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 #include "wrapper.h"
  49
  50 static VOLATILE_LIST_HEAD(tempfile_list);
  51
  52 static void remove_template_directory(struct tempfile *tempfile,
  53                                       int in_signal_handler)
  54 {
  55         if (tempfile->directory) {
  56                 if (in_signal_handler)
  57                         rmdir(tempfile->directory);
  58                 else
  59                         rmdir_or_warn(tempfile->directory);
  60         }
  61 }
  62
  63 static void remove_tempfiles(int in_signal_handler)
  64 {
  65         pid_t me = getpid();
  66         volatile struct volatile_list_head *pos;
  67
  68         list_for_each(pos, &tempfile_list) {
  69                 struct tempfile *p = list_entry(pos, struct tempfile, list);
  70
  71                 if (!is_tempfile_active(p) || p->owner != me)
  72                         continue;
  73
  74                 if (p->fd >= 0)
  75                         close(p->fd);
  76
  77                 if (in_signal_handler)
  78                         unlink(p->filename.buf);
  79                 else
  80                         unlink_or_warn(p->filename.buf);
  81                 remove_template_directory(p, in_signal_handler);
  82         }
  83 }
  84
  85 static void remove_tempfiles_on_exit(void)
  86 {
  87         remove_tempfiles(0);
  88 }
  89
  90 static void remove_tempfiles_on_signal(int signo)
  91 {
  92         remove_tempfiles(1);
  93         sigchain_pop(signo);
  94         raise(signo);
  95 }
  96
  97 static struct tempfile *new_tempfile(void)
  98 {
  99         struct tempfile *tempfile = xmalloc(sizeof(*tempfile));
 100         tempfile->fd = -1;
 101         tempfile->fp = NULL;
 102         tempfile->owner = 0;
 103         INIT_LIST_HEAD(&tempfile->list);
 104         strbuf_init(&tempfile->filename, 0);
 105         tempfile->directory = NULL;
 106         return tempfile;
 107 }
 108
 109 static void activate_tempfile(struct tempfile *tempfile)
 110 {
 111         static int initialized;
 112
 113         if (!initialized) {
 114                 sigchain_push_common(remove_tempfiles_on_signal);
 115                 atexit(remove_tempfiles_on_exit);
 116                 initialized = 1;
 117         }
 118
 119         volatile_list_add(&tempfile->list, &tempfile_list);
 120         tempfile->owner = getpid();
 121 }
 122
 123 static void deactivate_tempfile(struct tempfile *tempfile)
 124 {
 125         volatile_list_del(&tempfile->list);
 126         strbuf_release(&tempfile->filename);
 127         free(tempfile->directory);
 128         free(tempfile);
 129 }
 130
 131 /* Make sure errno contains a meaningful value on error */
 132 struct tempfile *create_tempfile_mode(const char *path, int mode)
 133 {
 134         struct tempfile *tempfile = new_tempfile();
 135
 136         strbuf_add_absolute_path(&tempfile->filename, path);
 137         tempfile->fd = open(tempfile->filename.buf,
 138                             O_RDWR | O_CREAT | O_EXCL | O_CLOEXEC, mode);
 139         if (O_CLOEXEC && tempfile->fd < 0 && errno == EINVAL)
 140                 /* Try again w/o O_CLOEXEC: the kernel might not support it */
 141                 tempfile->fd = open(tempfile->filename.buf,
 142                                     O_RDWR | O_CREAT | O_EXCL, mode);
 143         if (tempfile->fd < 0) {
 144                 deactivate_tempfile(tempfile);
 145                 return NULL;
 146         }
 147         activate_tempfile(tempfile);
 148         if (adjust_shared_perm(tempfile->filename.buf)) {
 149                 int save_errno = errno;
 150                 error("cannot fix permission bits on %s", tempfile->filename.buf);
 151                 delete_tempfile(&tempfile);
 152                 errno = save_errno;
 153                 return NULL;
 154         }
 155
 156         return tempfile;
 157 }
 158
 159 struct tempfile *register_tempfile(const char *path)
 160 {
 161         struct tempfile *tempfile = new_tempfile();
 162         strbuf_add_absolute_path(&tempfile->filename, path);
 163         activate_tempfile(tempfile);
 164         return tempfile;
 165 }
 166
 167 struct tempfile *mks_tempfile_sm(const char *filename_template, int suffixlen, int mode)
 168 {
 169         struct tempfile *tempfile = new_tempfile();
 170
 171         strbuf_add_absolute_path(&tempfile->filename, filename_template);
 172         tempfile->fd = git_mkstemps_mode(tempfile->filename.buf, suffixlen, mode);
 173         if (tempfile->fd < 0) {
 174                 deactivate_tempfile(tempfile);
 175                 return NULL;
 176         }
 177         activate_tempfile(tempfile);
 178         return tempfile;
 179 }
 180
 181 struct tempfile *mks_tempfile_tsm(const char *filename_template, int suffixlen, int mode)
 182 {
 183         struct tempfile *tempfile = new_tempfile();
 184         const char *tmpdir;
 185
 186         tmpdir = getenv("TMPDIR");
 187         if (!tmpdir)
 188                 tmpdir = "/tmp";
 189
 190         strbuf_addf(&tempfile->filename, "%s/%s", tmpdir, filename_template);
 191         tempfile->fd = git_mkstemps_mode(tempfile->filename.buf, suffixlen, mode);
 192         if (tempfile->fd < 0) {
 193                 deactivate_tempfile(tempfile);
 194                 return NULL;
 195         }
 196         activate_tempfile(tempfile);
 197         return tempfile;
 198 }
 199
 200 struct tempfile *mks_tempfile_dt(const char *directory_template,
 201                                  const char *filename)
 202 {
 203         struct tempfile *tempfile;
 204         const char *tmpdir;
 205         struct strbuf sb = STRBUF_INIT;
 206         int fd;
 207         size_t directorylen;
 208
 209         if (!ends_with(directory_template, "XXXXXX")) {
 210                 errno = EINVAL;
 211                 return NULL;
 212         }
 213
 214         tmpdir = getenv("TMPDIR");
 215         if (!tmpdir)
 216                 tmpdir = "/tmp";
 217
 218         strbuf_addf(&sb, "%s/%s", tmpdir, directory_template);
 219         directorylen = sb.len;
 220         if (!mkdtemp(sb.buf)) {
 221                 int orig_errno = errno;
 222                 strbuf_release(&sb);
 223                 errno = orig_errno;
 224                 return NULL;
 225         }
 226
 227         strbuf_addf(&sb, "/%s", filename);
 228         fd = open(sb.buf, O_CREAT | O_EXCL | O_RDWR, 0600);
 229         if (fd < 0) {
 230                 int orig_errno = errno;
 231                 strbuf_setlen(&sb, directorylen);
 232                 rmdir(sb.buf);
 233                 strbuf_release(&sb);
 234                 errno = orig_errno;
 235                 return NULL;
 236         }
 237
 238         tempfile = new_tempfile();
 239         strbuf_swap(&tempfile->filename, &sb);
 240         tempfile->directory = xmemdupz(tempfile->filename.buf, directorylen);
 241         tempfile->fd = fd;
 242         activate_tempfile(tempfile);
 243         return tempfile;
 244 }
 245
 246 struct tempfile *xmks_tempfile_m(const char *filename_template, int mode)
 247 {
 248         struct tempfile *tempfile;
 249         struct strbuf full_template = STRBUF_INIT;
 250
 251         strbuf_add_absolute_path(&full_template, filename_template);
 252         tempfile = mks_tempfile_m(full_template.buf, mode);
 253         if (!tempfile)
 254                 die_errno("Unable to create temporary file '%s'",
 255                           full_template.buf);
 256
 257         strbuf_release(&full_template);
 258         return tempfile;
 259 }
 260
 261 FILE *fdopen_tempfile(struct tempfile *tempfile, const char *mode)
 262 {
 263         if (!is_tempfile_active(tempfile))
 264                 BUG("fdopen_tempfile() called for inactive object");
 265         if (tempfile->fp)
 266                 BUG("fdopen_tempfile() called for open object");
 267
 268         tempfile->fp = fdopen(tempfile->fd, mode);
 269         return tempfile->fp;
 270 }
 271
 272 const char *get_tempfile_path(struct tempfile *tempfile)
 273 {
 274         if (!is_tempfile_active(tempfile))
 275                 BUG("get_tempfile_path() called for inactive object");
 276         return tempfile->filename.buf;
 277 }
 278
 279 int get_tempfile_fd(struct tempfile *tempfile)
 280 {
 281         if (!is_tempfile_active(tempfile))
 282                 BUG("get_tempfile_fd() called for inactive object");
 283         return tempfile->fd;
 284 }
 285
 286 FILE *get_tempfile_fp(struct tempfile *tempfile)
 287 {
 288         if (!is_tempfile_active(tempfile))
 289                 BUG("get_tempfile_fp() called for inactive object");
 290         return tempfile->fp;
 291 }
 292
 293 int close_tempfile_gently(struct tempfile *tempfile)
 294 {
 295         int fd;
 296         FILE *fp;
 297         int err;
 298
 299         if (!is_tempfile_active(tempfile) || tempfile->fd < 0)
 300                 return 0;
 301
 302         fd = tempfile->fd;
 303         fp = tempfile->fp;
 304         tempfile->fd = -1;
 305         if (fp) {
 306                 tempfile->fp = NULL;
 307                 if (ferror(fp)) {
 308                         err = -1;
 309                         if (!fclose(fp))
 310                                 errno = EIO;
 311                 } else {
 312                         err = fclose(fp);
 313                 }
 314         } else {
 315                 err = close(fd);
 316         }
 317
 318         return err ? -1 : 0;
 319 }
 320
 321 int reopen_tempfile(struct tempfile *tempfile)
 322 {
 323         if (!is_tempfile_active(tempfile))
 324                 BUG("reopen_tempfile called for an inactive object");
 325         if (0 <= tempfile->fd)
 326                 BUG("reopen_tempfile called for an open object");
 327         tempfile->fd = open(tempfile->filename.buf, O_WRONLY|O_TRUNC);
 328         return tempfile->fd;
 329 }
 330
 331 int rename_tempfile(struct tempfile **tempfile_p, const char *path)
 332 {
 333         struct tempfile *tempfile = *tempfile_p;
 334
 335         if (!is_tempfile_active(tempfile))
 336                 BUG("rename_tempfile called for inactive object");
 337
 338         if (close_tempfile_gently(tempfile)) {
 339                 delete_tempfile(tempfile_p);
 340                 return -1;
 341         }
 342
 343         if (rename(tempfile->filename.buf, path)) {
 344                 int save_errno = errno;
 345                 delete_tempfile(tempfile_p);
 346                 errno = save_errno;
 347                 return -1;
 348         }
 349
 350         deactivate_tempfile(tempfile);
 351         *tempfile_p = NULL;
 352         return 0;
 353 }
 354
 355 void delete_tempfile(struct tempfile **tempfile_p)
 356 {
 357         struct tempfile *tempfile = *tempfile_p;
 358
 359         if (!is_tempfile_active(tempfile))
 360                 return;
 361
 362         close_tempfile_gently(tempfile);
 363         unlink_or_warn(tempfile->filename.buf);
 364         remove_template_directory(tempfile, 0);
 365         deactivate_tempfile(tempfile);
 366         *tempfile_p = NULL;
 367 }