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_tempfiles(int in_signal_handler)
  60 {
  61         pid_t me = getpid();
  62         volatile struct volatile_list_head *pos;
  63
  64         list_for_each(pos, &tempfile_list) {
  65                 struct tempfile *p = list_entry(pos, struct tempfile, list);
  66
  67                 if (!is_tempfile_active(p) || p->owner != me)
  68                         continue;
  69
  70                 if (p->fd >= 0)
  71                         close(p->fd);
  72
  73                 if (in_signal_handler)
  74                         unlink(p->filename.buf);
  75                 else
  76                         unlink_or_warn(p->filename.buf);
  77
  78                 p->active = 0;
  79         }
  80 }
  81
  82 static void remove_tempfiles_on_exit(void)
  83 {
  84         remove_tempfiles(0);
  85 }
  86
  87 static void remove_tempfiles_on_signal(int signo)
  88 {
  89         remove_tempfiles(1);
  90         sigchain_pop(signo);
  91         raise(signo);
  92 }
  93
  94 static void prepare_tempfile_object(struct tempfile *tempfile)
  95 {
  96         tempfile->fd = -1;
  97         tempfile->fp = NULL;
  98         tempfile->active = 0;
  99         tempfile->owner = 0;
 100         INIT_LIST_HEAD(&tempfile->list);
 101         strbuf_init(&tempfile->filename, 0);
 102 }
 103
 104 static void activate_tempfile(struct tempfile *tempfile)
 105 {
 106         static int initialized;
 107
 108         if (is_tempfile_active(tempfile))
 109                 BUG("activate_tempfile called for active object");
 110
 111         if (!initialized) {
 112                 sigchain_push_common(remove_tempfiles_on_signal);
 113                 atexit(remove_tempfiles_on_exit);
 114                 initialized = 1;
 115         }
 116
 117         volatile_list_add(&tempfile->list, &tempfile_list);
 118         tempfile->owner = getpid();
 119         tempfile->active = 1;
 120 }
 121
 122 static void deactivate_tempfile(struct tempfile *tempfile)
 123 {
 124         tempfile->active = 0;
 125         strbuf_release(&tempfile->filename);
 126         volatile_list_del(&tempfile->list);
 127 }
 128
 129 /* Make sure errno contains a meaningful value on error */
 130 int create_tempfile(struct tempfile *tempfile, const char *path)
 131 {
 132         prepare_tempfile_object(tempfile);
 133
 134         strbuf_add_absolute_path(&tempfile->filename, path);
 135         tempfile->fd = open(tempfile->filename.buf,
 136                             O_RDWR | O_CREAT | O_EXCL | O_CLOEXEC, 0666);
 137         if (O_CLOEXEC && tempfile->fd < 0 && errno == EINVAL)
 138                 /* Try again w/o O_CLOEXEC: the kernel might not support it */
 139                 tempfile->fd = open(tempfile->filename.buf,
 140                                     O_RDWR | O_CREAT | O_EXCL, 0666);
 141         if (tempfile->fd < 0) {
 142                 deactivate_tempfile(tempfile);
 143                 return -1;
 144         }
 145         activate_tempfile(tempfile);
 146         if (adjust_shared_perm(tempfile->filename.buf)) {
 147                 int save_errno = errno;
 148                 error("cannot fix permission bits on %s", tempfile->filename.buf);
 149                 delete_tempfile(tempfile);
 150                 errno = save_errno;
 151                 return -1;
 152         }
 153         return tempfile->fd;
 154 }
 155
 156 void register_tempfile(struct tempfile *tempfile, const char *path)
 157 {
 158         prepare_tempfile_object(tempfile);
 159         strbuf_add_absolute_path(&tempfile->filename, path);
 160         activate_tempfile(tempfile);
 161 }
 162
 163 int mks_tempfile_sm(struct tempfile *tempfile,
 164                     const char *template, int suffixlen, int mode)
 165 {
 166         prepare_tempfile_object(tempfile);
 167
 168         strbuf_add_absolute_path(&tempfile->filename, template);
 169         tempfile->fd = git_mkstemps_mode(tempfile->filename.buf, suffixlen, mode);
 170         if (tempfile->fd < 0) {
 171                 deactivate_tempfile(tempfile);
 172                 return -1;
 173         }
 174         activate_tempfile(tempfile);
 175         return tempfile->fd;
 176 }
 177
 178 int mks_tempfile_tsm(struct tempfile *tempfile,
 179                      const char *template, int suffixlen, int mode)
 180 {
 181         const char *tmpdir;
 182
 183         prepare_tempfile_object(tempfile);
 184
 185         tmpdir = getenv("TMPDIR");
 186         if (!tmpdir)
 187                 tmpdir = "/tmp";
 188
 189         strbuf_addf(&tempfile->filename, "%s/%s", tmpdir, template);
 190         tempfile->fd = git_mkstemps_mode(tempfile->filename.buf, suffixlen, mode);
 191         if (tempfile->fd < 0) {
 192                 deactivate_tempfile(tempfile);
 193                 return -1;
 194         }
 195         activate_tempfile(tempfile);
 196         return tempfile->fd;
 197 }
 198
 199 int xmks_tempfile_m(struct tempfile *tempfile, const char *template, int mode)
 200 {
 201         int fd;
 202         struct strbuf full_template = STRBUF_INIT;
 203
 204         strbuf_add_absolute_path(&full_template, template);
 205         fd = mks_tempfile_m(tempfile, full_template.buf, mode);
 206         if (fd < 0)
 207                 die_errno("Unable to create temporary file '%s'",
 208                           full_template.buf);
 209
 210         strbuf_release(&full_template);
 211         return fd;
 212 }
 213
 214 FILE *fdopen_tempfile(struct tempfile *tempfile, const char *mode)
 215 {
 216         if (!is_tempfile_active(tempfile))
 217                 BUG("fdopen_tempfile() called for inactive object");
 218         if (tempfile->fp)
 219                 BUG("fdopen_tempfile() called for open object");
 220
 221         tempfile->fp = fdopen(tempfile->fd, mode);
 222         return tempfile->fp;
 223 }
 224
 225 const char *get_tempfile_path(struct tempfile *tempfile)
 226 {
 227         if (!is_tempfile_active(tempfile))
 228                 BUG("get_tempfile_path() called for inactive object");
 229         return tempfile->filename.buf;
 230 }
 231
 232 int get_tempfile_fd(struct tempfile *tempfile)
 233 {
 234         if (!is_tempfile_active(tempfile))
 235                 BUG("get_tempfile_fd() called for inactive object");
 236         return tempfile->fd;
 237 }
 238
 239 FILE *get_tempfile_fp(struct tempfile *tempfile)
 240 {
 241         if (!is_tempfile_active(tempfile))
 242                 BUG("get_tempfile_fp() called for inactive object");
 243         return tempfile->fp;
 244 }
 245
 246 int close_tempfile_gently(struct tempfile *tempfile)
 247 {
 248         int fd;
 249         FILE *fp;
 250         int err;
 251
 252         if (!is_tempfile_active(tempfile) || tempfile->fd < 0)
 253                 return 0;
 254
 255         fd = tempfile->fd;
 256         fp = tempfile->fp;
 257         tempfile->fd = -1;
 258         if (fp) {
 259                 tempfile->fp = NULL;
 260                 if (ferror(fp)) {
 261                         err = -1;
 262                         if (!fclose(fp))
 263                                 errno = EIO;
 264                 } else {
 265                         err = fclose(fp);
 266                 }
 267         } else {
 268                 err = close(fd);
 269         }
 270
 271         return err ? -1 : 0;
 272 }
 273
 274 int reopen_tempfile(struct tempfile *tempfile)
 275 {
 276         if (!is_tempfile_active(tempfile))
 277                 BUG("reopen_tempfile called for an inactive object");
 278         if (0 <= tempfile->fd)
 279                 BUG("reopen_tempfile called for an open object");
 280         tempfile->fd = open(tempfile->filename.buf, O_WRONLY);
 281         return tempfile->fd;
 282 }
 283
 284 int rename_tempfile(struct tempfile *tempfile, const char *path)
 285 {
 286         if (!is_tempfile_active(tempfile))
 287                 BUG("rename_tempfile called for inactive object");
 288
 289         if (close_tempfile_gently(tempfile)) {
 290                 delete_tempfile(tempfile);
 291                 return -1;
 292         }
 293
 294         if (rename(tempfile->filename.buf, path)) {
 295                 int save_errno = errno;
 296                 delete_tempfile(tempfile);
 297                 errno = save_errno;
 298                 return -1;
 299         }
 300
 301         deactivate_tempfile(tempfile);
 302         return 0;
 303 }
 304
 305 void delete_tempfile(struct tempfile *tempfile)
 306 {
 307         if (!is_tempfile_active(tempfile))
 308                 return;
 309
 310         close_tempfile_gently(tempfile);
 311         unlink_or_warn(tempfile->filename.buf);
 312         deactivate_tempfile(tempfile);
 313 }