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From: Vincenzo Frascino <vincenzo.frascino@arm.com>
To: Catalin Marinas <catalin.marinas@arm.com>,
	Andrey Konovalov <andreyknvl@google.com>
Cc: linux-arm-kernel@lists.infradead.org,
	Mark Rutland <mark.rutland@arm.com>,
	Marco Elver <elver@google.com>,
	Kevin Brodsky <kevin.brodsky@arm.com>,
	Branislav Rankov <Branislav.Rankov@arm.com>,
	kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org, Alexander Potapenko <glider@google.com>,
	Evgenii Stepanov <eugenis@google.com>,
	Andrey Ryabinin <aryabinin@virtuozzo.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Will Deacon <will@kernel.org>, Dmitry Vyukov <dvyukov@google.com>
Subject: Re: [PATCH mm v11 27/42] arm64: mte: Add in-kernel tag fault handler
Date: Thu, 3 Dec 2020 10:39:22 +0000
Message-ID: <c1e9c10a-c4d0-caf5-5501-6d676ac2abea@arm.com> (raw)
In-Reply-To: <20201203102628.GB2224@gaia>



On 12/3/20 10:26 AM, Catalin Marinas wrote:
>>  static inline void uaccess_enable(void)
>>  {
>> +	asm volatile(ALTERNATIVE("nop", SET_PSTATE_TCO(1),
>> +				 ARM64_MTE, CONFIG_KASAN_HW_TAGS));
>> +
>>  	__uaccess_enable(ARM64_HAS_PAN);
>>  }
> 
> I think that's insufficient if CONFIG_ARM64_PAN is disabled. In the !PAN
> case, the get/put_user() accessors use standard LDR/STR instructions
> which would follow the TCF rather than TCF0 mode checking. However, they
> don't use the above uaccess_disable/enable() functions.
> 
> The current user space support is affected as well but luckily we just
> skip tag checking on the uaccess routines if !PAN since the kernel TCF
> is 0. With the in-kernel MTE, TCF may be more strict than TCF0.
> 
> My suggestion is to simply make CONFIG_ARM64_MTE depend on (or select)
> PAN. Architecturally this should work since PAN is required for ARMv8.1,
> so present with any MTE implementation. This patch is on top of -next,
> though it has a Fixes tag in 5.10:
> 

Agreed, since PAN is required for ARMv8.1 we should not find any implementation
of MTE that lacks PAN.

> --------------------------8<---------------------------
> From ecc819804c1fb1ad498d7ced07e01e3b3e055a3f Mon Sep 17 00:00:00 2001
> From: Catalin Marinas <catalin.marinas@arm.com>
> Date: Thu, 3 Dec 2020 10:15:39 +0000
> Subject: [PATCH] arm64: mte: Ensure CONFIG_ARM64_PAN is enabled with MTE
> 
> The uaccess routines like get/put_user() rely on the user TCF0 mode
> setting for tag checking. However, if CONFIG_ARM64_PAN is disabled,
> these routines would use the standard LDR/STR instructions and therefore
> the kernel TCF mode. In 5.10, the kernel TCF==0, so no tag checking, but
> this will change with the in-kernel MTE support.
> 
> Make ARM64_MTE depend on ARM64_PAN.
> 
> Fixes: 89b94df9dfb1 ("arm64: mte: Kconfig entry")
> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>

> ---
>  arch/arm64/Kconfig | 2 ++
>  1 file changed, 2 insertions(+)
> 
> =======================================
> 
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 844d62df776c..f9eed3a5917e 100644
> 
> --- a/arch/arm64/Kconfig
> 
> +++ b/arch/arm64/Kconfig
> 
> @@ -1673,6 +1673,8 @@
> 
>  config ARM64_MTE
> 
> » default·y
> » depends·on·ARM64_AS_HAS_MTE·&&·ARM64_TAGGED_ADDR_ABI
> » depends·on·AS_HAS_ARMV8_5
> +» #·Required·for·tag·checking·in·the·uaccess·routines
> +» depends·on·ARM64_PAN
> » select·ARCH_USES_HIGH_VMA_FLAGS
> » help
> » ··Memory·Tagging·(part·of·the·ARMv8.5·Extensions)·provides

-- 
Regards,
Vincenzo

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Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-23 20:07 [PATCH mm v11 00/42] kasan: add hardware tag-based mode for arm64 Andrey Konovalov
2020-11-23 20:07 ` [PATCH mm v11 01/42] kasan: drop unnecessary GPL text from comment headers Andrey Konovalov
2020-11-23 20:07 ` [PATCH mm v11 02/42] kasan: KASAN_VMALLOC depends on KASAN_GENERIC Andrey Konovalov
2020-11-23 20:07 ` [PATCH mm v11 03/42] kasan: group vmalloc code Andrey Konovalov
2020-11-23 20:07 ` [PATCH mm v11 04/42] kasan: shadow declarations only for software modes Andrey Konovalov
2020-11-23 20:07 ` [PATCH mm v11 05/42] kasan: rename (un)poison_shadow to (un)poison_range Andrey Konovalov
2020-11-23 20:07 ` [PATCH mm v11 06/42] kasan: rename KASAN_SHADOW_* to KASAN_GRANULE_* Andrey Konovalov
2020-11-23 20:07 ` [PATCH mm v11 07/42] kasan: only build init.c for software modes Andrey Konovalov
2020-11-23 20:07 ` [PATCH mm v11 08/42] kasan: split out shadow.c from common.c Andrey Konovalov
2020-11-23 20:07 ` [PATCH mm v11 09/42] kasan: define KASAN_MEMORY_PER_SHADOW_PAGE Andrey Konovalov
2020-11-23 20:07 ` [PATCH mm v11 10/42] kasan: rename report and tags files Andrey Konovalov
2020-11-23 20:07 ` [PATCH mm v11 11/42] kasan: don't duplicate config dependencies Andrey Konovalov
2020-11-23 20:07 ` [PATCH mm v11 12/42] kasan: hide invalid free check implementation Andrey Konovalov
2020-11-23 20:07 ` [PATCH mm v11 13/42] kasan: decode stack frame only with KASAN_STACK_ENABLE Andrey Konovalov
2020-11-23 20:07 ` [PATCH mm v11 14/42] kasan, arm64: only init shadow for software modes Andrey Konovalov
2020-11-23 20:07 ` [PATCH mm v11 15/42] kasan, arm64: only use kasan_depth " Andrey Konovalov
2020-11-23 20:07 ` [PATCH mm v11 16/42] kasan, arm64: move initialization message Andrey Konovalov
2020-11-23 20:07 ` [PATCH mm v11 17/42] kasan, arm64: rename kasan_init_tags and mark as __init Andrey Konovalov
2020-11-23 20:07 ` [PATCH mm v11 18/42] kasan: rename addr_has_shadow to addr_has_metadata Andrey Konovalov
2020-11-23 20:07 ` [PATCH mm v11 19/42] kasan: rename print_shadow_for_address to print_memory_metadata Andrey Konovalov
2020-11-23 20:07 ` [PATCH mm v11 20/42] kasan: rename SHADOW layout macros to META Andrey Konovalov
2020-11-23 20:07 ` [PATCH mm v11 21/42] kasan: separate metadata_fetch_row for each mode Andrey Konovalov
2020-11-23 20:07 ` [PATCH mm v11 22/42] kasan, arm64: don't allow SW_TAGS with ARM64_MTE Andrey Konovalov
2020-11-23 20:07 ` [PATCH mm v11 23/42] kasan: introduce CONFIG_KASAN_HW_TAGS Andrey Konovalov
2020-11-23 20:07 ` [PATCH mm v11 24/42] arm64: Enable armv8.5-a asm-arch option Andrey Konovalov
2020-11-23 20:07 ` [PATCH mm v11 25/42] arm64: mte: Add in-kernel MTE helpers Andrey Konovalov
2020-11-23 20:07 ` [PATCH mm v11 26/42] arm64: mte: Reset the page tag in page->flags Andrey Konovalov
2020-11-23 20:07 ` [PATCH mm v11 27/42] arm64: mte: Add in-kernel tag fault handler Andrey Konovalov
2020-12-03 10:26   ` Catalin Marinas
2020-12-03 10:39     ` Vincenzo Frascino [this message]
2020-11-23 20:07 ` [PATCH mm v11 28/42] arm64: kasan: Allow enabling in-kernel MTE Andrey Konovalov
2020-11-23 20:07 ` [PATCH mm v11 29/42] arm64: mte: Convert gcr_user into an exclude mask Andrey Konovalov
2020-11-23 20:07 ` [PATCH mm v11 30/42] arm64: mte: Switch GCR_EL1 in kernel entry and exit Andrey Konovalov
2020-11-23 20:07 ` [PATCH mm v11 31/42] kasan, mm: untag page address in free_reserved_area Andrey Konovalov
2020-11-23 20:07 ` [PATCH mm v11 32/42] arm64: kasan: Align allocations for HW_TAGS Andrey Konovalov
2020-11-23 20:07 ` [PATCH mm v11 33/42] arm64: kasan: Add arch layer for memory tagging helpers Andrey Konovalov
2020-11-23 20:07 ` [PATCH mm v11 34/42] kasan: define KASAN_GRANULE_SIZE for HW_TAGS Andrey Konovalov
2020-11-23 20:07 ` [PATCH mm v11 35/42] kasan, x86, s390: update undef CONFIG_KASAN Andrey Konovalov
2020-11-23 20:08 ` [PATCH mm v11 36/42] kasan, arm64: expand CONFIG_KASAN checks Andrey Konovalov
2020-11-23 20:08 ` [PATCH mm v11 37/42] kasan, arm64: implement HW_TAGS runtime Andrey Konovalov
2020-11-23 20:08 ` [PATCH mm v11 38/42] kasan, arm64: print report from tag fault handler Andrey Konovalov
2020-11-23 20:08 ` [PATCH mm v11 39/42] kasan, mm: reset tags when accessing metadata Andrey Konovalov
2020-11-23 20:08 ` [PATCH mm v11 40/42] kasan, arm64: enable CONFIG_KASAN_HW_TAGS Andrey Konovalov
2020-11-23 20:08 ` [PATCH mm v11 41/42] kasan: add documentation for hardware tag-based mode Andrey Konovalov
2020-11-23 20:08 ` [PATCH mm v11 42/42] kselftest/arm64: Check GCR_EL1 after context switch Andrey Konovalov

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