src/lxc/namespace.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #ifndef _GNU_SOURCE
   4 #define _GNU_SOURCE 1
   5 #endif
   6 #include <errno.h>
   7 #include <fcntl.h>
   8 #include <sched.h>
   9 #include <signal.h>
  10 #include <sys/param.h>
  11 #include <sys/stat.h>
  12 #include <sys/syscall.h>
  13 #include <sys/types.h>
  14 #include <unistd.h>
  15
  16 #include "config.h"
  17 #include "log.h"
  18 #include "memory_utils.h"
  19 #include "namespace.h"
  20 #include "utils.h"
  21
  22 lxc_log_define(namespace, lxc);
  23
  24 /*
  25  * Let's use the "standard stack limit" (i.e. glibc thread size default) for
  26  * stack sizes: 8MB.
  27  */
  28 #define __LXC_STACK_SIZE (8 * 1024 * 1024)
  29 pid_t lxc_clone(int (*fn)(void *), void *arg, int flags, int *pidfd)
  30 {
  31         pid_t ret;
  32         void *stack;
  33
  34         stack = malloc(__LXC_STACK_SIZE);
  35         if (!stack) {
  36                 SYSERROR("Failed to allocate clone stack");
  37                 return -ENOMEM;
  38         }
  39
  40 #ifdef __ia64__
  41         ret = __clone2(fn, stack, __LXC_STACK_SIZE, flags | SIGCHLD, arg, pidfd);
  42 #else
  43         ret = clone(fn, stack + __LXC_STACK_SIZE, flags | SIGCHLD, arg, pidfd);
  44 #endif
  45         if (ret < 0)
  46                 SYSERROR("Failed to clone (%#x)", flags);
  47
  48         return ret;
  49 }
  50
  51 /* Leave the user namespace at the first position in the array of structs so
  52  * that we always attach to it first when iterating over the struct and using
  53  * setns() to switch namespaces. This especially affects lxc_attach(): Suppose
  54  * you cloned a new user namespace and mount namespace as an unprivileged user
  55  * on the host and want to setns() to the mount namespace. This requires you to
  56  * attach to the user namespace first otherwise the kernel will fail this check:
  57  *
  58  *        if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) ||
  59  *            !ns_capable(current_user_ns(), CAP_SYS_CHROOT) ||
  60  *            !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
  61  *            return -EPERM;
  62  *
  63  *    in
  64  *
  65  *        linux/fs/namespace.c:mntns_install().
  66  */
  67 const struct ns_info ns_info[LXC_NS_MAX] = {
  68         [LXC_NS_USER]    = { "user",   CLONE_NEWUSER,   "CLONE_NEWUSER",   "LXC_USER_NS"    },
  69         [LXC_NS_MNT]    =  { "mnt",    CLONE_NEWNS,     "CLONE_NEWNS",     "LXC_MNT_NS"     },
  70         [LXC_NS_PID]    =  { "pid",    CLONE_NEWPID,    "CLONE_NEWPID",    "LXC_PID_NS"     },
  71         [LXC_NS_UTS]    =  { "uts",    CLONE_NEWUTS,    "CLONE_NEWUTS",    "LXC_UTS_NS"     },
  72         [LXC_NS_IPC]    =  { "ipc",    CLONE_NEWIPC,    "CLONE_NEWIPC",    "LXC_IPC_NS"     },
  73         [LXC_NS_NET]    =  { "net",    CLONE_NEWNET,    "CLONE_NEWNET",    "LXC_NET_NS"     },
  74         [LXC_NS_CGROUP] =  { "cgroup", CLONE_NEWCGROUP, "CLONE_NEWCGROUP", "LXC_CGROUP_NS"  }
  75 };
  76
  77 int lxc_namespace_2_cloneflag(const char *namespace)
  78 {
  79         int i;
  80
  81         for (i = 0; i < LXC_NS_MAX; i++)
  82                 if (!strcasecmp(ns_info[i].proc_name, namespace))
  83                         return ns_info[i].clone_flag;
  84
  85         ERROR("Invalid namespace name \"%s\"", namespace);
  86         return -EINVAL;
  87 }
  88
  89 int lxc_namespace_2_ns_idx(const char *namespace)
  90 {
  91         int i;
  92
  93         for (i = 0; i < LXC_NS_MAX; i++)
  94                 if (!strcmp(ns_info[i].proc_name, namespace))
  95                         return i;
  96
  97         ERROR("Invalid namespace name \"%s\"", namespace);
  98         return -EINVAL;
  99 }
 100
 101 extern int lxc_namespace_2_std_identifiers(char *namespaces)
 102 {
 103         char **it;
 104         char *del;
 105
 106         /* The identifiers for namespaces used with lxc-attach and lxc-unshare
 107          * as given on the manpage do not align with the standard identifiers.
 108          * This affects network, mount, and uts namespaces. The standard identifiers
 109          * are: "mnt", "uts", and "net" whereas lxc-attach and lxc-unshare uses
 110          * "MOUNT", "UTSNAME", and "NETWORK". So let's use some cheap memmove()s
 111          * to replace them by their standard identifiers.
 112          * Let's illustrate this with an example:
 113          * Assume the string:
 114          *
 115          *      "IPC|MOUNT|PID"
 116          *
 117          * then we memmove()
 118          *
 119          *      dest: del + 1 == OUNT|PID
 120          *      src:  del + 3 == NT|PID
 121          */
 122         if (!namespaces)
 123                 return -1;
 124
 125         while ((del = strstr(namespaces, "MOUNT")))
 126                 memmove(del + 1, del + 3, strlen(del) - 2);
 127
 128         for (it = (char *[]){"NETWORK", "UTSNAME", NULL}; it && *it; it++)
 129                 while ((del = strstr(namespaces, *it)))
 130                         memmove(del + 3, del + 7, strlen(del) - 6);
 131
 132         return 0;
 133 }
 134
 135 int lxc_fill_namespace_flags(char *flaglist, int *flags)
 136 {
 137         char *token;
 138         int aflag;
 139
 140         if (!flaglist) {
 141                 ERROR("At least one namespace is needed.");
 142                 return -1;
 143         }
 144
 145         lxc_iterate_parts(token, flaglist, "|") {
 146                 aflag = lxc_namespace_2_cloneflag(token);
 147                 if (aflag < 0)
 148                         return -1;
 149
 150                 *flags |= aflag;
 151         }
 152
 153         return 0;
 154 }