src/lxc/initutils.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #ifndef _GNU_SOURCE
   4 #define _GNU_SOURCE 1
   5 #endif
   6 #include <sys/prctl.h>
   7
   8 #include "compiler.h"
   9 #include "config.h"
  10 #include "file_utils.h"
  11 #include "initutils.h"
  12 #include "log.h"
  13 #include "macro.h"
  14 #include "memory_utils.h"
  15
  16 #ifndef HAVE_STRLCPY
  17 #include "include/strlcpy.h"
  18 #endif
  19
  20 lxc_log_define(initutils, lxc);
  21
  22 static char *copy_global_config_value(char *p)
  23 {
  24         int len = strlen(p);
  25         char *retbuf;
  26
  27         if (len < 1)
  28                 return NULL;
  29
  30         if (p[len-1] == '\n') {
  31                 p[len-1] = '\0';
  32                 len--;
  33         }
  34
  35         retbuf = malloc(len + 1);
  36         if (!retbuf)
  37                 return NULL;
  38
  39         (void)strlcpy(retbuf, p, len + 1);
  40         return retbuf;
  41 }
  42
  43 const char *lxc_global_config_value(const char *option_name)
  44 {
  45         static const char * const options[][2] = {
  46                 { "lxc.bdev.lvm.vg",        DEFAULT_VG      },
  47                 { "lxc.bdev.lvm.thin_pool", DEFAULT_THIN_POOL },
  48                 { "lxc.bdev.zfs.root",      DEFAULT_ZFSROOT },
  49                 { "lxc.bdev.rbd.rbdpool",   DEFAULT_RBDPOOL },
  50                 { "lxc.lxcpath",            NULL            },
  51                 { "lxc.default_config",     NULL            },
  52                 { "lxc.cgroup.pattern",     NULL            },
  53                 { "lxc.cgroup.use",         NULL            },
  54                 { NULL, NULL },
  55         };
  56
  57         /* placed in the thread local storage pool for non-bionic targets */
  58 #ifdef HAVE_TLS
  59         static thread_local const char *values[sizeof(options) / sizeof(options[0])] = {0};
  60 #else
  61         static const char *values[sizeof(options) / sizeof(options[0])] = {0};
  62 #endif
  63
  64         /* user_config_path is freed as soon as it is used */
  65         char *user_config_path = NULL;
  66
  67         /*
  68          * The following variables are freed at bottom unconditionally.
  69          * So NULL the value if it is to be returned to the caller
  70          */
  71         char *user_default_config_path = NULL;
  72         char *user_lxc_path = NULL;
  73         char *user_cgroup_pattern = NULL;
  74
  75         if (geteuid() > 0) {
  76                 const char *user_home = getenv("HOME");
  77                 if (!user_home)
  78                         user_home = "/";
  79
  80                 user_config_path = malloc(sizeof(char) * (22 + strlen(user_home)));
  81                 user_default_config_path = malloc(sizeof(char) * (26 + strlen(user_home)));
  82                 user_lxc_path = malloc(sizeof(char) * (19 + strlen(user_home)));
  83
  84                 sprintf(user_config_path, "%s/.config/lxc/lxc.conf", user_home);
  85                 sprintf(user_default_config_path, "%s/.config/lxc/default.conf", user_home);
  86                 sprintf(user_lxc_path, "%s/.local/share/lxc/", user_home);
  87                 user_cgroup_pattern = strdup("%n");
  88         }
  89         else {
  90                 user_config_path = strdup(LXC_GLOBAL_CONF);
  91                 user_default_config_path = strdup(LXC_DEFAULT_CONFIG);
  92                 user_lxc_path = strdup(LXCPATH);
  93                 user_cgroup_pattern = strdup(DEFAULT_CGROUP_PATTERN);
  94         }
  95
  96         const char * const (*ptr)[2];
  97         size_t i;
  98         FILE *fin = NULL;
  99
 100         for (i = 0, ptr = options; (*ptr)[0]; ptr++, i++) {
 101                 if (!strcmp(option_name, (*ptr)[0]))
 102                         break;
 103         }
 104         if (!(*ptr)[0]) {
 105                 free(user_config_path);
 106                 free(user_default_config_path);
 107                 free(user_lxc_path);
 108                 free(user_cgroup_pattern);
 109                 errno = EINVAL;
 110                 return NULL;
 111         }
 112
 113         if (values[i]) {
 114                 free(user_config_path);
 115                 free(user_default_config_path);
 116                 free(user_lxc_path);
 117                 free(user_cgroup_pattern);
 118                 return values[i];
 119         }
 120
 121         fin = fopen_cloexec(user_config_path, "r");
 122         free(user_config_path);
 123         if (fin) {
 124                 __do_free char *line = NULL;
 125                 size_t len = 0;
 126                 char *slider1, *slider2;
 127
 128                 while (getline(&line, &len, fin) > 0) {
 129                         if (*line == '#')
 130                                 continue;
 131
 132                         slider1 = strstr(line, option_name);
 133                         if (!slider1)
 134                                 continue;
 135
 136                         /* see if there was just white space in front
 137                          * of the option name
 138                          */
 139                         for (slider2 = line; slider2 < slider1; slider2++)
 140                                 if (*slider2 != ' ' && *slider2 != '\t')
 141                                         break;
 142
 143                         if (slider2 < slider1)
 144                                 continue;
 145
 146                         slider1 = strchr(slider1, '=');
 147                         if (!slider1)
 148                                 continue;
 149
 150                         /* see if there was just white space after
 151                          * the option name
 152                          */
 153                         for (slider2 += strlen(option_name); slider2 < slider1;
 154                              slider2++)
 155                                 if (*slider2 != ' ' && *slider2 != '\t')
 156                                         break;
 157
 158                         if (slider2 < slider1)
 159                                 continue;
 160
 161                         slider1++;
 162                         while (*slider1 && (*slider1 == ' ' || *slider1 == '\t'))
 163                                 slider1++;
 164
 165                         if (!*slider1)
 166                                 continue;
 167
 168                         if (strcmp(option_name, "lxc.lxcpath") == 0) {
 169                                 free(user_lxc_path);
 170                                 user_lxc_path = copy_global_config_value(slider1);
 171                                 remove_trailing_slashes(user_lxc_path);
 172                                 values[i] = user_lxc_path;
 173                                 user_lxc_path = NULL;
 174                                 goto out;
 175                         }
 176
 177                         values[i] = copy_global_config_value(slider1);
 178                         goto out;
 179                 }
 180         }
 181
 182         /* could not find value, use default */
 183         if (strcmp(option_name, "lxc.lxcpath") == 0) {
 184                 remove_trailing_slashes(user_lxc_path);
 185                 values[i] = user_lxc_path;
 186                 user_lxc_path = NULL;
 187         }
 188         else if (strcmp(option_name, "lxc.default_config") == 0) {
 189                 values[i] = user_default_config_path;
 190                 user_default_config_path = NULL;
 191         }
 192         else if (strcmp(option_name, "lxc.cgroup.pattern") == 0) {
 193                 values[i] = user_cgroup_pattern;
 194                 user_cgroup_pattern = NULL;
 195         }
 196         else
 197                 values[i] = (*ptr)[1];
 198
 199         /* special case: if default value is NULL,
 200          * and there is no config, don't view that
 201          * as an error... */
 202         if (!values[i])
 203                 errno = 0;
 204
 205 out:
 206         if (fin)
 207                 fclose(fin);
 208
 209         free(user_cgroup_pattern);
 210         free(user_default_config_path);
 211         free(user_lxc_path);
 212
 213         return values[i];
 214 }
 215
 216 /*
 217  * Sets the process title to the specified title. Note that this may fail if
 218  * the kernel doesn't support PR_SET_MM_MAP (kernels <3.18).
 219  */
 220 int setproctitle(char *title)
 221 {
 222         __do_fclose FILE *f = NULL;
 223         int i, fd, len;
 224         char *buf_ptr, *tmp_proctitle;
 225         char buf[LXC_LINELEN];
 226         int ret = 0;
 227         ssize_t bytes_read = 0;
 228         static char *proctitle = NULL;
 229
 230         /*
 231          * We don't really need to know all of this stuff, but unfortunately
 232          * PR_SET_MM_MAP requires us to set it all at once, so we have to
 233          * figure it out anyway.
 234          */
 235         unsigned long start_data, end_data, start_brk, start_code, end_code,
 236             start_stack, arg_start, arg_end, env_start, env_end, brk_val;
 237         struct prctl_mm_map prctl_map;
 238
 239         f = fopen_cloexec("/proc/self/stat", "r");
 240         if (!f)
 241                 return -1;
 242
 243         fd = fileno(f);
 244         if (fd < 0)
 245                 return -1;
 246
 247         bytes_read = lxc_read_nointr(fd, buf, sizeof(buf) - 1);
 248         if (bytes_read <= 0)
 249                 return -1;
 250
 251         buf[bytes_read] = '\0';
 252
 253         /* Skip the first 25 fields, column 26-28 are start_code, end_code,
 254          * and start_stack */
 255         buf_ptr = strchr(buf, ' ');
 256         for (i = 0; i < 24; i++) {
 257                 if (!buf_ptr)
 258                         return -1;
 259                 buf_ptr = strchr(buf_ptr + 1, ' ');
 260         }
 261         if (!buf_ptr)
 262                 return -1;
 263
 264         i = sscanf(buf_ptr, "%lu %lu %lu", &start_code, &end_code, &start_stack);
 265         if (i != 3)
 266                 return -1;
 267
 268         /* Skip the next 19 fields, column 45-51 are start_data to arg_end */
 269         for (i = 0; i < 19; i++) {
 270                 if (!buf_ptr)
 271                         return -1;
 272                 buf_ptr = strchr(buf_ptr + 1, ' ');
 273         }
 274
 275         if (!buf_ptr)
 276                 return -1;
 277
 278         i = sscanf(buf_ptr, "%lu %lu %lu %*u %*u %lu %lu", &start_data,
 279                    &end_data, &start_brk, &env_start, &env_end);
 280         if (i != 5)
 281                 return -1;
 282
 283         /* Include the null byte here, because in the calculations below we
 284          * want to have room for it. */
 285         len = strlen(title) + 1;
 286
 287         tmp_proctitle = realloc(proctitle, len);
 288         if (!tmp_proctitle)
 289                 return -1;
 290
 291         proctitle = tmp_proctitle;
 292
 293         arg_start = (unsigned long)proctitle;
 294         arg_end = arg_start + len;
 295
 296         brk_val = syscall(__NR_brk, 0);
 297
 298         prctl_map = (struct prctl_mm_map){
 299             .start_code = start_code,
 300             .end_code = end_code,
 301             .start_stack = start_stack,
 302             .start_data = start_data,
 303             .end_data = end_data,
 304             .start_brk = start_brk,
 305             .brk = brk_val,
 306             .arg_start = arg_start,
 307             .arg_end = arg_end,
 308             .env_start = env_start,
 309             .env_end = env_end,
 310             .auxv = NULL,
 311             .auxv_size = 0,
 312             .exe_fd = -1,
 313         };
 314
 315         ret = prctl(PR_SET_MM, prctl_arg(PR_SET_MM_MAP), prctl_arg(&prctl_map),
 316                     prctl_arg(sizeof(prctl_map)), prctl_arg(0));
 317         if (ret == 0)
 318                 (void)strlcpy((char *)arg_start, title, len);
 319         else
 320                 SYSWARN("Failed to set cmdline");
 321
 322         return ret;
 323 }