media: videobuf2: revert "get_userptr: buffers are always writable"

Commit 707947247e95 ("media: videobuf2-vmalloc: get_userptr: buffers are
always writable") caused problems in a corner case (passing read-only
shmem memory as a userptr). So revert this patch.

The original problem for which that commit was originally made is
something that I could not reproduce after reverting it. So just go
back to the way it was for many years, and if problems arise in
the future, then another approach should be taken to resolve it.

This patch is based on a patch from Hirokazu.

Fixes: 707947247e95 ("media: videobuf2-vmalloc: get_userptr: buffers are always writable")
Signed-off-by: Hirokazu Honda <hiroh@chromium.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Acked-by: Tomasz Figa <tfiga@chromium.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

5 files changed, 19 insertions, 8 deletions

diff --git a/drivers/media/common/videobuf2/frame_vector.c b/drivers/media/common/videobuf2/frame_vector.c
index 542dde9d2609..aad72640f055 100644
--- a/drivers/media/common/videobuf2/frame_vector.c
+++ b/drivers/media/common/videobuf2/frame_vector.c
@@ -14,6 +14,7 @@
  * get_vaddr_frames() - map virtual addresses to pfns
  * @start:	starting user address
  * @nr_frames:	number of pages / pfns from start to map
+ * @write:	the mapped address has write permission
  * @vec:	structure which receives pages / pfns of the addresses mapped.
  *		It should have space for at least nr_frames entries.
  *
@@ -32,7 +33,7 @@
  *
  * This function takes care of grabbing mmap_lock as necessary.
  */
-int get_vaddr_frames(unsigned long start, unsigned int nr_frames,
+int get_vaddr_frames(unsigned long start, unsigned int nr_frames, bool write,
 		     struct frame_vector *vec)
 {
 	struct mm_struct *mm = current->mm;
@@ -40,6 +41,7 @@ int get_vaddr_frames(unsigned long start, unsigned int nr_frames,
 	int ret_pin_user_pages_fast = 0;
 	int ret = 0;
 	int err;
+	unsigned int gup_flags = FOLL_FORCE | FOLL_LONGTERM;
 
 	if (nr_frames == 0)
 		return 0;
@@ -49,8 +51,10 @@ int get_vaddr_frames(unsigned long start, unsigned int nr_frames,
 
 	start = untagged_addr(start);
 
-	ret = pin_user_pages_fast(start, nr_frames,
-				  FOLL_FORCE | FOLL_WRITE | FOLL_LONGTERM,
+	if (write)
+		gup_flags |= FOLL_WRITE;
+
+	ret = pin_user_pages_fast(start, nr_frames, gup_flags,
 				  (struct page **)(vec->ptrs));
 	if (ret > 0) {
 		vec->got_ref = true;
diff --git a/drivers/media/common/videobuf2/videobuf2-dma-contig.c b/drivers/media/common/videobuf2/videobuf2-dma-contig.c
index 678b359717c4..8e55468cb60d 100644
--- a/drivers/media/common/videobuf2/videobuf2-dma-contig.c
+++ b/drivers/media/common/videobuf2/videobuf2-dma-contig.c
@@ -603,7 +603,8 @@ static void *vb2_dc_get_userptr(struct vb2_buffer *vb, struct device *dev,
 	buf->vb = vb;
 
 	offset = lower_32_bits(offset_in_page(vaddr));
-	vec = vb2_create_framevec(vaddr, size);
+	vec = vb2_create_framevec(vaddr, size, buf->dma_dir == DMA_FROM_DEVICE ||
+					       buf->dma_dir == DMA_BIDIRECTIONAL);
 	if (IS_ERR(vec)) {
 		ret = PTR_ERR(vec);
 		goto fail_buf;
diff --git a/drivers/media/common/videobuf2/videobuf2-dma-sg.c b/drivers/media/common/videobuf2/videobuf2-dma-sg.c
index fa69158a65b1..099693e42bc6 100644
--- a/drivers/media/common/videobuf2/videobuf2-dma-sg.c
+++ b/drivers/media/common/videobuf2/videobuf2-dma-sg.c
@@ -241,7 +241,9 @@ static void *vb2_dma_sg_get_userptr(struct vb2_buffer *vb, struct device *dev,
 	buf->size = size;
 	buf->dma_sgt = &buf->sg_table;
 	buf->vb = vb;
-	vec = vb2_create_framevec(vaddr, size);
+	vec = vb2_create_framevec(vaddr, size,
+				  buf->dma_dir == DMA_FROM_DEVICE ||
+				  buf->dma_dir == DMA_BIDIRECTIONAL);
 	if (IS_ERR(vec))
 		goto userptr_fail_pfnvec;
 	buf->vec = vec;
diff --git a/drivers/media/common/videobuf2/videobuf2-memops.c b/drivers/media/common/videobuf2/videobuf2-memops.c
index 9dd6c27162f4..f9a4ec44422e 100644
--- a/drivers/media/common/videobuf2/videobuf2-memops.c
+++ b/drivers/media/common/videobuf2/videobuf2-memops.c
@@ -26,6 +26,7 @@
  * vb2_create_framevec() - map virtual addresses to pfns
  * @start:	Virtual user address where we start mapping
  * @length:	Length of a range to map
+ * @write:	Should we map for writing into the area
  *
  * This function allocates and fills in a vector with pfns corresponding to
  * virtual address range passed in arguments. If pfns have corresponding pages,
@@ -34,7 +35,8 @@
  * failure. Returned vector needs to be freed via vb2_destroy_pfnvec().
  */
 struct frame_vector *vb2_create_framevec(unsigned long start,
-					 unsigned long length)
+					 unsigned long length,
+					 bool write)
 {
 	int ret;
 	unsigned long first, last;
@@ -47,7 +49,7 @@ struct frame_vector *vb2_create_framevec(unsigned long start,
 	vec = frame_vector_create(nr);
 	if (!vec)
 		return ERR_PTR(-ENOMEM);
-	ret = get_vaddr_frames(start & PAGE_MASK, nr, vec);
+	ret = get_vaddr_frames(start & PAGE_MASK, nr, write, vec);
 	if (ret < 0)
 		goto out_destroy;
 	/* We accept only complete set of PFNs */
diff --git a/drivers/media/common/videobuf2/videobuf2-vmalloc.c b/drivers/media/common/videobuf2/videobuf2-vmalloc.c
index 948152f1596b..67d0b89e701b 100644
--- a/drivers/media/common/videobuf2/videobuf2-vmalloc.c
+++ b/drivers/media/common/videobuf2/videobuf2-vmalloc.c
@@ -85,7 +85,9 @@ static void *vb2_vmalloc_get_userptr(struct vb2_buffer *vb, struct device *dev,
 	buf->dma_dir = vb->vb2_queue->dma_dir;
 	offset = vaddr & ~PAGE_MASK;
 	buf->size = size;
-	vec = vb2_create_framevec(vaddr, size);
+	vec = vb2_create_framevec(vaddr, size,
+				  buf->dma_dir == DMA_FROM_DEVICE ||
+				  buf->dma_dir == DMA_BIDIRECTIONAL);
 	if (IS_ERR(vec)) {
 		ret = PTR_ERR(vec);
 		goto fail_pfnvec_create;