Re: [PATCH 1/2] media: intel-ipu3: cio2: fix a crash with out-of-bounds access

[Tomasz Figa]

On Thu, Jan 4, 2018 at 11:57 AM, Yong Zhi <yong....@intel.com> wrote:
> When dmabuf is used for BLOB type frame, the frame
> buffers allocated by gralloc will hold more pages
> than the valid frame data due to height alignment.
>
> In this case, the page numbers in sg list could exceed the
> FBPT upper limit value - max_lops(8)*1024 to cause crash.
>
> Limit the LOP access to the valid data length
> to avoid FBPT sub-entries overflow.
>
> Signed-off-by: Yong Zhi <yong....@intel.com>
> Signed-off-by: Cao Bing Bu <bingbu....@intel.com>
> ---
>  drivers/media/pci/intel/ipu3/ipu3-cio2.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/media/pci/intel/ipu3/ipu3-cio2.c 
> b/drivers/media/pci/intel/ipu3/ipu3-cio2.c
> index 941caa987dab..949f43d206ad 100644
> --- a/drivers/media/pci/intel/ipu3/ipu3-cio2.c
> +++ b/drivers/media/pci/intel/ipu3/ipu3-cio2.c
> @@ -838,8 +838,9 @@ static int cio2_vb2_buf_init(struct vb2_buffer *vb)
>                 container_of(vb, struct cio2_buffer, vbb.vb2_buf);
>         static const unsigned int entries_per_page =
>                 CIO2_PAGE_SIZE / sizeof(u32);
> -       unsigned int pages = DIV_ROUND_UP(vb->planes[0].length, 
> CIO2_PAGE_SIZE);
> -       unsigned int lops = DIV_ROUND_UP(pages + 1, entries_per_page);
> +       unsigned int pages = DIV_ROUND_UP(vb->planes[0].length,
> +                                         CIO2_PAGE_SIZE) + 1;

Why + 1? This would still overflow the buffer, wouldn't it?

> +       unsigned int lops = DIV_ROUND_UP(pages, entries_per_page);
>         struct sg_table *sg;
>         struct sg_page_iter sg_iter;
>         int i, j;
> @@ -869,6 +870,8 @@ static int cio2_vb2_buf_init(struct vb2_buffer *vb)
>
>         i = j = 0;
>         for_each_sg_page(sg->sgl, &sg_iter, sg->nents, 0) {
> +               if (!pages--)
> +                       break;

Or perhaps we should check here for (pages > 1)?

Best regards,
Tomasz