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@@ -0,0 +1,753 @@
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+#define _GNU_SOURCE
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+#include <endian.h>
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+#include <errno.h>
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+#include <fcntl.h>
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+#include <grp.h>
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+#include <sched.h>
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+#include <setjmp.h>
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+#include <signal.h>
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+#include <stdarg.h>
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+#include <stdbool.h>
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+#include <stdint.h>
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+#include <stdio.h>
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+#include <stdlib.h>
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+#include <stdbool.h>
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+#include <string.h>
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+#include <unistd.h>
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+
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+#include <sys/ioctl.h>
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+#include <sys/prctl.h>
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+#include <sys/socket.h>
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+#include <sys/types.h>
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+
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+#include <linux/limits.h>
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+#include <linux/netlink.h>
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+#include <linux/types.h>
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+
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+/* Get all of the CLONE_NEW* flags. */
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+#include "namespace.h"
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+
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+/* Synchronisation values. */
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+enum sync_t {
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+ SYNC_USERMAP_PLS = 0x40, /* Request parent to map our users. */
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+ SYNC_USERMAP_ACK = 0x41, /* Mapping finished by the parent. */
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+ SYNC_RECVPID_PLS = 0x42, /* Tell parent we're sending the PID. */
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+ SYNC_RECVPID_ACK = 0x43, /* PID was correctly received by parent. */
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+
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+ /* XXX: This doesn't help with segfaults and other such issues. */
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+ SYNC_ERR = 0xFF, /* Fatal error, no turning back. The error code follows. */
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+};
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+
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+/* longjmp() arguments. */
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+#define JUMP_PARENT 0x00
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+#define JUMP_CHILD 0xA0
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+#define JUMP_INIT 0xA1
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+
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+/* JSON buffer. */
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+#define JSON_MAX 4096
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+
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+/* Assume the stack grows down, so arguments should be above it. */
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+struct clone_t {
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+ /*
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+ * Reserve some space for clone() to locate arguments
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+ * and retcode in this place
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+ */
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+ char stack[4096] __attribute__ ((aligned(16)));
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+ char stack_ptr[0];
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+
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+ /* There's two children. This is used to execute the different code. */
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+ jmp_buf *env;
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+ int jmpval;
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+};
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+
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+struct nlconfig_t {
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+ char *data;
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+ uint32_t cloneflags;
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+ char *uidmap;
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+ size_t uidmap_len;
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+ char *gidmap;
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+ size_t gidmap_len;
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+ char *namespaces;
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+ size_t namespaces_len;
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+ uint8_t is_setgroup;
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+ int consolefd;
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+};
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+
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+/*
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+ * List of netlink message types sent to us as part of bootstrapping the init.
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+ * These constants are defined in libcontainer/message_linux.go.
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+ */
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+#define INIT_MSG 62000
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+#define CLONE_FLAGS_ATTR 27281
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+#define CONSOLE_PATH_ATTR 27282
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+#define NS_PATHS_ATTR 27283
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+#define UIDMAP_ATTR 27284
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+#define GIDMAP_ATTR 27285
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+#define SETGROUP_ATTR 27286
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+
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+/*
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+ * Use the raw syscall for versions of glibc which don't include a function for
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+ * it, namely (glibc 2.12).
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+ */
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+#if __GLIBC__ == 2 && __GLIBC_MINOR__ < 14
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+# define _GNU_SOURCE
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+# include "syscall.h"
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+# if !defined(SYS_setns) && defined(__NR_setns)
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+# define SYS_setns __NR_setns
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+# endif
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+
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+#ifndef SYS_setns
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+# error "setns(2) syscall not supported by glibc version"
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+#endif
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+
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+int setns(int fd, int nstype)
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+{
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+ return syscall(SYS_setns, fd, nstype);
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+}
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+#endif
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+
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+/* XXX: This is ugly. */
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+static int syncfd = -1;
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+
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+/* TODO(cyphar): Fix this so it correctly deals with syncT. */
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+#define bail(fmt, ...) \
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+ do { \
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+ int ret = __COUNTER__ + 1; \
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+ fprintf(stderr, "nsenter: " fmt ": %m\n", ##__VA_ARGS__); \
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+ if (syncfd >= 0) { \
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+ enum sync_t s = SYNC_ERR; \
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+ if (write(syncfd, &s, sizeof(s)) != sizeof(s)) \
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+ fprintf(stderr, "nsenter: failed: write(s)"); \
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+ if (write(syncfd, &ret, sizeof(ret)) != sizeof(ret)) \
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+ fprintf(stderr, "nsenter: failed: write(ret)"); \
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+ } \
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+ exit(ret); \
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+ } while(0)
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+
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+static int write_file(char *data, size_t data_len, char *pathfmt, ...)
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+{
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+ int fd, len, ret = 0;
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+ char path[PATH_MAX];
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+
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+ va_list ap;
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+ va_start(ap, pathfmt);
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+ len = vsnprintf(path, PATH_MAX, pathfmt, ap);
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+ va_end(ap);
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+ if (len < 0)
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+ return -1;
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+
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+ fd = open(path, O_RDWR);
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+ if (fd < 0) {
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+ ret = -1;
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+ goto out;
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+ }
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+
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+ len = write(fd, data, data_len);
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+ if (len != data_len) {
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+ ret = -1;
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+ goto out;
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+ }
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+
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+out:
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+ close(fd);
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+ return ret;
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+}
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+
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+enum policy_t {
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+ SETGROUPS_DEFAULT = 0,
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+ SETGROUPS_ALLOW,
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+ SETGROUPS_DENY,
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+};
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+
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+/* This *must* be called before we touch gid_map. */
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+static void update_setgroups(int pid, enum policy_t setgroup)
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+{
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+ char *policy;
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+
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+ switch (setgroup) {
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+ case SETGROUPS_ALLOW:
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+ policy = "allow";
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+ break;
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+ case SETGROUPS_DENY:
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+ policy = "deny";
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+ break;
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+ case SETGROUPS_DEFAULT:
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+ /* Nothing to do. */
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+ return;
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+ }
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+
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+ if (write_file(policy, strlen(policy), "/proc/%d/setgroups", pid) < 0) {
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+ /*
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+ * If the kernel is too old to support /proc/pid/setgroups,
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+ * open(2) or write(2) will return ENOENT. This is fine.
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+ */
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+ if (errno != ENOENT)
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+ bail("failed to write '%s' to /proc/%d/setgroups", policy, pid);
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+ }
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+}
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+
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+static void update_uidmap(int pid, char *map, int map_len)
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+{
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+ if (map == NULL || map_len <= 0)
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+ return;
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+
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+ if (write_file(map, map_len, "/proc/%d/uid_map", pid) < 0)
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+ bail("failed to update /proc/%d/uid_map", pid);
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+}
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+
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+static void update_gidmap(int pid, char *map, int map_len)
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+{
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+ if (map == NULL || map_len <= 0)
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+ return;
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+
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+ if (write_file(map, map_len, "/proc/%d/gid_map", pid) < 0)
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+ bail("failed to update /proc/%d/gid_map", pid);
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+}
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+
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+/* A dummy function that just jumps to the given jumpval. */
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+static int child_func(void *arg) __attribute__ ((noinline));
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+static int child_func(void *arg)
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+{
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+ struct clone_t *ca = (struct clone_t *)arg;
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+ longjmp(*ca->env, ca->jmpval);
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+}
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+
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+static int clone_parent(jmp_buf *env, int jmpval) __attribute__ ((noinline));
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+static int clone_parent(jmp_buf *env, int jmpval)
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+{
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+ struct clone_t ca = {
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+ .env = env,
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+ .jmpval = jmpval,
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+ };
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+
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+ return clone(child_func, ca.stack_ptr, CLONE_PARENT | SIGCHLD, &ca);
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+}
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+
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+/*
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+ * Gets the init pipe fd from the environment, which is used to read the
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+ * bootstrap data and tell the parent what the new pid is after we finish
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+ * setting up the environment.
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+ */
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+static int initpipe(void)
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+{
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+ int pipenum;
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+ char *initpipe, *endptr;
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+
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+ initpipe = getenv("_LIBCONTAINER_INITPIPE");
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+ if (initpipe == NULL || *initpipe == '\0')
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+ return -1;
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+
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+ pipenum = strtol(initpipe, &endptr, 10);
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+ if (*endptr != '\0')
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+ bail("unable to parse _LIBCONTAINER_INITPIPE");
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+
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+ return pipenum;
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+}
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+
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+/* Returns the clone(2) flag for a namespace, given the name of a namespace. */
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+static int nsflag(char *name)
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+{
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+ if (!strcmp(name, "cgroup"))
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+ return CLONE_NEWCGROUP;
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+ else if (!strcmp(name, "ipc"))
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+ return CLONE_NEWIPC;
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+ else if (!strcmp(name, "mnt"))
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+ return CLONE_NEWNS;
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+ else if (!strcmp(name, "net"))
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+ return CLONE_NEWNET;
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+ else if (!strcmp(name, "pid"))
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+ return CLONE_NEWPID;
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+ else if (!strcmp(name, "user"))
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+ return CLONE_NEWUSER;
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+ else if (!strcmp(name, "uts"))
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+ return CLONE_NEWUTS;
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+
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+ /* If we don't recognise a name, fallback to 0. */
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+ return 0;
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+}
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+
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+static uint32_t readint32(char *buf)
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+{
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+ return *(uint32_t *) buf;
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+}
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+
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+static uint8_t readint8(char *buf)
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+{
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+ return *(uint8_t *) buf;
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+}
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+
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+static void nl_parse(int fd, struct nlconfig_t *config)
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+{
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+ size_t len, size;
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+ struct nlmsghdr hdr;
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+ char *data, *current;
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+
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+ /* Retrieve the netlink header. */
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+ len = read(fd, &hdr, NLMSG_HDRLEN);
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+ if (len != NLMSG_HDRLEN)
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+ bail("invalid netlink header length %lu", len);
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+
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+ if (hdr.nlmsg_type == NLMSG_ERROR)
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+ bail("failed to read netlink message");
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+
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+ if (hdr.nlmsg_type != INIT_MSG)
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+ bail("unexpected msg type %d", hdr.nlmsg_type);
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+
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+ /* Retrieve data. */
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+ size = NLMSG_PAYLOAD(&hdr, 0);
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+ current = data = malloc(size);
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+ if (!data)
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+ bail("failed to allocate %zu bytes of memory for nl_payload", size);
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+
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+ len = read(fd, data, size);
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+ if (len != size)
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+ bail("failed to read netlink payload, %lu != %lu", len, size);
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+
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+ /* Parse the netlink payload. */
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+ config->data = data;
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+ config->consolefd = -1;
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+ while (current < data + size) {
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+ struct nlattr *nlattr = (struct nlattr *)current;
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+ size_t payload_len = nlattr->nla_len - NLA_HDRLEN;
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+
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+ /* Advance to payload. */
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+ current += NLA_HDRLEN;
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+
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+ /* Handle payload. */
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+ switch (nlattr->nla_type) {
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+ case CLONE_FLAGS_ATTR:
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+ config->cloneflags = readint32(current);
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+ break;
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+ case CONSOLE_PATH_ATTR:
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+ /*
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+ * We open the console here because we currently evaluate console
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+ * paths from the *host* namespaces.
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+ */
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+ config->consolefd = open(current, O_RDWR);
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+ if (config->consolefd < 0)
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+ bail("failed to open console %s", current);
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+ break;
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+ case NS_PATHS_ATTR:
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+ config->namespaces = current;
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+ config->namespaces_len = payload_len;
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+ break;
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+ case UIDMAP_ATTR:
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+ config->uidmap = current;
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+ config->uidmap_len = payload_len;
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+ break;
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+ case GIDMAP_ATTR:
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+ config->gidmap = current;
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+ config->gidmap_len = payload_len;
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+ break;
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+ case SETGROUP_ATTR:
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+ config->is_setgroup = readint8(current);
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+ break;
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+ default:
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+ bail("unknown netlink message type %d", nlattr->nla_type);
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+ }
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+
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+ current += NLA_ALIGN(payload_len);
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+ }
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+}
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+
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+void nl_free(struct nlconfig_t *config)
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+{
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+ free(config->data);
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+}
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+
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+void join_namespaces(char *nslist)
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+{
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+ int num = 0, i;
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+ char *saveptr = NULL;
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+ char *namespace = strtok_r(nslist, ",", &saveptr);
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+ struct namespace_t {
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+ int fd;
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+ int ns;
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+ char type[PATH_MAX];
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+ char path[PATH_MAX];
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+ } *namespaces = NULL;
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+
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+ if (!namespace || !strlen(namespace) || !strlen(nslist))
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+ bail("ns paths are empty");
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+
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+ /*
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+ * We have to open the file descriptors first, since after
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+ * we join the mnt namespace we might no longer be able to
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+ * access the paths.
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+ */
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+ do {
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+ int fd;
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+ char *path;
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+ struct namespace_t *ns;
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+
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+ /* Resize the namespace array. */
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+ namespaces = realloc(namespaces, ++num * sizeof(struct namespace_t));
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+ if (!namespaces)
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+ bail("failed to reallocate namespace array");
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+ ns = &namespaces[num - 1];
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+
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+ /* Split 'ns:path'. */
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+ path = strstr(namespace, ":");
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+ if (!path)
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+ bail("failed to parse %s", namespace);
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+ *path++ = '\0';
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+
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+ fd = open(path, O_RDONLY);
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+ if (fd < 0)
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+ bail("failed to open %s", namespace);
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+
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+ ns->fd = fd;
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+ ns->ns = nsflag(namespace);
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+ strncpy(ns->path, path, PATH_MAX);
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+ } while ((namespace = strtok_r(NULL, ",", &saveptr)) != NULL);
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+
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+ /*
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+ * The ordering in which we join namespaces is important. We should
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+ * always join the user namespace *first*. This is all guaranteed
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+ * from the container_linux.go side of this, so we're just going to
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+ * follow the order given to us.
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+ */
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+
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+ for (i = 0; i < num; i++) {
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+ struct namespace_t ns = namespaces[i];
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+
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+ if (setns(ns.fd, ns.ns) < 0)
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+ bail("failed to setns to %s", ns.path);
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+
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+ close(ns.fd);
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+ }
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+
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+ free(namespaces);
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+}
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+
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+void nsexec(void)
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+{
|
|
|
+ int pipenum;
|
|
|
+ jmp_buf env;
|
|
|
+ int syncpipe[2];
|
|
|
+ struct nlconfig_t config = {0};
|
|
|
+
|
|
|
+ /*
|
|
|
+ * If we don't have an init pipe, just return to the go routine.
|
|
|
+ * We'll only get an init pipe for start or exec.
|
|
|
+ */
|
|
|
+ pipenum = initpipe();
|
|
|
+ if (pipenum == -1)
|
|
|
+ return;
|
|
|
+
|
|
|
+ /* Parse all of the netlink configuration. */
|
|
|
+ nl_parse(pipenum, &config);
|
|
|
+
|
|
|
+ /* Pipe so we can tell the child when we've finished setting up. */
|
|
|
+ if (socketpair(AF_LOCAL, SOCK_STREAM, 0, syncpipe) < 0)
|
|
|
+ bail("failed to setup sync pipe between parent and child");
|
|
|
+
|
|
|
+ /* TODO: Currently we aren't dealing with child deaths properly. */
|
|
|
+
|
|
|
+ /*
|
|
|
+ * Okay, so this is quite annoying.
|
|
|
+ *
|
|
|
+ * In order for this unsharing code to be more extensible we need to split
|
|
|
+ * up unshare(CLONE_NEWUSER) and clone() in various ways. The ideal case
|
|
|
+ * would be if we did clone(CLONE_NEWUSER) and the other namespaces
|
|
|
+ * separately, but because of SELinux issues we cannot really do that. But
|
|
|
+ * we cannot just dump the namespace flags into clone(...) because several
|
|
|
+ * usecases (such as rootless containers) require more granularity around
|
|
|
+ * the namespace setup. In addition, some older kernels had issues where
|
|
|
+ * CLONE_NEWUSER wasn't handled before other namespaces (but we cannot
|
|
|
+ * handle this while also dealing with SELinux so we choose SELinux support
|
|
|
+ * over broken kernel support).
|
|
|
+ *
|
|
|
+ * However, if we unshare(2) the user namespace *before* we clone(2), then
|
|
|
+ * all hell breaks loose.
|
|
|
+ *
|
|
|
+ * The parent no longer has permissions to do many things (unshare(2) drops
|
|
|
+ * all capabilities in your old namespace), and the container cannot be set
|
|
|
+ * up to have more than one {uid,gid} mapping. This is obviously less than
|
|
|
+ * ideal. In order to fix this, we have to first clone(2) and then unshare.
|
|
|
+ *
|
|
|
+ * Unfortunately, it's not as simple as that. We have to fork to enter the
|
|
|
+ * PID namespace (the PID namespace only applies to children). Since we'll
|
|
|
+ * have to double-fork, this clone_parent() call won't be able to get the
|
|
|
+ * PID of the _actual_ init process (without doing more synchronisation than
|
|
|
+ * I can deal with at the moment). So we'll just get the parent to send it
|
|
|
+ * for us, the only job of this process is to update
|
|
|
+ * /proc/pid/{setgroups,uid_map,gid_map}.
|
|
|
+ *
|
|
|
+ * And as a result of the above, we also need to setns(2) in the first child
|
|
|
+ * because if we join a PID namespace in the topmost parent then our child
|
|
|
+ * will be in that namespace (and it will not be able to give us a PID value
|
|
|
+ * that makes sense without resorting to sending things with cmsg).
|
|
|
+ *
|
|
|
+ * This also deals with an older issue caused by dumping cloneflags into
|
|
|
+ * clone(2): On old kernels, CLONE_PARENT didn't work with CLONE_NEWPID, so
|
|
|
+ * we have to unshare(2) before clone(2) in order to do this. This was fixed
|
|
|
+ * in upstream commit 1f7f4dde5c945f41a7abc2285be43d918029ecc5, and was
|
|
|
+ * introduced by 40a0d32d1eaffe6aac7324ca92604b6b3977eb0e. As far as we're
|
|
|
+ * aware, the last mainline kernel which had this bug was Linux 3.12.
|
|
|
+ * However, we cannot comment on which kernels the broken patch was
|
|
|
+ * backported to.
|
|
|
+ *
|
|
|
+ * -- Aleksa "what has my life come to?" Sarai
|
|
|
+ */
|
|
|
+
|
|
|
+ switch (setjmp(env)) {
|
|
|
+ /*
|
|
|
+ * Stage 0: We're in the parent. Our job is just to create a new child
|
|
|
+ * (stage 1: JUMP_CHILD) process and write its uid_map and
|
|
|
+ * gid_map. That process will go on to create a new process, then
|
|
|
+ * it will send us its PID which we will send to the bootstrap
|
|
|
+ * process.
|
|
|
+ */
|
|
|
+ case JUMP_PARENT: {
|
|
|
+ int len;
|
|
|
+ pid_t child;
|
|
|
+ char buf[JSON_MAX];
|
|
|
+
|
|
|
+ /* For debugging. */
|
|
|
+ prctl(PR_SET_NAME, (unsigned long) "runc:[0:PARENT]", 0, 0, 0);
|
|
|
+
|
|
|
+ /* Start the process of getting a container. */
|
|
|
+ child = clone_parent(&env, JUMP_CHILD);
|
|
|
+ if (child < 0)
|
|
|
+ bail("unable to fork: child_func");
|
|
|
+
|
|
|
+ /* State machine for synchronisation with the children. */
|
|
|
+ while (true) {
|
|
|
+ enum sync_t s;
|
|
|
+
|
|
|
+ /* This doesn't need to be global, we're in the parent. */
|
|
|
+ int syncfd = syncpipe[1];
|
|
|
+
|
|
|
+ if (read(syncfd, &s, sizeof(s)) != sizeof(s))
|
|
|
+ bail("failed to sync with child: next state");
|
|
|
+
|
|
|
+ switch (s) {
|
|
|
+ case SYNC_ERR: {
|
|
|
+ /* We have to mirror the error code of the child. */
|
|
|
+ int ret;
|
|
|
+
|
|
|
+ if (read(syncfd, &ret, sizeof(ret)) != sizeof(ret))
|
|
|
+ bail("failed to sync with child: read(error code)");
|
|
|
+
|
|
|
+ exit(ret);
|
|
|
+ }
|
|
|
+ break;
|
|
|
+ case SYNC_USERMAP_PLS:
|
|
|
+ /* Enable setgroups(2) if we've been asked to. */
|
|
|
+ if (config.is_setgroup)
|
|
|
+ update_setgroups(child, SETGROUPS_ALLOW);
|
|
|
+
|
|
|
+ /* Set up mappings. */
|
|
|
+ update_uidmap(child, config.uidmap, config.uidmap_len);
|
|
|
+ update_gidmap(child, config.gidmap, config.gidmap_len);
|
|
|
+
|
|
|
+ s = SYNC_USERMAP_ACK;
|
|
|
+ if (write(syncfd, &s, sizeof(s)) != sizeof(s)) {
|
|
|
+ kill(child, SIGKILL);
|
|
|
+ bail("failed to sync with child: write(SYNC_USERMAP_ACK)");
|
|
|
+ }
|
|
|
+ break;
|
|
|
+ case SYNC_USERMAP_ACK:
|
|
|
+ /* We should _never_ receive acks. */
|
|
|
+ kill(child, SIGKILL);
|
|
|
+ bail("failed to sync with child: unexpected SYNC_USERMAP_ACK");
|
|
|
+ break;
|
|
|
+ case SYNC_RECVPID_PLS: {
|
|
|
+ pid_t old = child;
|
|
|
+
|
|
|
+ /* Get the init_func pid. */
|
|
|
+ if (read(syncfd, &child, sizeof(child)) != sizeof(child)) {
|
|
|
+ kill(old, SIGKILL);
|
|
|
+ bail("failed to sync with child: read(childpid)");
|
|
|
+ }
|
|
|
+
|
|
|
+ /* Send ACK. */
|
|
|
+ s = SYNC_RECVPID_ACK;
|
|
|
+ if (write(syncfd, &s, sizeof(s)) != sizeof(s)) {
|
|
|
+ kill(old, SIGKILL);
|
|
|
+ kill(child, SIGKILL);
|
|
|
+ bail("failed to sync with child: write(SYNC_RECVPID_ACK)");
|
|
|
+ }
|
|
|
+ }
|
|
|
+
|
|
|
+ /* Leave the loop. */
|
|
|
+ goto out;
|
|
|
+ case SYNC_RECVPID_ACK:
|
|
|
+ /* We should _never_ receive acks. */
|
|
|
+ kill(child, SIGKILL);
|
|
|
+ bail("failed to sync with child: unexpected SYNC_RECVPID_ACK");
|
|
|
+ break;
|
|
|
+ }
|
|
|
+ }
|
|
|
+
|
|
|
+ out:
|
|
|
+ /* Send the init_func pid back to our parent. */
|
|
|
+ len = snprintf(buf, JSON_MAX, "{\"pid\": %d}\n", child);
|
|
|
+ if (len < 0) {
|
|
|
+ kill(child, SIGKILL);
|
|
|
+ bail("unable to generate JSON for child pid");
|
|
|
+ }
|
|
|
+ if (write(pipenum, buf, len) != len) {
|
|
|
+ kill(child, SIGKILL);
|
|
|
+ bail("unable to send child pid to bootstrapper");
|
|
|
+ }
|
|
|
+
|
|
|
+ exit(0);
|
|
|
+ }
|
|
|
+
|
|
|
+ /*
|
|
|
+ * Stage 1: We're in the first child process. Our job is to join any
|
|
|
+ * provided user namespaces in the netlink payload. If we've been
|
|
|
+ * asked to CLONE_NEWUSER, we will unshare the user namespace and
|
|
|
+ * ask our parent (stage 0) to set up our user mappings for us.
|
|
|
+ * Then, we unshare the rest of the requested namespaces and
|
|
|
+ * create a new child (stage 2: JUMP_INIT). We then send the
|
|
|
+ * child's PID to our parent (stage 0).
|
|
|
+ */
|
|
|
+ case JUMP_CHILD: {
|
|
|
+ pid_t child;
|
|
|
+ enum sync_t s;
|
|
|
+
|
|
|
+ /* We're in a child and thus need to tell the parent if we die. */
|
|
|
+ syncfd = syncpipe[0];
|
|
|
+
|
|
|
+ /* For debugging. */
|
|
|
+ prctl(PR_SET_NAME, (unsigned long) "runc:[1:CHILD]", 0, 0, 0);
|
|
|
+
|
|
|
+ /*
|
|
|
+ * We need to setns first. We cannot do this earlier (in stage 0)
|
|
|
+ * because of the fact that we forked to get here (the PID of
|
|
|
+ * [stage 2: JUMP_INIT]) would be meaningless). We could send it
|
|
|
+ * using cmsg(3) but that's just annoying.
|
|
|
+ */
|
|
|
+ if (config.namespaces)
|
|
|
+ join_namespaces(config.namespaces);
|
|
|
+
|
|
|
+ /*
|
|
|
+ * Unshare all of the namespaces. Now, it should be noted that this
|
|
|
+ * ordering might break in the future (especially with rootless
|
|
|
+ * containers). But for now, it's not possible to split this into
|
|
|
+ * CLONE_NEWUSER + [the rest] because of some RHEL SELinux issues.
|
|
|
+ *
|
|
|
+ * Note that we don't merge this with clone() because there were
|
|
|
+ * some old kernel versions where clone(CLONE_PARENT | CLONE_NEWPID)
|
|
|
+ * was broken, so we'll just do it the long way anyway.
|
|
|
+ */
|
|
|
+ if (unshare(config.cloneflags) < 0)
|
|
|
+ bail("failed to unshare namespaces");
|
|
|
+
|
|
|
+ /*
|
|
|
+ * Deal with user namespaces first. They are quite special, as they
|
|
|
+ * affect our ability to unshare other namespaces and are used as
|
|
|
+ * context for privilege checks.
|
|
|
+ */
|
|
|
+ if (config.cloneflags & CLONE_NEWUSER) {
|
|
|
+ /*
|
|
|
+ * We don't have the privileges to do any mapping here (see the
|
|
|
+ * clone_parent rant). So signal our parent to hook us up.
|
|
|
+ */
|
|
|
+
|
|
|
+ s = SYNC_USERMAP_PLS;
|
|
|
+ if (write(syncfd, &s, sizeof(s)) != sizeof(s))
|
|
|
+ bail("failed to sync with parent: write(SYNC_USERMAP_PLS)");
|
|
|
+
|
|
|
+ /* ... wait for mapping ... */
|
|
|
+
|
|
|
+ if (read(syncfd, &s, sizeof(s)) != sizeof(s))
|
|
|
+ bail("failed to sync with parent: read(SYNC_USERMAP_ACK)");
|
|
|
+ if (s != SYNC_USERMAP_ACK)
|
|
|
+ bail("failed to sync with parent: SYNC_USERMAP_ACK: got %u", s);
|
|
|
+ }
|
|
|
+
|
|
|
+ /* TODO: What about non-namespace clone flags that we're dropping here? */
|
|
|
+ child = clone_parent(&env, JUMP_INIT);
|
|
|
+ if (child < 0)
|
|
|
+ bail("unable to fork: init_func");
|
|
|
+
|
|
|
+ /* Send the child to our parent, which knows what it's doing. */
|
|
|
+ s = SYNC_RECVPID_PLS;
|
|
|
+ if (write(syncfd, &s, sizeof(s)) != sizeof(s)) {
|
|
|
+ kill(child, SIGKILL);
|
|
|
+ bail("failed to sync with parent: write(SYNC_RECVPID_PLS)");
|
|
|
+ }
|
|
|
+ if (write(syncfd, &child, sizeof(child)) != sizeof(child)) {
|
|
|
+ kill(child, SIGKILL);
|
|
|
+ bail("failed to sync with parent: write(childpid)");
|
|
|
+ }
|
|
|
+
|
|
|
+ /* ... wait for parent to get the pid ... */
|
|
|
+
|
|
|
+ if (read(syncfd, &s, sizeof(s)) != sizeof(s)) {
|
|
|
+ kill(child, SIGKILL);
|
|
|
+ bail("failed to sync with parent: read(SYNC_RECVPID_ACK)");
|
|
|
+ }
|
|
|
+ if (s != SYNC_RECVPID_ACK) {
|
|
|
+ kill(child, SIGKILL);
|
|
|
+ bail("failed to sync with parent: SYNC_RECVPID_ACK: got %u", s);
|
|
|
+ }
|
|
|
+
|
|
|
+ /* Our work is done. [Stage 2: JUMP_INIT] is doing the rest of the work. */
|
|
|
+ exit(0);
|
|
|
+ }
|
|
|
+
|
|
|
+ /*
|
|
|
+ * Stage 2: We're the final child process, and the only process that will
|
|
|
+ * actually return to the Go runtime. Our job is to just do the
|
|
|
+ * final cleanup steps and then return to the Go runtime to allow
|
|
|
+ * init_linux.go to run.
|
|
|
+ */
|
|
|
+ case JUMP_INIT: {
|
|
|
+ /*
|
|
|
+ * We're inside the child now, having jumped from the
|
|
|
+ * start_child() code after forking in the parent.
|
|
|
+ */
|
|
|
+ int consolefd = config.consolefd;
|
|
|
+
|
|
|
+ /* We're in a child and thus need to tell the parent if we die. */
|
|
|
+ syncfd = syncpipe[0];
|
|
|
+
|
|
|
+ /* For debugging. */
|
|
|
+ prctl(PR_SET_NAME, (unsigned long) "runc:[2:INIT]", 0, 0, 0);
|
|
|
+
|
|
|
+ if (setsid() < 0)
|
|
|
+ bail("setsid failed");
|
|
|
+
|
|
|
+ if (setuid(0) < 0)
|
|
|
+ bail("setuid failed");
|
|
|
+
|
|
|
+ if (setgid(0) < 0)
|
|
|
+ bail("setgid failed");
|
|
|
+
|
|
|
+ if (setgroups(0, NULL) < 0)
|
|
|
+ bail("setgroups failed");
|
|
|
+
|
|
|
+ if (consolefd != -1) {
|
|
|
+ if (ioctl(consolefd, TIOCSCTTY, 0) < 0)
|
|
|
+ bail("ioctl TIOCSCTTY failed");
|
|
|
+ if (dup3(consolefd, STDIN_FILENO, 0) != STDIN_FILENO)
|
|
|
+ bail("failed to dup stdin");
|
|
|
+ if (dup3(consolefd, STDOUT_FILENO, 0) != STDOUT_FILENO)
|
|
|
+ bail("failed to dup stdout");
|
|
|
+ if (dup3(consolefd, STDERR_FILENO, 0) != STDERR_FILENO)
|
|
|
+ bail("failed to dup stderr");
|
|
|
+ }
|
|
|
+
|
|
|
+ /* Close sync pipes. */
|
|
|
+ close(syncpipe[0]);
|
|
|
+ close(syncpipe[1]);
|
|
|
+
|
|
|
+ /* Free netlink data. */
|
|
|
+ nl_free(&config);
|
|
|
+
|
|
|
+ /* Finish executing, let the Go runtime take over. */
|
|
|
+ return;
|
|
|
+ }
|
|
|
+ default:
|
|
|
+ bail("unexpected jump value");
|
|
|
+ break;
|
|
|
+ }
|
|
|
+
|
|
|
+ /* Should never be reached. */
|
|
|
+ bail("should never be reached");
|
|
|
+}
|
Michael Crosby