CVE-2020-15209

Tensorflow versions 1.15.4, 2.0.3, 2.1.2, 2.2.1, and 2.3.1 include a fix for CVE-2020-15209: In tensorflow-lite before versions 1.15.4, 2.0.3, 2.1.2, 2.2.1 and 2.3.1, a crafted TFLite model can force a node to have as input a tensor backed by a "nullptr" buffer. This can be achieved by changing a buffer index in the flatbuffer serialization to convert a read-only tensor to a read-write one. The runtime assumes that these buffers are written to before a possible read, hence they are initialized with "nullptr". However, by changing the buffer index for a tensor and implicitly converting that tensor to be a read-write one, as there is nothing in the model that writes to it, we get a null pointer dereference. The issue was patched in commit 0b5662bc.