1 files changed, 166 insertions, 38 deletions

diff --git a/tools/testing/selftests/mount/unprivileged-remount-test.c b/tools/testing/selftests/mount/unprivileged-remount-test.c
index 1b3ff2fda4d0..517785052f1c 100644
--- a/tools/testing/selftests/mount/unprivileged-remount-test.c
+++ b/tools/testing/selftests/mount/unprivileged-remount-test.c
@@ -6,6 +6,8 @@
 #include <sys/types.h>
 #include <sys/mount.h>
 #include <sys/wait.h>
+#include <sys/vfs.h>
+#include <sys/statvfs.h>
 #include <stdlib.h>
 #include <unistd.h>
 #include <fcntl.h>
@@ -32,11 +34,14 @@
 # define CLONE_NEWPID 0x20000000
 #endif
 
+#ifndef MS_REC
+# define MS_REC 16384
+#endif
 #ifndef MS_RELATIME
-#define MS_RELATIME (1 << 21)
+# define MS_RELATIME (1 << 21)
 #endif
 #ifndef MS_STRICTATIME
-#define MS_STRICTATIME (1 << 24)
+# define MS_STRICTATIME (1 << 24)
 #endif
 
 static void die(char *fmt, ...)
@@ -48,17 +53,14 @@ static void die(char *fmt, ...)
         exit(EXIT_FAILURE);
 }
 
-static void write_file(char *filename, char *fmt, ...)
+static void vmaybe_write_file(bool enoent_ok, char *filename, char *fmt, va_list ap)
 {
         char buf[4096];
         int fd;
         ssize_t written;
         int buf_len;
-        va_list ap;
 
-        va_start(ap, fmt);
         buf_len = vsnprintf(buf, sizeof(buf), fmt, ap);
-        va_end(ap);
         if (buf_len < 0) {
                 die("vsnprintf failed: %s\n",
                     strerror(errno));
@@ -69,6 +71,8 @@ static void write_file(char *filename, char *fmt, ...)
 
         fd = open(filename, O_WRONLY);
         if (fd < 0) {
+                if ((errno == ENOENT) && enoent_ok)
+                        return;
                 die("open of %s failed: %s\n",
                     filename, strerror(errno));
         }
@@ -87,6 +91,65 @@ static void write_file(char *filename, char *fmt, ...)
         }
 }
 
+static void maybe_write_file(char *filename, char *fmt, ...)
+{
+        va_list ap;
+
+        va_start(ap, fmt);
+        vmaybe_write_file(true, filename, fmt, ap);
+        va_end(ap);
+
+}
+
+static void write_file(char *filename, char *fmt, ...)
+{
+        va_list ap;
+
+        va_start(ap, fmt);
+        vmaybe_write_file(false, filename, fmt, ap);
+        va_end(ap);
+
+}
+
+static int read_mnt_flags(const char *path)
+{
+        int ret;
+        struct statvfs stat;
+        int mnt_flags;
+
+        ret = statvfs(path, &stat);
+        if (ret != 0) {
+                die("statvfs of %s failed: %s\n",
+                        path, strerror(errno));
+        }
+        if (stat.f_flag & ~(ST_RDONLY | ST_NOSUID | ST_NODEV | \
+                        ST_NOEXEC | ST_NOATIME | ST_NODIRATIME | ST_RELATIME | \
+                        ST_SYNCHRONOUS | ST_MANDLOCK)) {
+                die("Unrecognized mount flags\n");
+        }
+        mnt_flags = 0;
+        if (stat.f_flag & ST_RDONLY)
+                mnt_flags |= MS_RDONLY;
+        if (stat.f_flag & ST_NOSUID)
+                mnt_flags |= MS_NOSUID;
+        if (stat.f_flag & ST_NODEV)
+                mnt_flags |= MS_NODEV;
+        if (stat.f_flag & ST_NOEXEC)
+                mnt_flags |= MS_NOEXEC;
+        if (stat.f_flag & ST_NOATIME)
+                mnt_flags |= MS_NOATIME;
+        if (stat.f_flag & ST_NODIRATIME)
+                mnt_flags |= MS_NODIRATIME;
+        if (stat.f_flag & ST_RELATIME)
+                mnt_flags |= MS_RELATIME;
+        if (stat.f_flag & ST_SYNCHRONOUS)
+                mnt_flags |= MS_SYNCHRONOUS;
+        if (stat.f_flag & ST_MANDLOCK)
+                mnt_flags |= ST_MANDLOCK;
+
+        return mnt_flags;
+}
+
 static void create_and_enter_userns(void)
 {
         uid_t uid;
@@ -100,13 +163,10 @@ static void create_and_enter_userns(void)
                         strerror(errno));
         }
 
+        maybe_write_file("/proc/self/setgroups", "deny");
         write_file("/proc/self/uid_map", "0 %d 1", uid);
         write_file("/proc/self/gid_map", "0 %d 1", gid);
 
-        if (setgroups(0, NULL) != 0) {
-                die("setgroups failed: %s\n",
-                        strerror(errno));
-        }
         if (setgid(0) != 0) {
                 die ("setgid(0) failed %s\n",
                         strerror(errno));
@@ -118,7 +178,8 @@ static void create_and_enter_userns(void)
 }
 
 static
-bool test_unpriv_remount(int mount_flags, int remount_flags, int invalid_flags)
+bool test_unpriv_remount(const char *fstype, const char *mount_options,
+                         int mount_flags, int remount_flags, int invalid_flags)
 {
         pid_t child;
 
@@ -151,9 +212,11 @@ bool test_unpriv_remount(int mount_flags, int remount_flags, int invalid_flags)
                         strerror(errno));
         }
 
-        if (mount("testing", "/tmp", "ramfs", mount_flags, NULL) != 0) {
-                die("mount of /tmp failed: %s\n",
-                        strerror(errno));
+        if (mount("testing", "/tmp", fstype, mount_flags, mount_options) != 0) {
+                die("mount of %s with options '%s' on /tmp failed: %s\n",
+                    fstype,
+                    mount_options? mount_options : "",
+                    strerror(errno));
         }
 
         create_and_enter_userns();
@@ -181,62 +244,127 @@ bool test_unpriv_remount(int mount_flags, int remount_flags, int invalid_flags)
 
 static bool test_unpriv_remount_simple(int mount_flags)
 {
-        return test_unpriv_remount(mount_flags, mount_flags, 0);
+        return test_unpriv_remount("ramfs", NULL, mount_flags, mount_flags, 0);
 }
 
 static bool test_unpriv_remount_atime(int mount_flags, int invalid_flags)
 {
-        return test_unpriv_remount(mount_flags, mount_flags, invalid_flags);
+        return test_unpriv_remount("ramfs", NULL, mount_flags, mount_flags,
+                                   invalid_flags);
+}
+
+static bool test_priv_mount_unpriv_remount(void)
+{
+        pid_t child;
+        int ret;
+        const char *orig_path = "/dev";
+        const char *dest_path = "/tmp";
+        int orig_mnt_flags, remount_mnt_flags;
+
+        child = fork();
+        if (child == -1) {
+                die("fork failed: %s\n",
+                        strerror(errno));
+        }
+        if (child != 0) { /* parent */
+                pid_t pid;
+                int status;
+                pid = waitpid(child, &status, 0);
+                if (pid == -1) {
+                        die("waitpid failed: %s\n",
+                                strerror(errno));
+                }
+                if (pid != child) {
+                        die("waited for %d got %d\n",
+                                child, pid);
+                }
+                if (!WIFEXITED(status)) {
+                        die("child did not terminate cleanly\n");
+                }
+                return WEXITSTATUS(status) == EXIT_SUCCESS ? true : false;
+        }
+
+        orig_mnt_flags = read_mnt_flags(orig_path);
+
+        create_and_enter_userns();
+        ret = unshare(CLONE_NEWNS);
+        if (ret != 0) {
+                die("unshare(CLONE_NEWNS) failed: %s\n",
+                        strerror(errno));
+        }
+
+        ret = mount(orig_path, dest_path, "bind", MS_BIND | MS_REC, NULL);
+        if (ret != 0) {
+                die("recursive bind mount of %s onto %s failed: %s\n",
+                        orig_path, dest_path, strerror(errno));
+        }
+
+        ret = mount(dest_path, dest_path, "none",
+                    MS_REMOUNT | MS_BIND | orig_mnt_flags , NULL);
+        if (ret != 0) {
+                /* system("cat /proc/self/mounts"); */
+                die("remount of /tmp failed: %s\n",
+                    strerror(errno));
+        }
+
+        remount_mnt_flags = read_mnt_flags(dest_path);
+        if (orig_mnt_flags != remount_mnt_flags) {
+                die("Mount flags unexpectedly changed during remount of %s originally mounted on %s\n",
+                        dest_path, orig_path);
+        }
+        exit(EXIT_SUCCESS);
 }
 
 int main(int argc, char **argv)
 {
-        if (!test_unpriv_remount_simple(MS_RDONLY|MS_NODEV)) {
+        if (!test_unpriv_remount_simple(MS_RDONLY)) {
                 die("MS_RDONLY malfunctions\n");
         }
-        if (!test_unpriv_remount_simple(MS_NODEV)) {
+        if (!test_unpriv_remount("devpts", "newinstance", MS_NODEV, MS_NODEV, 0)) {
                 die("MS_NODEV malfunctions\n");
         }
-        if (!test_unpriv_remount_simple(MS_NOSUID|MS_NODEV)) {
+        if (!test_unpriv_remount_simple(MS_NOSUID)) {
                 die("MS_NOSUID malfunctions\n");
         }
-        if (!test_unpriv_remount_simple(MS_NOEXEC|MS_NODEV)) {
+        if (!test_unpriv_remount_simple(MS_NOEXEC)) {
                 die("MS_NOEXEC malfunctions\n");
         }
-        if (!test_unpriv_remount_atime(MS_RELATIME|MS_NODEV,
-                                       MS_NOATIME|MS_NODEV))
+        if (!test_unpriv_remount_atime(MS_RELATIME,
+                                       MS_NOATIME))
         {
                 die("MS_RELATIME malfunctions\n");
         }
-        if (!test_unpriv_remount_atime(MS_STRICTATIME|MS_NODEV,
-                                       MS_NOATIME|MS_NODEV))
+        if (!test_unpriv_remount_atime(MS_STRICTATIME,
+                                       MS_NOATIME))
         {
                 die("MS_STRICTATIME malfunctions\n");
         }
-        if (!test_unpriv_remount_atime(MS_NOATIME|MS_NODEV,
-                                       MS_STRICTATIME|MS_NODEV))
+        if (!test_unpriv_remount_atime(MS_NOATIME,
+                                       MS_STRICTATIME))
         {
-                die("MS_RELATIME malfunctions\n");
+                die("MS_NOATIME malfunctions\n");
         }
-        if (!test_unpriv_remount_atime(MS_RELATIME|MS_NODIRATIME|MS_NODEV,
-                                       MS_NOATIME|MS_NODEV))
+        if (!test_unpriv_remount_atime(MS_RELATIME|MS_NODIRATIME,
+                                       MS_NOATIME))
         {
-                die("MS_RELATIME malfunctions\n");
+                die("MS_RELATIME|MS_NODIRATIME malfunctions\n");
         }
-        if (!test_unpriv_remount_atime(MS_STRICTATIME|MS_NODIRATIME|MS_NODEV,
-                                       MS_NOATIME|MS_NODEV))
+        if (!test_unpriv_remount_atime(MS_STRICTATIME|MS_NODIRATIME,
+                                       MS_NOATIME))
         {
-                die("MS_RELATIME malfunctions\n");
+                die("MS_STRICTATIME|MS_NODIRATIME malfunctions\n");
         }
-        if (!test_unpriv_remount_atime(MS_NOATIME|MS_NODIRATIME|MS_NODEV,
-                                       MS_STRICTATIME|MS_NODEV))
+        if (!test_unpriv_remount_atime(MS_NOATIME|MS_NODIRATIME,
+                                       MS_STRICTATIME))
         {
-                die("MS_RELATIME malfunctions\n");
+                die("MS_NOATIME|MS_DIRATIME malfunctions\n");
         }
-        if (!test_unpriv_remount(MS_STRICTATIME|MS_NODEV, MS_NODEV,
-                                 MS_NOATIME|MS_NODEV))
+        if (!test_unpriv_remount("ramfs", NULL, MS_STRICTATIME, 0, MS_NOATIME))
         {
                 die("Default atime malfunctions\n");
         }
+        if (!test_priv_mount_unpriv_remount()) {
+                die("Mount flags unexpectedly changed after remount\n");
+        }
         return EXIT_SUCCESS;
 }