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 #include "wrapper.h"
  51
  52 static VOLATILE_LIST_HEAD(tempfile_list);
  53
  54 static void remove_template_directory(struct tempfile *tempfile,
  55                                       int in_signal_handler)
  56 {
  57         if (tempfile->directory) {
  58                 if (in_signal_handler)
  59                         rmdir(tempfile->directory);
  60                 else
  61                         rmdir_or_warn(tempfile->directory);
  62         }
  63 }
  64
  65 static void remove_tempfiles(int in_signal_handler)
  66 {
  67         pid_t me = getpid();
  68         volatile struct volatile_list_head *pos;
  69
  70         list_for_each(pos, &tempfile_list) {
  71                 struct tempfile *p = list_entry(pos, struct tempfile, list);
  72
  73                 if (!is_tempfile_active(p) || p->owner != me)
  74                         continue;
  75
  76                 if (p->fd >= 0)
  77                         close(p->fd);
  78
  79                 if (in_signal_handler)
  80                         unlink(p->filename.buf);
  81                 else
  82                         unlink_or_warn(p->filename.buf);
  83                 remove_template_directory(p, in_signal_handler);
  84         }
  85 }
  86
  87 static void remove_tempfiles_on_exit(void)
  88 {
  89         remove_tempfiles(0);
  90 }
  91
  92 static void remove_tempfiles_on_signal(int signo)
  93 {
  94         remove_tempfiles(1);
  95         sigchain_pop(signo);
  96         raise(signo);
  97 }
  98
  99 static struct tempfile *new_tempfile(void)
 100 {
 101         struct tempfile *tempfile = xmalloc(sizeof(*tempfile));
 102         tempfile->fd = -1;
 103         tempfile->fp = NULL;
 104         tempfile->owner = 0;
 105         INIT_LIST_HEAD(&tempfile->list);
 106         strbuf_init(&tempfile->filename, 0);
 107         tempfile->directory = NULL;
 108         return tempfile;
 109 }
 110
 111 static void activate_tempfile(struct tempfile *tempfile)
 112 {
 113         static int initialized;
 114
 115         if (!initialized) {
 116                 sigchain_push_common(remove_tempfiles_on_signal);
 117                 atexit(remove_tempfiles_on_exit);
 118                 initialized = 1;
 119         }
 120
 121         volatile_list_add(&tempfile->list, &tempfile_list);
 122         tempfile->owner = getpid();
 123 }
 124
 125 static void deactivate_tempfile(struct tempfile *tempfile)
 126 {
 127         volatile_list_del(&tempfile->list);
 128         strbuf_release(&tempfile->filename);
 129         free(tempfile->directory);
 130         free(tempfile);
 131 }
 132
 133 /* Make sure errno contains a meaningful value on error */
 134 struct tempfile *create_tempfile_mode(const char *path, int mode)
 135 {
 136         struct tempfile *tempfile = new_tempfile();
 137
 138         strbuf_add_absolute_path(&tempfile->filename, path);
 139         tempfile->fd = open(tempfile->filename.buf,
 140                             O_RDWR | O_CREAT | O_EXCL | O_CLOEXEC, mode);
 141         if (O_CLOEXEC && tempfile->fd < 0 && errno == EINVAL)
 142                 /* Try again w/o O_CLOEXEC: the kernel might not support it */
 143                 tempfile->fd = open(tempfile->filename.buf,
 144                                     O_RDWR | O_CREAT | O_EXCL, mode);
 145         if (tempfile->fd < 0) {
 146                 deactivate_tempfile(tempfile);
 147                 return NULL;
 148         }
 149         activate_tempfile(tempfile);
 150         if (adjust_shared_perm(tempfile->filename.buf)) {
 151                 int save_errno = errno;
 152                 error("cannot fix permission bits on %s", tempfile->filename.buf);
 153                 delete_tempfile(&tempfile);
 154                 errno = save_errno;
 155                 return NULL;
 156         }
 157
 158         return tempfile;
 159 }
 160
 161 struct tempfile *register_tempfile(const char *path)
 162 {
 163         struct tempfile *tempfile = new_tempfile();
 164         strbuf_add_absolute_path(&tempfile->filename, path);
 165         activate_tempfile(tempfile);
 166         return tempfile;
 167 }
 168
 169 struct tempfile *mks_tempfile_sm(const char *filename_template, int suffixlen, int mode)
 170 {
 171         struct tempfile *tempfile = new_tempfile();
 172
 173         strbuf_add_absolute_path(&tempfile->filename, filename_template);
 174         tempfile->fd = git_mkstemps_mode(tempfile->filename.buf, suffixlen, mode);
 175         if (tempfile->fd < 0) {
 176                 deactivate_tempfile(tempfile);
 177                 return NULL;
 178         }
 179         activate_tempfile(tempfile);
 180         return tempfile;
 181 }
 182
 183 struct tempfile *mks_tempfile_tsm(const char *filename_template, int suffixlen, int mode)
 184 {
 185         struct tempfile *tempfile = new_tempfile();
 186         const char *tmpdir;
 187
 188         tmpdir = getenv("TMPDIR");
 189         if (!tmpdir)
 190                 tmpdir = "/tmp";
 191
 192         strbuf_addf(&tempfile->filename, "%s/%s", tmpdir, filename_template);
 193         tempfile->fd = git_mkstemps_mode(tempfile->filename.buf, suffixlen, mode);
 194         if (tempfile->fd < 0) {
 195                 deactivate_tempfile(tempfile);
 196                 return NULL;
 197         }
 198         activate_tempfile(tempfile);
 199         return tempfile;
 200 }
 201
 202 struct tempfile *mks_tempfile_dt(const char *directory_template,
 203                                  const char *filename)
 204 {
 205         struct tempfile *tempfile;
 206         const char *tmpdir;
 207         struct strbuf sb = STRBUF_INIT;
 208         int fd;
 209         size_t directorylen;
 210
 211         if (!ends_with(directory_template, "XXXXXX")) {
 212                 errno = EINVAL;
 213                 return NULL;
 214         }
 215
 216         tmpdir = getenv("TMPDIR");
 217         if (!tmpdir)
 218                 tmpdir = "/tmp";
 219
 220         strbuf_addf(&sb, "%s/%s", tmpdir, directory_template);
 221         directorylen = sb.len;
 222         if (!mkdtemp(sb.buf)) {
 223                 int orig_errno = errno;
 224                 strbuf_release(&sb);
 225                 errno = orig_errno;
 226                 return NULL;
 227         }
 228
 229         strbuf_addf(&sb, "/%s", filename);
 230         fd = open(sb.buf, O_CREAT | O_EXCL | O_RDWR, 0600);
 231         if (fd < 0) {
 232                 int orig_errno = errno;
 233                 strbuf_setlen(&sb, directorylen);
 234                 rmdir(sb.buf);
 235                 strbuf_release(&sb);
 236                 errno = orig_errno;
 237                 return NULL;
 238         }
 239
 240         tempfile = new_tempfile();
 241         strbuf_swap(&tempfile->filename, &sb);
 242         tempfile->directory = xmemdupz(tempfile->filename.buf, directorylen);
 243         tempfile->fd = fd;
 244         activate_tempfile(tempfile);
 245         return tempfile;
 246 }
 247
 248 struct tempfile *xmks_tempfile_m(const char *filename_template, int mode)
 249 {
 250         struct tempfile *tempfile;
 251         struct strbuf full_template = STRBUF_INIT;
 252
 253         strbuf_add_absolute_path(&full_template, filename_template);
 254         tempfile = mks_tempfile_m(full_template.buf, mode);
 255         if (!tempfile)
 256                 die_errno("Unable to create temporary file '%s'",
 257                           full_template.buf);
 258
 259         strbuf_release(&full_template);
 260         return tempfile;
 261 }
 262
 263 FILE *fdopen_tempfile(struct tempfile *tempfile, const char *mode)
 264 {
 265         if (!is_tempfile_active(tempfile))
 266                 BUG("fdopen_tempfile() called for inactive object");
 267         if (tempfile->fp)
 268                 BUG("fdopen_tempfile() called for open object");
 269
 270         tempfile->fp = fdopen(tempfile->fd, mode);
 271         return tempfile->fp;
 272 }
 273
 274 const char *get_tempfile_path(struct tempfile *tempfile)
 275 {
 276         if (!is_tempfile_active(tempfile))
 277                 BUG("get_tempfile_path() called for inactive object");
 278         return tempfile->filename.buf;
 279 }
 280
 281 int get_tempfile_fd(struct tempfile *tempfile)
 282 {
 283         if (!is_tempfile_active(tempfile))
 284                 BUG("get_tempfile_fd() called for inactive object");
 285         return tempfile->fd;
 286 }
 287
 288 FILE *get_tempfile_fp(struct tempfile *tempfile)
 289 {
 290         if (!is_tempfile_active(tempfile))
 291                 BUG("get_tempfile_fp() called for inactive object");
 292         return tempfile->fp;
 293 }
 294
 295 int close_tempfile_gently(struct tempfile *tempfile)
 296 {
 297         int fd;
 298         FILE *fp;
 299         int err;
 300
 301         if (!is_tempfile_active(tempfile) || tempfile->fd < 0)
 302                 return 0;
 303
 304         fd = tempfile->fd;
 305         fp = tempfile->fp;
 306         tempfile->fd = -1;
 307         if (fp) {
 308                 tempfile->fp = NULL;
 309                 if (ferror(fp)) {
 310                         err = -1;
 311                         if (!fclose(fp))
 312                                 errno = EIO;
 313                 } else {
 314                         err = fclose(fp);
 315                 }
 316         } else {
 317                 err = close(fd);
 318         }
 319
 320         return err ? -1 : 0;
 321 }
 322
 323 int reopen_tempfile(struct tempfile *tempfile)
 324 {
 325         if (!is_tempfile_active(tempfile))
 326                 BUG("reopen_tempfile called for an inactive object");
 327         if (0 <= tempfile->fd)
 328                 BUG("reopen_tempfile called for an open object");
 329         tempfile->fd = open(tempfile->filename.buf, O_WRONLY|O_TRUNC);
 330         return tempfile->fd;
 331 }
 332
 333 int rename_tempfile(struct tempfile **tempfile_p, const char *path)
 334 {
 335         struct tempfile *tempfile = *tempfile_p;
 336
 337         if (!is_tempfile_active(tempfile))
 338                 BUG("rename_tempfile called for inactive object");
 339
 340         if (close_tempfile_gently(tempfile)) {
 341                 delete_tempfile(tempfile_p);
 342                 return -1;
 343         }
 344
 345         if (rename(tempfile->filename.buf, path)) {
 346                 int save_errno = errno;
 347                 delete_tempfile(tempfile_p);
 348                 errno = save_errno;
 349                 return -1;
 350         }
 351
 352         deactivate_tempfile(tempfile);
 353         *tempfile_p = NULL;
 354         return 0;
 355 }
 356
 357 void delete_tempfile(struct tempfile **tempfile_p)
 358 {
 359         struct tempfile *tempfile = *tempfile_p;
 360
 361         if (!is_tempfile_active(tempfile))
 362                 return;
 363
 364         close_tempfile_gently(tempfile);
 365         unlink_or_warn(tempfile->filename.buf);
 366         remove_template_directory(tempfile, 0);
 367         deactivate_tempfile(tempfile);
 368         *tempfile_p = NULL;
 369 }