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@@ -6,6 +6,8 @@
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#include <sys/types.h>
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#include <sys/mount.h>
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#include <sys/wait.h>
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+#include <sys/vfs.h>
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+#include <sys/statvfs.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <fcntl.h>
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@@ -32,11 +34,14 @@
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# define CLONE_NEWPID 0x20000000
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#endif
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+#ifndef MS_REC
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+# define MS_REC 16384
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+#endif
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#ifndef MS_RELATIME
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-#define MS_RELATIME (1 << 21)
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+# define MS_RELATIME (1 << 21)
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#endif
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#ifndef MS_STRICTATIME
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-#define MS_STRICTATIME (1 << 24)
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+# define MS_STRICTATIME (1 << 24)
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#endif
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static void die(char *fmt, ...)
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@@ -48,17 +53,14 @@ static void die(char *fmt, ...)
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exit(EXIT_FAILURE);
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}
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-static void write_file(char *filename, char *fmt, ...)
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+static void vmaybe_write_file(bool enoent_ok, char *filename, char *fmt, va_list ap)
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{
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char buf[4096];
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int fd;
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ssize_t written;
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int buf_len;
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- va_list ap;
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- va_start(ap, fmt);
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buf_len = vsnprintf(buf, sizeof(buf), fmt, ap);
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- va_end(ap);
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if (buf_len < 0) {
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die("vsnprintf failed: %s\n",
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strerror(errno));
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@@ -69,6 +71,8 @@ static void write_file(char *filename, char *fmt, ...)
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fd = open(filename, O_WRONLY);
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if (fd < 0) {
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+ if ((errno == ENOENT) && enoent_ok)
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+ return;
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die("open of %s failed: %s\n",
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filename, strerror(errno));
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}
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@@ -87,6 +91,65 @@ static void write_file(char *filename, char *fmt, ...)
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}
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}
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+static void maybe_write_file(char *filename, char *fmt, ...)
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+{
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+ va_list ap;
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+
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+ va_start(ap, fmt);
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+ vmaybe_write_file(true, filename, fmt, ap);
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+ va_end(ap);
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+
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+}
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+
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+static void write_file(char *filename, char *fmt, ...)
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+{
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+ va_list ap;
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+
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+ va_start(ap, fmt);
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+ vmaybe_write_file(false, filename, fmt, ap);
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+ va_end(ap);
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+
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+}
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+
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+static int read_mnt_flags(const char *path)
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+{
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+ int ret;
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+ struct statvfs stat;
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+ int mnt_flags;
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+
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+ ret = statvfs(path, &stat);
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+ if (ret != 0) {
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+ die("statvfs of %s failed: %s\n",
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+ path, strerror(errno));
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+ }
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+ if (stat.f_flag & ~(ST_RDONLY | ST_NOSUID | ST_NODEV | \
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+ ST_NOEXEC | ST_NOATIME | ST_NODIRATIME | ST_RELATIME | \
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+ ST_SYNCHRONOUS | ST_MANDLOCK)) {
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+ die("Unrecognized mount flags\n");
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+ }
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+ mnt_flags = 0;
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+ if (stat.f_flag & ST_RDONLY)
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+ mnt_flags |= MS_RDONLY;
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+ if (stat.f_flag & ST_NOSUID)
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+ mnt_flags |= MS_NOSUID;
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+ if (stat.f_flag & ST_NODEV)
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+ mnt_flags |= MS_NODEV;
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+ if (stat.f_flag & ST_NOEXEC)
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+ mnt_flags |= MS_NOEXEC;
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+ if (stat.f_flag & ST_NOATIME)
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+ mnt_flags |= MS_NOATIME;
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+ if (stat.f_flag & ST_NODIRATIME)
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+ mnt_flags |= MS_NODIRATIME;
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+ if (stat.f_flag & ST_RELATIME)
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+ mnt_flags |= MS_RELATIME;
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+ if (stat.f_flag & ST_SYNCHRONOUS)
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+ mnt_flags |= MS_SYNCHRONOUS;
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+ if (stat.f_flag & ST_MANDLOCK)
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+ mnt_flags |= ST_MANDLOCK;
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+
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+ return mnt_flags;
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+}
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+
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static void create_and_enter_userns(void)
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{
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uid_t uid;
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@@ -100,13 +163,10 @@ static void create_and_enter_userns(void)
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strerror(errno));
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}
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+ maybe_write_file("/proc/self/setgroups", "deny");
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write_file("/proc/self/uid_map", "0 %d 1", uid);
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write_file("/proc/self/gid_map", "0 %d 1", gid);
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- if (setgroups(0, NULL) != 0) {
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- die("setgroups failed: %s\n",
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- strerror(errno));
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- }
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if (setgid(0) != 0) {
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die ("setgid(0) failed %s\n",
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strerror(errno));
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@@ -118,7 +178,8 @@ static void create_and_enter_userns(void)
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}
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static
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-bool test_unpriv_remount(int mount_flags, int remount_flags, int invalid_flags)
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+bool test_unpriv_remount(const char *fstype, const char *mount_options,
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+ int mount_flags, int remount_flags, int invalid_flags)
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{
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pid_t child;
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@@ -151,9 +212,11 @@ bool test_unpriv_remount(int mount_flags, int remount_flags, int invalid_flags)
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strerror(errno));
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}
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- if (mount("testing", "/tmp", "ramfs", mount_flags, NULL) != 0) {
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- die("mount of /tmp failed: %s\n",
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- strerror(errno));
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+ if (mount("testing", "/tmp", fstype, mount_flags, mount_options) != 0) {
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+ die("mount of %s with options '%s' on /tmp failed: %s\n",
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+ fstype,
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+ mount_options? mount_options : "",
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+ strerror(errno));
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}
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create_and_enter_userns();
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@@ -181,62 +244,127 @@ bool test_unpriv_remount(int mount_flags, int remount_flags, int invalid_flags)
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static bool test_unpriv_remount_simple(int mount_flags)
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{
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- return test_unpriv_remount(mount_flags, mount_flags, 0);
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+ return test_unpriv_remount("ramfs", NULL, mount_flags, mount_flags, 0);
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}
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static bool test_unpriv_remount_atime(int mount_flags, int invalid_flags)
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{
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- return test_unpriv_remount(mount_flags, mount_flags, invalid_flags);
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+ return test_unpriv_remount("ramfs", NULL, mount_flags, mount_flags,
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+ invalid_flags);
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+}
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+
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+static bool test_priv_mount_unpriv_remount(void)
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+{
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+ pid_t child;
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+ int ret;
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+ const char *orig_path = "/dev";
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+ const char *dest_path = "/tmp";
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+ int orig_mnt_flags, remount_mnt_flags;
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+
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+ child = fork();
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+ if (child == -1) {
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+ die("fork failed: %s\n",
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+ strerror(errno));
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+ }
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+ if (child != 0) { /* parent */
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+ pid_t pid;
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+ int status;
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+ pid = waitpid(child, &status, 0);
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+ if (pid == -1) {
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+ die("waitpid failed: %s\n",
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+ strerror(errno));
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+ }
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+ if (pid != child) {
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+ die("waited for %d got %d\n",
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+ child, pid);
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+ }
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+ if (!WIFEXITED(status)) {
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+ die("child did not terminate cleanly\n");
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+ }
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+ return WEXITSTATUS(status) == EXIT_SUCCESS ? true : false;
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+ }
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+
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+ orig_mnt_flags = read_mnt_flags(orig_path);
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+
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+ create_and_enter_userns();
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+ ret = unshare(CLONE_NEWNS);
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+ if (ret != 0) {
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+ die("unshare(CLONE_NEWNS) failed: %s\n",
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+ strerror(errno));
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+ }
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+
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+ ret = mount(orig_path, dest_path, "bind", MS_BIND | MS_REC, NULL);
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+ if (ret != 0) {
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+ die("recursive bind mount of %s onto %s failed: %s\n",
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+ orig_path, dest_path, strerror(errno));
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+ }
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+
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+ ret = mount(dest_path, dest_path, "none",
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+ MS_REMOUNT | MS_BIND | orig_mnt_flags , NULL);
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+ if (ret != 0) {
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+ /* system("cat /proc/self/mounts"); */
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+ die("remount of /tmp failed: %s\n",
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+ strerror(errno));
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+ }
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+
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+ remount_mnt_flags = read_mnt_flags(dest_path);
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+ if (orig_mnt_flags != remount_mnt_flags) {
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+ die("Mount flags unexpectedly changed during remount of %s originally mounted on %s\n",
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+ dest_path, orig_path);
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+ }
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+ exit(EXIT_SUCCESS);
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}
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int main(int argc, char **argv)
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{
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- if (!test_unpriv_remount_simple(MS_RDONLY|MS_NODEV)) {
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+ if (!test_unpriv_remount_simple(MS_RDONLY)) {
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die("MS_RDONLY malfunctions\n");
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}
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- if (!test_unpriv_remount_simple(MS_NODEV)) {
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+ if (!test_unpriv_remount("devpts", "newinstance", MS_NODEV, MS_NODEV, 0)) {
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die("MS_NODEV malfunctions\n");
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}
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- if (!test_unpriv_remount_simple(MS_NOSUID|MS_NODEV)) {
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+ if (!test_unpriv_remount_simple(MS_NOSUID)) {
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die("MS_NOSUID malfunctions\n");
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}
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- if (!test_unpriv_remount_simple(MS_NOEXEC|MS_NODEV)) {
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+ if (!test_unpriv_remount_simple(MS_NOEXEC)) {
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die("MS_NOEXEC malfunctions\n");
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}
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- if (!test_unpriv_remount_atime(MS_RELATIME|MS_NODEV,
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- MS_NOATIME|MS_NODEV))
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+ if (!test_unpriv_remount_atime(MS_RELATIME,
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+ MS_NOATIME))
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{
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die("MS_RELATIME malfunctions\n");
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}
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- if (!test_unpriv_remount_atime(MS_STRICTATIME|MS_NODEV,
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- MS_NOATIME|MS_NODEV))
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+ if (!test_unpriv_remount_atime(MS_STRICTATIME,
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+ MS_NOATIME))
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{
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die("MS_STRICTATIME malfunctions\n");
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}
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- if (!test_unpriv_remount_atime(MS_NOATIME|MS_NODEV,
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- MS_STRICTATIME|MS_NODEV))
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+ if (!test_unpriv_remount_atime(MS_NOATIME,
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+ MS_STRICTATIME))
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{
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- die("MS_RELATIME malfunctions\n");
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+ die("MS_NOATIME malfunctions\n");
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}
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- if (!test_unpriv_remount_atime(MS_RELATIME|MS_NODIRATIME|MS_NODEV,
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- MS_NOATIME|MS_NODEV))
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+ if (!test_unpriv_remount_atime(MS_RELATIME|MS_NODIRATIME,
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+ MS_NOATIME))
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{
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- die("MS_RELATIME malfunctions\n");
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+ die("MS_RELATIME|MS_NODIRATIME malfunctions\n");
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}
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- if (!test_unpriv_remount_atime(MS_STRICTATIME|MS_NODIRATIME|MS_NODEV,
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- MS_NOATIME|MS_NODEV))
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+ if (!test_unpriv_remount_atime(MS_STRICTATIME|MS_NODIRATIME,
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+ MS_NOATIME))
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{
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- die("MS_RELATIME malfunctions\n");
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+ die("MS_STRICTATIME|MS_NODIRATIME malfunctions\n");
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}
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- if (!test_unpriv_remount_atime(MS_NOATIME|MS_NODIRATIME|MS_NODEV,
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- MS_STRICTATIME|MS_NODEV))
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+ if (!test_unpriv_remount_atime(MS_NOATIME|MS_NODIRATIME,
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+ MS_STRICTATIME))
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{
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- die("MS_RELATIME malfunctions\n");
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+ die("MS_NOATIME|MS_DIRATIME malfunctions\n");
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}
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- if (!test_unpriv_remount(MS_STRICTATIME|MS_NODEV, MS_NODEV,
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- MS_NOATIME|MS_NODEV))
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+ if (!test_unpriv_remount("ramfs", NULL, MS_STRICTATIME, 0, MS_NOATIME))
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{
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die("Default atime malfunctions\n");
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}
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+ if (!test_priv_mount_unpriv_remount()) {
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+ die("Mount flags unexpectedly changed after remount\n");
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+ }
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return EXIT_SUCCESS;
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}
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Linus Torvalds