media: exynos4-is: Fix a use after free in isp_video_release

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 uses a variable 'is_singular_file' to avoid the uaf.
v3: https://lore.kernel.org/patchwork/patch/1419058/

Fixes: 34947b8aebe3f ("[media] exynos4-is: Add the FIMC-IS ISP capture DMA driver")
Signed-off-by: Lv Yunlong <lyl2019@mail.ustc.edu.cn>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

diff --git a/drivers/media/platform/exynos4-is/fimc-isp-video.c b/drivers/media/platform/exynos4-is/fimc-isp-video.c
index 8d9dc59..83688a7 100644 (file)
--- a/drivers/media/platform/exynos4-is/fimc-isp-video.c
+++ b/drivers/media/platform/exynos4-is/fimc-isp-video.c
@@ -305,17 +305,20 @@ 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);