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 "git-compat-util.h"
  46 #include "abspath.h"
  47 #include "path.h"
  48 #include "tempfile.h"
  49 #include "sigchain.h"
  50
  51 static VOLATILE_LIST_HEAD(tempfile_list);
  52
  53 static void remove_template_directory(struct tempfile *tempfile,
  54                                       int in_signal_handler)
  55 {
  56         if (tempfile->directory) {
  57                 if (in_signal_handler)
  58                         rmdir(tempfile->directory);
  59                 else
  60                         rmdir_or_warn(tempfile->directory);
  61         }
  62 }
  63
  64 static void remove_tempfiles(int in_signal_handler)
  65 {
  66         pid_t me = getpid();
  67         volatile struct volatile_list_head *pos;
  68
  69         list_for_each(pos, &tempfile_list) {
  70                 struct tempfile *p = list_entry(pos, struct tempfile, list);
  71
  72                 if (!is_tempfile_active(p) || p->owner != me)
  73                         continue;
  74
  75                 if (p->fd >= 0)
  76                         close(p->fd);
  77
  78                 if (in_signal_handler)
  79                         unlink(p->filename.buf);
  80                 else
  81                         unlink_or_warn(p->filename.buf);
  82                 remove_template_directory(p, in_signal_handler);
  83         }
  84 }
  85
  86 static void remove_tempfiles_on_exit(void)
  87 {
  88         remove_tempfiles(0);
  89 }
  90
  91 static void remove_tempfiles_on_signal(int signo)
  92 {
  93         remove_tempfiles(1);
  94         sigchain_pop(signo);
  95         raise(signo);
  96 }
  97
  98 static struct tempfile *new_tempfile(void)
  99 {
 100         struct tempfile *tempfile = xmalloc(sizeof(*tempfile));
 101         tempfile->fd = -1;
 102         tempfile->fp = NULL;
 103         tempfile->owner = 0;
 104         INIT_LIST_HEAD(&tempfile->list);
 105         strbuf_init(&tempfile->filename, 0);
 106         tempfile->directory = NULL;
 107         return tempfile;
 108 }
 109
 110 static void activate_tempfile(struct tempfile *tempfile)
 111 {
 112         static int initialized;
 113
 114         if (!initialized) {
 115                 sigchain_push_common(remove_tempfiles_on_signal);
 116                 atexit(remove_tempfiles_on_exit);
 117                 initialized = 1;
 118         }
 119
 120         volatile_list_add(&tempfile->list, &tempfile_list);
 121         tempfile->owner = getpid();
 122 }
 123
 124 static void deactivate_tempfile(struct tempfile *tempfile)
 125 {
 126         volatile_list_del(&tempfile->list);
 127         strbuf_release(&tempfile->filename);
 128         free(tempfile->directory);
 129         free(tempfile);
 130 }
 131
 132 /* Make sure errno contains a meaningful value on error */
 133 struct tempfile *create_tempfile_mode(const char *path, int mode)
 134 {
 135         struct tempfile *tempfile = new_tempfile();
 136
 137         strbuf_add_absolute_path(&tempfile->filename, path);
 138         tempfile->fd = open(tempfile->filename.buf,
 139                             O_RDWR | O_CREAT | O_EXCL | O_CLOEXEC, mode);
 140         if (O_CLOEXEC && tempfile->fd < 0 && errno == EINVAL)
 141                 /* Try again w/o O_CLOEXEC: the kernel might not support it */
 142                 tempfile->fd = open(tempfile->filename.buf,
 143                                     O_RDWR | O_CREAT | O_EXCL, mode);
 144         if (tempfile->fd < 0) {
 145                 deactivate_tempfile(tempfile);
 146                 return NULL;
 147         }
 148         activate_tempfile(tempfile);
 149         if (adjust_shared_perm(tempfile->filename.buf)) {
 150                 int save_errno = errno;
 151                 error("cannot fix permission bits on %s", tempfile->filename.buf);
 152                 delete_tempfile(&tempfile);
 153                 errno = save_errno;
 154                 return NULL;
 155         }
 156
 157         return tempfile;
 158 }
 159
 160 struct tempfile *register_tempfile(const char *path)
 161 {
 162         struct tempfile *tempfile = new_tempfile();
 163         strbuf_add_absolute_path(&tempfile->filename, path);
 164         activate_tempfile(tempfile);
 165         return tempfile;
 166 }
 167
 168 struct tempfile *mks_tempfile_sm(const char *filename_template, int suffixlen, int mode)
 169 {
 170         struct tempfile *tempfile = new_tempfile();
 171
 172         strbuf_add_absolute_path(&tempfile->filename, filename_template);
 173         tempfile->fd = git_mkstemps_mode(tempfile->filename.buf, suffixlen, mode);
 174         if (tempfile->fd < 0) {
 175                 deactivate_tempfile(tempfile);
 176                 return NULL;
 177         }
 178         activate_tempfile(tempfile);
 179         return tempfile;
 180 }
 181
 182 struct tempfile *mks_tempfile_tsm(const char *filename_template, int suffixlen, int mode)
 183 {
 184         struct tempfile *tempfile = new_tempfile();
 185         const char *tmpdir;
 186
 187         tmpdir = getenv("TMPDIR");
 188         if (!tmpdir)
 189                 tmpdir = "/tmp";
 190
 191         strbuf_addf(&tempfile->filename, "%s/%s", tmpdir, filename_template);
 192         tempfile->fd = git_mkstemps_mode(tempfile->filename.buf, suffixlen, mode);
 193         if (tempfile->fd < 0) {
 194                 deactivate_tempfile(tempfile);
 195                 return NULL;
 196         }
 197         activate_tempfile(tempfile);
 198         return tempfile;
 199 }
 200
 201 struct tempfile *mks_tempfile_dt(const char *directory_template,
 202                                  const char *filename)
 203 {
 204         struct tempfile *tempfile;
 205         const char *tmpdir;
 206         struct strbuf sb = STRBUF_INIT;
 207         int fd;
 208         size_t directorylen;
 209
 210         if (!ends_with(directory_template, "XXXXXX")) {
 211                 errno = EINVAL;
 212                 return NULL;
 213         }
 214
 215         tmpdir = getenv("TMPDIR");
 216         if (!tmpdir)
 217                 tmpdir = "/tmp";
 218
 219         strbuf_addf(&sb, "%s/%s", tmpdir, directory_template);
 220         directorylen = sb.len;
 221         if (!mkdtemp(sb.buf)) {
 222                 int orig_errno = errno;
 223                 strbuf_release(&sb);
 224                 errno = orig_errno;
 225                 return NULL;
 226         }
 227
 228         strbuf_addf(&sb, "/%s", filename);
 229         fd = open(sb.buf, O_CREAT | O_EXCL | O_RDWR, 0600);
 230         if (fd < 0) {
 231                 int orig_errno = errno;
 232                 strbuf_setlen(&sb, directorylen);
 233                 rmdir(sb.buf);
 234                 strbuf_release(&sb);
 235                 errno = orig_errno;
 236                 return NULL;
 237         }
 238
 239         tempfile = new_tempfile();
 240         strbuf_swap(&tempfile->filename, &sb);
 241         tempfile->directory = xmemdupz(tempfile->filename.buf, directorylen);
 242         tempfile->fd = fd;
 243         activate_tempfile(tempfile);
 244         return tempfile;
 245 }
 246
 247 struct tempfile *xmks_tempfile_m(const char *filename_template, int mode)
 248 {
 249         struct tempfile *tempfile;
 250         struct strbuf full_template = STRBUF_INIT;
 251
 252         strbuf_add_absolute_path(&full_template, filename_template);
 253         tempfile = mks_tempfile_m(full_template.buf, mode);
 254         if (!tempfile)
 255                 die_errno("Unable to create temporary file '%s'",
 256                           full_template.buf);
 257
 258         strbuf_release(&full_template);
 259         return tempfile;
 260 }
 261
 262 FILE *fdopen_tempfile(struct tempfile *tempfile, const char *mode)
 263 {
 264         if (!is_tempfile_active(tempfile))
 265                 BUG("fdopen_tempfile() called for inactive object");
 266         if (tempfile->fp)
 267                 BUG("fdopen_tempfile() called for open object");
 268
 269         tempfile->fp = fdopen(tempfile->fd, mode);
 270         return tempfile->fp;
 271 }
 272
 273 const char *get_tempfile_path(struct tempfile *tempfile)
 274 {
 275         if (!is_tempfile_active(tempfile))
 276                 BUG("get_tempfile_path() called for inactive object");
 277         return tempfile->filename.buf;
 278 }
 279
 280 int get_tempfile_fd(struct tempfile *tempfile)
 281 {
 282         if (!is_tempfile_active(tempfile))
 283                 BUG("get_tempfile_fd() called for inactive object");
 284         return tempfile->fd;
 285 }
 286
 287 FILE *get_tempfile_fp(struct tempfile *tempfile)
 288 {
 289         if (!is_tempfile_active(tempfile))
 290                 BUG("get_tempfile_fp() called for inactive object");
 291         return tempfile->fp;
 292 }
 293
 294 int close_tempfile_gently(struct tempfile *tempfile)
 295 {
 296         int fd;
 297         FILE *fp;
 298         int err;
 299
 300         if (!is_tempfile_active(tempfile) || tempfile->fd < 0)
 301                 return 0;
 302
 303         fd = tempfile->fd;
 304         fp = tempfile->fp;
 305         tempfile->fd = -1;
 306         if (fp) {
 307                 tempfile->fp = NULL;
 308                 if (ferror(fp)) {
 309                         err = -1;
 310                         if (!fclose(fp))
 311                                 errno = EIO;
 312                 } else {
 313                         err = fclose(fp);
 314                 }
 315         } else {
 316                 err = close(fd);
 317         }
 318
 319         return err ? -1 : 0;
 320 }
 321
 322 int reopen_tempfile(struct tempfile *tempfile)
 323 {
 324         if (!is_tempfile_active(tempfile))
 325                 BUG("reopen_tempfile called for an inactive object");
 326         if (0 <= tempfile->fd)
 327                 BUG("reopen_tempfile called for an open object");
 328         tempfile->fd = open(tempfile->filename.buf, O_WRONLY|O_TRUNC);
 329         return tempfile->fd;
 330 }
 331
 332 int rename_tempfile(struct tempfile **tempfile_p, const char *path)
 333 {
 334         struct tempfile *tempfile = *tempfile_p;
 335
 336         if (!is_tempfile_active(tempfile))
 337                 BUG("rename_tempfile called for inactive object");
 338
 339         if (close_tempfile_gently(tempfile)) {
 340                 delete_tempfile(tempfile_p);
 341                 return -1;
 342         }
 343
 344         if (rename(tempfile->filename.buf, path)) {
 345                 int save_errno = errno;
 346                 delete_tempfile(tempfile_p);
 347                 errno = save_errno;
 348                 return -1;
 349         }
 350
 351         deactivate_tempfile(tempfile);
 352         *tempfile_p = NULL;
 353         return 0;
 354 }
 355
 356 void delete_tempfile(struct tempfile **tempfile_p)
 357 {
 358         struct tempfile *tempfile = *tempfile_p;
 359
 360         if (!is_tempfile_active(tempfile))
 361                 return;
 362
 363         close_tempfile_gently(tempfile);
 364         unlink_or_warn(tempfile->filename.buf);
 365         remove_template_directory(tempfile, 0);
 366         deactivate_tempfile(tempfile);
 367         *tempfile_p = NULL;
 368 }