1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
|
/*
* 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
|
