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From: Daniel Vetter <daniel.vetter@ffwll.ch>
To: DRI Development <dri-devel@lists.freedesktop.org>,
	LKML <linux-kernel@vger.kernel.org>
Cc: "Jan Kara" <jack@suse.cz>,
	kvm@vger.kernel.org, "Daniel Vetter" <daniel.vetter@ffwll.ch>,
	linux-mm@kvack.org, "Daniel Vetter" <daniel.vetter@intel.com>,
	"Michel Lespinasse" <walken@google.com>,
	"Marek Szyprowski" <m.szyprowski@samsung.com>,
	linux-s390@vger.kernel.org, linux-samsung-soc@vger.kernel.org,
	"Daniel Jordan" <daniel.m.jordan@oracle.com>,
	"Jason Gunthorpe" <jgg@ziepe.ca>,
	linux-arm-kernel@lists.infradead.org,
	linux-media@vger.kernel.org, "Kees Cook" <keescook@chromium.org>,
	"Pawel Osciak" <pawel@osciak.com>,
	"John Hubbard" <jhubbard@nvidia.com>,
	"Jérôme Glisse" <jglisse@redhat.com>,
	"Dan Williams" <dan.j.williams@intel.com>,
	"Laurent Dufour" <ldufour@linux.ibm.com>,
	"Vlastimil Babka" <vbabka@suse.cz>,
	"Tomasz Figa" <tfiga@chromium.org>,
	"Kyungmin Park" <kyungmin.park@samsung.com>,
	"Andrew Morton" <akpm@linux-foundation.org>
Subject: [PATCH v4 09/15] media/videbuf1|2: Mark follow_pfn usage as unsafe
Date: Mon, 26 Oct 2020 11:58:12 +0100
Message-ID: <20201026105818.2585306-10-daniel.vetter@ffwll.ch> (raw)
In-Reply-To: <20201026105818.2585306-1-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, this only affects
the zerocopy userptr usage enabled in 50ac952d2263 ("[media]
videobuf2-dma-sg: Support io userptr operations on io memory").

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>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
--
v3:
- Reference the commit that enabled the zerocopy userptr use case to
  make it abundandtly clear that this patch only affects that, and not
  normal memory userptr. The old commit message already explained that
  normal memory userptr is unaffected, but I guess that was not clear
  enough.
---
 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 6590987c14bd..e630494da65c 100644
--- a/drivers/media/common/videobuf2/frame_vector.c
+++ b/drivers/media/common/videobuf2/frame_vector.c
@@ -69,7 +69,7 @@ int get_vaddr_frames(unsigned long start, unsigned int nr_frames,
 			break;
 
 		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

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  parent reply index

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-26 10:58 [PATCH v4 00/15] follow_pfn and other iomap races Daniel Vetter
2020-10-26 10:58 ` [PATCH v4 01/15] drm/exynos: Stop using frame_vector helpers Daniel Vetter
2020-10-26 10:58 ` [PATCH v4 02/15] drm/exynos: Use FOLL_LONGTERM for g2d cmdlists Daniel Vetter
2020-10-26 10:58 ` [PATCH v4 03/15] misc/habana: Stop using frame_vector helpers Daniel Vetter
2020-10-26 10:58 ` [PATCH v4 04/15] misc/habana: Use FOLL_LONGTERM for userptr Daniel Vetter
2020-10-26 10:58 ` [PATCH v4 05/15] mm/frame-vector: Use FOLL_LONGTERM Daniel Vetter
2020-10-26 22:15   ` Tomasz Figa
2020-10-27  8:05     ` Daniel Vetter
2020-10-26 10:58 ` [PATCH v4 06/15] media: videobuf2: Move frame_vector into media subsystem Daniel Vetter
2020-10-26 22:03   ` Tomasz Figa
2020-10-26 10:58 ` [PATCH v4 07/15] mm: Close race in generic_access_phys Daniel Vetter
2020-10-26 10:58 ` [PATCH v4 08/15] mm: Add unsafe_follow_pfn Daniel Vetter
     [not found]   ` <20201029085644.GA25658@infradead.org>
2020-10-29  9:23     ` Daniel Vetter
2020-10-26 10:58 ` Daniel Vetter [this message]
2020-10-26 22:02   ` [PATCH v4 09/15] media/videbuf1|2: Mark follow_pfn usage as unsafe Tomasz Figa
2020-10-26 10:58 ` [PATCH v4 10/15] vfio/type1: Mark follow_pfn " Daniel Vetter
2020-10-26 10:58 ` [PATCH v4 11/15] PCI: Obey iomem restrictions for procfs mmap Daniel Vetter
2020-10-26 10:58 ` [PATCH v4 12/15] /dev/mem: Only set filp->f_mapping Daniel Vetter
2020-10-26 10:58 ` [PATCH v4 13/15] resource: Move devmem revoke code to resource framework Daniel Vetter
2020-10-26 10:58 ` [PATCH v4 14/15] sysfs: Support zapping of binary attr mmaps Daniel Vetter
2020-10-26 10:58 ` [PATCH v4 15/15] PCI: Revoke mappings like devmem Daniel Vetter
     [not found] ` <20201029085749.GB25658@infradead.org>
2020-10-29  9:25   ` [PATCH v4 00/15] follow_pfn and other iomap races Daniel Vetter
     [not found]     ` <20201029092800.GA494@infradead.org>
2020-10-29  9:38       ` Daniel Vetter

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