src/lxc/namespace.c

   1 /*
   2  * lxc: linux Container library
   3  *
   4  * (C) Copyright IBM Corp. 2007, 2009
   5  *
   6  * Authors:
   7  * Daniel Lezcano <daniel.lezcano at free.fr>
   8  *
   9  * This library is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU Lesser General Public
  11  * License as published by the Free Software Foundation; either
  12  * version 2.1 of the License, or (at your option) any later version.
  13  *
  14  * This library is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  17  * Lesser General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU Lesser General Public
  20  * License along with this library; if not, write to the Free Software
  21  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  22  */
  23
  24 #include <unistd.h>
  25 #include <alloca.h>
  26 #include <errno.h>
  27 #include <signal.h>
  28 #include <sys/param.h>
  29 #include <sys/types.h>
  30 #include <sys/stat.h>
  31 #include <fcntl.h>
  32
  33 #include "namespace.h"
  34 #include "log.h"
  35
  36 lxc_log_define(lxc_namespace, lxc);
  37
  38 struct clone_arg {
  39         int (*fn)(void *);
  40         void *arg;
  41 };
  42
  43 static int do_clone(void *arg)
  44 {
  45         struct clone_arg *clone_arg = arg;
  46         return clone_arg->fn(clone_arg->arg);
  47 }
  48
  49 pid_t lxc_clone(int (*fn)(void *), void *arg, int flags)
  50 {
  51         struct clone_arg clone_arg = {
  52                 .fn = fn,
  53                 .arg = arg,
  54         };
  55
  56         size_t stack_size = sysconf(_SC_PAGESIZE);
  57         void *stack = alloca(stack_size);
  58         pid_t ret;
  59
  60 #ifdef __ia64__
  61         ret = __clone2(do_clone, stack,
  62                        stack_size, flags | SIGCHLD, &clone_arg);
  63 #else
  64         ret = clone(do_clone, stack  + stack_size, flags | SIGCHLD, &clone_arg);
  65 #endif
  66         if (ret < 0)
  67                 ERROR("Failed to clone (%#x): %s.", flags, strerror(errno));
  68
  69         return ret;
  70 }
  71
  72 /* Leave the user namespace at the first position in the array of structs so
  73  * that we always attach to it first when iterating over the struct and using
  74  * setns() to switch namespaces. This especially affects lxc_attach(): Suppose
  75  * you cloned a new user namespace and mount namespace as an unprivileged user
  76  * on the host and want to setns() to the mount namespace. This requires you to
  77  * attach to the user namespace first otherwise the kernel will fail this check:
  78  *
  79  *        if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) ||
  80  *            !ns_capable(current_user_ns(), CAP_SYS_CHROOT) ||
  81  *            !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
  82  *            return -EPERM;
  83  *
  84  *    in
  85  *
  86  *        linux/fs/namespace.c:mntns_install().
  87  */
  88 const struct ns_info ns_info[LXC_NS_MAX] = {
  89         [LXC_NS_USER] = {"user", CLONE_NEWUSER, "CLONE_NEWUSER"},
  90         [LXC_NS_MNT] = {"mnt", CLONE_NEWNS, "CLONE_NEWNS"},
  91         [LXC_NS_PID] = {"pid", CLONE_NEWPID, "CLONE_NEWPID"},
  92         [LXC_NS_UTS] = {"uts", CLONE_NEWUTS, "CLONE_NEWUTS"},
  93         [LXC_NS_IPC] = {"ipc", CLONE_NEWIPC, "CLONE_NEWIPC"},
  94         [LXC_NS_NET] = {"net", CLONE_NEWNET, "CLONE_NEWNET"},
  95         [LXC_NS_CGROUP] = {"cgroup", CLONE_NEWCGROUP, "CLONE_NEWCGROUP"}
  96 };
  97
  98 int lxc_namespace_2_cloneflag(char *namespace)
  99 {
 100         int i;
 101         for (i = 0; i < LXC_NS_MAX; i++)
 102                 if (!strcasecmp(ns_info[i].proc_name, namespace))
 103                         return ns_info[i].clone_flag;
 104
 105         ERROR("Invalid namespace name: %s.", namespace);
 106         return -1;
 107 }
 108
 109 int lxc_fill_namespace_flags(char *flaglist, int *flags)
 110 {
 111         char *token, *saveptr = NULL;
 112         int aflag;
 113
 114         if (!flaglist) {
 115                 ERROR("At least one namespace is needed.");
 116                 return -1;
 117         }
 118
 119         token = strtok_r(flaglist, "|", &saveptr);
 120         while (token) {
 121
 122                 aflag = lxc_namespace_2_cloneflag(token);
 123                 if (aflag < 0)
 124                         return -1;
 125
 126                 *flags |= aflag;
 127
 128                 token = strtok_r(NULL, "|", &saveptr);
 129         }
 130         return 0;
 131 }