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 int remove_template_directory(struct tempfile *tempfile,
  54                                       int in_signal_handler)
  55 {
  56         if (tempfile->directory) {
  57                 if (in_signal_handler)
  58                         return rmdir(tempfile->directory);
  59                 else
  60                         return rmdir_or_warn(tempfile->directory);
  61         }
  62
  63         return 0;
  64 }
  65
  66 static void remove_tempfiles(int in_signal_handler)
  67 {
  68         pid_t me = getpid();
  69         volatile struct volatile_list_head *pos;
  70
  71         list_for_each(pos, &tempfile_list) {
  72                 struct tempfile *p = list_entry(pos, struct tempfile, list);
  73
  74                 if (!is_tempfile_active(p) || p->owner != me)
  75                         continue;
  76
  77                 if (p->fd >= 0)
  78                         close(p->fd);
  79
  80                 if (in_signal_handler)
  81                         unlink(p->filename.buf);
  82                 else
  83                         unlink_or_warn(p->filename.buf);
  84                 remove_template_directory(p, in_signal_handler);
  85         }
  86 }
  87
  88 static void remove_tempfiles_on_exit(void)
  89 {
  90         remove_tempfiles(0);
  91 }
  92
  93 static void remove_tempfiles_on_signal(int signo)
  94 {
  95         remove_tempfiles(1);
  96         sigchain_pop(signo);
  97         raise(signo);
  98 }
  99
 100 static struct tempfile *new_tempfile(void)
 101 {
 102         struct tempfile *tempfile = xmalloc(sizeof(*tempfile));
 103         tempfile->fd = -1;
 104         tempfile->fp = NULL;
 105         tempfile->owner = 0;
 106         INIT_LIST_HEAD(&tempfile->list);
 107         strbuf_init(&tempfile->filename, 0);
 108         tempfile->directory = NULL;
 109         return tempfile;
 110 }
 111
 112 static void activate_tempfile(struct tempfile *tempfile)
 113 {
 114         static int initialized;
 115
 116         if (!initialized) {
 117                 sigchain_push_common(remove_tempfiles_on_signal);
 118                 atexit(remove_tempfiles_on_exit);
 119                 initialized = 1;
 120         }
 121
 122         volatile_list_add(&tempfile->list, &tempfile_list);
 123         tempfile->owner = getpid();
 124 }
 125
 126 static void deactivate_tempfile(struct tempfile *tempfile)
 127 {
 128         volatile_list_del(&tempfile->list);
 129         strbuf_release(&tempfile->filename);
 130         free(tempfile->directory);
 131         free(tempfile);
 132 }
 133
 134 /* Make sure errno contains a meaningful value on error */
 135 struct tempfile *create_tempfile_mode(const char *path, int mode)
 136 {
 137         struct tempfile *tempfile = new_tempfile();
 138
 139         strbuf_add_absolute_path(&tempfile->filename, path);
 140         tempfile->fd = open(tempfile->filename.buf,
 141                             O_RDWR | O_CREAT | O_EXCL | O_CLOEXEC, mode);
 142         if (O_CLOEXEC && tempfile->fd < 0 && errno == EINVAL)
 143                 /* Try again w/o O_CLOEXEC: the kernel might not support it */
 144                 tempfile->fd = open(tempfile->filename.buf,
 145                                     O_RDWR | O_CREAT | O_EXCL, mode);
 146         if (tempfile->fd < 0) {
 147                 deactivate_tempfile(tempfile);
 148                 return NULL;
 149         }
 150         activate_tempfile(tempfile);
 151         if (adjust_shared_perm(tempfile->filename.buf)) {
 152                 int save_errno = errno;
 153                 error("cannot fix permission bits on %s", tempfile->filename.buf);
 154                 delete_tempfile(&tempfile);
 155                 errno = save_errno;
 156                 return NULL;
 157         }
 158
 159         return tempfile;
 160 }
 161
 162 struct tempfile *register_tempfile(const char *path)
 163 {
 164         struct tempfile *tempfile = new_tempfile();
 165         strbuf_add_absolute_path(&tempfile->filename, path);
 166         activate_tempfile(tempfile);
 167         return tempfile;
 168 }
 169
 170 struct tempfile *mks_tempfile_sm(const char *filename_template, int suffixlen, int mode)
 171 {
 172         struct tempfile *tempfile = new_tempfile();
 173
 174         strbuf_add_absolute_path(&tempfile->filename, filename_template);
 175         tempfile->fd = git_mkstemps_mode(tempfile->filename.buf, suffixlen, mode);
 176         if (tempfile->fd < 0) {
 177                 deactivate_tempfile(tempfile);
 178                 return NULL;
 179         }
 180         activate_tempfile(tempfile);
 181         return tempfile;
 182 }
 183
 184 struct tempfile *mks_tempfile_tsm(const char *filename_template, int suffixlen, int mode)
 185 {
 186         struct tempfile *tempfile = new_tempfile();
 187         const char *tmpdir;
 188
 189         tmpdir = getenv("TMPDIR");
 190         if (!tmpdir)
 191                 tmpdir = "/tmp";
 192
 193         strbuf_addf(&tempfile->filename, "%s/%s", tmpdir, filename_template);
 194         tempfile->fd = git_mkstemps_mode(tempfile->filename.buf, suffixlen, mode);
 195         if (tempfile->fd < 0) {
 196                 deactivate_tempfile(tempfile);
 197                 return NULL;
 198         }
 199         activate_tempfile(tempfile);
 200         return tempfile;
 201 }
 202
 203 struct tempfile *mks_tempfile_dt(const char *directory_template,
 204                                  const char *filename)
 205 {
 206         struct tempfile *tempfile;
 207         const char *tmpdir;
 208         struct strbuf sb = STRBUF_INIT;
 209         int fd;
 210         size_t directorylen;
 211
 212         if (!ends_with(directory_template, "XXXXXX")) {
 213                 errno = EINVAL;
 214                 return NULL;
 215         }
 216
 217         tmpdir = getenv("TMPDIR");
 218         if (!tmpdir)
 219                 tmpdir = "/tmp";
 220
 221         strbuf_addf(&sb, "%s/%s", tmpdir, directory_template);
 222         directorylen = sb.len;
 223         if (!mkdtemp(sb.buf)) {
 224                 int orig_errno = errno;
 225                 strbuf_release(&sb);
 226                 errno = orig_errno;
 227                 return NULL;
 228         }
 229
 230         strbuf_addf(&sb, "/%s", filename);
 231         fd = open(sb.buf, O_CREAT | O_EXCL | O_RDWR, 0600);
 232         if (fd < 0) {
 233                 int orig_errno = errno;
 234                 strbuf_setlen(&sb, directorylen);
 235                 rmdir(sb.buf);
 236                 strbuf_release(&sb);
 237                 errno = orig_errno;
 238                 return NULL;
 239         }
 240
 241         tempfile = new_tempfile();
 242         strbuf_swap(&tempfile->filename, &sb);
 243         tempfile->directory = xmemdupz(tempfile->filename.buf, directorylen);
 244         tempfile->fd = fd;
 245         activate_tempfile(tempfile);
 246         return tempfile;
 247 }
 248
 249 struct tempfile *xmks_tempfile_m(const char *filename_template, int mode)
 250 {
 251         struct tempfile *tempfile;
 252         struct strbuf full_template = STRBUF_INIT;
 253
 254         strbuf_add_absolute_path(&full_template, filename_template);
 255         tempfile = mks_tempfile_m(full_template.buf, mode);
 256         if (!tempfile)
 257                 die_errno("Unable to create temporary file '%s'",
 258                           full_template.buf);
 259
 260         strbuf_release(&full_template);
 261         return tempfile;
 262 }
 263
 264 FILE *fdopen_tempfile(struct tempfile *tempfile, const char *mode)
 265 {
 266         if (!is_tempfile_active(tempfile))
 267                 BUG("fdopen_tempfile() called for inactive object");
 268         if (tempfile->fp)
 269                 BUG("fdopen_tempfile() called for open object");
 270
 271         tempfile->fp = fdopen(tempfile->fd, mode);
 272         return tempfile->fp;
 273 }
 274
 275 const char *get_tempfile_path(struct tempfile *tempfile)
 276 {
 277         if (!is_tempfile_active(tempfile))
 278                 BUG("get_tempfile_path() called for inactive object");
 279         return tempfile->filename.buf;
 280 }
 281
 282 int get_tempfile_fd(struct tempfile *tempfile)
 283 {
 284         if (!is_tempfile_active(tempfile))
 285                 BUG("get_tempfile_fd() called for inactive object");
 286         return tempfile->fd;
 287 }
 288
 289 FILE *get_tempfile_fp(struct tempfile *tempfile)
 290 {
 291         if (!is_tempfile_active(tempfile))
 292                 BUG("get_tempfile_fp() called for inactive object");
 293         return tempfile->fp;
 294 }
 295
 296 int close_tempfile_gently(struct tempfile *tempfile)
 297 {
 298         int fd;
 299         FILE *fp;
 300         int err;
 301
 302         if (!is_tempfile_active(tempfile) || tempfile->fd < 0)
 303                 return 0;
 304
 305         fd = tempfile->fd;
 306         fp = tempfile->fp;
 307         tempfile->fd = -1;
 308         if (fp) {
 309                 tempfile->fp = NULL;
 310                 if (ferror(fp)) {
 311                         err = -1;
 312                         if (!fclose(fp))
 313                                 errno = EIO;
 314                 } else {
 315                         err = fclose(fp);
 316                 }
 317         } else {
 318                 err = close(fd);
 319         }
 320
 321         return err ? -1 : 0;
 322 }
 323
 324 int reopen_tempfile(struct tempfile *tempfile)
 325 {
 326         if (!is_tempfile_active(tempfile))
 327                 BUG("reopen_tempfile called for an inactive object");
 328         if (0 <= tempfile->fd)
 329                 BUG("reopen_tempfile called for an open object");
 330         tempfile->fd = open(tempfile->filename.buf, O_WRONLY|O_TRUNC);
 331         return tempfile->fd;
 332 }
 333
 334 int rename_tempfile(struct tempfile **tempfile_p, const char *path)
 335 {
 336         struct tempfile *tempfile = *tempfile_p;
 337
 338         if (!is_tempfile_active(tempfile))
 339                 BUG("rename_tempfile called for inactive object");
 340
 341         if (close_tempfile_gently(tempfile)) {
 342                 delete_tempfile(tempfile_p);
 343                 return -1;
 344         }
 345
 346         if (rename(tempfile->filename.buf, path)) {
 347                 int save_errno = errno;
 348                 delete_tempfile(tempfile_p);
 349                 errno = save_errno;
 350                 return -1;
 351         }
 352
 353         deactivate_tempfile(tempfile);
 354         *tempfile_p = NULL;
 355         return 0;
 356 }
 357
 358 int delete_tempfile(struct tempfile **tempfile_p)
 359 {
 360         struct tempfile *tempfile = *tempfile_p;
 361         int err = 0;
 362
 363         if (!is_tempfile_active(tempfile))
 364                 return 0;
 365
 366         err |= close_tempfile_gently(tempfile);
 367         err |= unlink_or_warn(tempfile->filename.buf);
 368         err |= remove_template_directory(tempfile, 0);
 369         deactivate_tempfile(tempfile);
 370         *tempfile_p = NULL;
 371
 372         return err ? -1 : 0;
 373 }