[PATCHv10 22/26] v4l: vb2-dma-contig: fail if user ptr buffer is not correctly aligned

[Tomasz Stanislawski]

From: Marek Szyprowski <m.szyprowski at samsung.com>

The DMA transfer must be aligned to a specific value. If userptr is not aligned
to DMA requirements then unexpected corruptions of the memory may occur before
or after a buffer.  To prevent such situations, all unligned userptr buffers
are rejected at VIDIOC_QBUF.

Signed-off-by: Marek Szyprowski <m.szyprowski at samsung.com>
Acked-by: Hans Verkuil <hans.verkuil at cisco.com>
---
 drivers/media/v4l2-core/videobuf2-dma-contig.c |   12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c b/drivers/media/v4l2-core/videobuf2-dma-contig.c
index 2d661fd..571a919 100644
--- a/drivers/media/v4l2-core/videobuf2-dma-contig.c
+++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c
@@ -493,6 +493,18 @@ static void *vb2_dc_get_userptr(void *alloc_ctx, unsigned long vaddr,
 	struct vm_area_struct *vma;
 	struct sg_table *sgt;
 	unsigned long contig_size;
+	unsigned long dma_align = dma_get_cache_alignment();
+
+	/* Only cache aligned DMA transfers are reliable */
+	if (!IS_ALIGNED(vaddr | size, dma_align)) {
+		pr_debug("user data must be aligned to %lu bytes\n", dma_align);
+		return ERR_PTR(-EINVAL);
+	}
+
+	if (!size) {
+		pr_debug("size is zero\n");
+		return ERR_PTR(-EINVAL);
+	}
 
 	buf = kzalloc(sizeof *buf, GFP_KERNEL);
 	if (!buf)
-- 
1.7.9.5