LXR linux/tools/testing/selftests/proc/proc-subset-pid.c

   1/*
   2 * Copyright (c) 2021 Alexey Dobriyan <adobriyan@gmail.com>
   3 *
   4 * Permission to use, copy, modify, and distribute this software for any
   5 * purpose with or without fee is hereby granted, provided that the above
   6 * copyright notice and this permission notice appear in all copies.
   7 *
   8 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
   9 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  10 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  11 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  12 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  13 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  14 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  15 */
  16/*
  17 * Test that "mount -t proc -o subset=pid" hides everything but pids,
  18 * /proc/self and /proc/thread-self.
  19 */
  20#undef NDEBUG
  21#include <assert.h>
  22#include <errno.h>
  23#include <sched.h>
  24#include <stdbool.h>
  25#include <stdlib.h>
  26#include <string.h>
  27#include <sys/mount.h>
  28#include <sys/types.h>
  29#include <sys/stat.h>
  30#include <fcntl.h>
  31#include <dirent.h>
  32#include <unistd.h>
  33#include <stdio.h>
  34
  35static inline bool streq(const char *a, const char *b)
  36{
  37        return strcmp(a, b) == 0;
  38}
  39
  40static void make_private_proc(void)
  41{
  42        if (unshare(CLONE_NEWNS) == -1) {
  43                if (errno == ENOSYS || errno == EPERM) {
  44                        exit(4);
  45                }
  46                exit(1);
  47        }
  48        if (mount(NULL, "/", NULL, MS_PRIVATE|MS_REC, NULL) == -1) {
  49                exit(1);
  50        }
  51        if (mount(NULL, "/proc", "proc", 0, "subset=pid") == -1) {
  52                exit(1);
  53        }
  54}
  55
  56static bool string_is_pid(const char *s)
  57{
  58        while (1) {
  59                switch (*s++) {
  60                case '0':case '1':case '2':case '3':case '4':
  61                case '5':case '6':case '7':case '8':case '9':
  62                        continue;
  63
  64                case '\0':
  65                        return true;
  66
  67                default:
  68                        return false;
  69                }
  70        }
  71}
  72
  73int main(void)
  74{
  75        make_private_proc();
  76
  77        DIR *d = opendir("/proc");
  78        assert(d);
  79
  80        struct dirent *de;
  81
  82        bool dot = false;
  83        bool dot_dot = false;
  84        bool self = false;
  85        bool thread_self = false;
  86
  87        while ((de = readdir(d))) {
  88                if (streq(de->d_name, ".")) {
  89                        assert(!dot);
  90                        dot = true;
  91                        assert(de->d_type == DT_DIR);
  92                } else if (streq(de->d_name, "..")) {
  93                        assert(!dot_dot);
  94                        dot_dot = true;
  95                        assert(de->d_type == DT_DIR);
  96                } else if (streq(de->d_name, "self")) {
  97                        assert(!self);
  98                        self = true;
  99                        assert(de->d_type == DT_LNK);
 100                } else if (streq(de->d_name, "thread-self")) {
 101                        assert(!thread_self);
 102                        thread_self = true;
 103                        assert(de->d_type == DT_LNK);
 104                } else {
 105                        if (!string_is_pid(de->d_name)) {
 106                                fprintf(stderr, "d_name '%s'\n", de->d_name);
 107                                assert(0);
 108                        }
 109                        assert(de->d_type == DT_DIR);
 110                }
 111        }
 112
 113        char c;
 114        int rv = readlink("/proc/cpuinfo", &c, 1);
 115        assert(rv == -1 && errno == ENOENT);
 116
 117        int fd = open("/proc/cpuinfo", O_RDONLY);
 118        assert(fd == -1 && errno == ENOENT);
 119
 120        return 0;
 121}
 122