1 // SPDX-License-Identifier: GPL-2.0
11 #include <sys/statvfs.h>
20 # define CLONE_NEWNS 0x00020000
23 # define CLONE_NEWUTS 0x04000000
26 # define CLONE_NEWIPC 0x08000000
29 # define CLONE_NEWNET 0x40000000
32 # define CLONE_NEWUSER 0x10000000
35 # define CLONE_NEWPID 0x20000000
42 # define MS_RELATIME (1 << 21)
44 #ifndef MS_STRICTATIME
45 # define MS_STRICTATIME (1 << 24)
48 static void die(char *fmt, ...)
52 vfprintf(stderr, fmt, ap);
57 static void vmaybe_write_file(bool enoent_ok, char *filename, char *fmt, va_list ap)
64 buf_len = vsnprintf(buf, sizeof(buf), fmt, ap);
66 die("vsnprintf failed: %s\n",
69 if (buf_len >= sizeof(buf)) {
70 die("vsnprintf output truncated\n");
73 fd = open(filename, O_WRONLY);
75 if ((errno == ENOENT) && enoent_ok)
77 die("open of %s failed: %s\n",
78 filename, strerror(errno));
80 written = write(fd, buf, buf_len);
81 if (written != buf_len) {
83 die("short write to %s\n", filename);
85 die("write to %s failed: %s\n",
86 filename, strerror(errno));
90 die("close of %s failed: %s\n",
91 filename, strerror(errno));
95 static void maybe_write_file(char *filename, char *fmt, ...)
100 vmaybe_write_file(true, filename, fmt, ap);
105 static void write_file(char *filename, char *fmt, ...)
110 vmaybe_write_file(false, filename, fmt, ap);
115 static int read_mnt_flags(const char *path)
121 ret = statvfs(path, &stat);
123 die("statvfs of %s failed: %s\n",
124 path, strerror(errno));
126 if (stat.f_flag & ~(ST_RDONLY | ST_NOSUID | ST_NODEV | \
127 ST_NOEXEC | ST_NOATIME | ST_NODIRATIME | ST_RELATIME | \
128 ST_SYNCHRONOUS | ST_MANDLOCK)) {
129 die("Unrecognized mount flags\n");
132 if (stat.f_flag & ST_RDONLY)
133 mnt_flags |= MS_RDONLY;
134 if (stat.f_flag & ST_NOSUID)
135 mnt_flags |= MS_NOSUID;
136 if (stat.f_flag & ST_NODEV)
137 mnt_flags |= MS_NODEV;
138 if (stat.f_flag & ST_NOEXEC)
139 mnt_flags |= MS_NOEXEC;
140 if (stat.f_flag & ST_NOATIME)
141 mnt_flags |= MS_NOATIME;
142 if (stat.f_flag & ST_NODIRATIME)
143 mnt_flags |= MS_NODIRATIME;
144 if (stat.f_flag & ST_RELATIME)
145 mnt_flags |= MS_RELATIME;
146 if (stat.f_flag & ST_SYNCHRONOUS)
147 mnt_flags |= MS_SYNCHRONOUS;
148 if (stat.f_flag & ST_MANDLOCK)
149 mnt_flags |= ST_MANDLOCK;
154 static void create_and_enter_userns(void)
162 if (unshare(CLONE_NEWUSER) !=0) {
163 die("unshare(CLONE_NEWUSER) failed: %s\n",
167 maybe_write_file("/proc/self/setgroups", "deny");
168 write_file("/proc/self/uid_map", "0 %d 1", uid);
169 write_file("/proc/self/gid_map", "0 %d 1", gid);
171 if (setgid(0) != 0) {
172 die ("setgid(0) failed %s\n",
175 if (setuid(0) != 0) {
176 die("setuid(0) failed %s\n",
182 bool test_unpriv_remount(const char *fstype, const char *mount_options,
183 int mount_flags, int remount_flags, int invalid_flags)
189 die("fork failed: %s\n",
192 if (child != 0) { /* parent */
195 pid = waitpid(child, &status, 0);
197 die("waitpid failed: %s\n",
201 die("waited for %d got %d\n",
204 if (!WIFEXITED(status)) {
205 die("child did not terminate cleanly\n");
207 return WEXITSTATUS(status) == EXIT_SUCCESS ? true : false;
210 create_and_enter_userns();
211 if (unshare(CLONE_NEWNS) != 0) {
212 die("unshare(CLONE_NEWNS) failed: %s\n",
216 if (mount("testing", "/tmp", fstype, mount_flags, mount_options) != 0) {
217 die("mount of %s with options '%s' on /tmp failed: %s\n",
219 mount_options? mount_options : "",
223 create_and_enter_userns();
225 if (unshare(CLONE_NEWNS) != 0) {
226 die("unshare(CLONE_NEWNS) failed: %s\n",
230 if (mount("/tmp", "/tmp", "none",
231 MS_REMOUNT | MS_BIND | remount_flags, NULL) != 0) {
232 /* system("cat /proc/self/mounts"); */
233 die("remount of /tmp failed: %s\n",
237 if (mount("/tmp", "/tmp", "none",
238 MS_REMOUNT | MS_BIND | invalid_flags, NULL) == 0) {
239 /* system("cat /proc/self/mounts"); */
240 die("remount of /tmp with invalid flags "
241 "succeeded unexpectedly\n");
246 static bool test_unpriv_remount_simple(int mount_flags)
248 return test_unpriv_remount("ramfs", NULL, mount_flags, mount_flags, 0);
251 static bool test_unpriv_remount_atime(int mount_flags, int invalid_flags)
253 return test_unpriv_remount("ramfs", NULL, mount_flags, mount_flags,
257 static bool test_priv_mount_unpriv_remount(void)
261 const char *orig_path = "/dev";
262 const char *dest_path = "/tmp";
263 int orig_mnt_flags, remount_mnt_flags;
267 die("fork failed: %s\n",
270 if (child != 0) { /* parent */
273 pid = waitpid(child, &status, 0);
275 die("waitpid failed: %s\n",
279 die("waited for %d got %d\n",
282 if (!WIFEXITED(status)) {
283 die("child did not terminate cleanly\n");
285 return WEXITSTATUS(status) == EXIT_SUCCESS ? true : false;
288 orig_mnt_flags = read_mnt_flags(orig_path);
290 create_and_enter_userns();
291 ret = unshare(CLONE_NEWNS);
293 die("unshare(CLONE_NEWNS) failed: %s\n",
297 ret = mount(orig_path, dest_path, "bind", MS_BIND | MS_REC, NULL);
299 die("recursive bind mount of %s onto %s failed: %s\n",
300 orig_path, dest_path, strerror(errno));
303 ret = mount(dest_path, dest_path, "none",
304 MS_REMOUNT | MS_BIND | orig_mnt_flags , NULL);
306 /* system("cat /proc/self/mounts"); */
307 die("remount of /tmp failed: %s\n",
311 remount_mnt_flags = read_mnt_flags(dest_path);
312 if (orig_mnt_flags != remount_mnt_flags) {
313 die("Mount flags unexpectedly changed during remount of %s originally mounted on %s\n",
314 dest_path, orig_path);
319 int main(int argc, char **argv)
321 if (!test_unpriv_remount_simple(MS_RDONLY)) {
322 die("MS_RDONLY malfunctions\n");
324 if (!test_unpriv_remount("devpts", "newinstance", MS_NODEV, MS_NODEV, 0)) {
325 die("MS_NODEV malfunctions\n");
327 if (!test_unpriv_remount_simple(MS_NOSUID)) {
328 die("MS_NOSUID malfunctions\n");
330 if (!test_unpriv_remount_simple(MS_NOEXEC)) {
331 die("MS_NOEXEC malfunctions\n");
333 if (!test_unpriv_remount_atime(MS_RELATIME,
336 die("MS_RELATIME malfunctions\n");
338 if (!test_unpriv_remount_atime(MS_STRICTATIME,
341 die("MS_STRICTATIME malfunctions\n");
343 if (!test_unpriv_remount_atime(MS_NOATIME,
346 die("MS_NOATIME malfunctions\n");
348 if (!test_unpriv_remount_atime(MS_RELATIME|MS_NODIRATIME,
351 die("MS_RELATIME|MS_NODIRATIME malfunctions\n");
353 if (!test_unpriv_remount_atime(MS_STRICTATIME|MS_NODIRATIME,
356 die("MS_STRICTATIME|MS_NODIRATIME malfunctions\n");
358 if (!test_unpriv_remount_atime(MS_NOATIME|MS_NODIRATIME,
361 die("MS_NOATIME|MS_DIRATIME malfunctions\n");
363 if (!test_unpriv_remount("ramfs", NULL, MS_STRICTATIME, 0, MS_NOATIME))
365 die("Default atime malfunctions\n");
367 if (!test_priv_mount_unpriv_remount()) {
368 die("Mount flags unexpectedly changed after remount\n");