1 /*- 2 * Copyright (c) 2009 Robert N. M. Watson 3 * All rights reserved. 4 * 5 * This software was developed at the University of Cambridge Computer 6 * Laboratory with support from a grant from Google, Inc. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 */ 29 30 /*- 31 * FreeBSD process descriptor facility. 32 * 33 * Some processes are represented by a file descriptor, which will be used in 34 * preference to signaling and pids for the purposes of process management, 35 * and is, in effect, a form of capability. When a process descriptor is 36 * used with a process, it ceases to be visible to certain traditional UNIX 37 * process facilities, such as waitpid(2). 38 * 39 * Some semantics: 40 * 41 * - At most one process descriptor will exist for any process, although 42 * references to that descriptor may be held from many processes (or even 43 * be in flight between processes over a local domain socket). 44 * - Last close on the process descriptor will terminate the process using 45 * SIGKILL and reparent it to init so that there's a process to reap it 46 * when it's done exiting. 47 * - If the process exits before the descriptor is closed, it will not 48 * generate SIGCHLD on termination, or be picked up by waitpid(). 49 * - The pdkill(2) system call may be used to deliver a signal to the process 50 * using its process descriptor. 51 * - The pdwait4(2) system call may be used to block (or not) on a process 52 * descriptor to collect termination information. 53 * 54 * Open questions: 55 * 56 * - How to handle ptrace(2)? 57 * - Will we want to add a pidtoprocdesc(2) system call to allow process 58 * descriptors to be created for processes without pdfork(2)? 59 */ 60 61 #include <sys/cdefs.h> 62 __FBSDID("$FreeBSD$"); 63 64 #include <sys/param.h> 65 #include <sys/capsicum.h> 66 #include <sys/fcntl.h> 67 #include <sys/file.h> 68 #include <sys/filedesc.h> 69 #include <sys/kernel.h> 70 #include <sys/lock.h> 71 #include <sys/mutex.h> 72 #include <sys/poll.h> 73 #include <sys/proc.h> 74 #include <sys/procdesc.h> 75 #include <sys/resourcevar.h> 76 #include <sys/stat.h> 77 #include <sys/sysproto.h> 78 #include <sys/sysctl.h> 79 #include <sys/systm.h> 80 #include <sys/ucred.h> 81 #include <sys/user.h> 82 83 #include <security/audit/audit.h> 84 85 #include <vm/uma.h> 86 87 FEATURE(process_descriptors, "Process Descriptors"); 88 89 static uma_zone_t procdesc_zone; 90 91 static fo_poll_t procdesc_poll; 92 static fo_kqfilter_t procdesc_kqfilter; 93 static fo_stat_t procdesc_stat; 94 static fo_close_t procdesc_close; 95 static fo_fill_kinfo_t procdesc_fill_kinfo; 96 97 static struct fileops procdesc_ops = { 98 .fo_read = invfo_rdwr, 99 .fo_write = invfo_rdwr, 100 .fo_truncate = invfo_truncate, 101 .fo_ioctl = invfo_ioctl, 102 .fo_poll = procdesc_poll, 103 .fo_kqfilter = procdesc_kqfilter, 104 .fo_stat = procdesc_stat, 105 .fo_close = procdesc_close, 106 .fo_chmod = invfo_chmod, 107 .fo_chown = invfo_chown, 108 .fo_sendfile = invfo_sendfile, 109 .fo_fill_kinfo = procdesc_fill_kinfo, 110 .fo_flags = DFLAG_PASSABLE, 111 }; 112 113 /* 114 * Initialize with VFS so that process descriptors are available along with 115 * other file descriptor types. As long as it runs before init(8) starts, 116 * there shouldn't be a problem. 117 */ 118 static void 119 procdesc_init(void *dummy __unused) 120 { 121 122 procdesc_zone = uma_zcreate("procdesc", sizeof(struct procdesc), 123 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0); 124 if (procdesc_zone == NULL) 125 panic("procdesc_init: procdesc_zone not initialized"); 126 } 127 SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_ANY, procdesc_init, NULL); 128 129 /* 130 * Return a locked process given a process descriptor, or ESRCH if it has 131 * died. 132 */ 133 int 134 procdesc_find(struct thread *td, int fd, cap_rights_t *rightsp, 135 struct proc **p) 136 { 137 struct procdesc *pd; 138 struct file *fp; 139 int error; 140 141 error = fget(td, fd, rightsp, &fp); 142 if (error) 143 return (error); 144 if (fp->f_type != DTYPE_PROCDESC) { 145 error = EBADF; 146 goto out; 147 } 148 pd = fp->f_data; 149 sx_slock(&proctree_lock); 150 if (pd->pd_proc != NULL) { 151 *p = pd->pd_proc; 152 PROC_LOCK(*p); 153 } else 154 error = ESRCH; 155 sx_sunlock(&proctree_lock); 156 out: 157 fdrop(fp, td); 158 return (error); 159 } 160 161 /* 162 * Function to be used by procstat(1) sysctls when returning procdesc 163 * information. 164 */ 165 pid_t 166 procdesc_pid(struct file *fp_procdesc) 167 { 168 struct procdesc *pd; 169 170 KASSERT(fp_procdesc->f_type == DTYPE_PROCDESC, 171 ("procdesc_pid: !procdesc")); 172 173 pd = fp_procdesc->f_data; 174 return (pd->pd_pid); 175 } 176 177 /* 178 * Retrieve the PID associated with a process descriptor. 179 */ 180 int 181 kern_pdgetpid(struct thread *td, int fd, cap_rights_t *rightsp, pid_t *pidp) 182 { 183 struct file *fp; 184 int error; 185 186 error = fget(td, fd, rightsp, &fp); 187 if (error) 188 return (error); 189 if (fp->f_type != DTYPE_PROCDESC) { 190 error = EBADF; 191 goto out; 192 } 193 *pidp = procdesc_pid(fp); 194 out: 195 fdrop(fp, td); 196 return (error); 197 } 198 199 /* 200 * System call to return the pid of a process given its process descriptor. 201 */ 202 int 203 sys_pdgetpid(struct thread *td, struct pdgetpid_args *uap) 204 { 205 cap_rights_t rights; 206 pid_t pid; 207 int error; 208 209 AUDIT_ARG_FD(uap->fd); 210 error = kern_pdgetpid(td, uap->fd, 211 cap_rights_init(&rights, CAP_PDGETPID), &pid); 212 if (error == 0) 213 error = copyout(&pid, uap->pidp, sizeof(pid)); 214 return (error); 215 } 216 217 /* 218 * When a new process is forked by pdfork(), a file descriptor is allocated 219 * by the fork code first, then the process is forked, and then we get a 220 * chance to set up the process descriptor. Failure is not permitted at this 221 * point, so procdesc_new() must succeed. 222 */ 223 void 224 procdesc_new(struct proc *p, int flags) 225 { 226 struct procdesc *pd; 227 228 pd = uma_zalloc(procdesc_zone, M_WAITOK | M_ZERO); 229 pd->pd_proc = p; 230 pd->pd_pid = p->p_pid; 231 p->p_procdesc = pd; 232 pd->pd_flags = 0; 233 if (flags & PD_DAEMON) 234 pd->pd_flags |= PDF_DAEMON; 235 PROCDESC_LOCK_INIT(pd); 236 knlist_init_mtx(&pd->pd_selinfo.si_note, &pd->pd_lock); 237 238 /* 239 * Process descriptors start out with two references: one from their 240 * struct file, and the other from their struct proc. 241 */ 242 refcount_init(&pd->pd_refcount, 2); 243 } 244 245 /* 246 * Initialize a file with a process descriptor. 247 */ 248 void 249 procdesc_finit(struct procdesc *pdp, struct file *fp) 250 { 251 252 finit(fp, FREAD | FWRITE, DTYPE_PROCDESC, pdp, &procdesc_ops); 253 } 254 255 static void 256 procdesc_free(struct procdesc *pd) 257 { 258 259 /* 260 * When the last reference is released, we assert that the descriptor 261 * has been closed, but not that the process has exited, as we will 262 * detach the descriptor before the process dies if the descript is 263 * closed, as we can't wait synchronously. 264 */ 265 if (refcount_release(&pd->pd_refcount)) { 266 KASSERT(pd->pd_proc == NULL, 267 ("procdesc_free: pd_proc != NULL")); 268 KASSERT((pd->pd_flags & PDF_CLOSED), 269 ("procdesc_free: !PDF_CLOSED")); 270 271 knlist_destroy(&pd->pd_selinfo.si_note); 272 PROCDESC_LOCK_DESTROY(pd); 273 uma_zfree(procdesc_zone, pd); 274 } 275 } 276 277 /* 278 * procdesc_exit() - notify a process descriptor that its process is exiting. 279 * We use the proctree_lock to ensure that process exit either happens 280 * strictly before or strictly after a concurrent call to procdesc_close(). 281 */ 282 int 283 procdesc_exit(struct proc *p) 284 { 285 struct procdesc *pd; 286 287 sx_assert(&proctree_lock, SA_XLOCKED); 288 PROC_LOCK_ASSERT(p, MA_OWNED); 289 KASSERT(p->p_procdesc != NULL, ("procdesc_exit: p_procdesc NULL")); 290 291 pd = p->p_procdesc; 292 293 PROCDESC_LOCK(pd); 294 KASSERT((pd->pd_flags & PDF_CLOSED) == 0 || p->p_pptr == initproc, 295 ("procdesc_exit: closed && parent not init")); 296 297 pd->pd_flags |= PDF_EXITED; 298 pd->pd_xstat = p->p_xstat; 299 300 /* 301 * If the process descriptor has been closed, then we have nothing 302 * to do; return 1 so that init will get SIGCHLD and do the reaping. 303 * Clean up the procdesc now rather than letting it happen during 304 * that reap. 305 */ 306 if (pd->pd_flags & PDF_CLOSED) { 307 PROCDESC_UNLOCK(pd); 308 pd->pd_proc = NULL; 309 p->p_procdesc = NULL; 310 procdesc_free(pd); 311 return (1); 312 } 313 if (pd->pd_flags & PDF_SELECTED) { 314 pd->pd_flags &= ~PDF_SELECTED; 315 selwakeup(&pd->pd_selinfo); 316 } 317 KNOTE_LOCKED(&pd->pd_selinfo.si_note, NOTE_EXIT); 318 PROCDESC_UNLOCK(pd); 319 return (0); 320 } 321 322 /* 323 * When a process descriptor is reaped, perhaps as a result of close() or 324 * pdwait4(), release the process's reference on the process descriptor. 325 */ 326 void 327 procdesc_reap(struct proc *p) 328 { 329 struct procdesc *pd; 330 331 sx_assert(&proctree_lock, SA_XLOCKED); 332 KASSERT(p->p_procdesc != NULL, ("procdesc_reap: p_procdesc == NULL")); 333 334 pd = p->p_procdesc; 335 pd->pd_proc = NULL; 336 p->p_procdesc = NULL; 337 procdesc_free(pd); 338 } 339 340 /* 341 * procdesc_close() - last close on a process descriptor. If the process is 342 * still running, terminate with SIGKILL (unless PDF_DAEMON is set) and let 343 * init(8) clean up the mess; if not, we have to clean up the zombie ourselves. 344 */ 345 static int 346 procdesc_close(struct file *fp, struct thread *td) 347 { 348 struct procdesc *pd; 349 struct proc *p; 350 351 KASSERT(fp->f_type == DTYPE_PROCDESC, ("procdesc_close: !procdesc")); 352 353 pd = fp->f_data; 354 fp->f_ops = &badfileops; 355 fp->f_data = NULL; 356 357 sx_xlock(&proctree_lock); 358 PROCDESC_LOCK(pd); 359 pd->pd_flags |= PDF_CLOSED; 360 PROCDESC_UNLOCK(pd); 361 p = pd->pd_proc; 362 if (p == NULL) { 363 /* 364 * This is the case where process' exit status was already 365 * collected and procdesc_reap() was already called. 366 */ 367 sx_xunlock(&proctree_lock); 368 } else { 369 PROC_LOCK(p); 370 if (p->p_state == PRS_ZOMBIE) { 371 /* 372 * If the process is already dead and just awaiting 373 * reaping, do that now. This will release the 374 * process's reference to the process descriptor when it 375 * calls back into procdesc_reap(). 376 */ 377 PROC_SLOCK(p); 378 proc_reap(curthread, p, NULL, 0); 379 } else { 380 /* 381 * If the process is not yet dead, we need to kill it, 382 * but we can't wait around synchronously for it to go 383 * away, as that path leads to madness (and deadlocks). 384 * First, detach the process from its descriptor so that 385 * its exit status will be reported normally. 386 */ 387 pd->pd_proc = NULL; 388 p->p_procdesc = NULL; 389 procdesc_free(pd); 390 391 /* 392 * Next, reparent it to init(8) so that there's someone 393 * to pick up the pieces; finally, terminate with 394 * prejudice. 395 */ 396 p->p_sigparent = SIGCHLD; 397 proc_reparent(p, initproc); 398 if ((pd->pd_flags & PDF_DAEMON) == 0) 399 kern_psignal(p, SIGKILL); 400 PROC_UNLOCK(p); 401 sx_xunlock(&proctree_lock); 402 } 403 } 404 405 /* 406 * Release the file descriptor's reference on the process descriptor. 407 */ 408 procdesc_free(pd); 409 return (0); 410 } 411 412 static int 413 procdesc_poll(struct file *fp, int events, struct ucred *active_cred, 414 struct thread *td) 415 { 416 struct procdesc *pd; 417 int revents; 418 419 revents = 0; 420 pd = fp->f_data; 421 PROCDESC_LOCK(pd); 422 if (pd->pd_flags & PDF_EXITED) 423 revents |= POLLHUP; 424 if (revents == 0) { 425 selrecord(td, &pd->pd_selinfo); 426 pd->pd_flags |= PDF_SELECTED; 427 } 428 PROCDESC_UNLOCK(pd); 429 return (revents); 430 } 431 432 static void 433 procdesc_kqops_detach(struct knote *kn) 434 { 435 struct procdesc *pd; 436 437 pd = kn->kn_fp->f_data; 438 knlist_remove(&pd->pd_selinfo.si_note, kn, 0); 439 } 440 441 static int 442 procdesc_kqops_event(struct knote *kn, long hint) 443 { 444 struct procdesc *pd; 445 u_int event; 446 447 pd = kn->kn_fp->f_data; 448 if (hint == 0) { 449 /* 450 * Initial test after registration. Generate a NOTE_EXIT in 451 * case the process already terminated before registration. 452 */ 453 event = pd->pd_flags & PDF_EXITED ? NOTE_EXIT : 0; 454 } else { 455 /* Mask off extra data. */ 456 event = (u_int)hint & NOTE_PCTRLMASK; 457 } 458 459 /* If the user is interested in this event, record it. */ 460 if (kn->kn_sfflags & event) 461 kn->kn_fflags |= event; 462 463 /* Process is gone, so flag the event as finished. */ 464 if (event == NOTE_EXIT) { 465 kn->kn_flags |= EV_EOF | EV_ONESHOT; 466 if (kn->kn_fflags & NOTE_EXIT) 467 kn->kn_data = pd->pd_xstat; 468 if (kn->kn_fflags == 0) 469 kn->kn_flags |= EV_DROP; 470 return (1); 471 } 472 473 return (kn->kn_fflags != 0); 474 } 475 476 static struct filterops procdesc_kqops = { 477 .f_isfd = 1, 478 .f_detach = procdesc_kqops_detach, 479 .f_event = procdesc_kqops_event, 480 }; 481 482 static int 483 procdesc_kqfilter(struct file *fp, struct knote *kn) 484 { 485 struct procdesc *pd; 486 487 pd = fp->f_data; 488 switch (kn->kn_filter) { 489 case EVFILT_PROCDESC: 490 kn->kn_fop = &procdesc_kqops; 491 kn->kn_flags |= EV_CLEAR; 492 knlist_add(&pd->pd_selinfo.si_note, kn, 0); 493 return (0); 494 default: 495 return (EINVAL); 496 } 497 } 498 499 static int 500 procdesc_stat(struct file *fp, struct stat *sb, struct ucred *active_cred, 501 struct thread *td) 502 { 503 struct procdesc *pd; 504 struct timeval pstart; 505 506 /* 507 * XXXRW: Perhaps we should cache some more information from the 508 * process so that we can return it reliably here even after it has 509 * died. For example, caching its credential data. 510 */ 511 bzero(sb, sizeof(*sb)); 512 pd = fp->f_data; 513 sx_slock(&proctree_lock); 514 if (pd->pd_proc != NULL) { 515 PROC_LOCK(pd->pd_proc); 516 517 /* Set birth and [acm] times to process start time. */ 518 pstart = pd->pd_proc->p_stats->p_start; 519 timevaladd(&pstart, &boottime); 520 TIMEVAL_TO_TIMESPEC(&pstart, &sb->st_birthtim); 521 sb->st_atim = sb->st_birthtim; 522 sb->st_ctim = sb->st_birthtim; 523 sb->st_mtim = sb->st_birthtim; 524 if (pd->pd_proc->p_state != PRS_ZOMBIE) 525 sb->st_mode = S_IFREG | S_IRWXU; 526 else 527 sb->st_mode = S_IFREG; 528 sb->st_uid = pd->pd_proc->p_ucred->cr_ruid; 529 sb->st_gid = pd->pd_proc->p_ucred->cr_rgid; 530 PROC_UNLOCK(pd->pd_proc); 531 } else 532 sb->st_mode = S_IFREG; 533 sx_sunlock(&proctree_lock); 534 return (0); 535 } 536 537 static int 538 procdesc_fill_kinfo(struct file *fp, struct kinfo_file *kif, 539 struct filedesc *fdp) 540 { 541 struct procdesc *pdp; 542 543 kif->kf_type = KF_TYPE_PROCDESC; 544 pdp = fp->f_data; 545 kif->kf_un.kf_proc.kf_pid = pdp->pd_pid; 546 return (0); 547 } 548