-----原始邮件-----
发件人: "Sylwester Nawrocki" [off-list ref]
发送时间: 2021-04-27 18:36:48 (星期二)
收件人: "Lv Yunlong" [off-list ref]
抄送: linux-media@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org, linux-kernel@vger.kernel.org, s.nawrocki@samsung.com, mchehab@kernel.org, krzk@kernel.org
主题: Re: [PATCH v2] media:exynos4-is: Fix a use after free in isp_video_release

On 27.04.2021 08:02, Lv Yunlong wrote:

quoted

In isp_video_release, file->private_data is freed via
_vb2_fop_release()->v4l2_fh_release(). But the freed
file->private_data is still used in v4l2_fh_is_singular_file()
->v4l2_fh_is_singular(file->private_data), which is a use
after free bug.

My patch set file->private_data to NULL after _vb2_fop_release()
to avoid the use after free.

Fixes: 34947b8aebe3f ("[media] exynos4-is: Add the FIMC-IS ISP capture DMA driver")
Signed-off-by: Lv Yunlong <redacted>
---
  drivers/media/platform/exynos4-is/fimc-isp-video.c | 3 ++-
  1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/media/platform/exynos4-is/fimc-isp-video.c b/drivers/media/platform/exynos4-is/fimc-isp-video.c
index 612b9872afc8..2e04589068b4 100644
--- a/drivers/media/platform/exynos4-is/fimc-isp-video.c
+++ b/drivers/media/platform/exynos4-is/fimc-isp-video.c

@@ -315,7 +315,8 @@ static int isp_video_release(struct file *file)
  	}
  
  	_vb2_fop_release(file, NULL);
-
+	file->private_data = NULL;

quoted

  	if (v4l2_fh_is_singular_file(file)) {
  		fimc_pipeline_call(&ivc->ve, close);
  

Thank you for the patch. To ensure the pipeline stop call is done
only when the last file handle is released we would need something
as below.

--------8<---------

diff --git a/drivers/media/platform/exynos4-is/fimc-isp-video.c 

b/drivers/media/platform/exynos4-is/fimc-isp-video.c
index 612b9872afc8..3335fec509cb 100644

--- a/drivers/media/platform/exynos4-is/fimc-isp-video.c
+++ b/drivers/media/platform/exynos4-is/fimc-isp-video.c

@@ -306,17 +306,20 @@ static int isp_video_release(struct file *file)
         struct fimc_is_video *ivc = &isp->video_capture;
         struct media_entity *entity = &ivc->ve.vdev.entity;
         struct media_device *mdev = entity->graph_obj.mdev;
+       bool is_singular_file;

         mutex_lock(&isp->video_lock);

-       if (v4l2_fh_is_singular_file(file) && ivc->streaming) {
+       is_singular_file = v4l2_fh_is_singular_file(file);
+
+       if (is_singular_file && ivc->streaming) {
                 media_pipeline_stop(entity);
                 ivc->streaming = 0;
         }

         _vb2_fop_release(file, NULL);

-       if (v4l2_fh_is_singular_file(file)) {
+       if (is_singular_file) {
                 fimc_pipeline_call(&ivc->ve, close);

                 mutex_lock(&mdev->graph_mutex);
--------8<---------

Regards,
Sylwester