From mboxrd@z Thu Jan  1 00:00:00 1970
From: Vincenzo Frascino <vincenzo.frascino@arm.com>
Subject: Re: [PATCH v17 05/15] mm, arm64: untag user pointers in mm/gup.c
Date: Wed, 12 Jun 2019 15:33:38 +0100
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To: Andrey Konovalov <andreyknvl@google.com>, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-rdma@vger.kernel.org, linux-media@vger.kernel.org, kvm@vger.kernel.org, linux-kselftest@vger.kernel.org
Cc: Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will.deacon@arm.com>, Mark Rutland <mark.rutland@arm.com>, Andrew Morton <akpm@linux-foundation.org>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Kees Cook <keescook@chromium.org>, Yishai Hadas <yishaih@mellanox.com>, Felix Kuehling <Felix.Kuehling@amd.com>, Alexander Deucher <Alexander.Deucher@amd.com>, Christian Koenig <Christian.Koenig@amd.com>, Mauro Carvalho Chehab <mchehab@kernel.org>, Jens Wiklander <jens.wiklander@linaro.org>, Alex Williamson <alex.williamson@redhat.com>, Leon Romanovsky <leon@kernel.org>, Luc Van Oostenryck <luc.vanoostenryck@gmail.com>, Dave Martin <Dave.Martin@arm.com>, Khalid Aziz <khalid.aziz@oracle.com>, enh <enh@google.com>, Jason Gunthorpe <jgg@ziepe.ca>
List-Id: linux-rdma@vger.kernel.org

On 12/06/2019 12:43, Andrey Konovalov wrote:
> This patch is a part of a series that extends arm64 kernel ABI to allow to
> pass tagged user pointers (with the top byte set to something else other
> than 0x00) as syscall arguments.
> 
> mm/gup.c provides a kernel interface that accepts user addresses and
> manipulates user pages directly (for example get_user_pages, that is used
> by the futex syscall). Since a user can provided tagged addresses, we need
> to handle this case.
> 
> Add untagging to gup.c functions that use user addresses for vma lookups.
> 
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>

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

> ---
>  mm/gup.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/mm/gup.c b/mm/gup.c
> index ddde097cf9e4..c37df3d455a2 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -802,6 +802,8 @@ static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
>  	if (!nr_pages)
>  		return 0;
>  
> +	start = untagged_addr(start);
> +
>  	VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET));
>  
>  	/*
> @@ -964,6 +966,8 @@ int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
>  	struct vm_area_struct *vma;
>  	vm_fault_t ret, major = 0;
>  
> +	address = untagged_addr(address);
> +
>  	if (unlocked)
>  		fault_flags |= FAULT_FLAG_ALLOW_RETRY;
>  
> 

-- 
Regards,
Vincenzo