blob: 01450a90a6b0a8818a66b2d08ac06774e6ac4e17 [file] [log] [blame]
#define _GNU_SOURCE
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <linux/limits.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <signal.h>
#include <setjmp.h>
#include <sched.h>
#include <signal.h>
/* All arguments should be above stack, because it grows down */
struct clone_arg {
/*
* Reserve some space for clone() to locate arguments
* and retcode in this place
*/
char stack[4096] __attribute__ ((aligned(16)));
char stack_ptr[0];
jmp_buf *env;
};
#define pr_perror(fmt, ...) fprintf(stderr, "nsenter: " fmt ": %m\n", ##__VA_ARGS__)
static int child_func(void *_arg)
{
struct clone_arg *arg = (struct clone_arg *)_arg;
longjmp(*arg->env, 1);
}
// Use raw setns syscall for versions of glibc that don't include it (namely glibc-2.12)
#if __GLIBC__ == 2 && __GLIBC_MINOR__ < 14
#define _GNU_SOURCE
#include "syscall.h"
#if defined(__NR_setns) && !defined(SYS_setns)
#define SYS_setns __NR_setns
#endif
#ifdef SYS_setns
int setns(int fd, int nstype)
{
return syscall(SYS_setns, fd, nstype);
}
#endif
#endif
static int clone_parent(jmp_buf * env) __attribute__ ((noinline));
static int clone_parent(jmp_buf * env)
{
struct clone_arg ca;
int child;
ca.env = env;
child = clone(child_func, ca.stack_ptr, CLONE_PARENT | SIGCHLD, &ca);
return child;
}
void nsexec()
{
char *namespaces[] = { "ipc", "uts", "net", "pid", "mnt", "user" };
const int num = sizeof(namespaces) / sizeof(char *);
jmp_buf env;
char buf[PATH_MAX], *val;
int i, tfd, self_tfd, child, len, pipenum, consolefd = -1;
pid_t pid;
char *console;
val = getenv("_LIBCONTAINER_INITPID");
if (val == NULL)
return;
pid = atoi(val);
snprintf(buf, sizeof(buf), "%d", pid);
if (strcmp(val, buf)) {
pr_perror("Unable to parse _LIBCONTAINER_INITPID");
exit(1);
}
val = getenv("_LIBCONTAINER_INITPIPE");
if (val == NULL) {
pr_perror("Child pipe not found");
exit(1);
}
pipenum = atoi(val);
snprintf(buf, sizeof(buf), "%d", pipenum);
if (strcmp(val, buf)) {
pr_perror("Unable to parse _LIBCONTAINER_INITPIPE");
exit(1);
}
console = getenv("_LIBCONTAINER_CONSOLE_PATH");
if (console != NULL) {
consolefd = open(console, O_RDWR);
if (consolefd < 0) {
pr_perror("Failed to open console %s", console);
exit(1);
}
}
/* Check that the specified process exists */
snprintf(buf, PATH_MAX - 1, "/proc/%d/ns", pid);
tfd = open(buf, O_DIRECTORY | O_RDONLY);
if (tfd == -1) {
pr_perror("Failed to open \"%s\"", buf);
exit(1);
}
self_tfd = open("/proc/self/ns", O_DIRECTORY | O_RDONLY);
if (self_tfd == -1) {
pr_perror("Failed to open /proc/self/ns");
exit(1);
}
for (i = 0; i < num; i++) {
struct stat st;
struct stat self_st;
int fd;
/* Symlinks on all namespaces exist for dead processes, but they can't be opened */
if (fstatat(tfd, namespaces[i], &st, 0) == -1) {
// Ignore nonexistent namespaces.
if (errno == ENOENT)
continue;
}
/* Skip namespaces we're already part of */
if (fstatat(self_tfd, namespaces[i], &self_st, 0) != -1 &&
st.st_ino == self_st.st_ino) {
continue;
}
fd = openat(tfd, namespaces[i], O_RDONLY);
if (fd == -1) {
pr_perror("Failed to open ns file %s for ns %s", buf,
namespaces[i]);
exit(1);
}
// Set the namespace.
if (setns(fd, 0) == -1) {
pr_perror("Failed to setns for %s", namespaces[i]);
exit(1);
}
close(fd);
}
close(self_tfd);
close(tfd);
if (setjmp(env) == 1) {
// Child
if (setsid() == -1) {
pr_perror("setsid failed");
exit(1);
}
if (consolefd != -1) {
if (ioctl(consolefd, TIOCSCTTY, 0) == -1) {
pr_perror("ioctl TIOCSCTTY failed");
exit(1);
}
if (dup3(consolefd, STDIN_FILENO, 0) != STDIN_FILENO) {
pr_perror("Failed to dup 0");
exit(1);
}
if (dup3(consolefd, STDOUT_FILENO, 0) != STDOUT_FILENO) {
pr_perror("Failed to dup 1");
exit(1);
}
if (dup3(consolefd, STDERR_FILENO, 0) != STDERR_FILENO) {
pr_perror("Failed to dup 2");
exit(1);
}
}
// Finish executing, let the Go runtime take over.
return;
}
// Parent
// We must fork to actually enter the PID namespace, use CLONE_PARENT
// so the child can have the right parent, and we don't need to forward
// the child's exit code or resend its death signal.
child = clone_parent(&env);
if (child < 0) {
pr_perror("Unable to fork");
exit(1);
}
len = snprintf(buf, sizeof(buf), "{ \"pid\" : %d }\n", child);
if (write(pipenum, buf, len) != len) {
pr_perror("Unable to send a child pid");
kill(child, SIGKILL);
exit(1);
}
exit(0);
}