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Subject: Re: [PATCH v17 05/15] mm, arm64: untag user pointers in mm/gup.c
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>,
        Vincenzo Frascino <vincenzo.frascino@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>, enh <enh@google.com>,
        Jason Gunthorpe <jgg@ziepe.ca>,
        Christoph Hellwig <hch@infradead.org>,
        Dmitry Vyukov <dvyukov@google.com>,
        Kostya Serebryany <kcc@google.com>,
        Evgeniy Stepanov <eugenis@google.com>,
        Lee Smith <Lee.Smith@arm.com>,
        Ramana Radhakrishnan <Ramana.Radhakrishnan@arm.com>,
        Jacob Bramley <Jacob.Bramley@arm.com>,
        Ruben Ayrapetyan <Ruben.Ayrapetyan@arm.com>,
        Robin Murphy <robin.murphy@arm.com>,
        Kevin Brodsky <kevin.brodsky@arm.com>,
        Szabolcs Nagy <Szabolcs.Nagy@arm.com>
References: <cover.1560339705.git.andreyknvl@google.com>
 <8f65548bef8544d49980a92d221b74440d544c1e.1560339705.git.andreyknvl@google.com>
From:   Khalid Aziz <khalid.aziz@oracle.com>
Organization: Oracle Corp
Message-ID: <dbf2dd46-0240-f8a9-203c-4f1234c16825@oracle.com>
Date:   Wed, 19 Jun 2019 10:41:12 -0600
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On 6/12/19 5:43 AM, 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 othe=
r
> than 0x00) as syscall arguments.
>=20
> mm/gup.c provides a kernel interface that accepts user addresses and
> manipulates user pages directly (for example get_user_pages, that is us=
ed
> by the futex syscall). Since a user can provided tagged addresses, we n=
eed
> to handle this case.
>=20
> Add untagging to gup.c functions that use user addresses for vma lookup=
s.
>=20
> 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: Khalid Aziz <khalid.aziz@oracle.com>


>  mm/gup.c | 4 ++++
>  1 file changed, 4 insertions(+)
>=20
> 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 *ts=
k, struct mm_struct *mm,
>  	if (!nr_pages)
>  		return 0;
> =20
> +	start =3D untagged_addr(start);
> +
>  	VM_BUG_ON(!!pages !=3D !!(gup_flags & FOLL_GET));
> =20
>  	/*
> @@ -964,6 +966,8 @@ int fixup_user_fault(struct task_struct *tsk, struc=
t mm_struct *mm,
>  	struct vm_area_struct *vma;
>  	vm_fault_t ret, major =3D 0;
> =20
> +	address =3D untagged_addr(address);
> +
>  	if (unlocked)
>  		fault_flags |=3D FAULT_FLAG_ALLOW_RETRY;
> =20
>=20