Fix copy / move behaviour of Maps object.

Currently, moving or copying a Maps object leads to double free of MapInfo.

Even moving a Maps object  did not prevent this, as after a move
the object only has to be in an "unspecified but valid state", which can
be the original state for a vector of raw pointers (but not for a vector
of unique_ptrs).

Changing to unique_ptrs is the most failsafe way to make sure we never
accidentally destruct MapInfo.

Test: atest libuwindstack_test
      Failed LocalUnwinderTest#unwind_after_dlopen which also fails at master.

Change-Id: Id1c9739b334da5c1ba532fd55366e115940a66d3

7 files changed, 66 insertions, 50 deletions

diff --git a/libbacktrace/UnwindStackMap.cpp b/libbacktrace/UnwindStackMap.cpp
index 9d15af2..4518891 100644
--- a/libbacktrace/UnwindStackMap.cpp
+++ b/libbacktrace/UnwindStackMap.cpp
@@ -55,7 +55,7 @@ bool UnwindStackMap::Build() {
   }
 
   // Iterate through the maps and fill in the backtrace_map_t structure.
-  for (auto* map_info : *stack_maps_) {
+  for (const auto& map_info : *stack_maps_) {
     backtrace_map_t map;
     map.start = map_info->start;
     map.end = map_info->end;
diff --git a/libunwindstack/Global.cpp b/libunwindstack/Global.cpp
index fdfd705..a20be00 100644
--- a/libunwindstack/Global.cpp
+++ b/libunwindstack/Global.cpp
@@ -77,7 +77,7 @@ void Global::FindAndReadVariable(Maps* maps, const char* var_str) {
   //   f0000-f2000 0 r-- /system/lib/libc.so
   //   f2000-f3000 2000 rw- /system/lib/libc.so
   MapInfo* map_start = nullptr;
-  for (MapInfo* info : *maps) {
+  for (const auto& info : *maps) {
     if (map_start != nullptr) {
       if (map_start->name == info->name) {
         if (info->offset != 0 &&
@@ -96,7 +96,7 @@ void Global::FindAndReadVariable(Maps* maps, const char* var_str) {
     }
     if (map_start == nullptr && (info->flags & PROT_READ) && info->offset == 0 &&
         !info->name.empty()) {
-      map_start = info;
+      map_start = info.get();
     }
   }
 }
diff --git a/libunwindstack/Maps.cpp b/libunwindstack/Maps.cpp
index 1e4f72e..5da73e4 100644
--- a/libunwindstack/Maps.cpp
+++ b/libunwindstack/Maps.cpp
@@ -47,9 +47,9 @@ MapInfo* Maps::Find(uint64_t pc) {
   size_t last = maps_.size();
   while (first < last) {
     size_t index = (first + last) / 2;
-    MapInfo* cur = maps_[index];
+    const auto& cur = maps_[index];
     if (pc >= cur->start && pc < cur->end) {
-      return cur;
+      return cur.get();
     } else if (pc < cur->start) {
       last = index;
     } else {
@@ -67,34 +67,31 @@ bool Maps::Parse() {
         if (strncmp(name, "/dev/", 5) == 0 && strncmp(name + 5, "ashmem/", 7) != 0) {
           flags |= unwindstack::MAPS_FLAGS_DEVICE_MAP;
         }
-        maps_.push_back(
-            new MapInfo(maps_.empty() ? nullptr : maps_.back(), start, end, pgoff, flags, name));
+        maps_.emplace_back(
+            new MapInfo(maps_.empty() ? nullptr : maps_.back().get(), start, end, pgoff,
+                        flags, name));
       });
 }
 
 void Maps::Add(uint64_t start, uint64_t end, uint64_t offset, uint64_t flags,
                const std::string& name, uint64_t load_bias) {
-  MapInfo* map_info =
-      new MapInfo(maps_.empty() ? nullptr : maps_.back(), start, end, offset, flags, name);
+  auto map_info =
+      std::make_unique<MapInfo>(maps_.empty() ? nullptr : maps_.back().get(), start, end, offset,
+                                flags, name);
   map_info->load_bias = load_bias;
-  maps_.push_back(map_info);
+  maps_.emplace_back(std::move(map_info));
 }
 
 void Maps::Sort() {
   std::sort(maps_.begin(), maps_.end(),
-            [](const MapInfo* a, const MapInfo* b) { return a->start < b->start; });
+            [](const std::unique_ptr<MapInfo>& a, const std::unique_ptr<MapInfo>& b) {
+              return a->start < b->start; });
 
   // Set the prev_map values on the info objects.
   MapInfo* prev_map = nullptr;
-  for (MapInfo* map_info : maps_) {
+  for (const auto& map_info : maps_) {
     map_info->prev_map = prev_map;
-    prev_map = map_info;
-  }
-}
-
-Maps::~Maps() {
-  for (auto& map : maps_) {
-    delete map;
+    prev_map = map_info.get();
   }
 }
 
@@ -107,8 +104,9 @@ bool BufferMaps::Parse() {
         if (strncmp(name, "/dev/", 5) == 0 && strncmp(name + 5, "ashmem/", 7) != 0) {
           flags |= unwindstack::MAPS_FLAGS_DEVICE_MAP;
         }
-        maps_.push_back(
-            new MapInfo(maps_.empty() ? nullptr : maps_.back(), start, end, pgoff, flags, name));
+        maps_.emplace_back(
+            new MapInfo(maps_.empty() ? nullptr : maps_.back().get(), start, end, pgoff,
+                        flags, name));
       });
 }
 
@@ -124,10 +122,6 @@ bool LocalUpdatableMaps::Reparse() {
   // New maps will be added at the end without deleting the old ones.
   size_t last_map_idx = maps_.size();
   if (!Parse()) {
-    // Delete any maps added by the Parse call.
-    for (size_t i = last_map_idx; i < maps_.size(); i++) {
-      delete maps_[i];
-    }
     maps_.resize(last_map_idx);
     return false;
   }
@@ -135,17 +129,16 @@ bool LocalUpdatableMaps::Reparse() {
   size_t total_entries = maps_.size();
   size_t search_map_idx = 0;
   for (size_t new_map_idx = last_map_idx; new_map_idx < maps_.size(); new_map_idx++) {
-    MapInfo* new_map_info = maps_[new_map_idx];
+    auto& new_map_info = maps_[new_map_idx];
     uint64_t start = new_map_info->start;
     uint64_t end = new_map_info->end;
     uint64_t flags = new_map_info->flags;
     std::string* name = &new_map_info->name;
     for (size_t old_map_idx = search_map_idx; old_map_idx < last_map_idx; old_map_idx++) {
-      MapInfo* info = maps_[old_map_idx];
+      auto& info = maps_[old_map_idx];
       if (start == info->start && end == info->end && flags == info->flags && *name == info->name) {
         // No need to check
         search_map_idx = old_map_idx + 1;
-        delete new_map_info;
         maps_[new_map_idx] = nullptr;
         total_entries--;
         break;
@@ -158,7 +151,7 @@ bool LocalUpdatableMaps::Reparse() {
       // Never delete these maps, they may be in use. The assumption is
       // that there will only every be a handfull of these so waiting
       // to destroy them is not too expensive.
-      saved_maps_.push_back(info);
+      saved_maps_.emplace_back(std::move(info));
       maps_[old_map_idx] = nullptr;
       total_entries--;
     }
@@ -169,14 +162,14 @@ bool LocalUpdatableMaps::Reparse() {
 
   // Now move out any of the maps that never were found.
   for (size_t i = search_map_idx; i < last_map_idx; i++) {
-    saved_maps_.push_back(maps_[i]);
+    saved_maps_.emplace_back(std::move(maps_[i]));
     maps_[i] = nullptr;
     total_entries--;
   }
 
   // Sort all of the values such that the nullptrs wind up at the end, then
   // resize them away.
-  std::sort(maps_.begin(), maps_.end(), [](const auto* a, const auto* b) {
+  std::sort(maps_.begin(), maps_.end(), [](const auto& a, const auto& b) {
     if (a == nullptr) {
       return false;
     } else if (b == nullptr) {
@@ -189,10 +182,4 @@ bool LocalUpdatableMaps::Reparse() {
   return true;
 }
 
-LocalUpdatableMaps::~LocalUpdatableMaps() {
-  for (auto map_info : saved_maps_) {
-    delete map_info;
-  }
-}
-
 }  // namespace unwindstack
diff --git a/libunwindstack/benchmarks/unwind_benchmarks.cpp b/libunwindstack/benchmarks/unwind_benchmarks.cpp
index 8caecc7..de9137a 100644
--- a/libunwindstack/benchmarks/unwind_benchmarks.cpp
+++ b/libunwindstack/benchmarks/unwind_benchmarks.cpp
@@ -92,9 +92,9 @@ static void Initialize(benchmark::State& state, unwindstack::Maps& maps,
 
   // Find the libc.so share library and use that for benchmark purposes.
   *build_id_map_info = nullptr;
-  for (unwindstack::MapInfo* map_info : maps) {
+  for (auto& map_info : maps) {
     if (map_info->offset == 0 && map_info->GetBuildID() != "") {
-      *build_id_map_info = map_info;
+      *build_id_map_info = map_info.get();
       break;
     }
   }
diff --git a/libunwindstack/include/unwindstack/Maps.h b/libunwindstack/include/unwindstack/Maps.h
index 67fbed2..1784394 100644
--- a/libunwindstack/include/unwindstack/Maps.h
+++ b/libunwindstack/include/unwindstack/Maps.h
@@ -20,6 +20,7 @@
 #include <sys/types.h>
 #include <unistd.h>
 
+#include <memory>
 #include <string>
 #include <vector>
 
@@ -37,8 +38,16 @@ static constexpr int MAPS_FLAGS_JIT_SYMFILE_MAP = 0x4000;
 
 class Maps {
  public:
+  virtual ~Maps() = default;
+
   Maps() = default;
-  virtual ~Maps();
+
+  // Maps are not copyable but movable, because they own pointers to MapInfo
+  // objects.
+  Maps(const Maps&) = delete;
+  Maps& operator=(const Maps&) = delete;
+  Maps(Maps&&) = default;
+  Maps& operator=(Maps&&) = default;
 
   MapInfo* Find(uint64_t pc);
 
@@ -51,11 +60,11 @@ class Maps {
 
   void Sort();
 
-  typedef std::vector<MapInfo*>::iterator iterator;
+  typedef std::vector<std::unique_ptr<MapInfo>>::iterator iterator;
   iterator begin() { return maps_.begin(); }
   iterator end() { return maps_.end(); }
 
-  typedef std::vector<MapInfo*>::const_iterator const_iterator;
+  typedef std::vector<std::unique_ptr<MapInfo>>::const_iterator const_iterator;
   const_iterator begin() const { return maps_.begin(); }
   const_iterator end() const { return maps_.end(); }
 
@@ -63,11 +72,11 @@ class Maps {
 
   MapInfo* Get(size_t index) {
     if (index >= maps_.size()) return nullptr;
-    return maps_[index];
+    return maps_[index].get();
   }
 
  protected:
-  std::vector<MapInfo*> maps_;
+  std::vector<std::unique_ptr<MapInfo>> maps_;
 };
 
 class RemoteMaps : public Maps {
@@ -90,14 +99,14 @@ class LocalMaps : public RemoteMaps {
 class LocalUpdatableMaps : public Maps {
  public:
   LocalUpdatableMaps() : Maps() {}
-  virtual ~LocalUpdatableMaps();
+  virtual ~LocalUpdatableMaps() = default;
 
   bool Reparse();
 
   const std::string GetMapsFile() const override;
 
  private:
-  std::vector<MapInfo*> saved_maps_;
+  std::vector<std::unique_ptr<MapInfo>> saved_maps_;
 };
 
 class BufferMaps : public Maps {
diff --git a/libunwindstack/tests/MapsTest.cpp b/libunwindstack/tests/MapsTest.cpp
index b4197f2..9e7a6ab 100644
--- a/libunwindstack/tests/MapsTest.cpp
+++ b/libunwindstack/tests/MapsTest.cpp
@@ -61,6 +61,26 @@ TEST(MapsTest, map_add) {
   ASSERT_EQ(0U, info->load_bias.load());
 }
 
+TEST(MapsTest, map_move) {
+  Maps maps;
+
+  maps.Add(0x1000, 0x2000, 0, PROT_READ, "fake_map", 0);
+  maps.Add(0x3000, 0x4000, 0x10, 0, "", 0x1234);
+  maps.Add(0x5000, 0x6000, 1, 2, "fake_map2", static_cast<uint64_t>(-1));
+
+  Maps maps2 = std::move(maps);
+
+  ASSERT_EQ(3U, maps2.Total());
+  MapInfo* info = maps2.Get(0);
+  ASSERT_EQ(0x1000U, info->start);
+  ASSERT_EQ(0x2000U, info->end);
+  ASSERT_EQ(0U, info->offset);
+  ASSERT_EQ(PROT_READ, info->flags);
+  ASSERT_EQ("fake_map", info->name);
+  ASSERT_EQ(0U, info->elf_offset);
+  ASSERT_EQ(0U, info->load_bias.load());
+}
+
 TEST(MapsTest, verify_parse_line) {
   MapInfo info(nullptr, 0, 0, 0, 0, "");
 
diff --git a/libunwindstack/tests/UnwinderTest.cpp b/libunwindstack/tests/UnwinderTest.cpp
index d88531f..2dc5118 100644
--- a/libunwindstack/tests/UnwinderTest.cpp
+++ b/libunwindstack/tests/UnwinderTest.cpp
@@ -49,7 +49,7 @@ class UnwinderTest : public ::testing::Test {
     std::string str_name(name);
     maps_->Add(start, end, offset, flags, name, static_cast<uint64_t>(-1));
     if (elf != nullptr) {
-      MapInfo* map_info = *--maps_->end();
+      const auto& map_info = *--maps_->end();
       map_info->elf.reset(elf);
     }
   }
@@ -85,7 +85,7 @@ class UnwinderTest : public ::testing::Test {
     AddMapInfo(0x53000, 0x54000, 0, PROT_READ | PROT_WRITE, "/fake/fake.oat");
 
     AddMapInfo(0xa3000, 0xa4000, 0, PROT_READ | PROT_WRITE | PROT_EXEC, "/fake/fake.vdex");
-    MapInfo* info = *--maps_->end();
+    const auto& info = *--maps_->end();
     info->load_bias = 0;
 
     elf = new ElfFake(new MemoryFake);
@@ -98,8 +98,8 @@ class UnwinderTest : public ::testing::Test {
     elf->FakeSetInterface(new ElfInterfaceFake(nullptr));
     AddMapInfo(0xa7000, 0xa8000, 0, PROT_READ | PROT_WRITE | PROT_EXEC, "/fake/fake_offset.oat",
                elf);
-    info = *--maps_->end();
-    info->elf_offset = 0x8000;
+    const auto& info2 = *--maps_->end();
+    info2->elf_offset = 0x8000;
 
     process_memory_.reset(new MemoryFake);
   }