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From: Catalin Marinas <catalin.marinas@arm.com>
To: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	stable@vger.kernel.org, Will Deacon <will.deacon@arm.com>,
	Jann Horn <jannh@google.com>
Subject: Re: [PATCH] arm64: compat: Reduce address limit
Date: Mon, 1 Apr 2019 11:59:14 +0100	[thread overview]
Message-ID: <20190401105913.GC14874@arrakis.emea.arm.com> (raw)
In-Reply-To: <20190401103201.9268-1-vincenzo.frascino@arm.com>

On Mon, Apr 01, 2019 at 11:32:01AM +0100, Vincenzo Frascino wrote:
> Currently, compat tasks running on arm64 can allocate memory up to
> TASK_SIZE_32 (UL(0x100000000)).
> 
> This means that mmap() allocations, if we treat them as returning an
> array, are not compliant with the sections 6.5.8 of the C standard
> (C99) which states that: "If the expression P points to an element of
> an array object and the expression Q points to the last element of the
> same array object, the pointer expression Q+1 compares greater than P".
> 
> Redefine TASK_SIZE_32 to address the issue.
> 
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> Cc: Jann Horn <jannh@google.com>
> Reported-by: Jann Horn <jannh@google.com>
> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
> ---
>  arch/arm64/include/asm/processor.h | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
> index 5d9ce62bdebd..f8235f7df29b 100644
> --- a/arch/arm64/include/asm/processor.h
> +++ b/arch/arm64/include/asm/processor.h
> @@ -57,7 +57,11 @@
>  #define TASK_SIZE_64		(UL(1) << vabits_user)
>  
>  #ifdef CONFIG_COMPAT
> +#ifdef CONFIG_ARM64_64K_PAGES
>  #define TASK_SIZE_32		UL(0x100000000)
> +#else
> +#define TASK_SIZE_32		(UL(0x100000000) - PAGE_SIZE)
> +#endif /* CONFIG_ARM64_64K_PAGES */

I'd add a comment above stating that with the 64K page configuration,
the last page is occupied by the compat vectors page.

-- 
Catalin

WARNING: multiple messages have this Message-ID (diff)
From: Catalin Marinas <catalin.marinas@arm.com>
To: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: linux-arch@vger.kernel.org, Will Deacon <will.deacon@arm.com>,
	stable@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	Jann Horn <jannh@google.com>
Subject: Re: [PATCH] arm64: compat: Reduce address limit
Date: Mon, 1 Apr 2019 11:59:14 +0100	[thread overview]
Message-ID: <20190401105913.GC14874@arrakis.emea.arm.com> (raw)
In-Reply-To: <20190401103201.9268-1-vincenzo.frascino@arm.com>

On Mon, Apr 01, 2019 at 11:32:01AM +0100, Vincenzo Frascino wrote:
> Currently, compat tasks running on arm64 can allocate memory up to
> TASK_SIZE_32 (UL(0x100000000)).
> 
> This means that mmap() allocations, if we treat them as returning an
> array, are not compliant with the sections 6.5.8 of the C standard
> (C99) which states that: "If the expression P points to an element of
> an array object and the expression Q points to the last element of the
> same array object, the pointer expression Q+1 compares greater than P".
> 
> Redefine TASK_SIZE_32 to address the issue.
> 
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> Cc: Jann Horn <jannh@google.com>
> Reported-by: Jann Horn <jannh@google.com>
> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
> ---
>  arch/arm64/include/asm/processor.h | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
> index 5d9ce62bdebd..f8235f7df29b 100644
> --- a/arch/arm64/include/asm/processor.h
> +++ b/arch/arm64/include/asm/processor.h
> @@ -57,7 +57,11 @@
>  #define TASK_SIZE_64		(UL(1) << vabits_user)
>  
>  #ifdef CONFIG_COMPAT
> +#ifdef CONFIG_ARM64_64K_PAGES
>  #define TASK_SIZE_32		UL(0x100000000)
> +#else
> +#define TASK_SIZE_32		(UL(0x100000000) - PAGE_SIZE)
> +#endif /* CONFIG_ARM64_64K_PAGES */

I'd add a comment above stating that with the 64K page configuration,
the last page is occupied by the compat vectors page.

-- 
Catalin

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  reply	other threads:[~2019-04-01 10:59 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-01 10:32 [PATCH] arm64: compat: Reduce address limit Vincenzo Frascino
2019-04-01 10:32 ` Vincenzo Frascino
2019-04-01 10:59 ` Catalin Marinas [this message]
2019-04-01 10:59   ` Catalin Marinas
2019-04-01 11:27   ` Vincenzo Frascino
2019-04-01 11:27     ` Vincenzo Frascino

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