From: Amit Kachhap <amit.kachhap@arm.com>
To: Marc Zyngier <maz@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>,
Kees Cook <keescook@chromium.org>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Kristina Martsenko <kristina.martsenko@arm.com>,
Dave Martin <Dave.Martin@arm.com>,
Mark Brown <broonie@kernel.org>,
James Morse <james.morse@arm.com>,
Ramana Radhakrishnan <ramana.radhakrishnan@arm.com>,
Vincenzo Frascino <Vincenzo.Frascino@arm.com>,
Will Deacon <will@kernel.org>, Ard Biesheuvel <ardb@kernel.org>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v6 00/18] (as long a
Date: Thu, 12 Mar 2020 18:51:56 +0530 [thread overview]
Message-ID: <7ba381f0-095d-6994-bb6d-12b2665b4a8e@arm.com> (raw)
In-Reply-To: <b5ca043cfaca30435957974d0f58524e@kernel.org>
Hi Marc,
On 3/12/20 6:17 PM, Marc Zyngier wrote:
> Hi Amit,
>
> On 2020-03-12 08:06, Amit Kachhap wrote:
>> Hi James,
>>
>> On 3/12/20 12:23 PM, Amit Kachhap wrote:
>>> Hi James,
>>>
>>> On 3/11/20 2:58 PM, James Morse wrote:
>>>> Hi Amit,
>>>>
>>>> (CC: +Marc)
>>>>
>>>> On 3/6/20 6:35 AM, Amit Daniel Kachhap wrote:
>>>>> This series improves function return address protection for the
>>>>> arm64 kernel, by
>>>>> compiling the kernel with ARMv8.3 Pointer Authentication
>>>>> instructions (referred
>>>>> ptrauth hereafter). This should help protect the kernel against
>>>>> attacks using
>>>>> return-oriented programming.
>>>>
>>>> (as it looks like there may be another version of this:)
>>>>
>>>> Am I right in thinking that after your patch 10 changing
>>>> cpu_switch_to(), only the A key is live during kernel execution?
>>>
>>> Yes
>>>
>>>>
>>>> KVM is still save/restoring 4 extra keys around guest-entry/exit. As
>>>> you
>>>> restore all the keys on return to user-space, is this still necessary?
>>>
>>> Yes Its a good optimization to skip 4 non-A keys. I was wondering
>>> whether to do it in this series or send it separately.
>>
>> I suppose we can only skip non-A keys save/restore for host context. If
>> we skip non-A keys for guest context then guest with old implementation
>> will break. Let me know your opinion.
>
> I don't think you can skip anything as far as the guest is concerned.
> But being able to skip the B keys (which is what I expect you call the
> non-A keys) on the host would certainly be useful.
Thanks for the clarification.
>
> I assume you have a way to hide them from userspace, though.
You mean hide all the keys from userspace like below,
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 3e909b1..29cc74f 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1023,7 +1023,7 @@ static bool trap_ptrauth(struct kvm_vcpu *vcpu,
static unsigned int ptrauth_visibility(const struct kvm_vcpu *vcpu,
const struct sys_reg_desc *rd)
{
- return vcpu_has_ptrauth(vcpu) ? 0 : REG_HIDDEN_USER |
REG_HIDDEN_GUEST;
+ return vcpu_has_ptrauth(vcpu) ? REG_HIDDEN_USER :
REG_HIDDEN_USER | REG_HIDDEN_GUEST;
}
#define __PTRAUTH_KEY(k)
I don't remember why it was not done this way last time.
Cheers,
Amit
>
> Thanks,
>
> M.
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next prev parent reply other threads:[~2020-03-12 13:22 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-06 6:35 [PATCH v6 00/18] arm64: return address signing Amit Daniel Kachhap
2020-03-06 6:35 ` [PATCH v6 01/18] arm64: cpufeature: Fix meta-capability cpufeature check Amit Daniel Kachhap
2020-03-10 10:59 ` Vincenzo Frascino
2020-03-06 6:35 ` [PATCH v6 02/18] arm64: cpufeature: add pointer auth meta-capabilities Amit Daniel Kachhap
2020-03-10 11:18 ` Vincenzo Frascino
2020-03-06 6:35 ` [PATCH v6 03/18] arm64: rename ptrauth key structures to be user-specific Amit Daniel Kachhap
2020-03-10 11:35 ` Vincenzo Frascino
2020-03-06 6:35 ` [PATCH v6 04/18] arm64: install user ptrauth keys at kernel exit time Amit Daniel Kachhap
2020-03-06 19:07 ` James Morse
2020-03-10 11:48 ` Vincenzo Frascino
2020-03-06 6:35 ` [PATCH v6 05/18] arm64: create macro to park cpu in an infinite loop Amit Daniel Kachhap
2020-03-10 12:02 ` Vincenzo Frascino
2020-03-06 6:35 ` [PATCH v6 06/18] arm64: ptrauth: Add bootup/runtime flags for __cpu_setup Amit Daniel Kachhap
2020-03-06 19:07 ` James Morse
2020-03-09 17:04 ` Catalin Marinas
2020-03-10 12:14 ` Vincenzo Frascino
2020-03-11 9:28 ` Amit Kachhap
2020-03-06 6:35 ` [PATCH v6 07/18] arm64: cpufeature: Move cpu capability helpers inside C file Amit Daniel Kachhap
2020-03-10 12:20 ` Vincenzo Frascino
2020-03-10 12:53 ` Amit Kachhap
2020-03-11 10:50 ` Catalin Marinas
2020-03-11 11:44 ` Vincenzo Frascino
2020-03-06 6:35 ` [PATCH v6 08/18] arm64: cpufeature: handle conflicts based on capability Amit Daniel Kachhap
2020-03-10 12:31 ` Vincenzo Frascino
2020-03-11 11:03 ` Catalin Marinas
2020-03-11 11:46 ` Vincenzo Frascino
2020-03-06 6:35 ` [PATCH v6 09/18] arm64: enable ptrauth earlier Amit Daniel Kachhap
2020-03-10 15:45 ` Vincenzo Frascino
2020-03-11 6:26 ` Amit Kachhap
2020-03-11 10:26 ` Vincenzo Frascino
2020-03-11 10:46 ` Amit Kachhap
2020-03-11 10:49 ` Vincenzo Frascino
2020-03-06 6:35 ` [PATCH v6 10/18] arm64: initialize and switch ptrauth kernel keys Amit Daniel Kachhap
2020-03-10 15:07 ` Vincenzo Frascino
2020-03-06 6:35 ` [PATCH v6 11/18] arm64: initialize ptrauth keys for kernel booting task Amit Daniel Kachhap
2020-03-10 15:09 ` Vincenzo Frascino
2020-03-06 6:35 ` [PATCH v6 12/18] arm64: mask PAC bits of __builtin_return_address Amit Daniel Kachhap
2020-03-06 19:07 ` James Morse
2020-03-09 12:27 ` Amit Kachhap
2020-03-06 6:35 ` [PATCH v6 13/18] arm64: unwind: strip PAC from kernel addresses Amit Daniel Kachhap
2020-03-09 19:03 ` James Morse
2020-03-10 12:28 ` Amit Kachhap
2020-03-10 17:37 ` James Morse
2020-03-11 6:07 ` Amit Kachhap
2020-03-11 9:09 ` James Morse
2020-03-06 6:35 ` [PATCH v6 14/18] arm64: __show_regs: strip PAC from lr in printk Amit Daniel Kachhap
2020-03-10 15:11 ` Vincenzo Frascino
2020-03-06 6:35 ` [PATCH v6 15/18] arm64: suspend: restore the kernel ptrauth keys Amit Daniel Kachhap
2020-03-10 15:18 ` Vincenzo Frascino
2020-03-06 6:35 ` [PATCH v6 16/18] kconfig: Add support for 'as-option' Amit Daniel Kachhap
2020-03-06 11:37 ` Masahiro Yamada
2020-03-06 11:49 ` Vincenzo Frascino
2020-03-06 6:35 ` [PATCH v6 17/18] arm64: compile the kernel with ptrauth return address signing Amit Daniel Kachhap
2020-03-10 15:20 ` Vincenzo Frascino
2020-03-06 6:35 ` [PATCH v6 18/18] lkdtm: arm64: test kernel pointer authentication Amit Daniel Kachhap
2020-03-10 15:59 ` [PATCH v6 00/18] arm64: return address signing Rémi Denis-Courmont
2020-03-11 9:28 ` James Morse
2020-03-12 6:53 ` Amit Kachhap
2020-03-12 8:06 ` Amit Kachhap
2020-03-12 12:47 ` [PATCH v6 00/18] (as long a Marc Zyngier
2020-03-12 13:21 ` Amit Kachhap [this message]
2020-03-12 15:05 ` [PATCH v6 00/18] arm64: return address signing Marc Zyngier
2020-03-12 17:26 ` James Morse
2020-03-12 17:31 ` Marc Zyngier
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