1 /*
2 * Copyright (C) 2008 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 #define TRACE_TAG ADB
18
19 #include "sysdeps.h"
20
21 #include <errno.h>
22 #include <fcntl.h>
23 #include <mntent.h>
24 #include <stdio.h>
25 #include <stdlib.h>
26 #include <string.h>
27 #include <sys/mount.h>
28 #include <unistd.h>
29
30 #include <string>
31
32 #include "adb.h"
33 #include "adb_io.h"
34 #include "adb_utils.h"
35 #include "cutils/properties.h"
36 #include "fs_mgr.h"
37
38 // Returns the device used to mount a directory in /proc/mounts.
find_proc_mount(const char * dir)39 static std::string find_proc_mount(const char* dir) {
40 std::unique_ptr<FILE, int(*)(FILE*)> fp(setmntent("/proc/mounts", "r"), endmntent);
41 if (!fp) {
42 return "";
43 }
44
45 mntent* e;
46 while ((e = getmntent(fp.get())) != nullptr) {
47 if (strcmp(dir, e->mnt_dir) == 0) {
48 return e->mnt_fsname;
49 }
50 }
51 return "";
52 }
53
54 // Returns the device used to mount a directory in the fstab.
find_fstab_mount(const char * dir)55 static std::string find_fstab_mount(const char* dir) {
56 char propbuf[PROPERTY_VALUE_MAX];
57
58 property_get("ro.hardware", propbuf, "");
59 std::string fstab_filename = std::string("/fstab.") + propbuf;
60 struct fstab* fstab = fs_mgr_read_fstab(fstab_filename.c_str());
61 struct fstab_rec* rec = fs_mgr_get_entry_for_mount_point(fstab, dir);
62 std::string dev = rec ? std::string(rec->blk_device) : "";
63 fs_mgr_free_fstab(fstab);
64 return dev;
65 }
66
67 // The proc entry for / is full of lies, so check fstab instead.
68 // /proc/mounts lists rootfs and /dev/root, neither of which is what we want.
find_mount(const char * dir)69 static std::string find_mount(const char* dir) {
70 if (strcmp(dir, "/") == 0) {
71 return find_fstab_mount(dir);
72 } else {
73 return find_proc_mount(dir);
74 }
75 }
76
make_block_device_writable(const std::string & dev)77 bool make_block_device_writable(const std::string& dev) {
78 int fd = unix_open(dev.c_str(), O_RDONLY | O_CLOEXEC);
79 if (fd == -1) {
80 return false;
81 }
82
83 int OFF = 0;
84 bool result = (ioctl(fd, BLKROSET, &OFF) != -1);
85 unix_close(fd);
86 return result;
87 }
88
remount_partition(int fd,const char * dir)89 static bool remount_partition(int fd, const char* dir) {
90 if (!directory_exists(dir)) {
91 return true;
92 }
93 std::string dev = find_mount(dir);
94 if (dev.empty()) {
95 return true;
96 }
97 if (!make_block_device_writable(dev)) {
98 WriteFdFmt(fd, "remount of %s failed; couldn't make block device %s writable: %s\n",
99 dir, dev.c_str(), strerror(errno));
100 return false;
101 }
102 if (mount(dev.c_str(), dir, "none", MS_REMOUNT, nullptr) == -1) {
103 WriteFdFmt(fd, "remount of %s failed: %s\n", dir, strerror(errno));
104 return false;
105 }
106 return true;
107 }
108
remount_service(int fd,void * cookie)109 void remount_service(int fd, void* cookie) {
110 if (getuid() != 0) {
111 WriteFdExactly(fd, "Not running as root. Try \"adb root\" first.\n");
112 adb_close(fd);
113 return;
114 }
115
116 char prop_buf[PROPERTY_VALUE_MAX];
117 property_get("partition.system.verified", prop_buf, "");
118 bool system_verified = (strlen(prop_buf) > 0);
119
120 property_get("partition.vendor.verified", prop_buf, "");
121 bool vendor_verified = (strlen(prop_buf) > 0);
122
123 if (system_verified || vendor_verified) {
124 // Allow remount but warn of likely bad effects
125 bool both = system_verified && vendor_verified;
126 WriteFdFmt(fd,
127 "dm_verity is enabled on the %s%s%s partition%s.\n",
128 system_verified ? "system" : "",
129 both ? " and " : "",
130 vendor_verified ? "vendor" : "",
131 both ? "s" : "");
132 WriteFdExactly(fd,
133 "Use \"adb disable-verity\" to disable verity.\n"
134 "If you do not, remount may succeed, however, you will still "
135 "not be able to write to these volumes.\n");
136 }
137
138 bool success = true;
139 property_get("ro.build.system_root_image", prop_buf, "");
140 bool system_root = !strcmp(prop_buf, "true");
141 if (system_root) {
142 success &= remount_partition(fd, "/");
143 } else {
144 success &= remount_partition(fd, "/system");
145 }
146 success &= remount_partition(fd, "/vendor");
147 success &= remount_partition(fd, "/oem");
148
149 WriteFdExactly(fd, success ? "remount succeeded\n" : "remount failed\n");
150
151 adb_close(fd);
152 }
153