Hi Lv Yunlong,
On 27/04/2021 15:27, Lv Yunlong wrote:
> 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 sets file->private_data to NULL after _vb2_fop_release()
> to avoid the use after free, and uses a variable 'is_singular_file'
> to keep the original function unchanged.
Actually, it is the use of 'is_singular_file' that fixes the bug,
the 'file->private_data = NULL;' is unnecessary here.
That said, it would be a really good idea if in a separate patch you
make v4l2_fh_release() more robust by setting filp->private_data to
NULL after the kfree(fh).
Regards,
Hans
>
> Fixes: 34947b8aebe3f ("[media] exynos4-is: Add the FIMC-IS ISP capture DMA driver")
> Signed-off-by: Lv Yunlong <lyl2019@xxxxxxxxxxxxxxxx>
> ---
> drivers/media/platform/exynos4-is/fimc-isp-video.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/media/platform/exynos4-is/fimc-isp-video.c b/drivers/media/platform/exynos4-is/fimc-isp-video.c
> index 612b9872afc8..c07dcb0bccc2 100644
> --- a/drivers/media/platform/exynos4-is/fimc-isp-video.c
> +++ b/drivers/media/platform/exynos4-is/fimc-isp-video.c
> @@ -306,17 +306,21 @@ 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);
> + file->private_data = NULL;
>
> - if (v4l2_fh_is_singular_file(file)) {
> + if (is_singular_file) {
> fimc_pipeline_call(&ivc->ve, close);
>
> mutex_lock(&mdev->graph_mutex);
>
