[Backport] CVE-2021-21160: Heap buffer overflow in WebAudio

Manual cherry-pick of patch originally reviewed on
https://chromium-review.googlesource.com/c/chromium/src/+/2727697:
Convert AudioParam NaN values to the default value

If any output value of an AudioParam (including the intrinsic values
and any inputs to the AudioParam), should be NaN, replace the NaN
value with the associated defaultValue.

This causes some slowdowns so SIMD/NEON code was added to mitigate the
degradation.  There is still some slowdown, but the worst case is now
about 7% slower on x86 and 10% on arm. Generally, the slowdown is less
than 2% and 5%, respectively.  (Perversely, some results got faster,
and the differences are statistically significant.)

Full details can be found at
https://docs.google.com/spreadsheets/d/1EhbLHm-9cUoEO5aj1vYemVBLQ3Dh4dCJPPLTfZPrZt4/edit?usp=sharing

Manually tested the test case from the bug and the issue no longer
occurs.

(cherry picked from commit ab1862017b5717271a28376659944dddc602195c)

(cherry picked from commit eb0c0353bf245885797d8ce0d1b864d88a381fbb)

Bug: 1170531
Change-Id: I00d902b40a9ef9da990c6d68b664b1dcfc31b091
Commit-Queue: Raymond Toy <[email protected]>
Reviewed-by: Hongchan Choi <[email protected]>
Cr-Original-Original-Commit-Position: refs/heads/master@{#851733}
Reviewed-by: Raymond Toy <[email protected]>
Cr-Original-Commit-Position: refs/branch-heads/4389@{#880}
Cr-Original-Branched-From: 9251c5db2b6d5a59fe4eac7aafa5fed37c139bb7-refs/heads/master@{#843830}
Reviewed-by: Victor-Gabriel Savu <[email protected]>
Commit-Queue: Artem Sumaneev <[email protected]>
Cr-Commit-Position: refs/branch-heads/4240@{#1551}
Cr-Branched-From: f297677702651916bbf65e59c0d4bbd4ce57d1ee-refs/heads/master@{#800218}
Reviewed-by: Allan Sandfeld Jensen <[email protected]>
Reviewed-by: Jüri Valdmann <[email protected]>

Author: Raymond Toy

chromium/third_party/blink/renderer/modules/webaudio/audio_param.cc

@@ -25,10 +25,12 @@
 
 #include "third_party/blink/renderer/modules/webaudio/audio_param.h"
 
+#include "build/build_config.h"
 #include "third_party/blink/renderer/core/inspector/console_message.h"
 #include "third_party/blink/renderer/modules/webaudio/audio_node.h"
 #include "third_party/blink/renderer/modules/webaudio/audio_node_output.h"
 #include "third_party/blink/renderer/platform/audio/audio_utilities.h"
+#include "third_party/blink/renderer/platform/audio/vector_math.h"
 #include "third_party/blink/renderer/platform/bindings/exception_state.h"
 #include "third_party/blink/renderer/platform/histogram.h"
 #include "third_party/blink/renderer/platform/wtf/math_extras.h"
@@ -227,6 +229,48 @@ void AudioParamHandler::CalculateSampleAccurateValues(
   CalculateFinalValues(values, number_of_values, IsAudioRate());
 }
 
+// Replace NaN values in |values| with |default_value|.
+static void HandleNaNValues(float* values,
+                            unsigned number_of_values,
+                            float default_value) {
+  unsigned k = 0;
+#if defined(ARCH_CPU_X86_FAMILY)
+  if (number_of_values >= 4) {
+    __m128 defaults = _mm_set1_ps(default_value);
+    for (k = 0; k < number_of_values; k += 4) {
+      __m128 v = _mm_loadu_ps(values + k);
+      // cmpuord returns all 1's if v is NaN for each elmeent of v.
+      __m128 isnan = _mm_cmpunord_ps(v, v);
+      // Replace NaN parts with default.
+      __m128 result = _mm_and_ps(isnan, defaults);
+      // Merge in the parts that aren't NaN
+      result = _mm_or_ps(_mm_andnot_ps(isnan, v), result);
+      _mm_storeu_ps(values + k, result);
+    }
+  }
+#elif defined(CPU_ARM_NEON)
+  if (number_of_values >= 4) {
+    uint32x4_t defaults = vreinterpretq_u32_f32(vdupq_n_f32(default_value));
+    for (k = 0; k < number_of_values; k += 4) {
+      float32x4_t v = vld1q_f32(values + k);
+      // Returns true (all ones) if v is not NaN
+      uint32x4_t is_not_nan = vceqq_f32(v, v);
+      // Get the parts that are not NaN
+      uint32x4_t result = vandq_u32(is_not_nan, vreinterpretq_u32_f32(v));
+      // Replace the parts that are NaN with the default and merge with previous
+      // result.  (Note: vbic_u32(x, y) = x and not y)
+      result = vorrq_u32(result, vbicq_u32(defaults, is_not_nan));
+      vst1q_f32(values + k, vreinterpretq_f32_u32(result));
+    }
+  }
+#endif
+  for (; k < number_of_values; ++k) {
+    if (std::isnan(values[k])) {
+      values[k] = default_value;
+    }
+  }
+}
+
 void AudioParamHandler::CalculateFinalValues(float* values,
                                              unsigned number_of_values,
                                              bool sample_accurate) {
@@ -276,6 +320,25 @@ void AudioParamHandler::CalculateFinalValues(float* values,
     // Sum, with unity-gain.
     summing_bus->SumFrom(*connection_bus);
   }
+
+    float min_value = MinValue();
+    float max_value = MaxValue();
+
+    if (NumberOfRenderingConnections() > 0) {
+      // AudioParams by themselves don't produce NaN because of the finite min
+      // and max values.  But an input to an AudioParam could have NaNs.
+      //
+      // NaN values in AudioParams must be replaced by the AudioParam's
+      // defaultValue.  Then these values must be clamped to lie in the nominal
+      // range between the AudioParam's minValue and maxValue.
+      //
+      // See https://webaudio.github.io/web-audio-api/#computation-of-value.
+      HandleNaNValues(values, number_of_values, DefaultValue());
+    }
+
+    VectorMath::Vclip(values, 1, &min_value, &max_value, values, 1,
+                       number_of_values);
+
 }
 
 void AudioParamHandler::CalculateTimelineValues(float* values,