From: Vincenzo Frascino <vincenzo.frascino@arm.com>
To: Catalin Marinas <catalin.marinas@arm.com>,
Dave Martin <Dave.Martin@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>,
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Khalid Aziz <khalid.aziz@oracle.com>,
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linux-media@vger.kernel.org, Kees Cook <keescook@chromium.org>,
Ruben Ayrapetyan <Ruben.Ayrapetyan@arm.com>,
Andrey Konovalov <andreyknvl@google.com>,
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Jens Wiklander <jens.wiklander@linaro.org>,
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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 16:45:54 +0100 [thread overview]
Message-ID: <99cc257d-5e99-922a-fbe7-3bbaf3621e38@arm.com> (raw)
In-Reply-To: <20190613153505.GU28951@C02TF0J2HF1T.local>
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:
>>> From: Catalin Marinas <catalin.marinas@arm.com>
>>>
>>> It is not desirable to relax the ABI to allow tagged user addresses into
>>> the kernel indiscriminately. This patch introduces a prctl() interface
>>> for enabling or disabling the tagged ABI with a global sysctl control
>>> for preventing applications from enabling the relaxed ABI (meant for
>>> testing user-space prctl() return error checking without reconfiguring
>>> the kernel). The ABI properties are inherited by threads of the same
>>> application and fork()'ed children but cleared on execve().
>>>
>>> The PR_SET_TAGGED_ADDR_CTRL will be expanded in the future to handle
>>> MTE-specific settings like imprecise vs precise exceptions.
>>>
>>> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
>>> ---
>>> arch/arm64/include/asm/processor.h | 6 +++
>>> arch/arm64/include/asm/thread_info.h | 1 +
>>> arch/arm64/include/asm/uaccess.h | 3 +-
>>> arch/arm64/kernel/process.c | 67 ++++++++++++++++++++++++++++
>>> include/uapi/linux/prctl.h | 5 +++
>>> kernel/sys.c | 16 +++++++
>>> 6 files changed, 97 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
>>> index fcd0e691b1ea..fee457456aa8 100644
>>> --- a/arch/arm64/include/asm/processor.h
>>> +++ b/arch/arm64/include/asm/processor.h
>>> @@ -307,6 +307,12 @@ extern void __init minsigstksz_setup(void);
>>> /* PR_PAC_RESET_KEYS prctl */
>>> #define PAC_RESET_KEYS(tsk, arg) ptrauth_prctl_reset_keys(tsk, arg)
>>>
>>> +/* PR_TAGGED_ADDR prctl */
>>
>> (A couple of comments I missed in my last reply:)
>>
>> Name mismatch?
>
> Yeah, it went through several names but it seems that I didn't update
> all places.
>
>>> +long set_tagged_addr_ctrl(unsigned long arg);
>>> +long get_tagged_addr_ctrl(void);
>>> +#define SET_TAGGED_ADDR_CTRL(arg) set_tagged_addr_ctrl(arg)
>>> +#define GET_TAGGED_ADDR_CTRL() get_tagged_addr_ctrl()
>>> +
>>
>> [...]
>>
>>> diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
>>> index 3767fb21a5b8..69d0be1fc708 100644
>>> --- a/arch/arm64/kernel/process.c
>>> +++ b/arch/arm64/kernel/process.c
>>> @@ -30,6 +30,7 @@
>>> #include <linux/kernel.h>
>>> #include <linux/mm.h>
>>> #include <linux/stddef.h>
>>> +#include <linux/sysctl.h>
>>> #include <linux/unistd.h>
>>> #include <linux/user.h>
>>> #include <linux/delay.h>
>>> @@ -323,6 +324,7 @@ void flush_thread(void)
>>> fpsimd_flush_thread();
>>> tls_thread_flush();
>>> flush_ptrace_hw_breakpoint(current);
>>> + clear_thread_flag(TIF_TAGGED_ADDR);
>>> }
>>>
>>> void release_thread(struct task_struct *dead_task)
>>> @@ -552,3 +554,68 @@ void arch_setup_new_exec(void)
>>>
>>> ptrauth_thread_init_user(current);
>>> }
>>> +
>>> +/*
>>> + * 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?
>> Do we want to allow a process that has tagging on to be able to turn
>> it off at all? Possibly things like CRIU might want to do that.
>
> I left it in for symmetry but I don't expect it to be used. A potential
> use-case is doing it per subsequent threads in an application.
>
>>> + if (is_compat_task())
>>> + return -EINVAL;
>>> + if (arg & ~PR_TAGGED_ADDR_ENABLE)
>>> + return -EINVAL;
>>
>> How do we expect this argument to be extended in the future?
>
> Yes, for MTE. That's why I wouldn't allow random bits here.
>
>> I'm wondering whether this is really a bitmask or an enum, or a mixture
>> of the two. Maybe it doesn't matter.
>
> User may want to set PR_TAGGED_ADDR_ENABLE | PR_MTE_PRECISE in a single
> call.
>
>>> + if (arg & PR_TAGGED_ADDR_ENABLE)
>>> + set_thread_flag(TIF_TAGGED_ADDR);
>>> + else
>>> + clear_thread_flag(TIF_TAGGED_ADDR);
>>
>> I think update_thread_flag() could be used here.
>
> Yes. I forgot you added this.
>
--
Regards,
Vincenzo
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next prev parent reply other threads:[~2019-06-13 15:46 UTC|newest]
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 [this message]
2019-06-13 15:57 ` Catalin Marinas
2019-06-13 16:15 ` Vincenzo Frascino
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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