[libcamera-devel] [PATCH] pipeline: vimc: Force complete of request on cancelled buffers

[Umang Jain]

When the stream is stopped, the V4L2VideoDevice sends back all
the queued buffers with FrameMetadata::FrameCancelled status.
It is the responsibility of the pipeline handler to handle
these buffers with FrameMetadata::FrameCancelled. VIMC is
currently missing this handling path.

As the FrameMetadata::FrameCancelled is set when the stream is
stopped, we can be sure that no more queued and re-use of request
shall happen.  Hence, cancel all the requests' buffers force a
complete with completeBuffer().

The issue is caught by the gstreamer_single_stream_test.cpp running
with vimc. During the check with meson built-in option
	'-Db_sanitize=address,undefined'
it was observed:

==118003==ERROR: AddressSanitizer: heap-use-after-free on address 0x60e000037108 at pc 0x7f225160c9ac bp 0x7f224a47b620 sp 0x7f224a47b618
READ of size 4 at 0x60e000037108 thread T1
    #0 0x7f225160c9ab in libcamera::Request::sequence() const ../include/libcamera/request.h:55
    #1 0x7f22518297aa in libcamera::VimcCameraData::bufferReady(libcamera::FrameBuffer*) ../src/libcamera/pipeline/vimc/vimc.cpp:577
    #2 0x7f225183b1ef in libcamera::BoundMethodMember<libcamera::VimcCameraData, void, libcamera::FrameBuffer*>::activate(libcamera::FrameBuffer*, bool) ../include/libcamera/base/bound_method.h:194
    #3 0x7f22515cc91f in libcamera::Signal<libcamera::FrameBuffer*>::emit(libcamera::FrameBuffer*) ../include/libcamera/base/signal.h:126
    #4 0x7f22515c3305 in libcamera::V4L2VideoDevice::streamOff() ../src/libcamera/v4l2_videodevice.cpp:1605
    #5 0x7f225181f345 in libcamera::PipelineHandlerVimc::stop(libcamera::Camera*) ../src/libcamera/pipeline/vimc/vimc.cpp:365

The VimcCameraData::bufferReady seems to emit even after the stream
is stopped. It's primarily due to vimc's lack of handling
FrameMetadata::FrameCancelled in its pipeline handler.

Signed-off-by: Umang Jain <umang.jain at ideasonboard.com>
---
 src/libcamera/pipeline/vimc/vimc.cpp | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/src/libcamera/pipeline/vimc/vimc.cpp b/src/libcamera/pipeline/vimc/vimc.cpp
index 92b30f2e..e98adab6 100644
--- a/src/libcamera/pipeline/vimc/vimc.cpp
+++ b/src/libcamera/pipeline/vimc/vimc.cpp
@@ -571,6 +571,18 @@ void VimcCameraData::bufferReady(FrameBuffer *buffer)
 	request->metadata().set(controls::SensorTimestamp,
 				buffer->metadata().timestamp);
 
+	/* If the buffer is cancelled force a complete of the whole request. */
+	if (buffer->metadata().status == FrameMetadata::FrameCancelled) {
+		for (auto it : request->buffers()) {
+			FrameBuffer *b = it.second;
+			b->cancel();
+			pipe_->completeBuffer(request, b);
+		}
+
+		pipe_->completeRequest(request);
+		return;
+	}
+
 	pipe_->completeBuffer(request, buffer);
 	pipe_->completeRequest(request);
 
-- 
2.31.1