tempfile.c

   1 /*
   2  * State diagram and cleanup
   3  * -------------------------
   4  *
   5  * If the program exits while a temporary file is active, we want to
   6  * make sure that we remove it. This is done by remembering the active
   7  * temporary files in a linked list, `tempfile_list`. An `atexit(3)`
   8  * handler and a signal handler are registered, to clean up any active
   9  * temporary files.
  10  *
  11  * Because the signal handler can run at any time, `tempfile_list` and
  12  * the `tempfile` objects that comprise it must be kept in
  13  * self-consistent states at all times.
  14  *
  15  * The possible states of a `tempfile` object are as follows:
  16  *
  17  * - Uninitialized. In this state the object's `on_list` field must be
  18  *   zero but the rest of its contents need not be initialized. As
  19  *   soon as the object is used in any way, it is irrevocably
  20  *   registered in `tempfile_list`, and `on_list` is set.
  21  *
  22  * - Active, file open (after `create_tempfile()` or
  23  *   `reopen_tempfile()`). In this state:
  24  *
  25  *   - the temporary file exists
  26  *   - `active` is set
  27  *   - `filename` holds the filename of the temporary file
  28  *   - `fd` holds a file descriptor open for writing to it
  29  *   - `fp` holds a pointer to an open `FILE` object if and only if
  30  *     `fdopen_tempfile()` has been called on the object
  31  *   - `owner` holds the PID of the process that created the file
  32  *
  33  * - Active, file closed (after `close_tempfile_gently()`). Same
  34  *   as the previous state, except that the temporary file is closed,
  35  *   `fd` is -1, and `fp` is `NULL`.
  36  *
  37  * - Inactive (after `delete_tempfile()`, `rename_tempfile()`, or a
  38  *   failed attempt to create a temporary file). In this state:
  39  *
  40  *   - `active` is unset
  41  *   - `filename` is empty (usually, though there are transitory
  42  *     states in which this condition doesn't hold). Client code should
  43  *     *not* rely on the filename being empty in this state.
  44  *   - `fd` is -1 and `fp` is `NULL`
  45  *   - the object is removed from `tempfile_list` (but could be used again)
  46  *
  47  * A temporary file is owned by the process that created it. The
  48  * `tempfile` has an `owner` field that records the owner's PID. This
  49  * field is used to prevent a forked process from deleting a temporary
  50  * file created by its parent.
  51  */
  52
  53 #include "cache.h"
  54 #include "tempfile.h"
  55 #include "sigchain.h"
  56
  57 static VOLATILE_LIST_HEAD(tempfile_list);
  58
  59 static void remove_template_directory(struct tempfile *tempfile,
  60                                       int in_signal_handler)
  61 {
  62         if (tempfile->directorylen > 0 &&
  63             tempfile->directorylen < tempfile->filename.len &&
  64             tempfile->filename.buf[tempfile->directorylen] == '/') {
  65                 strbuf_setlen(&tempfile->filename, tempfile->directorylen);
  66                 if (in_signal_handler)
  67                         rmdir(tempfile->filename.buf);
  68                 else
  69                         rmdir_or_warn(tempfile->filename.buf);
  70         }
  71 }
  72
  73 static void remove_tempfiles(int in_signal_handler)
  74 {
  75         pid_t me = getpid();
  76         volatile struct volatile_list_head *pos;
  77
  78         list_for_each(pos, &tempfile_list) {
  79                 struct tempfile *p = list_entry(pos, struct tempfile, list);
  80
  81                 if (!is_tempfile_active(p) || p->owner != me)
  82                         continue;
  83
  84                 if (p->fd >= 0)
  85                         close(p->fd);
  86
  87                 if (in_signal_handler)
  88                         unlink(p->filename.buf);
  89                 else
  90                         unlink_or_warn(p->filename.buf);
  91                 remove_template_directory(p, in_signal_handler);
  92
  93                 p->active = 0;
  94         }
  95 }
  96
  97 static void remove_tempfiles_on_exit(void)
  98 {
  99         remove_tempfiles(0);
 100 }
 101
 102 static void remove_tempfiles_on_signal(int signo)
 103 {
 104         remove_tempfiles(1);
 105         sigchain_pop(signo);
 106         raise(signo);
 107 }
 108
 109 static struct tempfile *new_tempfile(void)
 110 {
 111         struct tempfile *tempfile = xmalloc(sizeof(*tempfile));
 112         tempfile->fd = -1;
 113         tempfile->fp = NULL;
 114         tempfile->active = 0;
 115         tempfile->owner = 0;
 116         INIT_LIST_HEAD(&tempfile->list);
 117         strbuf_init(&tempfile->filename, 0);
 118         tempfile->directorylen = 0;
 119         return tempfile;
 120 }
 121
 122 static void activate_tempfile(struct tempfile *tempfile)
 123 {
 124         static int initialized;
 125
 126         if (is_tempfile_active(tempfile))
 127                 BUG("activate_tempfile called for active object");
 128
 129         if (!initialized) {
 130                 sigchain_push_common(remove_tempfiles_on_signal);
 131                 atexit(remove_tempfiles_on_exit);
 132                 initialized = 1;
 133         }
 134
 135         volatile_list_add(&tempfile->list, &tempfile_list);
 136         tempfile->owner = getpid();
 137         tempfile->active = 1;
 138 }
 139
 140 static void deactivate_tempfile(struct tempfile *tempfile)
 141 {
 142         tempfile->active = 0;
 143         strbuf_release(&tempfile->filename);
 144         volatile_list_del(&tempfile->list);
 145         free(tempfile);
 146 }
 147
 148 /* Make sure errno contains a meaningful value on error */
 149 struct tempfile *create_tempfile_mode(const char *path, int mode)
 150 {
 151         struct tempfile *tempfile = new_tempfile();
 152
 153         strbuf_add_absolute_path(&tempfile->filename, path);
 154         tempfile->fd = open(tempfile->filename.buf,
 155                             O_RDWR | O_CREAT | O_EXCL | O_CLOEXEC, mode);
 156         if (O_CLOEXEC && tempfile->fd < 0 && errno == EINVAL)
 157                 /* Try again w/o O_CLOEXEC: the kernel might not support it */
 158                 tempfile->fd = open(tempfile->filename.buf,
 159                                     O_RDWR | O_CREAT | O_EXCL, mode);
 160         if (tempfile->fd < 0) {
 161                 deactivate_tempfile(tempfile);
 162                 return NULL;
 163         }
 164         activate_tempfile(tempfile);
 165         if (adjust_shared_perm(tempfile->filename.buf)) {
 166                 int save_errno = errno;
 167                 error("cannot fix permission bits on %s", tempfile->filename.buf);
 168                 delete_tempfile(&tempfile);
 169                 errno = save_errno;
 170                 return NULL;
 171         }
 172
 173         return tempfile;
 174 }
 175
 176 struct tempfile *register_tempfile(const char *path)
 177 {
 178         struct tempfile *tempfile = new_tempfile();
 179         strbuf_add_absolute_path(&tempfile->filename, path);
 180         activate_tempfile(tempfile);
 181         return tempfile;
 182 }
 183
 184 struct tempfile *mks_tempfile_sm(const char *filename_template, int suffixlen, int mode)
 185 {
 186         struct tempfile *tempfile = new_tempfile();
 187
 188         strbuf_add_absolute_path(&tempfile->filename, filename_template);
 189         tempfile->fd = git_mkstemps_mode(tempfile->filename.buf, suffixlen, mode);
 190         if (tempfile->fd < 0) {
 191                 deactivate_tempfile(tempfile);
 192                 return NULL;
 193         }
 194         activate_tempfile(tempfile);
 195         return tempfile;
 196 }
 197
 198 struct tempfile *mks_tempfile_tsm(const char *filename_template, int suffixlen, int mode)
 199 {
 200         struct tempfile *tempfile = new_tempfile();
 201         const char *tmpdir;
 202
 203         tmpdir = getenv("TMPDIR");
 204         if (!tmpdir)
 205                 tmpdir = "/tmp";
 206
 207         strbuf_addf(&tempfile->filename, "%s/%s", tmpdir, filename_template);
 208         tempfile->fd = git_mkstemps_mode(tempfile->filename.buf, suffixlen, mode);
 209         if (tempfile->fd < 0) {
 210                 deactivate_tempfile(tempfile);
 211                 return NULL;
 212         }
 213         activate_tempfile(tempfile);
 214         return tempfile;
 215 }
 216
 217 struct tempfile *mks_tempfile_dt(const char *directory_template,
 218                                  const char *filename)
 219 {
 220         struct tempfile *tempfile;
 221         const char *tmpdir;
 222         struct strbuf sb = STRBUF_INIT;
 223         int fd;
 224         size_t directorylen;
 225
 226         if (!ends_with(directory_template, "XXXXXX")) {
 227                 errno = EINVAL;
 228                 return NULL;
 229         }
 230
 231         tmpdir = getenv("TMPDIR");
 232         if (!tmpdir)
 233                 tmpdir = "/tmp";
 234
 235         strbuf_addf(&sb, "%s/%s", tmpdir, directory_template);
 236         directorylen = sb.len;
 237         if (!mkdtemp(sb.buf)) {
 238                 int orig_errno = errno;
 239                 strbuf_release(&sb);
 240                 errno = orig_errno;
 241                 return NULL;
 242         }
 243
 244         strbuf_addf(&sb, "/%s", filename);
 245         fd = open(sb.buf, O_CREAT | O_EXCL | O_RDWR, 0600);
 246         if (fd < 0) {
 247                 int orig_errno = errno;
 248                 strbuf_setlen(&sb, directorylen);
 249                 rmdir(sb.buf);
 250                 strbuf_release(&sb);
 251                 errno = orig_errno;
 252                 return NULL;
 253         }
 254
 255         tempfile = new_tempfile();
 256         strbuf_swap(&tempfile->filename, &sb);
 257         tempfile->directorylen = directorylen;
 258         tempfile->fd = fd;
 259         activate_tempfile(tempfile);
 260         return tempfile;
 261 }
 262
 263 struct tempfile *xmks_tempfile_m(const char *filename_template, int mode)
 264 {
 265         struct tempfile *tempfile;
 266         struct strbuf full_template = STRBUF_INIT;
 267
 268         strbuf_add_absolute_path(&full_template, filename_template);
 269         tempfile = mks_tempfile_m(full_template.buf, mode);
 270         if (!tempfile)
 271                 die_errno("Unable to create temporary file '%s'",
 272                           full_template.buf);
 273
 274         strbuf_release(&full_template);
 275         return tempfile;
 276 }
 277
 278 FILE *fdopen_tempfile(struct tempfile *tempfile, const char *mode)
 279 {
 280         if (!is_tempfile_active(tempfile))
 281                 BUG("fdopen_tempfile() called for inactive object");
 282         if (tempfile->fp)
 283                 BUG("fdopen_tempfile() called for open object");
 284
 285         tempfile->fp = fdopen(tempfile->fd, mode);
 286         return tempfile->fp;
 287 }
 288
 289 const char *get_tempfile_path(struct tempfile *tempfile)
 290 {
 291         if (!is_tempfile_active(tempfile))
 292                 BUG("get_tempfile_path() called for inactive object");
 293         return tempfile->filename.buf;
 294 }
 295
 296 int get_tempfile_fd(struct tempfile *tempfile)
 297 {
 298         if (!is_tempfile_active(tempfile))
 299                 BUG("get_tempfile_fd() called for inactive object");
 300         return tempfile->fd;
 301 }
 302
 303 FILE *get_tempfile_fp(struct tempfile *tempfile)
 304 {
 305         if (!is_tempfile_active(tempfile))
 306                 BUG("get_tempfile_fp() called for inactive object");
 307         return tempfile->fp;
 308 }
 309
 310 int close_tempfile_gently(struct tempfile *tempfile)
 311 {
 312         int fd;
 313         FILE *fp;
 314         int err;
 315
 316         if (!is_tempfile_active(tempfile) || tempfile->fd < 0)
 317                 return 0;
 318
 319         fd = tempfile->fd;
 320         fp = tempfile->fp;
 321         tempfile->fd = -1;
 322         if (fp) {
 323                 tempfile->fp = NULL;
 324                 if (ferror(fp)) {
 325                         err = -1;
 326                         if (!fclose(fp))
 327                                 errno = EIO;
 328                 } else {
 329                         err = fclose(fp);
 330                 }
 331         } else {
 332                 err = close(fd);
 333         }
 334
 335         return err ? -1 : 0;
 336 }
 337
 338 int reopen_tempfile(struct tempfile *tempfile)
 339 {
 340         if (!is_tempfile_active(tempfile))
 341                 BUG("reopen_tempfile called for an inactive object");
 342         if (0 <= tempfile->fd)
 343                 BUG("reopen_tempfile called for an open object");
 344         tempfile->fd = open(tempfile->filename.buf, O_WRONLY|O_TRUNC);
 345         return tempfile->fd;
 346 }
 347
 348 int rename_tempfile(struct tempfile **tempfile_p, const char *path)
 349 {
 350         struct tempfile *tempfile = *tempfile_p;
 351
 352         if (!is_tempfile_active(tempfile))
 353                 BUG("rename_tempfile called for inactive object");
 354
 355         if (close_tempfile_gently(tempfile)) {
 356                 delete_tempfile(tempfile_p);
 357                 return -1;
 358         }
 359
 360         if (rename(tempfile->filename.buf, path)) {
 361                 int save_errno = errno;
 362                 delete_tempfile(tempfile_p);
 363                 errno = save_errno;
 364                 return -1;
 365         }
 366
 367         deactivate_tempfile(tempfile);
 368         *tempfile_p = NULL;
 369         return 0;
 370 }
 371
 372 void delete_tempfile(struct tempfile **tempfile_p)
 373 {
 374         struct tempfile *tempfile = *tempfile_p;
 375
 376         if (!is_tempfile_active(tempfile))
 377                 return;
 378
 379         close_tempfile_gently(tempfile);
 380         unlink_or_warn(tempfile->filename.buf);
 381         remove_template_directory(tempfile, 0);
 382         deactivate_tempfile(tempfile);
 383         *tempfile_p = NULL;
 384 }