linux-kernel - Re: [PATCH v18 09/15] drm/amdgpu: untag user pointers

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Date:   Mon, 24 Jun 2019 08:00:57 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Andrey Konovalov <andreyknvl@...gle.com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, linux-rdma@...r.kernel.org,
        linux-media@...r.kernel.org, kvm@...r.kernel.org,
        linux-kselftest@...r.kernel.org,
        Catalin Marinas <catalin.marinas@....com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Will Deacon <will.deacon@....com>,
        Mark Rutland <mark.rutland@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Yishai Hadas <yishaih@...lanox.com>,
        Felix Kuehling <Felix.Kuehling@....com>,
        Alexander Deucher <Alexander.Deucher@....com>,
        Christian Koenig <Christian.Koenig@....com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Jens Wiklander <jens.wiklander@...aro.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Leon Romanovsky <leon@...nel.org>,
        Luc Van Oostenryck <luc.vanoostenryck@...il.com>,
        Dave Martin <Dave.Martin@....com>,
        Khalid Aziz <khalid.aziz@...cle.com>, enh <enh@...gle.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Christoph Hellwig <hch@...radead.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Kostya Serebryany <kcc@...gle.com>,
        Evgeniy Stepanov <eugenis@...gle.com>,
        Lee Smith <Lee.Smith@....com>,
        Ramana Radhakrishnan <Ramana.Radhakrishnan@....com>,
        Jacob Bramley <Jacob.Bramley@....com>,
        Ruben Ayrapetyan <Ruben.Ayrapetyan@....com>,
        Robin Murphy <robin.murphy@....com>,
        Kevin Brodsky <kevin.brodsky@....com>,
        Szabolcs Nagy <Szabolcs.Nagy@....com>
Subject: Re: [PATCH v18 09/15] drm/amdgpu: untag user pointers

On Mon, Jun 24, 2019 at 04:32:54PM +0200, Andrey Konovalov wrote:
> This patch is a part of a series that extends kernel ABI to allow to pass
> tagged user pointers (with the top byte set to something else other than
> 0x00) as syscall arguments.
> 
> In amdgpu_gem_userptr_ioctl() and amdgpu_amdkfd_gpuvm.c/init_user_pages()
> an MMU notifier is set up with a (tagged) userspace pointer. The untagged
> address should be used so that MMU notifiers for the untagged address get
> correctly matched up with the right BO. This patch untag user pointers in
> amdgpu_gem_userptr_ioctl() for the GEM case and in amdgpu_amdkfd_gpuvm_
> alloc_memory_of_gpu() for the KFD case. This also makes sure that an
> untagged pointer is passed to amdgpu_ttm_tt_get_user_pages(), which uses
> it for vma lookups.
> 
> Suggested-by: Felix Kuehling <Felix.Kuehling@....com>
> Acked-by: Felix Kuehling <Felix.Kuehling@....com>
> Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>

Reviewed-by: Kees Cook <keescook@...omium.org>

-Kees

> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c | 2 +-
>  drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c          | 2 ++
>  2 files changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
> index a6e5184d436c..5d476e9bbc43 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
> @@ -1108,7 +1108,7 @@ int amdgpu_amdkfd_gpuvm_alloc_memory_of_gpu(
>  		alloc_flags = 0;
>  		if (!offset || !*offset)
>  			return -EINVAL;
> -		user_addr = *offset;
> +		user_addr = untagged_addr(*offset);
>  	} else if (flags & ALLOC_MEM_FLAGS_DOORBELL) {
>  		domain = AMDGPU_GEM_DOMAIN_GTT;
>  		alloc_domain = AMDGPU_GEM_DOMAIN_CPU;
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> index d4fcf5475464..e91df1407618 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> @@ -287,6 +287,8 @@ int amdgpu_gem_userptr_ioctl(struct drm_device *dev, void *data,
>  	uint32_t handle;
>  	int r;
>  
> +	args->addr = untagged_addr(args->addr);
> +
>  	if (offset_in_page(args->addr | args->size))
>  		return -EINVAL;
>  
> -- 
> 2.22.0.410.gd8fdbe21b5-goog
> 

-- 
Kees Cook