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From: Vincenzo Frascino <vincenzo.frascino@arm.com>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
	kvm@vger.kernel.org, Christian Koenig <Christian.Koenig@amd.com>,
	Szabolcs Nagy <Szabolcs.Nagy@arm.com>,
	Will Deacon <will.deacon@arm.com>,
	dri-devel@lists.freedesktop.org,
	Kostya Serebryany <kcc@google.com>,
	Khalid Aziz <khalid.aziz@oracle.com>,
	Lee Smith <Lee.Smith@arm.com>,
	linux-kselftest@vger.kernel.org,
	Jacob Bramley <Jacob.Bramley@arm.com>,
	Leon Romanovsky <leon@kernel.org>,
	linux-rdma@vger.kernel.org, amd-gfx@lists.freedesktop.org,
	Christoph Hellwig <hch@infradead.org>,
	Jason Gunthorpe <jgg@ziepe.ca>,
	Dmitry Vyukov <dvyukov@google.com>,
	Dave Martin <Dave.Martin@arm.com>,
	Evgeniy Stepanov <eugenis@google.com>,
	linux-media@vger.kernel.org, Kees Cook <keescook@chromium.org>,
	Ruben Ayrapetyan <Ruben.Ayrapetyan@arm.com>,
	Andrey Konovalov <andreyknvl@google.com>,
	Kevin Brodsky <kevin.brodsky@arm.com>,
	Alex Williamson <alex.williamson@redhat.com>,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Felix Kuehling <Felix.Kuehling@amd.com>,
	linux-kernel@vger.kernel.org,
	Jens Wiklander <jens.wiklander@linaro.org>,
	Ramana Radhakrishnan <Ramana.Radhakrishnan@arm.com>,
	Alexander Deucher <Alexander.Deucher@amd.com>,
	Andrew Morton <akpm@linux-foundation.org>, enh <enh@google.com>,
	Robin Murphy <robin.murphy@arm.com>,
	Yishai Hadas <yishaih@mellanox.com>,
	Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Subject: Re: [PATCH v17 03/15] arm64: Introduce prctl() options to control the tagged user addresses ABI
Date: Thu, 13 Jun 2019 17:15:57 +0100
Message-ID: <e481dbf9-880e-c77e-5200-1dbc35be7a48@arm.com> (raw)
In-Reply-To: <20190613155754.GX28951@C02TF0J2HF1T.local>


On 13/06/2019 16:57, Catalin Marinas wrote:
> On Thu, Jun 13, 2019 at 04:45:54PM +0100, Vincenzo Frascino wrote:
>> On 13/06/2019 16:35, Catalin Marinas wrote:
>>> On Thu, Jun 13, 2019 at 12:16:59PM +0100, Dave P Martin wrote:
>>>> On Wed, Jun 12, 2019 at 01:43:20PM +0200, Andrey Konovalov wrote:
>>>>> +
>>>>> +/*
>>>>> + * Control the relaxed ABI allowing tagged user addresses into the kernel.
>>>>> + */
>>>>> +static unsigned int tagged_addr_prctl_allowed = 1;
>>>>> +
>>>>> +long set_tagged_addr_ctrl(unsigned long arg)
>>>>> +{
>>>>> +	if (!tagged_addr_prctl_allowed)
>>>>> +		return -EINVAL;
>>>>
>>>> So, tagging can actually be locked on by having a process enable it and
>>>> then some possibly unrelated process clearing tagged_addr_prctl_allowed.
>>>> That feels a bit weird.
>>>
>>> The problem is that if you disable the ABI globally, lots of
>>> applications would crash. This sysctl is meant as a way to disable the
>>> opt-in to the TBI ABI. Another option would be a kernel command line
>>> option (I'm not keen on a Kconfig option).
>>
>> Why you are not keen on a Kconfig option?
> 
> Because I don't want to rebuild the kernel/reboot just to be able to
> test how user space handles the ABI opt-in. I'm ok with a Kconfig option
> to disable this globally in addition to a run-time option (if actually
> needed, I'm not sure).
> 
There might be scenarios (i.e. embedded) in which this is not needed, hence
having a config option (maybe Y by default) that removes from the kernel the
whole feature would be good, obviously in conjunction with the run-time option.

Based on my previous review, if we move out the code from process.c in its own
independent file when the Kconfig option is turned off we could remove the
entire object from the kernel (this would remove the sysctl and let still the
prctl return -EINVAL).

These changes though could be done successively with a separate patch set, if
the Kconfig is meant to be Y by default.

-- 
Regards,
Vincenzo

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  reply index

Thread overview: 78+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-12 11:43 [PATCH v17 00/15] arm64: untag user pointers passed to the kernel Andrey Konovalov
2019-06-12 11:43 ` [PATCH v17 01/15] arm64: untag user pointers in access_ok and __uaccess_mask_ptr Andrey Konovalov
2019-06-12 14:26   ` Vincenzo Frascino
2019-06-12 11:43 ` [PATCH v17 02/15] lib, arm64: untag user pointers in strn*_user Andrey Konovalov
2019-06-12 14:28   ` Vincenzo Frascino
2019-06-12 11:43 ` [PATCH v17 03/15] arm64: Introduce prctl() options to control the tagged user addresses ABI Andrey Konovalov
2019-06-12 14:30   ` Vincenzo Frascino
2019-06-12 14:55   ` Catalin Marinas
2019-06-13 11:02   ` Dave Martin
2019-06-13 15:26     ` Catalin Marinas
2019-06-14  5:13       ` Kees Cook
2019-06-18  9:18         ` Dave Martin
2019-06-13 11:16   ` Dave Martin
2019-06-13 15:35     ` Catalin Marinas
2019-06-13 15:45       ` Vincenzo Frascino
2019-06-13 15:57         ` Catalin Marinas
2019-06-13 16:15           ` Vincenzo Frascino [this message]
2019-06-17 13:56   ` Catalin Marinas
2019-06-17 16:56     ` Szabolcs Nagy
2019-06-17 16:57     ` Evgenii Stepanov
2019-06-17 17:18       ` Catalin Marinas
2019-06-17 21:59         ` Evgenii Stepanov
2019-06-19 14:45   ` Andrey Konovalov
2019-06-19 15:29     ` Catalin Marinas
2019-06-12 11:43 ` [PATCH v17 04/15] mm, arm64: untag user pointers passed to memory syscalls Andrey Konovalov
2019-06-12 14:31   ` Vincenzo Frascino
2019-06-19 15:55   ` Khalid Aziz
2019-06-19 16:46     ` Khalid Aziz
2019-06-24 14:22       ` Andrey Konovalov
2019-06-12 11:43 ` [PATCH v17 05/15] mm, arm64: untag user pointers in mm/gup.c Andrey Konovalov
2019-06-12 14:33   ` Vincenzo Frascino
2019-06-19 16:41   ` Khalid Aziz
2019-06-12 11:43 ` [PATCH v17 06/15] mm, arm64: untag user pointers in get_vaddr_frames Andrey Konovalov
2019-06-12 14:34   ` Vincenzo Frascino
2019-06-19 16:48   ` Khalid Aziz
2019-06-12 11:43 ` [PATCH v17 07/15] fs, arm64: untag user pointers in copy_mount_options Andrey Konovalov
2019-06-12 14:35   ` Vincenzo Frascino
2019-06-19 20:01   ` Khalid Aziz
2019-06-12 11:43 ` [PATCH v17 08/15] userfaultfd, arm64: untag user pointers Andrey Konovalov
2019-06-12 14:40   ` Vincenzo Frascino
2019-06-12 11:43 ` [PATCH v17 09/15] drm/amdgpu, " Andrey Konovalov
2019-06-12 11:43 ` [PATCH v17 10/15] drm/radeon, arm64: untag user pointers in radeon_gem_userptr_ioctl Andrey Konovalov
2019-06-12 11:43 ` [PATCH v17 11/15] IB/mlx4, arm64: untag user pointers in mlx4_get_umem_mr Andrey Konovalov
2019-06-12 11:43 ` [PATCH v17 12/15] media/v4l2-core, arm64: untag user pointers in videobuf_dma_contig_user_get Andrey Konovalov
2019-06-19 20:05   ` Khalid Aziz
2019-06-12 11:43 ` [PATCH v17 13/15] tee/shm, arm64: untag user pointers in tee_shm_register Andrey Konovalov
2019-06-12 11:43 ` [PATCH v17 14/15] vfio/type1, arm64: untag user pointers in vaddr_get_pfn Andrey Konovalov
2019-06-12 14:41   ` Vincenzo Frascino
2019-06-12 15:58   ` Auger Eric
2019-06-12 11:43 ` [PATCH v17 15/15] selftests, arm64: add a selftest for passing tagged pointers to kernel Andrey Konovalov
2019-06-12 12:30   ` Szabolcs Nagy
2019-06-12 15:00     ` Catalin Marinas
2019-06-19 14:42       ` Andrey Konovalov
2019-06-12 14:21 ` [PATCH v4 0/2] arm64 relaxed ABI Vincenzo Frascino
2019-06-12 14:21   ` [PATCH v4 1/2] arm64: Define Documentation/arm64/tagged-address-abi.txt Vincenzo Frascino
2019-06-12 15:35     ` Catalin Marinas
2019-06-13 10:15       ` Vincenzo Frascino
2019-06-13 11:37         ` Dave Martin
2019-06-13 12:28           ` Catalin Marinas
2019-06-13 13:23             ` Dave Martin
2019-06-13 15:39               ` Catalin Marinas
2019-06-12 16:30     ` Szabolcs Nagy
2019-06-13  9:20       ` Catalin Marinas
2019-06-13 10:14         ` Szabolcs Nagy
2019-06-13 11:16           ` Vincenzo Frascino
2019-06-13 12:28             ` Szabolcs Nagy
2019-06-13 14:03               ` Vincenzo Frascino
2019-06-13 15:32                 ` Szabolcs Nagy
2019-06-13 15:35                   ` Vincenzo Frascino
2019-06-12 14:21   ` [PATCH v4 2/2] arm64: Relax Documentation/arm64/tagged-pointers.txt Vincenzo Frascino
2019-06-12 15:56     ` Catalin Marinas
2019-06-12 16:37     ` Szabolcs Nagy
2019-06-13 15:51 ` [PATCH v5 0/2] arm64 relaxed ABI Vincenzo Frascino
2019-06-13 15:51   ` [PATCH v5 1/2] arm64: Define Documentation/arm64/tagged-address-abi.txt Vincenzo Frascino
2019-06-18 11:02     ` Szabolcs Nagy
2019-06-18 13:13     ` Kevin Brodsky
2019-06-21 15:16       ` Catalin Marinas
2019-06-13 15:51   ` [PATCH v5 2/2] arm64: Relax Documentation/arm64/tagged-pointers.txt Vincenzo Frascino

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