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#define _GNU_SOURCE
#include <sched.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <sys/prctl.h>
#include <sys/wait.h>
#define pr_err(fmt, ...) \
({ \
fprintf(stderr, "%s:%d:" fmt ": %m\n", \
__func__, __LINE__, ##__VA_ARGS__); \
1; \
})
#define NSIO 0xb7
#define NS_GET_USERNS _IO(NSIO, 0x1)
#define NS_GET_PARENT _IO(NSIO, 0x2)
#define __stack_aligned__ __attribute__((aligned(16)))
struct cr_clone_arg {
char stack[128] __stack_aligned__;
char stack_ptr[0];
};
static int child(void *args)
{
prctl(PR_SET_PDEATHSIG, SIGKILL);
while (1)
sleep(1);
exit(0);
}
int main(int argc, char *argv[])
{
char *ns_strs[] = {"pid", "user"};
char path[] = "/proc/0123456789/ns/pid";
struct cr_clone_arg ca;
struct stat st1, st2;
int ns, pns, i;
pid_t pid;
pid = clone(child, ca.stack_ptr, CLONE_NEWUSER | CLONE_NEWPID | SIGCHLD, NULL);
if (pid < 0)
return pr_err("clone");
for (i = 0; i < 2; i++) {
snprintf(path, sizeof(path), "/proc/%d/ns/%s", pid, ns_strs[i]);
ns = open(path, O_RDONLY);
if (ns < 0)
return pr_err("Unable to open %s", path);
pns = ioctl(ns, NS_GET_PARENT);
if (pns < 0)
return pr_err("Unable to get a parent pidns");
snprintf(path, sizeof(path), "/proc/self/ns/%s", ns_strs[i]);
if (stat(path, &st2))
return pr_err("Unable to stat %s", path);
if (fstat(pns, &st1))
return pr_err("Unable to stat the parent pidns");
if (st1.st_ino != st2.st_ino)
return pr_err("NS_GET_PARENT returned a wrong namespace");
if (ioctl(pns, NS_GET_PARENT) >= 0 || errno != EPERM)
return pr_err("Don't get EPERM");;
}
kill(pid, SIGKILL);
wait(NULL);
return 0;
}
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