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/*
* Copyright (C) 2018 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "AppFuseUtil.h"
#include <sys/mount.h>
#include <utils/Errors.h>
#include <android-base/logging.h>
#include <android-base/stringprintf.h>
#include "Utils.h"
using android::base::StringPrintf;
namespace android {
namespace vold {
namespace {
static size_t kAppFuseMaxMountPointName = 32;
static android::status_t GetMountPath(uid_t uid, const std::string& name, std::string* path) {
if (name.size() > kAppFuseMaxMountPointName) {
LOG(ERROR) << "AppFuse mount name is too long.";
return -EINVAL;
}
for (size_t i = 0; i < name.size(); i++) {
if (!isalnum(name[i])) {
LOG(ERROR) << "AppFuse mount name contains invalid character.";
return -EINVAL;
}
}
*path = StringPrintf("/mnt/appfuse/%d_%s", uid, name.c_str());
return android::OK;
}
static android::status_t Mount(int device_fd, const std::string& path) {
const auto opts = StringPrintf(
"fd=%i,"
"rootmode=40000,"
"default_permissions,"
"allow_other,"
"user_id=0,group_id=0,"
"context=\"u:object_r:app_fuse_file:s0\","
"fscontext=u:object_r:app_fusefs:s0",
device_fd);
const int result =
TEMP_FAILURE_RETRY(mount("/dev/fuse", path.c_str(), "fuse",
MS_NOSUID | MS_NODEV | MS_NOEXEC | MS_NOATIME, opts.c_str()));
if (result != 0) {
PLOG(ERROR) << "Failed to mount " << path;
return -errno;
}
return android::OK;
}
static android::status_t RunCommand(const std::string& command, uid_t uid, const std::string& path,
int device_fd) {
if (DEBUG_APPFUSE) {
LOG(DEBUG) << "Run app fuse command " << command << " for the path " << path << " and uid "
<< uid;
}
if (command == "mount") {
return Mount(device_fd, path);
} else if (command == "unmount") {
// If it's just after all FD opened on mount point are closed, umount2 can fail with
// EBUSY. To avoid the case, specify MNT_DETACH.
if (umount2(path.c_str(), UMOUNT_NOFOLLOW | MNT_DETACH) != 0 && errno != EINVAL &&
errno != ENOENT) {
PLOG(ERROR) << "Failed to unmount directory.";
return -errno;
}
if (rmdir(path.c_str()) != 0) {
PLOG(ERROR) << "Failed to remove the mount directory.";
return -errno;
}
return android::OK;
} else {
LOG(ERROR) << "Unknown appfuse command " << command;
return -EPERM;
}
return android::OK;
}
} // namespace
int MountAppFuse(uid_t uid, int mountId, android::base::unique_fd* device_fd) {
std::string name = std::to_string(mountId);
// Check mount point name.
std::string path;
if (GetMountPath(uid, name, &path) != android::OK) {
LOG(ERROR) << "Invalid mount point name";
return -1;
}
// Forcibly remove the existing mount before we attempt to prepare the
// directory. If we have a dangling mount, then PrepareDir may fail if the
// indirection to FUSE doesn't work.
android::vold::ForceUnmount(path);
// Create directories.
const android::status_t result = android::vold::PrepareDir(path, 0700, 0, 0);
if (result != android::OK) {
PLOG(ERROR) << "Failed to prepare directory " << path;
return -1;
}
// Open device FD.
// NOLINTNEXTLINE(android-cloexec-open): Deliberately not O_CLOEXEC
device_fd->reset(open("/dev/fuse", O_RDWR));
if (device_fd->get() == -1) {
PLOG(ERROR) << "Failed to open /dev/fuse";
return -1;
}
// Mount.
return RunCommand("mount", uid, path, device_fd->get());
}
int UnmountAppFuse(uid_t uid, int mountId) {
std::string name = std::to_string(mountId);
// Check mount point name.
std::string path;
if (GetMountPath(uid, name, &path) != android::OK) {
LOG(ERROR) << "Invalid mount point name";
return -1;
}
return RunCommand("unmount", uid, path, -1 /* device_fd */);
}
int OpenAppFuseFile(uid_t uid, int mountId, int fileId, int flags) {
std::string name = std::to_string(mountId);
// Check mount point name.
std::string mountPoint;
if (GetMountPath(uid, name, &mountPoint) != android::OK) {
LOG(ERROR) << "Invalid mount point name";
return -1;
}
std::string path = StringPrintf("%s/%d", mountPoint.c_str(), fileId);
return TEMP_FAILURE_RETRY(open(path.c_str(), flags));
}
} // namespace vold
} // namespace android