LXR linux/tools/testing/selftests/nsfs/owner.c

   1#define _GNU_SOURCE
   2#include <sched.h>
   3#include <unistd.h>
   4#include <stdio.h>
   5#include <stdlib.h>
   6#include <signal.h>
   7#include <errno.h>
   8#include <sys/types.h>
   9#include <sys/stat.h>
  10#include <fcntl.h>
  11#include <sys/ioctl.h>
  12#include <sys/prctl.h>
  13#include <sys/wait.h>
  14
  15#define NSIO    0xb7
  16#define NS_GET_USERNS   _IO(NSIO, 0x1)
  17
  18#define pr_err(fmt, ...) \
  19                ({ \
  20                        fprintf(stderr, "%s:%d:" fmt ": %m\n", \
  21                                __func__, __LINE__, ##__VA_ARGS__); \
  22                        1; \
  23                })
  24
  25int main(int argc, char *argvp[])
  26{
  27        int pfd[2], ns, uns, init_uns;
  28        struct stat st1, st2;
  29        char path[128];
  30        pid_t pid;
  31        char c;
  32
  33        if (pipe(pfd))
  34                return 1;
  35
  36        pid = fork();
  37        if (pid < 0)
  38                return pr_err("fork");
  39        if (pid == 0) {
  40                prctl(PR_SET_PDEATHSIG, SIGKILL);
  41                if (unshare(CLONE_NEWUTS | CLONE_NEWUSER))
  42                        return pr_err("unshare");
  43                close(pfd[0]);
  44                close(pfd[1]);
  45                while (1)
  46                        sleep(1);
  47                return 0;
  48        }
  49        close(pfd[1]);
  50        if (read(pfd[0], &c, 1) != 0)
  51                return pr_err("Unable to read from pipe");
  52        close(pfd[0]);
  53
  54        snprintf(path, sizeof(path), "/proc/%d/ns/uts", pid);
  55        ns = open(path, O_RDONLY);
  56        if (ns < 0)
  57                return pr_err("Unable to open %s", path);
  58
  59        uns = ioctl(ns, NS_GET_USERNS);
  60        if (uns < 0)
  61                return pr_err("Unable to get an owning user namespace");
  62
  63        if (fstat(uns, &st1))
  64                return pr_err("fstat");
  65
  66        snprintf(path, sizeof(path), "/proc/%d/ns/user", pid);
  67        if (stat(path, &st2))
  68                return pr_err("stat");
  69
  70        if (st1.st_ino != st2.st_ino)
  71                return pr_err("NS_GET_USERNS returned a wrong namespace");
  72
  73        init_uns = ioctl(uns, NS_GET_USERNS);
  74        if (uns < 0)
  75                return pr_err("Unable to get an owning user namespace");
  76
  77        if (ioctl(init_uns, NS_GET_USERNS) >= 0 || errno != EPERM)
  78                return pr_err("Don't get EPERM");
  79
  80        if (unshare(CLONE_NEWUSER))
  81                return pr_err("unshare");
  82
  83        if (ioctl(ns, NS_GET_USERNS) >= 0 || errno != EPERM)
  84                return pr_err("Don't get EPERM");
  85        if (ioctl(init_uns, NS_GET_USERNS) >= 0 || errno != EPERM)
  86                return pr_err("Don't get EPERM");
  87
  88        kill(pid, SIGKILL);
  89        wait(NULL);
  90        return 0;
  91}
  92