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-rw-r--r--src/libcamera/v4l2_videodevice.cpp21
1 files changed, 20 insertions, 1 deletions
diff --git a/src/libcamera/v4l2_videodevice.cpp b/src/libcamera/v4l2_videodevice.cpp
index da2af6a1..33cd9fa4 100644
--- a/src/libcamera/v4l2_videodevice.cpp
+++ b/src/libcamera/v4l2_videodevice.cpp
@@ -1519,9 +1519,28 @@ FrameBuffer *V4L2VideoDevice::dequeueBuffer()
LOG(V4L2, Debug) << "Dequeuing buffer " << buf.index;
+ auto it = queuedBuffers_.find(buf.index);
+ /*
+ * If the video node fails to stream-on successfully (which can occur
+ * when queuing a buffer), a vb2 kernel bug can lead to the buffer which
+ * returns a failure upon queuing, being mistakenly kept in the kernel.
+ * This leads to the kernel notifying us that a buffer is available to
+ * dequeue, which we have no awareness of being queued, and thus we will
+ * not find it in the queuedBuffers_ list.
+ *
+ * Whilst this is a kernel bug and should be fixed there, ensure that we
+ * safely ignore buffers which are unexpected to prevent crashes on
+ * unpatched kernels.
+ */
+ if (it == queuedBuffers_.end()) {
+ LOG(V4L2, Error)
+ << "Dequeued an unexpected buffer: " << buf.index;
+
+ return nullptr;
+ }
+
cache_->put(buf.index);
- auto it = queuedBuffers_.find(buf.index);
FrameBuffer *buffer = it->second;
queuedBuffers_.erase(it);