CVE-2020-15190: NULL Pointer Dereference (CWE-476)
value: In Tensorflow before versions 1.15.4, 2.0.3, 2.1.2, 2.2.1 and 2.3.1, the `tf.raw_ops.Switch` operation takes as input a tensor and a boolean and outputs two tensors. Depending on the boolean value, one of the tensors is exactly the input tensor whereas the other one should be an empty tensor. However, the eager runtime traverses all tensors in the output. Since only one of the tensors is defined, the other one is `nullptr`, hence we are binding a reference to `nullptr`. This is undefined behavior and reported as an error if compiling with `-fsanitize=null`. In this case, this results in a segmentation fault The issue is patched in commit da8558533d925694483d2c136a9220d6d49d843c, and is released in TensorFlow versions 1.15.4, 2.0.3, 2.1.2, 2.2.1, or 2.3.1.
CWE description: The product dereferences a pointer that it expects to be valid but is NULL.
CVSS v3 base score: 5.3
Published: 2020-09-25T19:15Z
Repository: https://github.com/tensorflow/tensorflow
Language: Python
Files changed: tensorflow/core/common_runtime/eager/kernel_and_device.cc, tensorflow/python/kernel_tests/control_flow_ops_py_test.py
Commit date: 2020-09-18 21:20:16 -0700
Commit message: Fix undefined behavior in `tf.raw_ops.Switch` in eager mode.

PiperOrigin-RevId: 332578058
Change-Id: I9727571d2f21476b10d8aa27c1b7176564b76ac9

Diff: diff --git a/tensorflow/core/common_runtime/eager/kernel_and_device.cc b/tensorflow/core/common_runtime/eager/kernel_and_device.cc
index a022b6defbc..e0e87c36f03 100644
--- a/tensorflow/core/common_runtime/eager/kernel_and_device.cc
+++ b/tensorflow/core/common_runtime/eager/kernel_and_device.cc
@@ -306,11 +306,16 @@ Status KernelAndDeviceOp::Run(
   if (!context.status().ok()) return context.status();
 
   if (outputs != nullptr) {
     outputs->clear();
     for (int i = 0; i < context.num_outputs(); ++i) {
-      outputs->push_back(Tensor(*context.mutable_output(i)));
+      const auto* output_tensor = context.mutable_output(i);
+      if (output_tensor != nullptr) {
+        outputs->push_back(Tensor(*output_tensor));
+      } else {
+        outputs->push_back(Tensor());
+      }
     }
   }
   return Status::OK();
 }
 
diff --git a/tensorflow/python/kernel_tests/control_flow_ops_py_test.py b/tensorflow/python/kernel_tests/control_flow_ops_py_test.py
index 2e13414f720..68ddbe12f16 100644
--- a/tensorflow/python/kernel_tests/control_flow_ops_py_test.py
+++ b/tensorflow/python/kernel_tests/control_flow_ops_py_test.py
@@ -4577,10 +4577,18 @@ class ControlFlowTest(test.TestCase, parameterized.TestCase):
       cond = constant_op.constant(True, dtypes.bool)
       v_f, v_t = control_flow_ops.switch(constant_uint64, cond)
       result = control_flow_ops.merge([v_f, v_t])
       self.evaluate(result)
 
+  def testSwitchEagerMode(self):
+    if not context.executing_eagerly():
+      return
+    input_data = [1, 2, 3, 4]
+    vf, vt = control_flow_ops.switch(input_data, False)
+    self.assertAllEqual(vf, input_data)
+    self.assertAllEqual(vt, [])
+
   @test_util.run_deprecated_v1
   def testQIntArgAndRet(self):
 
     @function.Defun(dtypes.qint8)
     def func(x):

Vulnerable code:       outputs->push_back(Tensor(*context.mutable_output(i)));
Fixed code:       const auto* output_tensor = context.mutable_output(i);
      if (output_tensor != nullptr) {
        outputs->push_back(Tensor(*output_tensor));
      } else {
        outputs->push_back(Tensor());
      }
  def testSwitchEagerMode(self):
    if not context.executing_eagerly():
      return
    input_data = [1, 2, 3, 4]
    vf, vt = control_flow_ops.switch(input_data, False)
    self.assertAllEqual(vf, input_data)
    self.assertAllEqual(vt, [])