[PATCH] media: intel-ipu3: cio2: fixup off-by-one bug in cio2_vb2_buf_init

[PATCH] media: intel-ipu3: cio2: fixup off-by-one bug in cio2_vb2_buf_init

[Yong Zhi]

With "pages" initialized to vb length + 1 pages, the condition
check if(!pages--) will break at one more page than intended,
this can result in out-of-bound access to b->lop[i][j] when setting
the last dummy page.

Fix: commit c7cbef1fdb54 ("media: intel-ipu3: cio2: fix a crash with out-of-bounds access")
Signed-off-by: Yong Zhi <yong.zhi@intel.com>
Signed-off-by: Cao Bing Bu <bingbu.cao@intel.com>
---
 drivers/media/pci/intel/ipu3/ipu3-cio2.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/media/pci/intel/ipu3/ipu3-cio2.c b/drivers/media/pci/intel/ipu3/ipu3-cio2.c
index 9db752a7f363..8c9f8f56f5df 100644
--- a/drivers/media/pci/intel/ipu3/ipu3-cio2.c
+++ b/drivers/media/pci/intel/ipu3/ipu3-cio2.c
@@ -839,9 +839,8 @@ 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) + 1;
-	unsigned int lops = DIV_ROUND_UP(pages, entries_per_page);
+	unsigned int pages = DIV_ROUND_UP(vb->planes[0].length, CIO2_PAGE_SIZE);
+	unsigned int lops = DIV_ROUND_UP(pages + 1, entries_per_page);
 	struct sg_table *sg;
 	struct sg_page_iter sg_iter;
 	int i, j;
-- 
2.7.4

Re: [PATCH] media: intel-ipu3: cio2: fixup off-by-one bug in cio2_vb2_buf_init

[Sakari Ailus]

Hi Yong,

Thanks for the patch.

On Fri, Jan 19, 2018 at 12:27:34AM -0600, Yong Zhi wrote:
> With "pages" initialized to vb length + 1 pages, the condition
> check if(!pages--) will break at one more page than intended,
> this can result in out-of-bound access to b->lop[i][j] when setting
> the last dummy page.
> 
> Fix: commit c7cbef1fdb54 ("media: intel-ipu3: cio2: fix a crash with out-of-bounds access")

Fixes: c7cbef1fdb54 ("media: intel-ipu3: cio2: fix a crash with out-of-bounds access")

I've applied the patch with that change.

> Signed-off-by: Yong Zhi <yong.zhi@intel.com>
> Signed-off-by: Cao Bing Bu <bingbu.cao@intel.com>
> ---
>  drivers/media/pci/intel/ipu3/ipu3-cio2.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/media/pci/intel/ipu3/ipu3-cio2.c b/drivers/media/pci/intel/ipu3/ipu3-cio2.c
> index 9db752a7f363..8c9f8f56f5df 100644
> --- a/drivers/media/pci/intel/ipu3/ipu3-cio2.c
> +++ b/drivers/media/pci/intel/ipu3/ipu3-cio2.c
> @@ -839,9 +839,8 @@ 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) + 1;
> -	unsigned int lops = DIV_ROUND_UP(pages, entries_per_page);
> +	unsigned int pages = DIV_ROUND_UP(vb->planes[0].length, CIO2_PAGE_SIZE);
> +	unsigned int lops = DIV_ROUND_UP(pages + 1, entries_per_page);
>  	struct sg_table *sg;
>  	struct sg_page_iter sg_iter;
>  	int i, j;

-- 
Regards,

Sakari Ailus
sakari.ailus@linux.intel.com