Merge changes I129b5a7f,I633f293e

* changes:
  Allow screen capture for a specified uid.
  Store Layer ownerUid based on metadata or callingUid.
diff --git a/libs/gui/LayerState.cpp b/libs/gui/LayerState.cpp
index b215756..d07d435 100644
--- a/libs/gui/LayerState.cpp
+++ b/libs/gui/LayerState.cpp
@@ -509,7 +509,8 @@
     status_t status = output.writeInt32(static_cast<int32_t>(pixelFormat)) ?:
         output.write(sourceCrop) ?:
         output.writeFloat(frameScale) ?:
-        output.writeBool(captureSecureLayers);
+        output.writeBool(captureSecureLayers) ?:
+        output.writeInt32(uid);
     return status;
 }
 
@@ -518,7 +519,8 @@
     status_t status = input.readInt32(&format) ?:
         input.read(sourceCrop) ?:
         input.readFloat(&frameScale) ?:
-        input.readBool(&captureSecureLayers);
+        input.readBool(&captureSecureLayers) ?:
+        input.readInt32(&uid);
 
     pixelFormat = static_cast<ui::PixelFormat>(format);
     return status;
diff --git a/libs/gui/include/gui/LayerState.h b/libs/gui/include/gui/LayerState.h
index 5e1066b..387ddea 100644
--- a/libs/gui/include/gui/LayerState.h
+++ b/libs/gui/include/gui/LayerState.h
@@ -314,12 +314,14 @@
 bool ValidateFrameRate(float frameRate, int8_t compatibility, const char* functionName);
 
 struct CaptureArgs {
+    const static int32_t UNSET_UID = -1;
     virtual ~CaptureArgs() = default;
 
     ui::PixelFormat pixelFormat{ui::PixelFormat::RGBA_8888};
     Rect sourceCrop;
     float frameScale{1};
     bool captureSecureLayers{false};
+    int32_t uid{UNSET_UID};
 
     virtual status_t write(Parcel& output) const;
     virtual status_t read(const Parcel& input);
diff --git a/services/surfaceflinger/Layer.cpp b/services/surfaceflinger/Layer.cpp
index 89c95d2..9fae1a8 100644
--- a/services/surfaceflinger/Layer.cpp
+++ b/services/surfaceflinger/Layer.cpp
@@ -39,6 +39,7 @@
 #include <gui/LayerDebugInfo.h>
 #include <gui/Surface.h>
 #include <math.h>
+#include <private/android_filesystem_config.h>
 #include <renderengine/RenderEngine.h>
 #include <stdint.h>
 #include <stdlib.h>
@@ -139,6 +140,14 @@
 
     mCallingPid = args.callingPid;
     mCallingUid = args.callingUid;
+
+    if (mCallingUid == AID_GRAPHICS || mCallingUid == AID_SYSTEM) {
+        // If the system didn't send an ownerUid, use the callingUid for the ownerUid.
+        mOwnerUid = args.metadata.getInt32(METADATA_OWNER_UID, mCallingUid);
+    } else {
+        // A create layer request from a non system request cannot specify the owner uid
+        mOwnerUid = mCallingUid;
+    }
 }
 
 void Layer::onFirstRef() {
@@ -1669,8 +1678,8 @@
 }
 
 void Layer::dumpCallingUidPid(std::string& result) const {
-    StringAppendF(&result, "Layer %s (%s) pid:%d uid:%d\n", getName().c_str(), getType(),
-                  mCallingPid, mCallingUid);
+    StringAppendF(&result, "Layer %s (%s) callingPid:%d callingUid:%d ownerUid:%d\n",
+                  getName().c_str(), getType(), mCallingPid, mCallingUid, mOwnerUid);
 }
 
 void Layer::onDisconnect() {
@@ -2343,6 +2352,8 @@
         }
 
         layerInfo->set_is_relative_of(state.isRelativeOf);
+
+        layerInfo->set_owner_uid(mOwnerUid);
     }
 
     if (traceFlags & SurfaceTracing::TRACE_INPUT) {
diff --git a/services/surfaceflinger/Layer.h b/services/surfaceflinger/Layer.h
index 99b1bb1..8d8ab6d 100644
--- a/services/surfaceflinger/Layer.h
+++ b/services/surfaceflinger/Layer.h
@@ -436,9 +436,7 @@
     // Deprecated, please use compositionengine::Output::belongsInOutput()
     // instead.
     // TODO(lpique): Move the remaining callers (screencap) to the new function.
-    bool belongsToDisplay(uint32_t layerStack, bool isPrimaryDisplay) const {
-        return getLayerStack() == layerStack && (!mPrimaryDisplayOnly || isPrimaryDisplay);
-    }
+    bool belongsToDisplay(uint32_t layerStack) const { return getLayerStack() == layerStack; }
 
     FloatRect getBounds(const Region& activeTransparentRegion) const;
     FloatRect getBounds() const;
@@ -967,6 +965,8 @@
      */
     virtual bool needsInputInfo() const { return hasInputInfo(); }
 
+    uid_t getOwnerUid() { return mOwnerUid; }
+
 protected:
     compositionengine::OutputLayer* findOutputLayerForDisplay(const DisplayDevice*) const;
 
@@ -1089,6 +1089,10 @@
     pid_t mCallingPid;
     uid_t mCallingUid;
 
+    // The owner of the layer. If created from a non system process, it will be the calling uid.
+    // If created from a system process, the value can be passed in.
+    uid_t mOwnerUid;
+
     // The current layer is a clone of mClonedFrom. This means that this layer will update it's
     // properties based on mClonedFrom. When mClonedFrom latches a new buffer for BufferLayers,
     // this layer will update it's buffer. When mClonedFrom updates it's drawing state, children,
diff --git a/services/surfaceflinger/RegionSamplingThread.cpp b/services/surfaceflinger/RegionSamplingThread.cpp
index 17daadb..4e841e9 100644
--- a/services/surfaceflinger/RegionSamplingThread.cpp
+++ b/services/surfaceflinger/RegionSamplingThread.cpp
@@ -429,7 +429,7 @@
                   bounds.top, bounds.right, bounds.bottom);
             visitor(layer);
         };
-        mFlinger.traverseLayersInLayerStack(layerStack, filterVisitor);
+        mFlinger.traverseLayersInLayerStack(layerStack, CaptureArgs::UNSET_UID, filterVisitor);
     };
 
     sp<GraphicBuffer> buffer = nullptr;
diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index 9d9a4cf..6fae56a 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -4958,11 +4958,13 @@
         // special permissions.
         case SET_FRAME_RATE:
         case GET_DISPLAY_BRIGHTNESS_SUPPORT:
+        // captureLayers and captureDisplay will handle the permission check in the function
+        case CAPTURE_LAYERS:
+        case CAPTURE_DISPLAY:
         case SET_DISPLAY_BRIGHTNESS: {
             return OK;
         }
-        case CAPTURE_LAYERS:
-        case CAPTURE_DISPLAY:
+
         case ADD_REGION_SAMPLING_LISTENER:
         case REMOVE_REGION_SAMPLING_LISTENER: {
             // codes that require permission check
@@ -5434,10 +5436,33 @@
     }
 }
 
+static status_t validateScreenshotPermissions(const CaptureArgs& captureArgs) {
+    IPCThreadState* ipc = IPCThreadState::self();
+    const int pid = ipc->getCallingPid();
+    const int uid = ipc->getCallingUid();
+    if (uid == AID_GRAPHICS || PermissionCache::checkPermission(sReadFramebuffer, pid, uid)) {
+        return OK;
+    }
+
+    // If the caller doesn't have the correct permissions but is only attempting to screenshot
+    // itself, we allow it to continue.
+    if (captureArgs.uid == uid) {
+        return OK;
+    }
+
+    ALOGE("Permission Denial: can't take screenshot pid=%d, uid=%d", pid, uid);
+    return PERMISSION_DENIED;
+}
+
 status_t SurfaceFlinger::captureDisplay(const DisplayCaptureArgs& args,
                                         ScreenCaptureResults& captureResults) {
     ATRACE_CALL();
 
+    status_t validate = validateScreenshotPermissions(args);
+    if (validate != OK) {
+        return validate;
+    }
+
     if (!args.displayToken) return BAD_VALUE;
 
     auto renderAreaRotation = ui::Transform::toRotationFlags(args.rotation);
@@ -5472,8 +5497,8 @@
                                          renderAreaRotation, args.captureSecureLayers);
     });
 
-    auto traverseLayers = [this, layerStack](const LayerVector::Visitor& visitor) {
-        traverseLayersInLayerStack(layerStack, visitor);
+    auto traverseLayers = [this, args, layerStack](const LayerVector::Visitor& visitor) {
+        traverseLayersInLayerStack(layerStack, args.uid, visitor);
     };
     return captureScreenCommon(std::move(renderAreaFuture), traverseLayers, reqSize,
                                args.pixelFormat, args.useIdentityTransform, captureResults);
@@ -5567,7 +5592,7 @@
     });
 
     auto traverseLayers = [this, layerStack](const LayerVector::Visitor& visitor) {
-        traverseLayersInLayerStack(layerStack, visitor);
+        traverseLayersInLayerStack(layerStack, CaptureArgs::UNSET_UID, visitor);
     };
 
     return captureScreenCommon(std::move(renderAreaFuture), traverseLayers, size,
@@ -5579,6 +5604,11 @@
                                        ScreenCaptureResults& captureResults) {
     ATRACE_CALL();
 
+    status_t validate = validateScreenshotPermissions(args);
+    if (validate != OK) {
+        return validate;
+    }
+
     ui::Size reqSize;
     sp<Layer> parent;
     Rect crop(args.sourceCrop);
@@ -5652,19 +5682,19 @@
     }
 
     bool childrenOnly = args.childrenOnly;
-
     RenderAreaFuture renderAreaFuture = promise::defer([=]() -> std::unique_ptr<RenderArea> {
         return std::make_unique<LayerRenderArea>(*this, parent, crop, reqSize, dataspace,
                                                  childrenOnly, displayViewport,
                                                  captureSecureLayers);
     });
 
-    auto traverseLayers = [parent, childrenOnly,
-                           &excludeLayers](const LayerVector::Visitor& visitor) {
+    auto traverseLayers = [parent, args, &excludeLayers](const LayerVector::Visitor& visitor) {
         parent->traverseChildrenInZOrder(LayerVector::StateSet::Drawing, [&](Layer* layer) {
             if (!layer->isVisible()) {
                 return;
-            } else if (childrenOnly && layer == parent.get()) {
+            } else if (args.childrenOnly && layer == parent.get()) {
+                return;
+            } else if (args.uid != CaptureArgs::UNSET_UID && args.uid != layer->getOwnerUid()) {
                 return;
             }
 
@@ -5890,22 +5920,25 @@
     layersSortedByZ.traverseInReverseZOrder(stateSet, visitor);
 }
 
-void SurfaceFlinger::traverseLayersInLayerStack(ui::LayerStack layerStack,
+void SurfaceFlinger::traverseLayersInLayerStack(ui::LayerStack layerStack, const int32_t uid,
                                                 const LayerVector::Visitor& visitor) {
     // We loop through the first level of layers without traversing,
     // as we need to determine which layers belong to the requested display.
     for (const auto& layer : mDrawingState.layersSortedByZ) {
-        if (!layer->belongsToDisplay(layerStack, false)) {
+        if (!layer->belongsToDisplay(layerStack)) {
             continue;
         }
         // relative layers are traversed in Layer::traverseInZOrder
         layer->traverseInZOrder(LayerVector::StateSet::Drawing, [&](Layer* layer) {
-            if (!layer->belongsToDisplay(layerStack, false)) {
+            if (layer->getPrimaryDisplayOnly()) {
                 return;
             }
             if (!layer->isVisible()) {
                 return;
             }
+            if (uid != CaptureArgs::UNSET_UID && layer->getOwnerUid() != uid) {
+                return;
+            }
             visitor(layer);
         });
     }
diff --git a/services/surfaceflinger/SurfaceFlinger.h b/services/surfaceflinger/SurfaceFlinger.h
index 6c00931..a1b9b14 100644
--- a/services/surfaceflinger/SurfaceFlinger.h
+++ b/services/surfaceflinger/SurfaceFlinger.h
@@ -731,7 +731,9 @@
     sp<DisplayDevice> getDisplayByIdOrLayerStack(uint64_t displayOrLayerStack) REQUIRES(mStateLock);
     sp<DisplayDevice> getDisplayByLayerStack(uint64_t layerStack) REQUIRES(mStateLock);
 
-    void traverseLayersInLayerStack(ui::LayerStack, const LayerVector::Visitor&);
+    // If the uid provided is not UNSET_UID, the traverse will skip any layers that don't have a
+    // matching ownerUid
+    void traverseLayersInLayerStack(ui::LayerStack, const int32_t uid, const LayerVector::Visitor&);
 
     sp<StartPropertySetThread> mStartPropertySetThread;
 
diff --git a/services/surfaceflinger/layerproto/LayerProtoParser.cpp b/services/surfaceflinger/layerproto/LayerProtoParser.cpp
index 8fce0c9..aef670d 100644
--- a/services/surfaceflinger/layerproto/LayerProtoParser.cpp
+++ b/services/surfaceflinger/layerproto/LayerProtoParser.cpp
@@ -115,6 +115,7 @@
     }
     layer.cornerRadiusCrop = generateFloatRect(layerProto.corner_radius_crop());
     layer.shadowRadius = layerProto.shadow_radius();
+    layer.ownerUid = layerProto.owner_uid();
     return layer;
 }
 
@@ -276,7 +277,7 @@
 
 std::string LayerProtoParser::Layer::to_string() const {
     std::string result;
-    StringAppendF(&result, "+ %s (%s)\n", type.c_str(), name.c_str());
+    StringAppendF(&result, "+ %s (%s) uid=%d\n", type.c_str(), name.c_str(), ownerUid);
     result.append(transparentRegion.to_string("TransparentRegion").c_str());
     result.append(visibleRegion.to_string("VisibleRegion").c_str());
     result.append(damageRegion.to_string("SurfaceDamageRegion").c_str());
diff --git a/services/surfaceflinger/layerproto/include/layerproto/LayerProtoParser.h b/services/surfaceflinger/layerproto/include/layerproto/LayerProtoParser.h
index 52b9165..c48354f 100644
--- a/services/surfaceflinger/layerproto/include/layerproto/LayerProtoParser.h
+++ b/services/surfaceflinger/layerproto/include/layerproto/LayerProtoParser.h
@@ -114,6 +114,7 @@
         LayerMetadata metadata;
         LayerProtoParser::FloatRect cornerRadiusCrop;
         float shadowRadius;
+        uid_t ownerUid;
 
         std::string to_string() const;
     };
diff --git a/services/surfaceflinger/layerproto/layers.proto b/services/surfaceflinger/layerproto/layers.proto
index 8458d54..41d6d08 100644
--- a/services/surfaceflinger/layerproto/layers.proto
+++ b/services/surfaceflinger/layerproto/layers.proto
@@ -123,6 +123,8 @@
   bool is_relative_of = 51;
   // Layer's background blur radius in pixels.
   int32 background_blur_radius = 52;
+
+  uint32 owner_uid = 53;
 }
 
 message PositionProto {
diff --git a/services/surfaceflinger/tests/LayerTransaction_test.cpp b/services/surfaceflinger/tests/LayerTransaction_test.cpp
index 0ef4150..8d715e1 100644
--- a/services/surfaceflinger/tests/LayerTransaction_test.cpp
+++ b/services/surfaceflinger/tests/LayerTransaction_test.cpp
@@ -18,7 +18,6 @@
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wconversion"
 
-#include <private/android_filesystem_config.h>
 #include <thread>
 #include "LayerTransactionTest.h"
 
@@ -26,40 +25,6 @@
 
 using android::hardware::graphics::common::V1_1::BufferUsage;
 
-TEST_F(LayerTransactionTest, SetFlagsSecureEUidSystem) {
-    sp<SurfaceControl> layer;
-    ASSERT_NO_FATAL_FAILURE(layer = createLayer("test", 32, 32));
-    ASSERT_NO_FATAL_FAILURE(fillBufferQueueLayerColor(layer, Color::RED, 32, 32));
-
-    sp<ISurfaceComposer> composer = ComposerService::getComposerService();
-    Transaction()
-            .setFlags(layer, layer_state_t::eLayerSecure, layer_state_t::eLayerSecure)
-            .apply(true);
-    ASSERT_EQ(PERMISSION_DENIED, composer->captureDisplay(mCaptureArgs, mCaptureResults));
-
-    UIDFaker f(AID_SYSTEM);
-
-    // By default the system can capture screenshots with secure layers but they
-    // will be blacked out
-    ASSERT_EQ(NO_ERROR, composer->captureDisplay(mCaptureArgs, mCaptureResults));
-
-    {
-        SCOPED_TRACE("as system");
-        auto shot = screenshot();
-        shot->expectColor(Rect(0, 0, 32, 32), Color::BLACK);
-    }
-
-    // Here we pass captureSecureLayers = true and since we are AID_SYSTEM we should be able
-    // to receive them...we are expected to take care with the results.
-    DisplayCaptureArgs args;
-    args.displayToken = mDisplay;
-    args.captureSecureLayers = true;
-    ASSERT_EQ(NO_ERROR, composer->captureDisplay(args, mCaptureResults));
-    ASSERT_EQ(true, mCaptureResults.capturedSecureLayers);
-    ScreenCapture sc(mCaptureResults.buffer);
-    sc.expectColor(Rect(0, 0, 32, 32), Color::RED);
-}
-
 TEST_F(LayerTransactionTest, SetTransformToDisplayInverse_BufferState) {
     sp<SurfaceControl> layer;
     ASSERT_NO_FATAL_FAILURE(
diff --git a/services/surfaceflinger/tests/ScreenCapture_test.cpp b/services/surfaceflinger/tests/ScreenCapture_test.cpp
index 149e4d7..690f758 100644
--- a/services/surfaceflinger/tests/ScreenCapture_test.cpp
+++ b/services/surfaceflinger/tests/ScreenCapture_test.cpp
@@ -74,6 +74,42 @@
     std::unique_ptr<ScreenCapture> mCapture;
 };
 
+TEST_F(ScreenCaptureTest, SetFlagsSecureEUidSystem) {
+    sp<SurfaceControl> layer;
+    ASSERT_NO_FATAL_FAILURE(
+            layer = createLayer("test", 32, 32,
+                                ISurfaceComposerClient::eSecure |
+                                        ISurfaceComposerClient::eFXSurfaceBufferQueue));
+    ASSERT_NO_FATAL_FAILURE(fillBufferQueueLayerColor(layer, Color::RED, 32, 32));
+
+    Transaction().show(layer).setLayer(layer, INT32_MAX).apply(true);
+
+    sp<ISurfaceComposer> composer = ComposerService::getComposerService();
+    ASSERT_EQ(PERMISSION_DENIED, composer->captureDisplay(mCaptureArgs, mCaptureResults));
+
+    UIDFaker f(AID_SYSTEM);
+
+    // By default the system can capture screenshots with secure layers but they
+    // will be blacked out
+    ASSERT_EQ(NO_ERROR, composer->captureDisplay(mCaptureArgs, mCaptureResults));
+
+    {
+        SCOPED_TRACE("as system");
+        auto shot = screenshot();
+        shot->expectColor(Rect(0, 0, 32, 32), Color::BLACK);
+    }
+
+    // Here we pass captureSecureLayers = true and since we are AID_SYSTEM we should be able
+    // to receive them...we are expected to take care with the results.
+    DisplayCaptureArgs args;
+    args.displayToken = mDisplay;
+    args.captureSecureLayers = true;
+    ASSERT_EQ(NO_ERROR, composer->captureDisplay(args, mCaptureResults));
+    ASSERT_TRUE(mCaptureResults.capturedSecureLayers);
+    ScreenCapture sc(mCaptureResults.buffer);
+    sc.expectColor(Rect(0, 0, 32, 32), Color::RED);
+}
+
 TEST_F(ScreenCaptureTest, CaptureSingleLayer) {
     LayerCaptureArgs captureArgs;
     captureArgs.layerHandle = mBGSurfaceControl->getHandle();
@@ -494,6 +530,128 @@
     mCapture->expectColor(Rect(30, 30, 60, 60), Color::RED);
 }
 
+TEST_F(ScreenCaptureTest, CaptureDisplayWithUid) {
+    uid_t fakeUid = 12345;
+
+    DisplayCaptureArgs captureArgs;
+    captureArgs.displayToken = mDisplay;
+
+    sp<SurfaceControl> layer;
+    ASSERT_NO_FATAL_FAILURE(layer = createLayer("test layer", 32, 32,
+                                                ISurfaceComposerClient::eFXSurfaceBufferQueue,
+                                                mBGSurfaceControl.get()));
+    ASSERT_NO_FATAL_FAILURE(fillBufferQueueLayerColor(layer, Color::RED, 32, 32));
+
+    Transaction().show(layer).setLayer(layer, INT32_MAX).apply();
+
+    // Make sure red layer with the background layer is screenshot.
+    ScreenCapture::captureDisplay(&mCapture, captureArgs);
+    mCapture->expectColor(Rect(0, 0, 32, 32), Color::RED);
+    mCapture->expectBorder(Rect(0, 0, 32, 32), {63, 63, 195, 255});
+
+    // From non system uid, can't request screenshot without a specified uid.
+    UIDFaker f(fakeUid);
+    sp<ISurfaceComposer> composer = ComposerService::getComposerService();
+    ASSERT_EQ(PERMISSION_DENIED, composer->captureDisplay(captureArgs, mCaptureResults));
+
+    // Make screenshot request with current uid set. No layers were created with the current
+    // uid so screenshot will be black.
+    captureArgs.uid = fakeUid;
+    ScreenCapture::captureDisplay(&mCapture, captureArgs);
+    mCapture->expectColor(Rect(0, 0, 32, 32), Color::BLACK);
+    mCapture->expectBorder(Rect(0, 0, 32, 32), Color::BLACK);
+
+    sp<SurfaceControl> layerWithFakeUid;
+    // Create a new layer with the current uid
+    ASSERT_NO_FATAL_FAILURE(layerWithFakeUid =
+                                    createLayer("new test layer", 32, 32,
+                                                ISurfaceComposerClient::eFXSurfaceBufferQueue,
+                                                mBGSurfaceControl.get()));
+    ASSERT_NO_FATAL_FAILURE(fillBufferQueueLayerColor(layerWithFakeUid, Color::GREEN, 32, 32));
+    Transaction()
+            .show(layerWithFakeUid)
+            .setLayer(layerWithFakeUid, INT32_MAX)
+            .setPosition(layerWithFakeUid, 128, 128)
+            .apply();
+
+    // Screenshot from the fakeUid caller with the uid requested allows the layer
+    // with that uid to be screenshotted. Everything else is black
+    ScreenCapture::captureDisplay(&mCapture, captureArgs);
+    mCapture->expectColor(Rect(128, 128, 160, 160), Color::GREEN);
+    mCapture->expectBorder(Rect(128, 128, 160, 160), Color::BLACK);
+}
+
+TEST_F(ScreenCaptureTest, CaptureLayerWithUid) {
+    uid_t fakeUid = 12345;
+
+    sp<SurfaceControl> layer;
+    ASSERT_NO_FATAL_FAILURE(layer = createLayer("test layer", 32, 32,
+                                                ISurfaceComposerClient::eFXSurfaceBufferQueue,
+                                                mBGSurfaceControl.get()));
+    ASSERT_NO_FATAL_FAILURE(fillBufferQueueLayerColor(layer, Color::RED, 32, 32));
+
+    Transaction().show(layer).setLayer(layer, INT32_MAX).apply();
+
+    LayerCaptureArgs captureArgs;
+    captureArgs.layerHandle = mBGSurfaceControl->getHandle();
+    captureArgs.childrenOnly = false;
+
+    // Make sure red layer with the background layer is screenshot.
+    ScreenCapture::captureLayers(&mCapture, captureArgs);
+    mCapture->expectColor(Rect(0, 0, 32, 32), Color::RED);
+    mCapture->expectBorder(Rect(0, 0, 32, 32), {63, 63, 195, 255});
+
+    // From non system uid, can't request screenshot without a specified uid.
+    std::unique_ptr<UIDFaker> uidFaker = std::make_unique<UIDFaker>(fakeUid);
+
+    sp<ISurfaceComposer> composer = ComposerService::getComposerService();
+    ASSERT_EQ(PERMISSION_DENIED, composer->captureLayers(captureArgs, mCaptureResults));
+
+    // Make screenshot request with current uid set. No layers were created with the current
+    // uid so screenshot will be black.
+    captureArgs.uid = fakeUid;
+    ScreenCapture::captureLayers(&mCapture, captureArgs);
+    mCapture->expectColor(Rect(0, 0, 32, 32), Color::TRANSPARENT);
+    mCapture->expectBorder(Rect(0, 0, 32, 32), Color::TRANSPARENT);
+
+    sp<SurfaceControl> layerWithFakeUid;
+    // Create a new layer with the current uid
+    ASSERT_NO_FATAL_FAILURE(layerWithFakeUid =
+                                    createLayer("new test layer", 32, 32,
+                                                ISurfaceComposerClient::eFXSurfaceBufferQueue,
+                                                mBGSurfaceControl.get()));
+    ASSERT_NO_FATAL_FAILURE(fillBufferQueueLayerColor(layerWithFakeUid, Color::GREEN, 32, 32));
+    Transaction()
+            .show(layerWithFakeUid)
+            .setLayer(layerWithFakeUid, INT32_MAX)
+            .setPosition(layerWithFakeUid, 128, 128)
+            // reparent a layer that was created with a different uid to the new layer.
+            .reparent(layer, layerWithFakeUid->getHandle())
+            .apply();
+
+    // Screenshot from the fakeUid caller with the uid requested allows the layer
+    // with that uid to be screenshotted. The child layer is skipped since it was created
+    // from a different uid.
+    ScreenCapture::captureLayers(&mCapture, captureArgs);
+    mCapture->expectColor(Rect(128, 128, 160, 160), Color::GREEN);
+    mCapture->expectBorder(Rect(128, 128, 160, 160), Color::TRANSPARENT);
+
+    // Clear fake calling uid so it's back to system.
+    uidFaker = nullptr;
+    // Screenshot from the test caller with the uid requested allows the layer
+    // with that uid to be screenshotted. The child layer is skipped since it was created
+    // from a different uid.
+    ScreenCapture::captureLayers(&mCapture, captureArgs);
+    mCapture->expectColor(Rect(128, 128, 160, 160), Color::GREEN);
+    mCapture->expectBorder(Rect(128, 128, 160, 160), Color::TRANSPARENT);
+
+    // Screenshot from the fakeUid caller with no uid requested allows everything to be screenshot.
+    captureArgs.uid = -1;
+    ScreenCapture::captureLayers(&mCapture, captureArgs);
+    mCapture->expectColor(Rect(128, 128, 160, 160), Color::RED);
+    mCapture->expectBorder(Rect(128, 128, 160, 160), {63, 63, 195, 255});
+}
+
 // In the following tests we verify successful skipping of a parent layer,
 // so we use the same verification logic and only change how we mutate
 // the parent layer to verify that various properties are ignored.
diff --git a/services/surfaceflinger/tests/unittests/CompositionTest.cpp b/services/surfaceflinger/tests/unittests/CompositionTest.cpp
index 48c4e18..dc8b31e 100644
--- a/services/surfaceflinger/tests/unittests/CompositionTest.cpp
+++ b/services/surfaceflinger/tests/unittests/CompositionTest.cpp
@@ -241,7 +241,8 @@
                                                 ui::Dataspace::V0_SRGB, ui::Transform::ROT_0);
 
     auto traverseLayers = [this](const LayerVector::Visitor& visitor) {
-        return mFlinger.traverseLayersInLayerStack(mDisplay->getLayerStack(), visitor);
+        return mFlinger.traverseLayersInLayerStack(mDisplay->getLayerStack(),
+                                                   CaptureArgs::UNSET_UID, visitor);
     };
 
     // TODO: Eliminate expensive/real allocation if possible.
diff --git a/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h b/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h
index 3941d42..8972907 100644
--- a/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h
+++ b/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h
@@ -343,9 +343,9 @@
                                                 regionSampling, captureResults);
     }
 
-    auto traverseLayersInLayerStack(ui::LayerStack layerStack,
+    auto traverseLayersInLayerStack(ui::LayerStack layerStack, int32_t uid,
                                     const LayerVector::Visitor& visitor) {
-        return mFlinger->SurfaceFlinger::traverseLayersInLayerStack(layerStack, visitor);
+        return mFlinger->SurfaceFlinger::traverseLayersInLayerStack(layerStack, uid, visitor);
     }
 
     auto getDisplayNativePrimaries(const sp<IBinder>& displayToken,
diff --git a/services/surfaceflinger/tests/utils/ScreenshotUtils.h b/services/surfaceflinger/tests/utils/ScreenshotUtils.h
index 56628f8..081d18b 100644
--- a/services/surfaceflinger/tests/utils/ScreenshotUtils.h
+++ b/services/surfaceflinger/tests/utils/ScreenshotUtils.h
@@ -31,16 +31,20 @@
         captureScreen(sc, SurfaceComposerClient::getInternalDisplayToken());
     }
 
-    static void captureScreen(std::unique_ptr<ScreenCapture>* sc, sp<IBinder> displayToken) {
+    static void captureDisplay(std::unique_ptr<ScreenCapture>* sc,
+                               const DisplayCaptureArgs& captureArgs) {
         const auto sf = ComposerService::getComposerService();
         SurfaceComposerClient::Transaction().apply(true);
 
+        ScreenCaptureResults captureResults;
+        ASSERT_EQ(NO_ERROR, sf->captureDisplay(captureArgs, captureResults));
+        *sc = std::make_unique<ScreenCapture>(captureResults.buffer);
+    }
+
+    static void captureScreen(std::unique_ptr<ScreenCapture>* sc, sp<IBinder> displayToken) {
         DisplayCaptureArgs args;
         args.displayToken = displayToken;
-
-        ScreenCaptureResults captureResults;
-        ASSERT_EQ(NO_ERROR, sf->captureDisplay(args, captureResults));
-        *sc = std::make_unique<ScreenCapture>(captureResults.buffer);
+        captureDisplay(sc, args);
     }
 
     static void captureLayers(std::unique_ptr<ScreenCapture>* sc,