1 // SPDX-License-Identifier: GPL-2.0 2 #define _GNU_SOURCE 3 #include <sched.h> 4 #include <unistd.h> 5 #include <stdio.h> 6 #include <stdlib.h> 7 #include <signal.h> 8 #include <errno.h> 9 #include <sys/types.h> 10 #include <sys/stat.h> 11 #include <fcntl.h> 12 #include <sys/ioctl.h> 13 #include <sys/prctl.h> 14 #include <sys/wait.h> 15 16 #define pr_err(fmt, ...) \ 17 ({ \ 18 fprintf(stderr, "%s:%d:" fmt ": %m\n", \ 19 __func__, __LINE__, ##__VA_ARGS__); \ 20 1; \ 21 }) 22 23 #define NSIO 0xb7 24 #define NS_GET_USERNS _IO(NSIO, 0x1) 25 #define NS_GET_PARENT _IO(NSIO, 0x2) 26 27 #define __stack_aligned__ __attribute__((aligned(16))) 28 struct cr_clone_arg { 29 char stack[128] __stack_aligned__; 30 char stack_ptr[0]; 31 }; 32 33 static int child(void *args) 34 { 35 prctl(PR_SET_PDEATHSIG, SIGKILL); 36 while (1) 37 sleep(1); 38 exit(0); 39 } 40 41 int main(int argc, char *argv[]) 42 { 43 char *ns_strs[] = {"pid", "user"}; 44 char path[] = "/proc/0123456789/ns/pid"; 45 struct cr_clone_arg ca; 46 struct stat st1, st2; 47 int ns, pns, i; 48 pid_t pid; 49 50 pid = clone(child, ca.stack_ptr, CLONE_NEWUSER | CLONE_NEWPID | SIGCHLD, NULL); 51 if (pid < 0) 52 return pr_err("clone"); 53 54 for (i = 0; i < 2; i++) { 55 snprintf(path, sizeof(path), "/proc/%d/ns/%s", pid, ns_strs[i]); 56 ns = open(path, O_RDONLY); 57 if (ns < 0) 58 return pr_err("Unable to open %s", path); 59 60 pns = ioctl(ns, NS_GET_PARENT); 61 if (pns < 0) 62 return pr_err("Unable to get a parent pidns"); 63 64 snprintf(path, sizeof(path), "/proc/self/ns/%s", ns_strs[i]); 65 if (stat(path, &st2)) 66 return pr_err("Unable to stat %s", path); 67 if (fstat(pns, &st1)) 68 return pr_err("Unable to stat the parent pidns"); 69 if (st1.st_ino != st2.st_ino) 70 return pr_err("NS_GET_PARENT returned a wrong namespace"); 71 72 if (ioctl(pns, NS_GET_PARENT) >= 0 || errno != EPERM) 73 return pr_err("Don't get EPERM");; 74 } 75 76 kill(pid, SIGKILL); 77 wait(NULL); 78 return 0; 79 } 80