1 /*
2 * Copyright (C) 2018 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #include <dirent.h>
18 #include <selinux/selinux.h>
19 #include <sys/mount.h>
20 #include <unistd.h>
21
22 #include <memory>
23 #include <string>
24 #include <vector>
25
26 #include <android-base/logging.h>
27 #include <android-base/properties.h>
28 #include <fs_mgr_vendor_overlay.h>
29 #include <fstab/fstab.h>
30
31 #include "fs_mgr_priv.h"
32
33 using namespace std::literals;
34
35 namespace {
36
37 // The order of the list means the priority to show the files in the directory.
38 // The last one has the highest priority.
39 const std::vector<const std::string> kVendorOverlaySourceDirs = {
40 "/system/vendor_overlay/",
41 "/product/vendor_overlay/",
42 };
43 const auto kVndkVersionPropertyName = "ro.vndk.version"s;
44 const auto kVendorTopDir = "/vendor/"s;
45 const auto kLowerdirOption = "lowerdir="s;
46
fs_mgr_get_vendor_overlay_dirs(const std::string & vndk_version)47 std::vector<std::pair<std::string, std::string>> fs_mgr_get_vendor_overlay_dirs(
48 const std::string& vndk_version) {
49 std::vector<std::pair<std::string, std::string>> vendor_overlay_dirs;
50 for (const auto& vendor_overlay_source : kVendorOverlaySourceDirs) {
51 const auto overlay_top = vendor_overlay_source + vndk_version;
52 std::unique_ptr<DIR, decltype(&closedir)> vendor_overlay_top(opendir(overlay_top.c_str()),
53 closedir);
54 if (!vendor_overlay_top) continue;
55
56 // Vendor overlay root for current vendor version found!
57 LINFO << "vendor overlay root: " << overlay_top;
58
59 struct dirent* dp;
60 while ((dp = readdir(vendor_overlay_top.get())) != nullptr) {
61 if (dp->d_type != DT_DIR || dp->d_name[0] == '.') {
62 continue;
63 }
64 vendor_overlay_dirs.emplace_back(overlay_top, dp->d_name);
65 }
66 }
67 return vendor_overlay_dirs;
68 }
69
fs_mgr_vendor_overlay_mount(const std::pair<std::string,std::string> & mount_point)70 bool fs_mgr_vendor_overlay_mount(const std::pair<std::string, std::string>& mount_point) {
71 const auto [overlay_top, mount_dir] = mount_point;
72 const auto vendor_mount_point = kVendorTopDir + mount_dir;
73 LINFO << "vendor overlay mount on " << vendor_mount_point;
74
75 const auto target_context = fs_mgr_get_context(vendor_mount_point);
76 if (target_context.empty()) {
77 PERROR << " failed: cannot find the target vendor mount point";
78 return false;
79 }
80 const auto source_directory = overlay_top + "/" + mount_dir;
81 const auto source_context = fs_mgr_get_context(source_directory);
82 if (target_context != source_context) {
83 LERROR << " failed: source and target contexts do not match (source:" << source_context
84 << ", target:" << target_context << ")";
85 return false;
86 }
87
88 const auto options = kLowerdirOption + source_directory + ":" + vendor_mount_point +
89 android::fs_mgr::CheckOverlayfs().mount_flags;
90 auto report = "__mount(source=overlay,target="s + vendor_mount_point + ",type=overlay," +
91 options + ")=";
92 auto ret = mount("overlay", vendor_mount_point.c_str(), "overlay", MS_RDONLY | MS_NOATIME,
93 options.c_str());
94 if (ret) {
95 PERROR << report << ret;
96 return false;
97 } else {
98 LINFO << report << ret;
99 return true;
100 }
101 }
102
103 } // namespace
104
105 // Since the vendor overlay requires to know the version of the vendor partition,
106 // it is not possible to mount vendor overlay at the first stage that cannot
107 // initialize properties.
108 // To read the properties, vendor overlay must be mounted at the second stage, right
109 // after "property_load_boot_defaults()" is called.
fs_mgr_vendor_overlay_mount_all()110 bool fs_mgr_vendor_overlay_mount_all() {
111 // To read the property, it must be called at the second init stage after the default
112 // properties are loaded.
113 static const auto vndk_version = android::base::GetProperty(kVndkVersionPropertyName, "");
114 if (vndk_version.empty()) {
115 // Vendor overlay is disabled from VNDK deprecated devices.
116 LINFO << "vendor overlay: vndk version not defined";
117 return false;
118 }
119
120 const auto vendor_overlay_dirs = fs_mgr_get_vendor_overlay_dirs(vndk_version);
121 if (vendor_overlay_dirs.empty()) return true;
122 if (!android::fs_mgr::CheckOverlayfs().supported) {
123 LINFO << "vendor overlay: kernel does not support overlayfs";
124 return false;
125 }
126
127 // Mount each directory in /(system|product)/vendor_overlay/<ver> on /vendor
128 auto ret = true;
129 for (const auto& vendor_overlay_dir : vendor_overlay_dirs) {
130 if (!fs_mgr_vendor_overlay_mount(vendor_overlay_dir)) {
131 ret = false;
132 }
133 }
134 return ret;
135 }
136