HDFS-15910. Improve security with explicit_bzero (#2793)

(cherry picked from commit 714427c41401eacf3cab7c087d9e5d61a658716b)

hadoop-hdfs-project/hadoop-hdfs-native-client/src/main/native/libhdfspp/lib/bindings/c/hdfs.cc

@@ -1402,7 +1402,7 @@ int hdfsGetBlockLocations(hdfsFS fs, const char *path, struct hdfsBlockLocations
     hdfsBlockLocations *locations = new struct hdfsBlockLocations();
     (*locations_out) = locations;
 
-    bzero(locations, sizeof(*locations));
+    explicit_bzero(locations, sizeof(*locations));
     locations->fileLength = ppLocations->getFileLength();
     locations->isLastBlockComplete = ppLocations->isLastBlockComplete();
     locations->isUnderConstruction = ppLocations->isUnderConstruction();

hadoop-hdfs-project/hadoop-hdfs-native-client/src/main/native/libhdfspp/tests/hdfs_ext_test.cc

@@ -475,7 +475,7 @@ TEST_F(HdfsExtTest, TestReadStats) {
   hdfsFile file = hdfsOpenFile(fs, path.c_str(), O_WRONLY, 0, 0, 0);
   EXPECT_NE(nullptr, file);
   void * buf = malloc(size);
-  bzero(buf, size);
+  explicit_bzero(buf, size);
   EXPECT_EQ(size, hdfsWrite(fs, file, buf, size));
   free(buf);
   EXPECT_EQ(0, hdfsCloseFile(fs, file));

hadoop-hdfs-project/hadoop-hdfs-native-client/src/main/native/libhdfspp/tests/hdfspp_mini_dfs.h

@@ -92,7 +92,7 @@ public:
     hdfsFile file = hdfsOpenFile(*this, path.c_str(), O_WRONLY, 0, 0, 0);
     EXPECT_NE(nullptr, file);
     void * buf = malloc(size);
-    bzero(buf, size);
+    explicit_bzero(buf, size);
     EXPECT_EQ(1024, hdfsWrite(*this, file, buf, size));
     EXPECT_EQ(0, hdfsCloseFile(*this, file));
     free(buf);