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-rw-r--r--tools/testing/selftests/mount/nosymfollow-test.c218
1 files changed, 218 insertions, 0 deletions
diff --git a/tools/testing/selftests/mount/nosymfollow-test.c b/tools/testing/selftests/mount/nosymfollow-test.c
new file mode 100644
index 000000000000..650d6d80a1d2
--- /dev/null
+++ b/tools/testing/selftests/mount/nosymfollow-test.c
@@ -0,0 +1,218 @@
+// SPDX-License-Identifier: GPL-2.0
+#define _GNU_SOURCE
+#include <errno.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <sched.h>
+#include <stdarg.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mount.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/vfs.h>
+#include <unistd.h>
+
+#ifndef MS_NOSYMFOLLOW
+# define MS_NOSYMFOLLOW 256 /* Do not follow symlinks */
+#endif
+
+#ifndef ST_NOSYMFOLLOW
+# define ST_NOSYMFOLLOW 0x2000 /* Do not follow symlinks */
+#endif
+
+#define DATA "/tmp/data"
+#define LINK "/tmp/symlink"
+#define TMP "/tmp"
+
+static void die(char *fmt, ...)
+{
+ va_list ap;
+
+ va_start(ap, fmt);
+ vfprintf(stderr, fmt, ap);
+ va_end(ap);
+ exit(EXIT_FAILURE);
+}
+
+static void vmaybe_write_file(bool enoent_ok, char *filename, char *fmt,
+ va_list ap)
+{
+ ssize_t written;
+ char buf[4096];
+ int buf_len;
+ int fd;
+
+ buf_len = vsnprintf(buf, sizeof(buf), fmt, ap);
+ if (buf_len < 0)
+ die("vsnprintf failed: %s\n", strerror(errno));
+
+ if (buf_len >= sizeof(buf))
+ die("vsnprintf output truncated\n");
+
+ fd = open(filename, O_WRONLY);
+ if (fd < 0) {
+ if ((errno == ENOENT) && enoent_ok)
+ return;
+ die("open of %s failed: %s\n", filename, strerror(errno));
+ }
+
+ written = write(fd, buf, buf_len);
+ if (written != buf_len) {
+ if (written >= 0) {
+ die("short write to %s\n", filename);
+ } else {
+ die("write to %s failed: %s\n",
+ filename, strerror(errno));
+ }
+ }
+
+ if (close(fd) != 0)
+ die("close of %s failed: %s\n", filename, strerror(errno));
+}
+
+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 void create_and_enter_ns(void)
+{
+ uid_t uid = getuid();
+ gid_t gid = getgid();
+
+ if (unshare(CLONE_NEWUSER) != 0)
+ die("unshare(CLONE_NEWUSER) failed: %s\n", 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 (setgid(0) != 0)
+ die("setgid(0) failed %s\n", strerror(errno));
+ if (setuid(0) != 0)
+ die("setuid(0) failed %s\n", strerror(errno));
+
+ if (unshare(CLONE_NEWNS) != 0)
+ die("unshare(CLONE_NEWNS) failed: %s\n", strerror(errno));
+}
+
+static void setup_symlink(void)
+{
+ int data, err;
+
+ data = creat(DATA, O_RDWR);
+ if (data < 0)
+ die("creat failed: %s\n", strerror(errno));
+
+ err = symlink(DATA, LINK);
+ if (err < 0)
+ die("symlink failed: %s\n", strerror(errno));
+
+ if (close(data) != 0)
+ die("close of %s failed: %s\n", DATA, strerror(errno));
+}
+
+static void test_link_traversal(bool nosymfollow)
+{
+ int link;
+
+ link = open(LINK, 0, O_RDWR);
+ if (nosymfollow) {
+ if ((link != -1 || errno != ELOOP)) {
+ die("link traversal unexpected result: %d, %s\n",
+ link, strerror(errno));
+ }
+ } else {
+ if (link < 0)
+ die("link traversal failed: %s\n", strerror(errno));
+
+ if (close(link) != 0)
+ die("close of link failed: %s\n", strerror(errno));
+ }
+}
+
+static void test_readlink(void)
+{
+ char buf[4096];
+ ssize_t ret;
+
+ bzero(buf, sizeof(buf));
+
+ ret = readlink(LINK, buf, sizeof(buf));
+ if (ret < 0)
+ die("readlink failed: %s\n", strerror(errno));
+ if (strcmp(buf, DATA) != 0)
+ die("readlink strcmp failed: '%s' '%s'\n", buf, DATA);
+}
+
+static void test_realpath(void)
+{
+ char *path = realpath(LINK, NULL);
+
+ if (!path)
+ die("realpath failed: %s\n", strerror(errno));
+ if (strcmp(path, DATA) != 0)
+ die("realpath strcmp failed\n");
+
+ free(path);
+}
+
+static void test_statfs(bool nosymfollow)
+{
+ struct statfs buf;
+ int ret;
+
+ ret = statfs(TMP, &buf);
+ if (ret)
+ die("statfs failed: %s\n", strerror(errno));
+
+ if (nosymfollow) {
+ if ((buf.f_flags & ST_NOSYMFOLLOW) == 0)
+ die("ST_NOSYMFOLLOW not set on %s\n", TMP);
+ } else {
+ if ((buf.f_flags & ST_NOSYMFOLLOW) != 0)
+ die("ST_NOSYMFOLLOW set on %s\n", TMP);
+ }
+}
+
+static void run_tests(bool nosymfollow)
+{
+ test_link_traversal(nosymfollow);
+ test_readlink();
+ test_realpath();
+ test_statfs(nosymfollow);
+}
+
+int main(int argc, char **argv)
+{
+ create_and_enter_ns();
+
+ if (mount("testing", TMP, "ramfs", 0, NULL) != 0)
+ die("mount failed: %s\n", strerror(errno));
+
+ setup_symlink();
+ run_tests(false);
+
+ if (mount("testing", TMP, "ramfs", MS_REMOUNT|MS_NOSYMFOLLOW, NULL) != 0)
+ die("remount failed: %s\n", strerror(errno));
+
+ run_tests(true);
+
+ return EXIT_SUCCESS;
+}