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
  25 int 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 }