am b9b75697: am 9b5ee4aa: Merge "Handle empty relro segment or incorrectly sized file."

* commit 'b9b75697fa6c58a85f48d7f31113814385a709bd':
  Handle empty relro segment or incorrectly sized file.

linker/linker_phdr.cpp

@@ -591,10 +591,13 @@ int phdr_table_map_gnu_relro(const ElfW(Phdr)* phdr_table, size_t phdr_count, El
     return -1;
   }
   off_t file_size = file_stat.st_size;
-  void* temp_mapping = mmap(NULL, file_size, PROT_READ, MAP_PRIVATE, fd, 0);
+  void* temp_mapping = NULL;
+  if (file_size > 0) {
+    temp_mapping = mmap(NULL, file_size, PROT_READ, MAP_PRIVATE, fd, 0);
     if (temp_mapping == MAP_FAILED) {
       return -1;
     }
+  }
   size_t file_offset = 0;
 
   // Iterate over the relro segments and compare/remap the pages.
@@ -614,6 +617,13 @@ int phdr_table_map_gnu_relro(const ElfW(Phdr)* phdr_table, size_t phdr_count, El
     size_t match_offset = 0;
     size_t size = seg_page_end - seg_page_start;
 
+    if (file_size - file_offset < size) {
+      // File is too short to compare to this segment. The contents are likely
+      // different as well (it's probably for a different library version) so
+      // just don't bother checking.
+      break;
+    }
+
     while (match_offset < size) {
       // Skip over dissimilar pages.
       while (match_offset < size &&

tests/Android.mk

@@ -198,17 +198,32 @@ include $(LOCAL_PATH)/Android.build.mk
 endif
 
 # -----------------------------------------------------------------------------
-# Library used by dlext tests.
+# Library used by dlext tests - with/without GNU RELRO program header
 # -----------------------------------------------------------------------------
 libdlext_test_src_files := \
     dlext_test_library.cpp \
 
+libdlext_test_ldflags := \
+    -Wl,-z,relro \
+
 module := libdlext_test
 module_tag := optional
 build_type := target
 build_target := SHARED_LIBRARY
 include $(LOCAL_PATH)/Android.build.mk
 
+libdlext_test_norelro_src_files := \
+    dlext_test_library.cpp \
+
+libdlext_test_norelro_ldflags := \
+    -Wl,-z,norelro \
+
+module := libdlext_test_norelro
+module_tag := optional
+build_type := target
+build_target := SHARED_LIBRARY
+include $(LOCAL_PATH)/Android.build.mk
+
 # -----------------------------------------------------------------------------
 # This library used by atexit tests
 # -----------------------------------------------------------------------------

tests/dlext_test.cpp

@@ -39,6 +39,7 @@
 
 typedef int (*fn)(void);
 #define LIBNAME "libdlext_test.so"
+#define LIBNAME_NORELRO "libdlext_test_norelro.so"
 #define LIBSIZE 1024*1024 // how much address space to reserve for it
 
 
@@ -144,28 +145,40 @@ TEST_F(DlExtTest, ReservedHintTooSmall) {
   EXPECT_EQ(4, f());
 }
 
-TEST_F(DlExtTest, RelroShareChildWrites) {
+class DlExtRelroSharingTest : public DlExtTest {
+protected:
+  virtual void SetUp() {
+    DlExtTest::SetUp();
     void* start = mmap(NULL, LIBSIZE, PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS,
                        -1, 0);
     ASSERT_TRUE(start != MAP_FAILED);
-  android_dlextinfo extinfo;
-  extinfo.reserved_addr = start;
-  extinfo.reserved_size = LIBSIZE;
+    extinfo_.flags = ANDROID_DLEXT_RESERVED_ADDRESS;
+    extinfo_.reserved_addr = start;
+    extinfo_.reserved_size = LIBSIZE;
+    extinfo_.relro_fd = -1;
 
-  int relro_fd;
-  char relro_file[PATH_MAX];
     const char* android_data = getenv("ANDROID_DATA");
     ASSERT_TRUE(android_data != NULL);
-  snprintf(relro_file, sizeof(relro_file), "%s/local/tmp/libdlext_test.relro", android_data);
-  relro_fd = open(relro_file, O_CREAT | O_RDWR | O_TRUNC, 0644);
-  extinfo.flags = ANDROID_DLEXT_RESERVED_ADDRESS | ANDROID_DLEXT_WRITE_RELRO;
+    snprintf(relro_file_, sizeof(relro_file_), "%s/local/tmp/libdlext_test.relro", android_data);
+  }
+
+  virtual void TearDown() {
+    DlExtTest::TearDown();
+    if (extinfo_.relro_fd != -1) {
+      ASSERT_NOERROR(close(extinfo_.relro_fd));
+    }
+  }
+
+  void CreateRelroFile(const char* lib) {
+    int relro_fd = open(relro_file_, O_CREAT | O_RDWR | O_TRUNC, 0644);
     ASSERT_NOERROR(relro_fd);
-  extinfo.relro_fd = relro_fd;
 
     pid_t pid = fork();
     if (pid == 0) {
       // child process
-    void* handle = android_dlopen_ext(LIBNAME, RTLD_NOW, &extinfo);
+      extinfo_.flags |= ANDROID_DLEXT_WRITE_RELRO;
+      extinfo_.relro_fd = relro_fd;
+      void* handle = android_dlopen_ext(lib, RTLD_NOW, &extinfo_);
       if (handle == NULL) {
         fprintf(stderr, "in child: %s\n", dlerror());
         exit(1);
@@ -181,15 +194,39 @@ TEST_F(DlExtTest, RelroShareChildWrites) {
     ASSERT_TRUE(WIFEXITED(status));
     ASSERT_EQ(0, WEXITSTATUS(status));
 
-  relro_fd = open(relro_file, O_RDONLY);
+    // reopen file for reading so it can be used
+    relro_fd = open(relro_file_, O_RDONLY);
     ASSERT_NOERROR(relro_fd);
-  extinfo.flags = ANDROID_DLEXT_RESERVED_ADDRESS | ANDROID_DLEXT_USE_RELRO;
-  extinfo.relro_fd = relro_fd;
-  handle_ = android_dlopen_ext(LIBNAME, RTLD_NOW, &extinfo);
-  ASSERT_NOERROR(close(relro_fd));
+    extinfo_.flags |= ANDROID_DLEXT_USE_RELRO;
+    extinfo_.relro_fd = relro_fd;
+  }
 
+  void TryUsingRelro(const char* lib) {
+    handle_ = android_dlopen_ext(lib, RTLD_NOW, &extinfo_);
     ASSERT_DL_NOTNULL(handle_);
     fn f = reinterpret_cast<fn>(dlsym(handle_, "getRandomNumber"));
     ASSERT_DL_NOTNULL(f);
     EXPECT_EQ(4, f());
+  }
+
+  android_dlextinfo extinfo_;
+  char relro_file_[PATH_MAX];
+};
+
+TEST_F(DlExtRelroSharingTest, ChildWritesGoodData) {
+  ASSERT_NO_FATAL_FAILURE(CreateRelroFile(LIBNAME));
+  ASSERT_NO_FATAL_FAILURE(TryUsingRelro(LIBNAME));
+}
+
+TEST_F(DlExtRelroSharingTest, ChildWritesNoRelro) {
+  ASSERT_NO_FATAL_FAILURE(CreateRelroFile(LIBNAME_NORELRO));
+  ASSERT_NO_FATAL_FAILURE(TryUsingRelro(LIBNAME_NORELRO));
+}
+
+TEST_F(DlExtRelroSharingTest, RelroFileEmpty) {
+  int relro_fd = open(relro_file_, O_CREAT | O_RDWR | O_TRUNC, 0644);
+  ASSERT_NOERROR(relro_fd);
+  ASSERT_NOERROR(close(relro_fd));
+
+  ASSERT_NO_FATAL_FAILURE(TryUsingRelro(LIBNAME));
 }