diff options
Diffstat (limited to 'tools/testing/selftests/mount/nosymfollow-test.c')
| -rw-r--r-- | tools/testing/selftests/mount/nosymfollow-test.c | 218 |
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; +} |