[PATCH 12/13] media/videbuf1|2: Mark follow_pfn usage as unsafe

From: Daniel Vetter <daniel.vetter@ffwll.ch>
To: DRI Development <dri-devel@lists.freedesktop.org>,
	LKML <linux-kernel@vger.kernel.org>
Cc: kvm@vger.kernel.org, linux-mm@kvack.org,
	linux-arm-kernel@lists.infradead.org,
	linux-samsung-soc@vger.kernel.org, linux-media@vger.kernel.org,
	linux-s390@vger.kernel.org,
	"Daniel Vetter" <daniel.vetter@ffwll.ch>,
	"Daniel Vetter" <daniel.vetter@intel.com>,
	"Jason Gunthorpe" <jgg@ziepe.ca>,
	"Kees Cook" <keescook@chromium.org>,
	"Dan Williams" <dan.j.williams@intel.com>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"John Hubbard" <jhubbard@nvidia.com>,
	"Jérôme Glisse" <jglisse@redhat.com>, "Jan Kara" <jack@suse.cz>,
	"Pawel Osciak" <pawel@osciak.com>,
	"Marek Szyprowski" <m.szyprowski@samsung.com>,
	"Kyungmin Park" <kyungmin.park@samsung.com>,
	"Tomasz Figa" <tfiga@chromium.org>,
	"Laurent Dufour" <ldufour@linux.ibm.com>,
	"Vlastimil Babka" <vbabka@suse.cz>,
	"Daniel Jordan" <daniel.m.jordan@oracle.com>,
	"Michel Lespinasse" <walken@google.com>
Subject: [PATCH 12/13] media/videbuf1|2: Mark follow_pfn usage as unsafe
Date: Wed,  7 Oct 2020 18:44:25 +0200	[thread overview]
Message-ID: <20201007164426.1812530-13-daniel.vetter@ffwll.ch> (raw)
In-Reply-To: <20201007164426.1812530-1-daniel.vetter@ffwll.ch>

The media model assumes that buffers are all preallocated, so that
when a media pipeline is running we never miss a deadline because the
buffers aren't allocated or available.

This means we cannot fix the v4l follow_pfn usage through
mmu_notifier, without breaking how this all works. The only real fix
is to deprecate userptr support for VM_IO | VM_PFNMAP mappings and
tell everyone to cut over to dma-buf memory sharing for zerocopy.

userptr for normal memory will keep working as-is.

Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Kees Cook <keescook@chromium.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: linux-mm@kvack.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-samsung-soc@vger.kernel.org
Cc: linux-media@vger.kernel.org
Cc: Pawel Osciak <pawel@osciak.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Tomasz Figa <tfiga@chromium.org>
Cc: Laurent Dufour <ldufour@linux.ibm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: Michel Lespinasse <walken@google.com>
---
 drivers/media/common/videobuf2/frame_vector.c | 2 +-
 drivers/media/v4l2-core/videobuf-dma-contig.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/media/common/videobuf2/frame_vector.c b/drivers/media/common/videobuf2/frame_vector.c
index b95f4f371681..d56eb6258f09 100644
--- a/drivers/media/common/videobuf2/frame_vector.c
+++ b/drivers/media/common/videobuf2/frame_vector.c
@@ -71,7 +71,7 @@ int get_vaddr_frames(unsigned long start, unsigned int nr_frames,
 		unsigned long *nums = frame_vector_pfns(vec);
 
 		while (ret < nr_frames && start + PAGE_SIZE <= vma->vm_end) {
-			err = follow_pfn(vma, start, &nums[ret]);
+			err = unsafe_follow_pfn(vma, start, &nums[ret]);
 			if (err) {
 				if (ret == 0)
 					ret = err;
diff --git a/drivers/media/v4l2-core/videobuf-dma-contig.c b/drivers/media/v4l2-core/videobuf-dma-contig.c
index 52312ce2ba05..821c4a76ab96 100644
--- a/drivers/media/v4l2-core/videobuf-dma-contig.c
+++ b/drivers/media/v4l2-core/videobuf-dma-contig.c
@@ -183,7 +183,7 @@ static int videobuf_dma_contig_user_get(struct videobuf_dma_contig_memory *mem,
 	user_address = untagged_baddr;
 
 	while (pages_done < (mem->size >> PAGE_SHIFT)) {
-		ret = follow_pfn(vma, user_address, &this_pfn);
+		ret = unsafe_follow_pfn(vma, user_address, &this_pfn);
 		if (ret)
 			break;
 
-- 
2.28.0

