sysdeps/posix/spawni.c

   1 /* Guts of POSIX spawn interface.  Generic POSIX.1 version.
   2    Copyright (C) 2000-2015 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <errno.h>
  20 #include <fcntl.h>
  21 #include <paths.h>
  22 #include <spawn.h>
  23 #include <stdbool.h>
  24 #include <stdlib.h>
  25 #include <string.h>
  26 #include <unistd.h>
  27 #include <signal.h>
  28 #include <sys/resource.h>
  29 #include "spawn_int.h"
  30 #include <not-cancel.h>
  31 #include <local-setxid.h>
  32 #include <shlib-compat.h>
  33
  34
  35 /* The Unix standard contains a long explanation of the way to signal
  36    an error after the fork() was successful.  Since no new wait status
  37    was wanted there is no way to signal an error using one of the
  38    available methods.  The committee chose to signal an error by a
  39    normal program exit with the exit code 127.  */
  40 #define SPAWN_ERROR     127
  41
  42
  43 /* The file is accessible but it is not an executable file.  Invoke
  44    the shell to interpret it as a script.  */
  45 static void
  46 internal_function
  47 script_execute (const char *file, char *const argv[], char *const envp[])
  48 {
  49   /* Count the arguments.  */
  50   int argc = 0;
  51   while (argv[argc++])
  52     ;
  53
  54   /* Construct an argument list for the shell.  */
  55   {
  56     char *new_argv[argc + 1];
  57     new_argv[0] = (char *) _PATH_BSHELL;
  58     new_argv[1] = (char *) file;
  59     while (argc > 1)
  60       {
  61         new_argv[argc] = argv[argc - 1];
  62         --argc;
  63       }
  64
  65     /* Execute the shell.  */
  66     __execve (new_argv[0], new_argv, envp);
  67   }
  68 }
  69
  70 static inline void
  71 maybe_script_execute (const char *file, char *const argv[], char *const envp[],
  72                       int xflags)
  73 {
  74   if (SHLIB_COMPAT (libc, GLIBC_2_2, GLIBC_2_15)
  75       && (xflags & SPAWN_XFLAGS_TRY_SHELL)
  76       && errno == ENOEXEC)
  77     script_execute (file, argv, envp);
  78 }
  79
  80 /* Spawn a new process executing PATH with the attributes describes in *ATTRP.
  81    Before running the process perform the actions described in FILE-ACTIONS. */
  82 int
  83 __spawni (pid_t *pid, const char *file,
  84           const posix_spawn_file_actions_t *file_actions,
  85           const posix_spawnattr_t *attrp, char *const argv[],
  86           char *const envp[], int xflags)
  87 {
  88   pid_t new_pid;
  89   char *path, *p, *name;
  90   size_t len;
  91   size_t pathlen;
  92
  93   /* Do this once.  */
  94   short int flags = attrp == NULL ? 0 : attrp->__flags;
  95
  96   /* Generate the new process.  */
  97   if ((flags & POSIX_SPAWN_USEVFORK) != 0
  98       /* If no major work is done, allow using vfork.  Note that we
  99          might perform the path searching.  But this would be done by
 100          a call to execvp(), too, and such a call must be OK according
 101          to POSIX.  */
 102       || ((flags & (POSIX_SPAWN_SETSIGMASK | POSIX_SPAWN_SETSIGDEF
 103                     | POSIX_SPAWN_SETSCHEDPARAM | POSIX_SPAWN_SETSCHEDULER
 104                     | POSIX_SPAWN_SETPGROUP | POSIX_SPAWN_RESETIDS)) == 0
 105           && file_actions == NULL))
 106     new_pid = __vfork ();
 107   else
 108     new_pid = __fork ();
 109
 110   if (new_pid != 0)
 111     {
 112       if (new_pid < 0)
 113         return errno;
 114
 115       /* The call was successful.  Store the PID if necessary.  */
 116       if (pid != NULL)
 117         *pid = new_pid;
 118
 119       return 0;
 120     }
 121
 122   /* Set signal mask.  */
 123   if ((flags & POSIX_SPAWN_SETSIGMASK) != 0
 124       && __sigprocmask (SIG_SETMASK, &attrp->__ss, NULL) != 0)
 125     _exit (SPAWN_ERROR);
 126
 127   /* Set signal default action.  */
 128   if ((flags & POSIX_SPAWN_SETSIGDEF) != 0)
 129     {
 130       /* We have to iterate over all signals.  This could possibly be
 131          done better but it requires system specific solutions since
 132          the sigset_t data type can be very different on different
 133          architectures.  */
 134       int sig;
 135       struct sigaction sa;
 136
 137       memset (&sa, '\0', sizeof (sa));
 138       sa.sa_handler = SIG_DFL;
 139
 140       for (sig = 1; sig <= _NSIG; ++sig)
 141         if (__sigismember (&attrp->__sd, sig) != 0
 142             && __sigaction (sig, &sa, NULL) != 0)
 143           _exit (SPAWN_ERROR);
 144
 145     }
 146
 147 #ifdef _POSIX_PRIORITY_SCHEDULING
 148   /* Set the scheduling algorithm and parameters.  */
 149   if ((flags & (POSIX_SPAWN_SETSCHEDPARAM | POSIX_SPAWN_SETSCHEDULER))
 150       == POSIX_SPAWN_SETSCHEDPARAM)
 151     {
 152       if (__sched_setparam (0, &attrp->__sp) == -1)
 153         _exit (SPAWN_ERROR);
 154     }
 155   else if ((flags & POSIX_SPAWN_SETSCHEDULER) != 0)
 156     {
 157       if (__sched_setscheduler (0, attrp->__policy, &attrp->__sp) == -1)
 158         _exit (SPAWN_ERROR);
 159     }
 160 #endif
 161
 162   /* Set the process group ID.  */
 163   if ((flags & POSIX_SPAWN_SETPGROUP) != 0
 164       && __setpgid (0, attrp->__pgrp) != 0)
 165     _exit (SPAWN_ERROR);
 166
 167   /* Set the effective user and group IDs.  */
 168   if ((flags & POSIX_SPAWN_RESETIDS) != 0
 169       && (local_seteuid (__getuid ()) != 0
 170           || local_setegid (__getgid ()) != 0))
 171     _exit (SPAWN_ERROR);
 172
 173   /* Execute the file actions.  */
 174   if (file_actions != NULL)
 175     {
 176       int cnt;
 177       struct rlimit64 fdlimit;
 178       bool have_fdlimit = false;
 179
 180       for (cnt = 0; cnt < file_actions->__used; ++cnt)
 181         {
 182           struct __spawn_action *action = &file_actions->__actions[cnt];
 183
 184           switch (action->tag)
 185             {
 186             case spawn_do_close:
 187               if (close_not_cancel (action->action.close_action.fd) != 0)
 188                 {
 189                   if (! have_fdlimit)
 190                     {
 191                       getrlimit64 (RLIMIT_NOFILE, &fdlimit);
 192                       have_fdlimit = true;
 193                     }
 194
 195                   /* Only signal errors for file descriptors out of range.  */
 196                   if (action->action.close_action.fd < 0
 197                       || action->action.close_action.fd >= fdlimit.rlim_cur)
 198                     /* Signal the error.  */
 199                     _exit (SPAWN_ERROR);
 200                 }
 201               break;
 202
 203             case spawn_do_open:
 204               {
 205                 int new_fd = open_not_cancel (action->action.open_action.path,
 206                                               action->action.open_action.oflag
 207                                               | O_LARGEFILE,
 208                                               action->action.open_action.mode);
 209
 210                 if (new_fd == -1)
 211                   /* The `open' call failed.  */
 212                   _exit (SPAWN_ERROR);
 213
 214                 /* Make sure the desired file descriptor is used.  */
 215                 if (new_fd != action->action.open_action.fd)
 216                   {
 217                     if (__dup2 (new_fd, action->action.open_action.fd)
 218                         != action->action.open_action.fd)
 219                       /* The `dup2' call failed.  */
 220                       _exit (SPAWN_ERROR);
 221
 222                     if (close_not_cancel (new_fd) != 0)
 223                       /* The `close' call failed.  */
 224                       _exit (SPAWN_ERROR);
 225                   }
 226               }
 227               break;
 228
 229             case spawn_do_dup2:
 230               if (__dup2 (action->action.dup2_action.fd,
 231                           action->action.dup2_action.newfd)
 232                   != action->action.dup2_action.newfd)
 233                 /* The `dup2' call failed.  */
 234                 _exit (SPAWN_ERROR);
 235               break;
 236             }
 237         }
 238     }
 239
 240   if ((xflags & SPAWN_XFLAGS_USE_PATH) == 0 || strchr (file, '/') != NULL)
 241     {
 242       /* The FILE parameter is actually a path.  */
 243       __execve (file, argv, envp);
 244
 245       maybe_script_execute (file, argv, envp, xflags);
 246
 247       /* Oh, oh.  `execve' returns.  This is bad.  */
 248       _exit (SPAWN_ERROR);
 249     }
 250
 251   /* We have to search for FILE on the path.  */
 252   path = getenv ("PATH");
 253   if (path == NULL)
 254     {
 255       /* There is no `PATH' in the environment.
 256          The default search path is the current directory
 257          followed by the path `confstr' returns for `_CS_PATH'.  */
 258       len = confstr (_CS_PATH, (char *) NULL, 0);
 259       path = (char *) __alloca (1 + len);
 260       path[0] = ':';
 261       (void) confstr (_CS_PATH, path + 1, len);
 262     }
 263
 264   len = strlen (file) + 1;
 265   pathlen = strlen (path);
 266   name = __alloca (pathlen + len + 1);
 267   /* Copy the file name at the top.  */
 268   name = (char *) memcpy (name + pathlen + 1, file, len);
 269   /* And add the slash.  */
 270   *--name = '/';
 271
 272   p = path;
 273   do
 274     {
 275       char *startp;
 276
 277       path = p;
 278       p = __strchrnul (path, ':');
 279
 280       if (p == path)
 281         /* Two adjacent colons, or a colon at the beginning or the end
 282            of `PATH' means to search the current directory.  */
 283         startp = name + 1;
 284       else
 285         startp = (char *) memcpy (name - (p - path), path, p - path);
 286
 287       /* Try to execute this name.  If it works, execv will not return.  */
 288       __execve (startp, argv, envp);
 289
 290       maybe_script_execute (startp, argv, envp, xflags);
 291
 292       switch (errno)
 293         {
 294         case EACCES:
 295         case ENOENT:
 296         case ESTALE:
 297         case ENOTDIR:
 298           /* Those errors indicate the file is missing or not executable
 299              by us, in which case we want to just try the next path
 300              directory.  */
 301           break;
 302
 303         default:
 304           /* Some other error means we found an executable file, but
 305              something went wrong executing it; return the error to our
 306              caller.  */
 307           _exit (SPAWN_ERROR);
 308             }
 309     }
 310   while (*p++ != '\0');
 311
 312   /* Return with an error.  */
 313   _exit (SPAWN_ERROR);
 314 }