Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <e0701648-fec1-f1fd-0c69-8ed85e162a01@xs4all.nl>
Date:   Wed, 23 Nov 2022 14:18:31 +0100
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Thunderbird/102.4.1
Subject: Re: [PATCH mm-unstable v1 15/20] media: pci/ivtv: remove FOLL_FORCE
 usage
Content-Language: en-US
To:     David Hildenbrand <david@redhat.com>, linux-kernel@vger.kernel.org
Cc:     x86@kernel.org, linux-alpha@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org,
        linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
        sparclinux@vger.kernel.org, linux-um@lists.infradead.org,
        etnaviv@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
        linux-samsung-soc@vger.kernel.org, linux-rdma@vger.kernel.org,
        linux-media@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-mm@kvack.org, linux-perf-users@vger.kernel.org,
        linux-security-module@vger.kernel.org,
        linux-kselftest@vger.kernel.org,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Jason Gunthorpe <jgg@ziepe.ca>,
        John Hubbard <jhubbard@nvidia.com>,
        Peter Xu <peterx@redhat.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Hugh Dickins <hughd@google.com>, Nadav Amit <namit@vmware.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Matthew Wilcox <willy@infradead.org>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Muchun Song <songmuchun@bytedance.com>,
        Shuah Khan <shuah@kernel.org>,
        Lucas Stach <l.stach@pengutronix.de>,
        David Airlie <airlied@gmail.com>,
        Oded Gabbay <ogabbay@kernel.org>,
        Arnd Bergmann <arnd@arndb.de>,
        Christoph Hellwig <hch@infradead.org>,
        Alex Williamson <alex.williamson@redhat.com>,
        Andy Walls <awalls@md.metrocast.net>,
        Mauro Carvalho Chehab <mchehab@kernel.org>
References: <20221116102659.70287-1-david@redhat.com>
 <20221116102659.70287-16-david@redhat.com>
From:   Hans Verkuil <hverkuil@xs4all.nl>
In-Reply-To: <20221116102659.70287-16-david@redhat.com>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 16/11/2022 11:26, David Hildenbrand wrote:
> FOLL_FORCE is really only for ptrace access. R/O pinning a page is
> supposed to fail if the VMA misses proper access permissions (no VM_READ).
> 
> Let's just remove FOLL_FORCE usage here; there would have to be a pretty
> good reason to allow arbitrary drivers to R/O pin pages in a PROT_NONE
> VMA. Most probably, FOLL_FORCE usage is just some legacy leftover.

I'm pretty sure about that as well, so:

Acked-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>

Regards,

	Hans

> 
> Cc: Andy Walls <awalls@md.metrocast.net>
> Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
>  drivers/media/pci/ivtv/ivtv-udma.c | 2 +-
>  drivers/media/pci/ivtv/ivtv-yuv.c  | 5 ++---
>  2 files changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/media/pci/ivtv/ivtv-udma.c b/drivers/media/pci/ivtv/ivtv-udma.c
> index 210be8290f24..99b9f55ca829 100644
> --- a/drivers/media/pci/ivtv/ivtv-udma.c
> +++ b/drivers/media/pci/ivtv/ivtv-udma.c
> @@ -115,7 +115,7 @@ int ivtv_udma_setup(struct ivtv *itv, unsigned long ivtv_dest_addr,
>  
>  	/* Pin user pages for DMA Xfer */
>  	err = pin_user_pages_unlocked(user_dma.uaddr, user_dma.page_count,
> -			dma->map, FOLL_FORCE);
> +			dma->map, 0);
>  
>  	if (user_dma.page_count != err) {
>  		IVTV_DEBUG_WARN("failed to map user pages, returned %d instead of %d\n",
> diff --git a/drivers/media/pci/ivtv/ivtv-yuv.c b/drivers/media/pci/ivtv/ivtv-yuv.c
> index 4ba10c34a16a..582146f8d70d 100644
> --- a/drivers/media/pci/ivtv/ivtv-yuv.c
> +++ b/drivers/media/pci/ivtv/ivtv-yuv.c
> @@ -63,12 +63,11 @@ static int ivtv_yuv_prep_user_dma(struct ivtv *itv, struct ivtv_user_dma *dma,
>  
>  	/* Pin user pages for DMA Xfer */
>  	y_pages = pin_user_pages_unlocked(y_dma.uaddr,
> -			y_dma.page_count, &dma->map[0], FOLL_FORCE);
> +			y_dma.page_count, &dma->map[0], 0);
>  	uv_pages = 0; /* silence gcc. value is set and consumed only if: */
>  	if (y_pages == y_dma.page_count) {
>  		uv_pages = pin_user_pages_unlocked(uv_dma.uaddr,
> -				uv_dma.page_count, &dma->map[y_pages],
> -				FOLL_FORCE);
> +				uv_dma.page_count, &dma->map[y_pages], 0);
>  	}
>  
>  	if (y_pages != y_dma.page_count || uv_pages != uv_dma.page_count) {