Re: [PATCH mm-unstable v1 15/20] media: pci/ivtv: remove FOLL_FORCE usage

Hans Verkuil
2022-11-23T13:34:29Z

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) {