[libcamera-devel] [PATCH] android: camera_device: Fix crash in calling CameraDevice::close()

[Umang Jain]

Hi Hiro,

The commit message can be somewhat more contextual of the problem.

On 8/31/21 1:35 PM, Hirokazu Honda wrote:
> This fixes the crash when post processing is needed and some capture
> request is being processed by PipelineHandler upon calling
> CameraDevice::close().
> The crash happens in Request::completeBuffer(), which is invoked by
> Camera::stop(). It uses FrameBuffer after free. The FrameBuffer is
> allocated and owned by FrameBufferAllocator, and FrameBufferAllocator
> is owned by CamerStream. So Camera::stop() should be executed before
> destroying CameraStream.


One question: I can see the problem but what's exactly is crashing in 
Request::completeBuffer() is something we should know? Is it the ASSERT? 
That might help us to define the problem statement better.

The problem is happening because we seem to add a CameraStream 
associated buffer(depending on the CameraStream::Type) to the Request, 
in CameraDevice::processCaptureRequest().

However, when the camera stops, all the current buffers are marked with 
FrameMetadata::FrameCancelled and proceed to completion. But the buffer 
associated with the CameraStream (that was previously added to the 
request) has now been cleared out with a part of streams_.clear(), even 
before the camera stop() has been invoked. Any access to those request 
buffers after they have been cleared, shall result in a crash.


>
> Signed-off-by: Hirokazu Honda <hiroh at chromium.org>
> ---
>   src/android/camera_device.cpp | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/src/android/camera_device.cpp b/src/android/camera_device.cpp
> index 8ca76719..74a95a2a 100644
> --- a/src/android/camera_device.cpp
> +++ b/src/android/camera_device.cpp
> @@ -423,10 +423,10 @@ int CameraDevice::open(const hw_module_t *hardwareModule)
>   
>   void CameraDevice::close()
>   {
> -	streams_.clear();
> -
>   	stop();
>   
> +	streams_.clear();


How about this being a part of a CameraDevice::stop() instead ?

> +
>   	camera_->release();
>   }
>