libio/iopopen.c

   1 /* Copyright (C) 1993-2018 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Written by Per Bothner <bothner@cygnus.com>.
   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    As a special exception, if you link the code in this file with
  20    files compiled with a GNU compiler to produce an executable,
  21    that does not cause the resulting executable to be covered by
  22    the GNU Lesser General Public License.  This exception does not
  23    however invalidate any other reasons why the executable file
  24    might be covered by the GNU Lesser General Public License.
  25    This exception applies to code released by its copyright holders
  26    in files containing the exception.  */
  27
  28 #include "libioP.h"
  29 #include <fcntl.h>
  30 #include <signal.h>
  31 #include <unistd.h>
  32 #include <stdlib.h>
  33 #include <shlib-compat.h>
  34 #include <not-cancel.h>
  35 #include <sys/types.h>
  36 #include <sys/wait.h>
  37 #include <kernel-features.h>
  38
  39 struct _IO_proc_file
  40 {
  41   struct _IO_FILE_plus file;
  42   /* Following fields must match those in class procbuf (procbuf.h) */
  43   pid_t pid;
  44   struct _IO_proc_file *next;
  45 };
  46 typedef struct _IO_proc_file _IO_proc_file;
  47
  48 static const struct _IO_jump_t _IO_proc_jumps;
  49
  50 static struct _IO_proc_file *proc_file_chain;
  51
  52 #ifdef _IO_MTSAFE_IO
  53 static _IO_lock_t proc_file_chain_lock = _IO_lock_initializer;
  54
  55 static void
  56 unlock (void *not_used)
  57 {
  58   _IO_lock_unlock (proc_file_chain_lock);
  59 }
  60 #endif
  61
  62 FILE *
  63 _IO_new_proc_open (FILE *fp, const char *command, const char *mode)
  64 {
  65   int read_or_write;
  66   int parent_end, child_end;
  67   int pipe_fds[2];
  68   pid_t child_pid;
  69
  70   int do_read = 0;
  71   int do_write = 0;
  72   int do_cloexec = 0;
  73   while (*mode != '\0')
  74     switch (*mode++)
  75       {
  76       case 'r':
  77         do_read = 1;
  78         break;
  79       case 'w':
  80         do_write = 1;
  81         break;
  82       case 'e':
  83         do_cloexec = 1;
  84         break;
  85       default:
  86       errout:
  87         __set_errno (EINVAL);
  88         return NULL;
  89       }
  90
  91   if ((do_read ^ do_write) == 0)
  92     goto errout;
  93
  94   if (_IO_file_is_open (fp))
  95     return NULL;
  96
  97   /* Atomically set the O_CLOEXEC flag for the pipe end used by the
  98      child process (to avoid leaking the file descriptor in case of a
  99      concurrent fork).  This is later reverted in the child process.
 100      When popen returns, the parent pipe end can be O_CLOEXEC or not,
 101      depending on the 'e' open mode, but there is only one flag which
 102      controls both descriptors.  The parent end is adjusted below,
 103      after creating the child process.  (In the child process, the
 104      parent end should be closed on execve, so O_CLOEXEC remains set
 105      there.)  */
 106   if (__pipe2 (pipe_fds, O_CLOEXEC) < 0)
 107     return NULL;
 108
 109   if (do_read)
 110     {
 111       parent_end = pipe_fds[0];
 112       child_end = pipe_fds[1];
 113       read_or_write = _IO_NO_WRITES;
 114     }
 115   else
 116     {
 117       parent_end = pipe_fds[1];
 118       child_end = pipe_fds[0];
 119       read_or_write = _IO_NO_READS;
 120     }
 121
 122   ((_IO_proc_file *) fp)->pid = child_pid = __fork ();
 123   if (child_pid == 0)
 124     {
 125       int child_std_end = do_read ? 1 : 0;
 126       struct _IO_proc_file *p;
 127
 128       if (child_end != child_std_end)
 129         __dup2 (child_end, child_std_end);
 130       else
 131         /* The descriptor is already the one we will use.  But it must
 132            not be marked close-on-exec.  Undo the effects.  */
 133         __fcntl (child_end, F_SETFD, 0);
 134       /* POSIX.2:  "popen() shall ensure that any streams from previous
 135          popen() calls that remain open in the parent process are closed
 136          in the new child process." */
 137       for (p = proc_file_chain; p; p = p->next)
 138         {
 139           int fd = _IO_fileno ((FILE *) p);
 140
 141           /* If any stream from previous popen() calls has fileno
 142              child_std_end, it has been already closed by the dup2 syscall
 143              above.  */
 144           if (fd != child_std_end)
 145             __close_nocancel (fd);
 146         }
 147
 148       execl ("/bin/sh", "sh", "-c", command, (char *) 0);
 149       _exit (127);
 150     }
 151   __close_nocancel (child_end);
 152   if (child_pid < 0)
 153     {
 154       __close_nocancel (parent_end);
 155       return NULL;
 156     }
 157
 158   if (!do_cloexec)
 159     /* Undo the effects of the pipe2 call which set the
 160        close-on-exec flag.  */
 161     __fcntl (parent_end, F_SETFD, 0);
 162
 163   _IO_fileno (fp) = parent_end;
 164
 165   /* Link into proc_file_chain. */
 166 #ifdef _IO_MTSAFE_IO
 167   _IO_cleanup_region_start_noarg (unlock);
 168   _IO_lock_lock (proc_file_chain_lock);
 169 #endif
 170   ((_IO_proc_file *) fp)->next = proc_file_chain;
 171   proc_file_chain = (_IO_proc_file *) fp;
 172 #ifdef _IO_MTSAFE_IO
 173   _IO_lock_unlock (proc_file_chain_lock);
 174   _IO_cleanup_region_end (0);
 175 #endif
 176
 177   _IO_mask_flags (fp, read_or_write, _IO_NO_READS|_IO_NO_WRITES);
 178   return fp;
 179 }
 180
 181 FILE *
 182 _IO_new_popen (const char *command, const char *mode)
 183 {
 184   struct locked_FILE
 185   {
 186     struct _IO_proc_file fpx;
 187 #ifdef _IO_MTSAFE_IO
 188     _IO_lock_t lock;
 189 #endif
 190   } *new_f;
 191   FILE *fp;
 192
 193   new_f = (struct locked_FILE *) malloc (sizeof (struct locked_FILE));
 194   if (new_f == NULL)
 195     return NULL;
 196 #ifdef _IO_MTSAFE_IO
 197   new_f->fpx.file.file._lock = &new_f->lock;
 198 #endif
 199   fp = &new_f->fpx.file.file;
 200   _IO_init_internal (fp, 0);
 201   _IO_JUMPS (&new_f->fpx.file) = &_IO_proc_jumps;
 202   _IO_new_file_init_internal (&new_f->fpx.file);
 203   if (_IO_new_proc_open (fp, command, mode) != NULL)
 204     return (FILE *) &new_f->fpx.file;
 205   _IO_un_link (&new_f->fpx.file);
 206   free (new_f);
 207   return NULL;
 208 }
 209
 210 int
 211 _IO_new_proc_close (FILE *fp)
 212 {
 213   /* This is not name-space clean. FIXME! */
 214   int wstatus;
 215   _IO_proc_file **ptr = &proc_file_chain;
 216   pid_t wait_pid;
 217   int status = -1;
 218
 219   /* Unlink from proc_file_chain. */
 220 #ifdef _IO_MTSAFE_IO
 221   _IO_cleanup_region_start_noarg (unlock);
 222   _IO_lock_lock (proc_file_chain_lock);
 223 #endif
 224   for ( ; *ptr != NULL; ptr = &(*ptr)->next)
 225     {
 226       if (*ptr == (_IO_proc_file *) fp)
 227         {
 228           *ptr = (*ptr)->next;
 229           status = 0;
 230           break;
 231         }
 232     }
 233 #ifdef _IO_MTSAFE_IO
 234   _IO_lock_unlock (proc_file_chain_lock);
 235   _IO_cleanup_region_end (0);
 236 #endif
 237
 238   if (status < 0 || __close_nocancel (_IO_fileno(fp)) < 0)
 239     return -1;
 240   /* POSIX.2 Rationale:  "Some historical implementations either block
 241      or ignore the signals SIGINT, SIGQUIT, and SIGHUP while waiting
 242      for the child process to terminate.  Since this behavior is not
 243      described in POSIX.2, such implementations are not conforming." */
 244   do
 245     {
 246       wait_pid = __waitpid_nocancel (((_IO_proc_file *) fp)->pid, &wstatus, 0);
 247     }
 248   while (wait_pid == -1 && errno == EINTR);
 249   if (wait_pid == -1)
 250     return -1;
 251   return wstatus;
 252 }
 253
 254 static const struct _IO_jump_t _IO_proc_jumps libio_vtable = {
 255   JUMP_INIT_DUMMY,
 256   JUMP_INIT(finish, _IO_new_file_finish),
 257   JUMP_INIT(overflow, _IO_new_file_overflow),
 258   JUMP_INIT(underflow, _IO_new_file_underflow),
 259   JUMP_INIT(uflow, _IO_default_uflow),
 260   JUMP_INIT(pbackfail, _IO_default_pbackfail),
 261   JUMP_INIT(xsputn, _IO_new_file_xsputn),
 262   JUMP_INIT(xsgetn, _IO_default_xsgetn),
 263   JUMP_INIT(seekoff, _IO_new_file_seekoff),
 264   JUMP_INIT(seekpos, _IO_default_seekpos),
 265   JUMP_INIT(setbuf, _IO_new_file_setbuf),
 266   JUMP_INIT(sync, _IO_new_file_sync),
 267   JUMP_INIT(doallocate, _IO_file_doallocate),
 268   JUMP_INIT(read, _IO_file_read),
 269   JUMP_INIT(write, _IO_new_file_write),
 270   JUMP_INIT(seek, _IO_file_seek),
 271   JUMP_INIT(close, _IO_new_proc_close),
 272   JUMP_INIT(stat, _IO_file_stat),
 273   JUMP_INIT(showmanyc, _IO_default_showmanyc),
 274   JUMP_INIT(imbue, _IO_default_imbue)
 275 };
 276
 277 strong_alias (_IO_new_popen, __new_popen)
 278 versioned_symbol (libc, _IO_new_popen, _IO_popen, GLIBC_2_1);
 279 versioned_symbol (libc, __new_popen, popen, GLIBC_2_1);
 280 versioned_symbol (libc, _IO_new_proc_open, _IO_proc_open, GLIBC_2_1);
 281 versioned_symbol (libc, _IO_new_proc_close, _IO_proc_close, GLIBC_2_1);