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