| // Copyright (c) 2012 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #include "base/memory/shared_memory.h" |
| |
| #include <fcntl.h> |
| #include <sys/mman.h> |
| #include <sys/stat.h> |
| #include <unistd.h> |
| |
| #include "base/files/file_util.h" |
| #include "base/files/scoped_file.h" |
| #include "base/logging.h" |
| #include "base/posix/eintr_wrapper.h" |
| #include "base/posix/safe_strerror.h" |
| #include "base/process/process_metrics.h" |
| #include "base/profiler/scoped_tracker.h" |
| #include "base/scoped_generic.h" |
| #include "base/strings/utf_string_conversions.h" |
| |
| #if defined(OS_MACOSX) |
| #include "base/mac/foundation_util.h" |
| #endif // OS_MACOSX |
| |
| namespace base { |
| |
| namespace { |
| |
| struct ScopedPathUnlinkerTraits { |
| static FilePath* InvalidValue() { return nullptr; } |
| |
| static void Free(FilePath* path) { |
| // TODO(erikchen): Remove ScopedTracker below once http://crbug.com/466437 |
| // is fixed. |
| tracked_objects::ScopedTracker tracking_profile( |
| FROM_HERE_WITH_EXPLICIT_FUNCTION( |
| "466437 SharedMemory::Create::Unlink")); |
| if (unlink(path->value().c_str())) |
| PLOG(WARNING) << "unlink"; |
| } |
| }; |
| |
| // Unlinks the FilePath when the object is destroyed. |
| typedef ScopedGeneric<FilePath*, ScopedPathUnlinkerTraits> ScopedPathUnlinker; |
| |
| // Makes a temporary file, fdopens it, and then unlinks it. |fp| is populated |
| // with the fdopened FILE. |readonly_fd| is populated with the opened fd if |
| // options.share_read_only is true. |path| is populated with the location of |
| // the file before it was unlinked. |
| // Returns false if there's an unhandled failure. |
| bool CreateAnonymousSharedMemory(const SharedMemoryCreateOptions& options, |
| ScopedFILE* fp, |
| ScopedFD* readonly_fd, |
| FilePath* path) { |
| // It doesn't make sense to have a open-existing private piece of shmem |
| DCHECK(!options.open_existing_deprecated); |
| // Q: Why not use the shm_open() etc. APIs? |
| // A: Because they're limited to 4mb on OS X. FFFFFFFUUUUUUUUUUU |
| FilePath directory; |
| ScopedPathUnlinker path_unlinker; |
| if (GetShmemTempDir(options.executable, &directory)) { |
| // TODO(erikchen): Remove ScopedTracker below once http://crbug.com/466437 |
| // is fixed. |
| tracked_objects::ScopedTracker tracking_profile( |
| FROM_HERE_WITH_EXPLICIT_FUNCTION( |
| "466437 SharedMemory::Create::OpenTemporaryFile")); |
| fp->reset(base::CreateAndOpenTemporaryFileInDir(directory, path)); |
| |
| // Deleting the file prevents anyone else from mapping it in (making it |
| // private), and prevents the need for cleanup (once the last fd is |
| // closed, it is truly freed). |
| if (*fp) |
| path_unlinker.reset(path); |
| } |
| |
| if (*fp) { |
| if (options.share_read_only) { |
| // TODO(erikchen): Remove ScopedTracker below once |
| // http://crbug.com/466437 is fixed. |
| tracked_objects::ScopedTracker tracking_profile( |
| FROM_HERE_WITH_EXPLICIT_FUNCTION( |
| "466437 SharedMemory::Create::OpenReadonly")); |
| // Also open as readonly so that we can ShareReadOnlyToProcess. |
| readonly_fd->reset(HANDLE_EINTR(open(path->value().c_str(), O_RDONLY))); |
| if (!readonly_fd->is_valid()) { |
| DPLOG(ERROR) << "open(\"" << path->value() << "\", O_RDONLY) failed"; |
| fp->reset(); |
| return false; |
| } |
| } |
| } |
| return true; |
| } |
| } |
| |
| SharedMemory::SharedMemory() |
| : mapped_file_(-1), |
| readonly_mapped_file_(-1), |
| mapped_size_(0), |
| memory_(NULL), |
| read_only_(false), |
| requested_size_(0) { |
| } |
| |
| SharedMemory::SharedMemory(const SharedMemoryHandle& handle, bool read_only) |
| : mapped_file_(GetFdFromSharedMemoryHandle(handle)), |
| readonly_mapped_file_(-1), |
| mapped_size_(0), |
| memory_(NULL), |
| read_only_(read_only), |
| requested_size_(0) { |
| } |
| |
| SharedMemory::SharedMemory(const SharedMemoryHandle& handle, |
| bool read_only, |
| ProcessHandle process) |
| : mapped_file_(GetFdFromSharedMemoryHandle(handle)), |
| readonly_mapped_file_(-1), |
| mapped_size_(0), |
| memory_(NULL), |
| read_only_(read_only), |
| requested_size_(0) { |
| // We don't handle this case yet (note the ignored parameter); let's die if |
| // someone comes calling. |
| NOTREACHED(); |
| } |
| |
| SharedMemory::~SharedMemory() { |
| Unmap(); |
| Close(); |
| } |
| |
| // static |
| bool SharedMemory::IsHandleValid(const SharedMemoryHandle& handle) { |
| return handle.IsValid(); |
| } |
| |
| // static |
| SharedMemoryHandle SharedMemory::NULLHandle() { |
| return SharedMemoryHandle(); |
| } |
| |
| // static |
| void SharedMemory::CloseHandle(const SharedMemoryHandle& handle) { |
| DCHECK_GE(GetFdFromSharedMemoryHandle(handle), 0); |
| if (close(GetFdFromSharedMemoryHandle(handle)) < 0) |
| DPLOG(ERROR) << "close"; |
| } |
| |
| // static |
| size_t SharedMemory::GetHandleLimit() { |
| return base::GetMaxFds(); |
| } |
| |
| // static |
| SharedMemoryHandle SharedMemory::DuplicateHandle( |
| const SharedMemoryHandle& handle) { |
| return handle.Duplicate(); |
| } |
| |
| // static |
| int SharedMemory::GetFdFromSharedMemoryHandle( |
| const SharedMemoryHandle& handle) { |
| return handle.GetFileDescriptor().fd; |
| } |
| |
| bool SharedMemory::CreateAndMapAnonymous(size_t size) { |
| return CreateAnonymous(size) && Map(size); |
| } |
| |
| // static |
| int SharedMemory::GetSizeFromSharedMemoryHandle( |
| const SharedMemoryHandle& handle) { |
| struct stat st; |
| if (fstat(GetFdFromSharedMemoryHandle(handle), &st) != 0) |
| return -1; |
| return st.st_size; |
| } |
| |
| // Chromium mostly only uses the unique/private shmem as specified by |
| // "name == L"". The exception is in the StatsTable. |
| // TODO(jrg): there is no way to "clean up" all unused named shmem if |
| // we restart from a crash. (That isn't a new problem, but it is a problem.) |
| // In case we want to delete it later, it may be useful to save the value |
| // of mem_filename after FilePathForMemoryName(). |
| bool SharedMemory::Create(const SharedMemoryCreateOptions& options) { |
| // TODO(erikchen): Remove ScopedTracker below once http://crbug.com/466437 |
| // is fixed. |
| tracked_objects::ScopedTracker tracking_profile1( |
| FROM_HERE_WITH_EXPLICIT_FUNCTION( |
| "466437 SharedMemory::Create::Start")); |
| DCHECK_EQ(-1, mapped_file_); |
| if (options.size == 0) return false; |
| |
| if (options.size > static_cast<size_t>(std::numeric_limits<int>::max())) |
| return false; |
| |
| // This function theoretically can block on the disk, but realistically |
| // the temporary files we create will just go into the buffer cache |
| // and be deleted before they ever make it out to disk. |
| base::ThreadRestrictions::ScopedAllowIO allow_io; |
| |
| ScopedFILE fp; |
| bool fix_size = true; |
| ScopedFD readonly_fd; |
| |
| FilePath path; |
| if (options.name_deprecated == NULL || options.name_deprecated->empty()) { |
| bool result = |
| CreateAnonymousSharedMemory(options, &fp, &readonly_fd, &path); |
| if (!result) |
| return false; |
| } else { |
| if (!FilePathForMemoryName(*options.name_deprecated, &path)) |
| return false; |
| |
| // Make sure that the file is opened without any permission |
| // to other users on the system. |
| const mode_t kOwnerOnly = S_IRUSR | S_IWUSR; |
| |
| // First, try to create the file. |
| int fd = HANDLE_EINTR( |
| open(path.value().c_str(), O_RDWR | O_CREAT | O_EXCL, kOwnerOnly)); |
| if (fd == -1 && options.open_existing_deprecated) { |
| // If this doesn't work, try and open an existing file in append mode. |
| // Opening an existing file in a world writable directory has two main |
| // security implications: |
| // - Attackers could plant a file under their control, so ownership of |
| // the file is checked below. |
| // - Attackers could plant a symbolic link so that an unexpected file |
| // is opened, so O_NOFOLLOW is passed to open(). |
| fd = HANDLE_EINTR( |
| open(path.value().c_str(), O_RDWR | O_APPEND | O_NOFOLLOW)); |
| |
| // Check that the current user owns the file. |
| // If uid != euid, then a more complex permission model is used and this |
| // API is not appropriate. |
| const uid_t real_uid = getuid(); |
| const uid_t effective_uid = geteuid(); |
| struct stat sb; |
| if (fd >= 0 && |
| (fstat(fd, &sb) != 0 || sb.st_uid != real_uid || |
| sb.st_uid != effective_uid)) { |
| LOG(ERROR) << |
| "Invalid owner when opening existing shared memory file."; |
| close(fd); |
| return false; |
| } |
| |
| // An existing file was opened, so its size should not be fixed. |
| fix_size = false; |
| } |
| |
| if (options.share_read_only) { |
| // Also open as readonly so that we can ShareReadOnlyToProcess. |
| readonly_fd.reset(HANDLE_EINTR(open(path.value().c_str(), O_RDONLY))); |
| if (!readonly_fd.is_valid()) { |
| DPLOG(ERROR) << "open(\"" << path.value() << "\", O_RDONLY) failed"; |
| close(fd); |
| fd = -1; |
| return false; |
| } |
| } |
| if (fd >= 0) { |
| // "a+" is always appropriate: if it's a new file, a+ is similar to w+. |
| fp.reset(fdopen(fd, "a+")); |
| } |
| } |
| if (fp && fix_size) { |
| // Get current size. |
| struct stat stat; |
| if (fstat(fileno(fp.get()), &stat) != 0) |
| return false; |
| const size_t current_size = stat.st_size; |
| if (current_size != options.size) { |
| if (HANDLE_EINTR(ftruncate(fileno(fp.get()), options.size)) != 0) |
| return false; |
| } |
| requested_size_ = options.size; |
| } |
| if (fp == NULL) { |
| PLOG(ERROR) << "Creating shared memory in " << path.value() << " failed"; |
| return false; |
| } |
| |
| return PrepareMapFile(fp.Pass(), readonly_fd.Pass()); |
| } |
| |
| // Our current implementation of shmem is with mmap()ing of files. |
| // These files need to be deleted explicitly. |
| // In practice this call is only needed for unit tests. |
| bool SharedMemory::Delete(const std::string& name) { |
| FilePath path; |
| if (!FilePathForMemoryName(name, &path)) |
| return false; |
| |
| if (PathExists(path)) |
| return base::DeleteFile(path, false); |
| |
| // Doesn't exist, so success. |
| return true; |
| } |
| |
| bool SharedMemory::Open(const std::string& name, bool read_only) { |
| FilePath path; |
| if (!FilePathForMemoryName(name, &path)) |
| return false; |
| |
| read_only_ = read_only; |
| |
| const char *mode = read_only ? "r" : "r+"; |
| ScopedFILE fp(base::OpenFile(path, mode)); |
| ScopedFD readonly_fd(HANDLE_EINTR(open(path.value().c_str(), O_RDONLY))); |
| if (!readonly_fd.is_valid()) { |
| DPLOG(ERROR) << "open(\"" << path.value() << "\", O_RDONLY) failed"; |
| return false; |
| } |
| return PrepareMapFile(fp.Pass(), readonly_fd.Pass()); |
| } |
| |
| bool SharedMemory::MapAt(off_t offset, size_t bytes) { |
| if (mapped_file_ == -1) |
| return false; |
| |
| if (bytes > static_cast<size_t>(std::numeric_limits<int>::max())) |
| return false; |
| |
| if (memory_) |
| return false; |
| |
| memory_ = mmap(NULL, bytes, PROT_READ | (read_only_ ? 0 : PROT_WRITE), |
| MAP_SHARED, mapped_file_, offset); |
| |
| bool mmap_succeeded = memory_ != (void*)-1 && memory_ != NULL; |
| if (mmap_succeeded) { |
| mapped_size_ = bytes; |
| DCHECK_EQ(0U, reinterpret_cast<uintptr_t>(memory_) & |
| (SharedMemory::MAP_MINIMUM_ALIGNMENT - 1)); |
| } else { |
| memory_ = NULL; |
| } |
| |
| return mmap_succeeded; |
| } |
| |
| bool SharedMemory::Unmap() { |
| if (memory_ == NULL) |
| return false; |
| |
| munmap(memory_, mapped_size_); |
| memory_ = NULL; |
| mapped_size_ = 0; |
| return true; |
| } |
| |
| SharedMemoryHandle SharedMemory::handle() const { |
| return SharedMemoryHandle(mapped_file_, false); |
| } |
| |
| void SharedMemory::Close() { |
| if (mapped_file_ > 0) { |
| if (close(mapped_file_) < 0) |
| PLOG(ERROR) << "close"; |
| mapped_file_ = -1; |
| } |
| if (readonly_mapped_file_ > 0) { |
| if (close(readonly_mapped_file_) < 0) |
| PLOG(ERROR) << "close"; |
| readonly_mapped_file_ = -1; |
| } |
| } |
| |
| bool SharedMemory::PrepareMapFile(ScopedFILE fp, ScopedFD readonly_fd) { |
| DCHECK_EQ(-1, mapped_file_); |
| DCHECK_EQ(-1, readonly_mapped_file_); |
| if (fp == NULL) |
| return false; |
| |
| // This function theoretically can block on the disk, but realistically |
| // the temporary files we create will just go into the buffer cache |
| // and be deleted before they ever make it out to disk. |
| base::ThreadRestrictions::ScopedAllowIO allow_io; |
| |
| struct stat st = {}; |
| if (fstat(fileno(fp.get()), &st)) |
| NOTREACHED(); |
| if (readonly_fd.is_valid()) { |
| struct stat readonly_st = {}; |
| if (fstat(readonly_fd.get(), &readonly_st)) |
| NOTREACHED(); |
| if (st.st_dev != readonly_st.st_dev || st.st_ino != readonly_st.st_ino) { |
| LOG(ERROR) << "writable and read-only inodes don't match; bailing"; |
| return false; |
| } |
| } |
| |
| mapped_file_ = HANDLE_EINTR(dup(fileno(fp.get()))); |
| if (mapped_file_ == -1) { |
| if (errno == EMFILE) { |
| LOG(WARNING) << "Shared memory creation failed; out of file descriptors"; |
| return false; |
| } else { |
| NOTREACHED() << "Call to dup failed, errno=" << errno; |
| } |
| } |
| readonly_mapped_file_ = readonly_fd.release(); |
| |
| return true; |
| } |
| |
| // For the given shmem named |mem_name|, return a filename to mmap() |
| // (and possibly create). Modifies |filename|. Return false on |
| // error, or true of we are happy. |
| bool SharedMemory::FilePathForMemoryName(const std::string& mem_name, |
| FilePath* path) { |
| // mem_name will be used for a filename; make sure it doesn't |
| // contain anything which will confuse us. |
| DCHECK_EQ(std::string::npos, mem_name.find('/')); |
| DCHECK_EQ(std::string::npos, mem_name.find('\0')); |
| |
| FilePath temp_dir; |
| if (!GetShmemTempDir(false, &temp_dir)) |
| return false; |
| |
| std::string name_base = std::string(base::mac::BaseBundleID()); |
| *path = temp_dir.AppendASCII(name_base + ".shmem." + mem_name); |
| return true; |
| } |
| |
| bool SharedMemory::ShareToProcessCommon(ProcessHandle process, |
| SharedMemoryHandle* new_handle, |
| bool close_self, |
| ShareMode share_mode) { |
| int handle_to_dup = -1; |
| switch(share_mode) { |
| case SHARE_CURRENT_MODE: |
| handle_to_dup = mapped_file_; |
| break; |
| case SHARE_READONLY: |
| // We could imagine re-opening the file from /dev/fd, but that can't make |
| // it readonly on Mac: https://codereview.chromium.org/27265002/#msg10 |
| CHECK_GE(readonly_mapped_file_, 0); |
| handle_to_dup = readonly_mapped_file_; |
| break; |
| } |
| |
| const int new_fd = HANDLE_EINTR(dup(handle_to_dup)); |
| if (new_fd < 0) { |
| DPLOG(ERROR) << "dup() failed."; |
| return false; |
| } |
| |
| new_handle->SetFileHandle(new_fd, true); |
| |
| if (close_self) { |
| Unmap(); |
| Close(); |
| } |
| |
| return true; |
| } |
| |
| } // namespace base |