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Implement Library Load Order Randomization

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Bug: http://b/24047022
Change-Id: I36e05b403bfbaae8542a95147f9114a8b9c8ac0e
This commit is contained in:
Dmitriy Ivanov
2015-10-15 12:07:25 -07:00
parent cf1cbbe432
commit 4f7a7ad3fe
5 changed files with 413 additions and 133 deletions
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353
linker/linker.cpp
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@@ -50,7 +50,6 @@
#include "private/KernelArgumentBlock.h"
#include "private/ScopedPthreadMutexLocker.h"
#include "private/ScopeGuard.h"
#include "private/UniquePtr.h"
#include "linker.h"
#include "linker_block_allocator.h"
@@ -325,7 +324,10 @@ static void parse_LD_LIBRARY_PATH(const char* path) {
}
void soinfo::set_dt_runpath(const char* path) {
if (!has_min_version(2)) return;
if (!has_min_version(2)) {
return;
}
parse_path(path, ":", &dt_runpath_);
std::string origin = dirname(get_realpath());
@@ -897,17 +899,17 @@ class LoadTask {
public:
struct deleter_t {
void operator()(LoadTask* t) {
t->~LoadTask();
TypeBasedAllocator<LoadTask>::free(t);
}
};
typedef UniquePtr<LoadTask, deleter_t> unique_ptr;
static deleter_t deleter;
static LoadTask* create(const char* name, soinfo* needed_by) {
static LoadTask* create(const char* name, soinfo* needed_by,
std::unordered_map<const soinfo*, ElfReader>* readers_map) {
LoadTask* ptr = TypeBasedAllocator<LoadTask>::alloc();
return new (ptr) LoadTask(name, needed_by);
return new (ptr) LoadTask(name, needed_by, readers_map);
}
const char* get_name() const {
@@ -917,12 +919,94 @@ class LoadTask {
soinfo* get_needed_by() const {
return needed_by_;
}
soinfo* get_soinfo() const {
return si_;
}
void set_soinfo(soinfo* si) {
si_ = si;
}
off64_t get_file_offset() const {
return file_offset_;
}
void set_file_offset(off64_t offset) {
file_offset_ = offset;
}
int get_fd() const {
return fd_;
}
void set_fd(int fd, bool assume_ownership) {
fd_ = fd;
close_fd_ = assume_ownership;
}
const android_dlextinfo* get_extinfo() const {
return extinfo_;
}
void set_extinfo(const android_dlextinfo* extinfo) {
extinfo_ = extinfo;
}
const ElfReader& get_elf_reader() const {
CHECK(si_ != nullptr);
return (*elf_readers_map_)[si_];
}
ElfReader& get_elf_reader() {
CHECK(si_ != nullptr);
return (*elf_readers_map_)[si_];
}
std::unordered_map<const soinfo*, ElfReader>* get_readers_map() {
return elf_readers_map_;
}
bool read(const char* realpath, off64_t file_size) {
ElfReader& elf_reader = get_elf_reader();
return elf_reader.Read(realpath, fd_, file_offset_, file_size);
}
bool load() {
ElfReader& elf_reader = get_elf_reader();
if (!elf_reader.Load(extinfo_)) {
return false;
}
si_->base = elf_reader.load_start();
si_->size = elf_reader.load_size();
si_->load_bias = elf_reader.load_bias();
si_->phnum = elf_reader.phdr_count();
si_->phdr = elf_reader.loaded_phdr();
return true;
}
private:
LoadTask(const char* name, soinfo* needed_by)
: name_(name), needed_by_(needed_by) {}
LoadTask(const char* name, soinfo* needed_by,
std::unordered_map<const soinfo*, ElfReader>* readers_map)
: name_(name), needed_by_(needed_by), si_(nullptr),
fd_(-1), close_fd_(false), file_offset_(0), elf_readers_map_(readers_map) {}
~LoadTask() {
if (fd_ != -1 && close_fd_) {
close(fd_);
}
}
const char* name_;
soinfo* needed_by_;
soinfo* si_;
const android_dlextinfo* extinfo_;
int fd_;
bool close_fd_;
off64_t file_offset_;
std::unordered_map<const soinfo*, ElfReader>* elf_readers_map_;
DISALLOW_IMPLICIT_CONSTRUCTORS(LoadTask);
};
@@ -934,7 +1018,7 @@ using linked_list_t = LinkedList<T, TypeBasedAllocator<LinkedListEntry<T>>>;
typedef linked_list_t<soinfo> SoinfoLinkedList;
typedef linked_list_t<const char> StringLinkedList;
typedef linked_list_t<LoadTask> LoadTaskList;
typedef std::vector<LoadTask*> LoadTaskList;
// This function walks down the tree of soinfo dependencies
@@ -1336,7 +1420,7 @@ static int open_library(ZipArchiveCache* zip_archive_cache,
// Otherwise we try LD_LIBRARY_PATH first, and fall back to the built-in well known paths.
int fd = open_library_on_paths(zip_archive_cache, name, file_offset, g_ld_library_paths, realpath);
if (fd == -1 && needed_by) {
if (fd == -1 && needed_by != nullptr) {
fd = open_library_on_paths(zip_archive_cache, name, file_offset, needed_by->get_dt_runpath(), realpath);
}
@@ -1364,36 +1448,48 @@ static const char* fix_dt_needed(const char* dt_needed, const char* sopath __unu
template<typename F>
static void for_each_dt_needed(const soinfo* si, F action) {
for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) {
for (const ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) {
if (d->d_tag == DT_NEEDED) {
action(fix_dt_needed(si->get_string(d->d_un.d_val), si->get_realpath()));
}
}
}
static soinfo* load_library(int fd, off64_t file_offset,
LoadTaskList& load_tasks,
const char* name, int rtld_flags,
const android_dlextinfo* extinfo,
const std::string& realpath) {
template<typename F>
static void for_each_dt_needed(const ElfReader& elf_reader, F action) {
for (const ElfW(Dyn)* d = elf_reader.dynamic(); d->d_tag != DT_NULL; ++d) {
if (d->d_tag == DT_NEEDED) {
action(fix_dt_needed(elf_reader.get_string(d->d_un.d_val), elf_reader.name()));
}
}
}
static bool load_library(LoadTask* task,
LoadTaskList* load_tasks,
int rtld_flags,
const std::string& realpath) {
off64_t file_offset = task->get_file_offset();
const char* name = task->get_name();
const android_dlextinfo* extinfo = task->get_extinfo();
if ((file_offset % PAGE_SIZE) != 0) {
DL_ERR("file offset for the library \"%s\" is not page-aligned: %" PRId64, name, file_offset);
return nullptr;
return false;
}
if (file_offset < 0) {
DL_ERR("file offset for the library \"%s\" is negative: %" PRId64, name, file_offset);
return nullptr;
return false;
}
struct stat file_stat;
if (TEMP_FAILURE_RETRY(fstat(fd, &file_stat)) != 0) {
if (TEMP_FAILURE_RETRY(fstat(task->get_fd(), &file_stat)) != 0) {
DL_ERR("unable to stat file for the library \"%s\": %s", name, strerror(errno));
return nullptr;
return false;
}
if (file_offset >= file_stat.st_size) {
DL_ERR("file offset for the library \"%s\" >= file size: %" PRId64 " >= %" PRId64,
name, file_offset, file_stat.st_size);
return nullptr;
return false;
}
// Check for symlink and other situations where
@@ -1407,48 +1503,59 @@ static soinfo* load_library(int fd, off64_t file_offset,
si->get_file_offset() == file_offset) {
TRACE("library \"%s\" is already loaded under different name/path \"%s\" - "
"will return existing soinfo", name, si->get_realpath());
return si;
task->set_soinfo(si);
return true;
}
}
}
if ((rtld_flags & RTLD_NOLOAD) != 0) {
DL_ERR("library \"%s\" wasn't loaded and RTLD_NOLOAD prevented it", name);
return nullptr;
}
// Read the ELF header and load the segments.
ElfReader elf_reader(realpath.c_str(), fd, file_offset, file_stat.st_size);
if (!elf_reader.Load(extinfo)) {
return nullptr;
return false;
}
soinfo* si = soinfo_alloc(realpath.c_str(), &file_stat, file_offset, rtld_flags);
if (si == nullptr) {
return nullptr;
}
si->base = elf_reader.load_start();
si->size = elf_reader.load_size();
si->load_bias = elf_reader.load_bias();
si->phnum = elf_reader.phdr_count();
si->phdr = elf_reader.loaded_phdr();
if (!si->prelink_image()) {
soinfo_free(si);
return nullptr;
return false;
}
for_each_dt_needed(si, [&] (const char* name) {
load_tasks.push_back(LoadTask::create(name, si));
task->set_soinfo(si);
// Read the ELF header and some of the segments.
if (!task->read(realpath.c_str(), file_stat.st_size)) {
return false;
}
// find and set DT_RUNPATH and dt_soname
// Note that these field values are temporary and are
// going to be overwritten on soinfo::prelink_image
// with values from PT_LOAD segments.
const ElfReader& elf_reader = task->get_elf_reader();
for (const ElfW(Dyn)* d = elf_reader.dynamic(); d->d_tag != DT_NULL; ++d) {
if (d->d_tag == DT_RUNPATH) {
si->set_dt_runpath(elf_reader.get_string(d->d_un.d_val));
}
if (d->d_tag == DT_SONAME) {
si->set_soname(elf_reader.get_string(d->d_un.d_val));
}
}
for_each_dt_needed(task->get_elf_reader(), [&](const char* name) {
load_tasks->push_back(LoadTask::create(name, si, task->get_readers_map()));
});
return si;
return true;
}
static soinfo* load_library(ZipArchiveCache* zip_archive_cache,
LoadTaskList& load_tasks, const char* name,
soinfo* needed_by, int rtld_flags,
const android_dlextinfo* extinfo) {
static bool load_library(LoadTask* task,
ZipArchiveCache* zip_archive_cache,
LoadTaskList* load_tasks,
int rtld_flags) {
const char* name = task->get_name();
soinfo* needed_by = task->get_needed_by();
const android_dlextinfo* extinfo = task->get_extinfo();
off64_t file_offset;
std::string realpath;
if (extinfo != nullptr && (extinfo->flags & ANDROID_DLEXT_USE_LIBRARY_FD) != 0) {
@@ -1462,18 +1569,23 @@ static soinfo* load_library(ZipArchiveCache* zip_archive_cache,
"Will use given name.", name);
realpath = name;
}
return load_library(extinfo->library_fd, file_offset, load_tasks, name, rtld_flags, extinfo, realpath);
task->set_fd(extinfo->library_fd, false);
task->set_file_offset(file_offset);
return load_library(task, load_tasks, rtld_flags, realpath);
}
// Open the file.
int fd = open_library(zip_archive_cache, name, needed_by, &file_offset, &realpath);
if (fd == -1) {
DL_ERR("library \"%s\" not found", name);
return nullptr;
return false;
}
soinfo* result = load_library(fd, file_offset, load_tasks, name, rtld_flags, extinfo, realpath);
close(fd);
return result;
task->set_fd(fd, true);
task->set_file_offset(file_offset);
return load_library(task, load_tasks, rtld_flags, realpath);
}
// Returns true if library was found and false in 2 cases
@@ -1513,31 +1625,35 @@ static bool find_loaded_library_by_soname(const char* name, soinfo** candidate)
return false;
}
static soinfo* find_library_internal(ZipArchiveCache* zip_archive_cache,
LoadTaskList& load_tasks, const char* name,
soinfo* needed_by, int rtld_flags,
const android_dlextinfo* extinfo) {
static bool find_library_internal(LoadTask* task,
ZipArchiveCache* zip_archive_cache,
LoadTaskList* load_tasks,
int rtld_flags) {
soinfo* candidate;
if (find_loaded_library_by_soname(name, &candidate)) {
return candidate;
if (find_loaded_library_by_soname(task->get_name(), &candidate)) {
task->set_soinfo(candidate);
return true;
}
// Library might still be loaded, the accurate detection
// of this fact is done by load_library.
TRACE("[ '%s' find_loaded_library_by_soname returned false (*candidate=%s@%p). Trying harder...]",
name, candidate == nullptr ? "n/a" : candidate->get_realpath(), candidate);
task->get_name(), candidate == nullptr ? "n/a" : candidate->get_realpath(), candidate);
soinfo* si = load_library(zip_archive_cache, load_tasks, name, needed_by, rtld_flags, extinfo);
// In case we were unable to load the library but there
// is a candidate loaded under the same soname but different
// sdk level - return it anyways.
if (si == nullptr && candidate != nullptr) {
si = candidate;
if (load_library(task, zip_archive_cache, load_tasks, rtld_flags)) {
return true;
} else {
// In case we were unable to load the library but there
// is a candidate loaded under the same soname but different
// sdk level - return it anyways.
if (candidate != nullptr) {
task->set_soinfo(candidate);
return true;
}
}
return si;
return false;
}
static void soinfo_unload(soinfo* si);
@@ -1560,6 +1676,14 @@ static soinfo::soinfo_list_t make_global_group() {
return global_group;
}
static void shuffle(std::vector<LoadTask*>* v) {
for (size_t i = 0, size = v->size(); i < size; ++i) {
size_t n = size - i;
size_t r = arc4random_uniform(n);
std::swap((*v)[n-1], (*v)[r]);
}
}
// add_as_children - add first-level loaded libraries (i.e. library_names[], but
// not their transitive dependencies) as children of the start_with library.
// This is false when find_libraries is called for dlopen(), when newly loaded
@@ -1573,9 +1697,11 @@ static bool find_libraries(soinfo* start_with,
bool add_as_children) {
// Step 0: prepare.
LoadTaskList load_tasks;
std::unordered_map<const soinfo*, ElfReader> readers_map;
for (size_t i = 0; i < library_names_count; ++i) {
const char* name = library_names[i];
load_tasks.push_back(LoadTask::create(name, start_with));
load_tasks.push_back(LoadTask::create(name, start_with, &readers_map));
}
// Construct global_group.
@@ -1597,12 +1723,14 @@ static bool find_libraries(soinfo* start_with,
// list of libraries to link - see step 2.
size_t soinfos_count = 0;
auto scope_guard = make_scope_guard([&]() {
for (LoadTask* t : load_tasks) {
LoadTask::deleter(t);
}
});
auto failure_guard = make_scope_guard([&]() {
// Housekeeping
load_tasks.for_each([] (LoadTask* t) {
LoadTask::deleter(t);
});
for (size_t i = 0; i<soinfos_count; ++i) {
soinfo_unload(soinfos[i]);
}
@@ -1610,20 +1738,21 @@ static bool find_libraries(soinfo* start_with,
ZipArchiveCache zip_archive_cache;
// Step 1: load and pre-link all DT_NEEDED libraries in breadth first order.
for (LoadTask::unique_ptr task(load_tasks.pop_front());
task.get() != nullptr; task.reset(load_tasks.pop_front())) {
// Step 1: expand the list of load_tasks to include
// all DT_NEEDED libraries (do not load them just yet)
for (size_t i = 0; i<load_tasks.size(); ++i) {
LoadTask* task = load_tasks[i];
soinfo* needed_by = task->get_needed_by();
bool is_dt_needed = needed_by != nullptr && (needed_by != start_with || add_as_children);
task->set_extinfo(is_dt_needed ? nullptr : extinfo);
soinfo* si = find_library_internal(&zip_archive_cache, load_tasks,
task->get_name(), needed_by, rtld_flags,
is_dt_needed ? nullptr : extinfo);
if (si == nullptr) {
if(!find_library_internal(task, &zip_archive_cache, &load_tasks, rtld_flags)) {
return false;
}
soinfo* si = task->get_soinfo();
if (is_dt_needed) {
needed_by->add_child(si);
}
@@ -1635,11 +1764,6 @@ static bool find_libraries(soinfo* start_with,
// When ld_preloads is not null, the first
// ld_preloads_count libs are in fact ld_preloads.
if (ld_preloads != nullptr && soinfos_count < ld_preloads_count) {
// Add LD_PRELOADed libraries to the global group for future runs.
// There is no need to explicitly add them to the global group
// for this run because they are going to appear in the local
// group in the correct order.
si->set_dt_flags_1(si->get_dt_flags_1() | DF_1_GLOBAL);
ld_preloads->push_back(si);
}
@@ -1648,7 +1772,47 @@ static bool find_libraries(soinfo* start_with,
}
}
// Step 2: link libraries.
// Step 2: Load libraries in random order (see b/24047022)
LoadTaskList load_list;
for (auto&& task : load_tasks) {
soinfo* si = task->get_soinfo();
auto pred = [&](const LoadTask* t) {
return t->get_soinfo() == si;
};
if (!si->is_linked() &&
std::find_if(load_list.begin(), load_list.end(), pred) == load_list.end() ) {
load_list.push_back(task);
}
}
shuffle(&load_list);
for (auto&& task : load_list) {
if (!task->load()) {
return false;
}
}
// Step 3: pre-link all DT_NEEDED libraries in breadth first order.
for (auto&& task : load_tasks) {
soinfo* si = task->get_soinfo();
if (!si->is_linked() && !si->prelink_image()) {
return false;
}
}
// Step 4: Add LD_PRELOADed libraries to the global group for
// future runs. There is no need to explicitly add them to
// the global group for this run because they are going to
// appear in the local group in the correct order.
if (ld_preloads != nullptr) {
for (auto&& si : *ld_preloads) {
si->set_dt_flags_1(si->get_dt_flags_1() | DF_1_GLOBAL);
}
}
// Step 5: link libraries.
soinfo::soinfo_list_t local_group;
walk_dependencies_tree(
(start_with != nullptr && add_as_children) ? &start_with : soinfos,
@@ -2532,6 +2696,17 @@ const char* soinfo::get_realpath() const {
#endif
}
void soinfo::set_soname(const char* soname) {
#if defined(__work_around_b_24465209__)
if (has_min_version(2)) {
soname_ = soname;
}
strlcpy(old_name_, soname_, sizeof(old_name_));
#else
soname_ = soname;
#endif
}
const char* soinfo::get_soname() const {
#if defined(__work_around_b_24465209__)
if (has_min_version(2)) {
@@ -3063,13 +3238,9 @@ bool soinfo::prelink_image() {
for (ElfW(Dyn)* d = dynamic; d->d_tag != DT_NULL; ++d) {
switch (d->d_tag) {
case DT_SONAME:
soname_ = get_string(d->d_un.d_val);
#if defined(__work_around_b_24465209__)
strlcpy(old_name_, soname_, sizeof(old_name_));
#endif
set_soname(get_string(d->d_un.d_val));
break;
case DT_RUNPATH:
// FIXME: $LIB, $PLATFORM unsupported.
set_dt_runpath(get_string(d->d_un.d_val));
break;
}