptrauth keys to thread_info Kristina Martsenko
2018-10-19 11:38   ` Catalin Marinas
2018-10-05  8:47 ` [RFC 13/17] arm64: install user ptrauth keys at kernel exit time Kristina Martsenko
2018-10-05  8:47 ` [RFC 14/17] arm64: unwind: strip PAC from kernel addresses Kristina Martsenko
2018-10-05  8:47 ` [RFC 15/17] arm64: enable ptrauth earlier Kristina Martsenko
2018-10-06 12:51   ` Amit Kachhap
2018-10-05  8:47 ` [RFC 16/17] arm64: initialize and switch ptrauth kernel keys Kristina Martsenko
2018-10-06 12:56   ` Amit Kachhap
2018-10-05  8:47 ` [RFC 17/17] arm64: compile the kernel with ptrauth -msign-return-address Kristina Martsenko
2018-10-05  9:01   ` Ramana Radhakrishnan
2018-10-11 14:00     ` Kristina Martsenko
2018-10-11 14:23   ` Vladimir Murzin
2018-10-15 22:38     ` Kees Cook
2018-10-15 22:42 ` [PATCH 00/17] ARMv8.3 pointer authentication support Kees Cook
2018-11-13 16:17   ` Kristina Martsenko
2018-11-13 23:09     ` Kees Cook
2018-11-14 15:54       ` Kristina Martsenko
2018-11-14 21:47       ` Mark Rutland
2018-11-14 22:48         ` Kees Cook
2018-10-19 12:36 ` Will Deacon
2018-10-23  8:39   ` Ramana Radhakrishnan

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