audiortp: prevent out of bounds read

Add zero padding to pcm buffers (if needed) before encoding them to avoid
out of bounds memory access.

Refs #49181

Change-Id: I804aef3e1acf08301dde388780f4502e51bf57f2

daemon/src/audio/audiortp/audio_rtp_stream.cpp

@@ -343,6 +343,16 @@ size_t AudioRtpStream::processDataEncode()
             ERROR("Audio codec already destroyed");
             return 0;
         }
+
+        const auto frameSize = out->frames();
+        const auto codecFrameSize = codec->getFrameSize();
+        if (codecFrameSize > frameSize) {
+            // PCM too small (underflow), add zero padding to avoid reading past
+            // end of buffer when encoding, for every channel
+            for (auto &c : out->getData())
+                c.resize(codecFrameSize, 0);
+        }
+
         size_t encoded = codec->encode(out->getData(), encodedData_.data(), encodedData_.size());
         return encoded;
     }