From: Derrick McKee <derrick.mckee@gmail.com>
To: Mark Rutland <mark.rutland@arm.com>
Cc: Nathan Harrison Burow <Nathan.Burow@ll.mit.edu>,
Yianni Giannaris <yiannig@mit.edu>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] Ensure kernel AI key is not changed on fork
Date: Thu, 20 May 2021 14:24:04 -0400 [thread overview]
Message-ID: <CAJoBWHyUkP4nkgxHJAZr+291GLy2UCOhC-cn=ez416N4xWSk=w@mail.gmail.com> (raw)
In-Reply-To: <20210520160035.GP17233@C02TD0UTHF1T.local>
On Thu, May 20, 2021 at 12:00 PM Mark Rutland <mark.rutland@arm.com> wrote:
> On the kernel side, we use a unique IA key per kernel thread, and while
> this must remain the same *for that kernel thread*, the kernel IA key
> should differ across kernel threads when a fork() occurs.
Thank you for the clarification.
> I think you're trying to use the keys in a different way than upstream
> intends to, and we do not need this change as-is.
>
> So NAK to this patch as it stands.
Given the above discussion, I agree with the NAK.
>
> > ---
> > arch/arm64/include/asm/pointer_auth.h | 9 ++++++---
> > 1 file changed, 6 insertions(+), 3 deletions(-)
> >
> > diff --git a/arch/arm64/include/asm/pointer_auth.h b/arch/arm64/include/asm/pointer_auth.h
> > index d50416be99be..9748413e72fd 100644
> > --- a/arch/arm64/include/asm/pointer_auth.h
> > +++ b/arch/arm64/include/asm/pointer_auth.h
> > @@ -69,10 +69,13 @@ static inline void ptrauth_keys_init_user(struct ptrauth_keys_user *keys)
> > ptrauth_keys_install_user(keys);
> > }
> >
> > -static __always_inline void ptrauth_keys_init_kernel(struct ptrauth_keys_kernel *keys)
> > +static __always_inline void
> > +ptrauth_keys_init_kernel(struct ptrauth_keys_kernel *keys)
> > {
> > - if (system_supports_address_auth())
> > - get_random_bytes(&keys->apia, sizeof(keys->apia));
> > + if (keys->apia.lo == 0 && keys->apia.hi == 0) {
> > + if (system_supports_address_auth())
> > + get_random_bytes(&keys->apia, sizeof(keys->apia));
> > + }
> > }
> >
> > static __always_inline void ptrauth_keys_switch_kernel(struct ptrauth_keys_kernel *keys)
> > --
> > 2.31.1
> >
--
Derrick McKee
Phone: (703) 957-9362
Email: derrick.mckee@gmail.com
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prev parent reply other threads:[~2021-05-20 18:26 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-30 14:40 PAC key changes when kernel code is preempted Derrick McKee
2021-04-30 15:04 ` Mark Rutland
2021-05-07 20:24 ` Derrick McKee
2021-05-20 15:18 ` [PATCH] Ensure kernel AI key is not changed on fork Derrick McKee
2021-05-20 16:00 ` Mark Rutland
2021-05-20 18:24 ` Derrick McKee [this message]
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