LayerStats: Fix a use-after-free

std::string::c_str returns memory that's freed when the string dies. So,
this method should be returning the string, rather than a pointer to
it's freshly-deleted contents.

Caught by our static analyzer.

Bug: None
Test: Builds

Change-Id: I3dce7b60c6cfb4e3bfbd6c0dd6fe30dfe7f4313c

2 files changed, 4 insertions, 4 deletions

diff --git a/services/surfaceflinger/LayerStats.cpp b/services/surfaceflinger/LayerStats.cpp
index 04ab121560..2a679552eb 100644
--- a/services/surfaceflinger/LayerStats.cpp
+++ b/services/surfaceflinger/LayerStats.cpp
@@ -68,7 +68,7 @@ void LayerStats::traverseLayerTreeStatsLocked(
         base::StringAppendF(&key, ",%s", layerCompositionType(layer->hwcCompositionType));
         base::StringAppendF(&key, ",%d", layer->isProtected);
         base::StringAppendF(&key, ",%s", layerTransform(layer->hwcTransform));
-        base::StringAppendF(&key, ",%s", layerPixelFormat(layer->activeBuffer.format));
+        base::StringAppendF(&key, ",%s", layerPixelFormat(layer->activeBuffer.format).c_str());
         base::StringAppendF(&key, ",%s", layer->dataspace.c_str());
         base::StringAppendF(&key, ",%s",
                             destinationLocation(layer->hwcFrame.left, layerGlobal.resolution[0],
@@ -162,8 +162,8 @@ const char* LayerStats::layerCompositionType(int32_t compositionType) {
     return getCompositionName(static_cast<hwc2_composition_t>(compositionType));
 }
 
-const char* LayerStats::layerPixelFormat(int32_t pixelFormat) {
-    return decodePixelFormat(pixelFormat).c_str();
+std::string LayerStats::layerPixelFormat(int32_t pixelFormat) {
+    return decodePixelFormat(pixelFormat);
 }
 
 std::string LayerStats::scaleRatioWH(const LayerProtoParser::Layer* layer) {
diff --git a/services/surfaceflinger/LayerStats.h b/services/surfaceflinger/LayerStats.h
index 7a190fdb41..bd17d82781 100644
--- a/services/surfaceflinger/LayerStats.h
+++ b/services/surfaceflinger/LayerStats.h
@@ -50,7 +50,7 @@ private:
     // Return the name of the composition type
     static const char* layerCompositionType(int32_t compositionType);
     // Return the name of the pixel format
-    static const char* layerPixelFormat(int32_t pixelFormat);
+    static std::string layerPixelFormat(int32_t pixelFormat);
     // Calculate scale ratios of layer's width/height with rotation information
     static std::string scaleRatioWH(const LayerProtoParser::Layer* layer);
     // Calculate scale ratio from source to destination and convert to string