[media] v4l: vb2-dma-contig: fail if user ptr buffer is not correctly aligned

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@samsung.com>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c b/drivers/media/v4l2-core/videobuf2-dma-contig.c
index b35f38e9f2d73b08b3ebe9113d8d94014c81b570..27de1bb731db0a537d09a76c88c03fd7df7a5d04 100644 (file)
--- a/drivers/media/v4l2-core/videobuf2-dma-contig.c
+++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c
@@ -491,6 +491,18 @@ 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)