1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD 3 * 4 * Copyright (c) 2009, 2016 Robert N. M. Watson 5 * All rights reserved. 6 * 7 * This software was developed at the University of Cambridge Computer 8 * Laboratory with support from a grant from Google, Inc. 9 * 10 * Portions of this software were developed by BAE Systems, the University of 11 * Cambridge Computer Laboratory, and Memorial University under DARPA/AFRL 12 * contract FA8650-15-C-7558 ("CADETS"), as part of the DARPA Transparent 13 * Computing (TC) research program. 14 * 15 * Redistribution and use in source and binary forms, with or without 16 * modification, are permitted provided that the following conditions 17 * are met: 18 * 1. Redistributions of source code must retain the above copyright 19 * notice, this list of conditions and the following disclaimer. 20 * 2. Redistributions in binary form must reproduce the above copyright 21 * notice, this list of conditions and the following disclaimer in the 22 * documentation and/or other materials provided with the distribution. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 */ 36 37 /*- 38 * FreeBSD process descriptor facility. 39 * 40 * Some processes are represented by a file descriptor, which will be used in 41 * preference to signaling and pids for the purposes of process management, 42 * and is, in effect, a form of capability. When a process descriptor is 43 * used with a process, it ceases to be visible to certain traditional UNIX 44 * process facilities, such as waitpid(2). 45 * 46 * Some semantics: 47 * 48 * - At most one process descriptor will exist for any process, although 49 * references to that descriptor may be held from many processes (or even 50 * be in flight between processes over a local domain socket). 51 * - Last close on the process descriptor will terminate the process using 52 * SIGKILL and reparent it to init so that there's a process to reap it 53 * when it's done exiting. 54 * - If the process exits before the descriptor is closed, it will not 55 * generate SIGCHLD on termination, or be picked up by waitpid(). 56 * - The pdkill(2) system call may be used to deliver a signal to the process 57 * using its process descriptor. 58 * - The pdwait4(2) system call may be used to block (or not) on a process 59 * descriptor to collect termination information. 60 * 61 * Open questions: 62 * 63 * - Will we want to add a pidtoprocdesc(2) system call to allow process 64 * descriptors to be created for processes without pdfork(2)? 65 */ 66 67 #include <sys/cdefs.h> 68 __FBSDID("$FreeBSD$"); 69 70 #include <sys/param.h> 71 #include <sys/capsicum.h> 72 #include <sys/fcntl.h> 73 #include <sys/file.h> 74 #include <sys/filedesc.h> 75 #include <sys/kernel.h> 76 #include <sys/lock.h> 77 #include <sys/mutex.h> 78 #include <sys/poll.h> 79 #include <sys/proc.h> 80 #include <sys/procdesc.h> 81 #include <sys/resourcevar.h> 82 #include <sys/stat.h> 83 #include <sys/sysproto.h> 84 #include <sys/sysctl.h> 85 #include <sys/systm.h> 86 #include <sys/ucred.h> 87 #include <sys/user.h> 88 89 #include <security/audit/audit.h> 90 91 #include <vm/uma.h> 92 93 FEATURE(process_descriptors, "Process Descriptors"); 94 95 MALLOC_DEFINE(M_PROCDESC, "procdesc", "process descriptors"); 96 97 static fo_poll_t procdesc_poll; 98 static fo_kqfilter_t procdesc_kqfilter; 99 static fo_stat_t procdesc_stat; 100 static fo_close_t procdesc_close; 101 static fo_fill_kinfo_t procdesc_fill_kinfo; 102 103 static struct fileops procdesc_ops = { 104 .fo_read = invfo_rdwr, 105 .fo_write = invfo_rdwr, 106 .fo_truncate = invfo_truncate, 107 .fo_ioctl = invfo_ioctl, 108 .fo_poll = procdesc_poll, 109 .fo_kqfilter = procdesc_kqfilter, 110 .fo_stat = procdesc_stat, 111 .fo_close = procdesc_close, 112 .fo_chmod = invfo_chmod, 113 .fo_chown = invfo_chown, 114 .fo_sendfile = invfo_sendfile, 115 .fo_fill_kinfo = procdesc_fill_kinfo, 116 .fo_flags = DFLAG_PASSABLE, 117 }; 118 119 /* 120 * Return a locked process given a process descriptor, or ESRCH if it has 121 * died. 122 */ 123 int 124 procdesc_find(struct thread *td, int fd, cap_rights_t *rightsp, 125 struct proc **p) 126 { 127 struct procdesc *pd; 128 struct file *fp; 129 int error; 130 131 error = fget(td, fd, rightsp, &fp); 132 if (error) 133 return (error); 134 if (fp->f_type != DTYPE_PROCDESC) { 135 error = EBADF; 136 goto out; 137 } 138 pd = fp->f_data; 139 sx_slock(&proctree_lock); 140 if (pd->pd_proc != NULL) { 141 *p = pd->pd_proc; 142 PROC_LOCK(*p); 143 } else 144 error = ESRCH; 145 sx_sunlock(&proctree_lock); 146 out: 147 fdrop(fp, td); 148 return (error); 149 } 150 151 /* 152 * Function to be used by procstat(1) sysctls when returning procdesc 153 * information. 154 */ 155 pid_t 156 procdesc_pid(struct file *fp_procdesc) 157 { 158 struct procdesc *pd; 159 160 KASSERT(fp_procdesc->f_type == DTYPE_PROCDESC, 161 ("procdesc_pid: !procdesc")); 162 163 pd = fp_procdesc->f_data; 164 return (pd->pd_pid); 165 } 166 167 /* 168 * Retrieve the PID associated with a process descriptor. 169 */ 170 int 171 kern_pdgetpid(struct thread *td, int fd, cap_rights_t *rightsp, pid_t *pidp) 172 { 173 struct file *fp; 174 int error; 175 176 error = fget(td, fd, rightsp, &fp); 177 if (error) 178 return (error); 179 if (fp->f_type != DTYPE_PROCDESC) { 180 error = EBADF; 181 goto out; 182 } 183 *pidp = procdesc_pid(fp); 184 out: 185 fdrop(fp, td); 186 return (error); 187 } 188 189 /* 190 * System call to return the pid of a process given its process descriptor. 191 */ 192 int 193 sys_pdgetpid(struct thread *td, struct pdgetpid_args *uap) 194 { 195 pid_t pid; 196 int error; 197 198 AUDIT_ARG_FD(uap->fd); 199 error = kern_pdgetpid(td, uap->fd, &cap_pdgetpid_rights, &pid); 200 if (error == 0) 201 error = copyout(&pid, uap->pidp, sizeof(pid)); 202 return (error); 203 } 204 205 /* 206 * When a new process is forked by pdfork(), a file descriptor is allocated 207 * by the fork code first, then the process is forked, and then we get a 208 * chance to set up the process descriptor. Failure is not permitted at this 209 * point, so procdesc_new() must succeed. 210 */ 211 void 212 procdesc_new(struct proc *p, int flags) 213 { 214 struct procdesc *pd; 215 216 pd = malloc(sizeof(*pd), M_PROCDESC, M_WAITOK | M_ZERO); 217 pd->pd_proc = p; 218 pd->pd_pid = p->p_pid; 219 p->p_procdesc = pd; 220 pd->pd_flags = 0; 221 if (flags & PD_DAEMON) 222 pd->pd_flags |= PDF_DAEMON; 223 PROCDESC_LOCK_INIT(pd); 224 knlist_init_mtx(&pd->pd_selinfo.si_note, &pd->pd_lock); 225 226 /* 227 * Process descriptors start out with two references: one from their 228 * struct file, and the other from their struct proc. 229 */ 230 refcount_init(&pd->pd_refcount, 2); 231 } 232 233 /* 234 * Create a new process decriptor for the process that refers to it. 235 */ 236 int 237 procdesc_falloc(struct thread *td, struct file **resultfp, int *resultfd, 238 int flags, struct filecaps *fcaps) 239 { 240 int fflags; 241 242 fflags = 0; 243 if (flags & PD_CLOEXEC) 244 fflags = O_CLOEXEC; 245 246 return (falloc_caps(td, resultfp, resultfd, fflags, fcaps)); 247 } 248 249 /* 250 * Initialize a file with a process descriptor. 251 */ 252 void 253 procdesc_finit(struct procdesc *pdp, struct file *fp) 254 { 255 256 finit(fp, FREAD | FWRITE, DTYPE_PROCDESC, pdp, &procdesc_ops); 257 } 258 259 static void 260 procdesc_free(struct procdesc *pd) 261 { 262 263 /* 264 * When the last reference is released, we assert that the descriptor 265 * has been closed, but not that the process has exited, as we will 266 * detach the descriptor before the process dies if the descript is 267 * closed, as we can't wait synchronously. 268 */ 269 if (refcount_release(&pd->pd_refcount)) { 270 KASSERT(pd->pd_proc == NULL, 271 ("procdesc_free: pd_proc != NULL")); 272 KASSERT((pd->pd_flags & PDF_CLOSED), 273 ("procdesc_free: !PDF_CLOSED")); 274 275 knlist_destroy(&pd->pd_selinfo.si_note); 276 PROCDESC_LOCK_DESTROY(pd); 277 free(pd, M_PROCDESC); 278 } 279 } 280 281 /* 282 * procdesc_exit() - notify a process descriptor that its process is exiting. 283 * We use the proctree_lock to ensure that process exit either happens 284 * strictly before or strictly after a concurrent call to procdesc_close(). 285 */ 286 int 287 procdesc_exit(struct proc *p) 288 { 289 struct procdesc *pd; 290 291 sx_assert(&proctree_lock, SA_XLOCKED); 292 PROC_LOCK_ASSERT(p, MA_OWNED); 293 KASSERT(p->p_procdesc != NULL, ("procdesc_exit: p_procdesc NULL")); 294 295 pd = p->p_procdesc; 296 297 PROCDESC_LOCK(pd); 298 KASSERT((pd->pd_flags & PDF_CLOSED) == 0 || p->p_pptr == p->p_reaper, 299 ("procdesc_exit: closed && parent not reaper")); 300 301 pd->pd_flags |= PDF_EXITED; 302 pd->pd_xstat = KW_EXITCODE(p->p_xexit, p->p_xsig); 303 304 /* 305 * If the process descriptor has been closed, then we have nothing 306 * to do; return 1 so that init will get SIGCHLD and do the reaping. 307 * Clean up the procdesc now rather than letting it happen during 308 * that reap. 309 */ 310 if (pd->pd_flags & PDF_CLOSED) { 311 PROCDESC_UNLOCK(pd); 312 pd->pd_proc = NULL; 313 p->p_procdesc = NULL; 314 procdesc_free(pd); 315 return (1); 316 } 317 if (pd->pd_flags & PDF_SELECTED) { 318 pd->pd_flags &= ~PDF_SELECTED; 319 selwakeup(&pd->pd_selinfo); 320 } 321 KNOTE_LOCKED(&pd->pd_selinfo.si_note, NOTE_EXIT); 322 PROCDESC_UNLOCK(pd); 323 return (0); 324 } 325 326 /* 327 * When a process descriptor is reaped, perhaps as a result of close() or 328 * pdwait4(), release the process's reference on the process descriptor. 329 */ 330 void 331 procdesc_reap(struct proc *p) 332 { 333 struct procdesc *pd; 334 335 sx_assert(&proctree_lock, SA_XLOCKED); 336 KASSERT(p->p_procdesc != NULL, ("procdesc_reap: p_procdesc == NULL")); 337 338 pd = p->p_procdesc; 339 pd->pd_proc = NULL; 340 p->p_procdesc = NULL; 341 procdesc_free(pd); 342 } 343 344 /* 345 * procdesc_close() - last close on a process descriptor. If the process is 346 * still running, terminate with SIGKILL (unless PDF_DAEMON is set) and let 347 * its reaper clean up the mess; if not, we have to clean up the zombie 348 * ourselves. 349 */ 350 static int 351 procdesc_close(struct file *fp, struct thread *td) 352 { 353 struct procdesc *pd; 354 struct proc *p; 355 356 KASSERT(fp->f_type == DTYPE_PROCDESC, ("procdesc_close: !procdesc")); 357 358 pd = fp->f_data; 359 fp->f_ops = &badfileops; 360 fp->f_data = NULL; 361 362 sx_xlock(&proctree_lock); 363 PROCDESC_LOCK(pd); 364 pd->pd_flags |= PDF_CLOSED; 365 PROCDESC_UNLOCK(pd); 366 p = pd->pd_proc; 367 if (p == NULL) { 368 /* 369 * This is the case where process' exit status was already 370 * collected and procdesc_reap() was already called. 371 */ 372 sx_xunlock(&proctree_lock); 373 } else { 374 PROC_LOCK(p); 375 AUDIT_ARG_PROCESS(p); 376 if (p->p_state == PRS_ZOMBIE) { 377 /* 378 * If the process is already dead and just awaiting 379 * reaping, do that now. This will release the 380 * process's reference to the process descriptor when it 381 * calls back into procdesc_reap(). 382 */ 383 proc_reap(curthread, p, NULL, 0); 384 } else { 385 /* 386 * If the process is not yet dead, we need to kill it, 387 * but we can't wait around synchronously for it to go 388 * away, as that path leads to madness (and deadlocks). 389 * First, detach the process from its descriptor so that 390 * its exit status will be reported normally. 391 */ 392 pd->pd_proc = NULL; 393 p->p_procdesc = NULL; 394 procdesc_free(pd); 395 396 /* 397 * Next, reparent it to its reaper (usually init(8)) so 398 * that there's someone to pick up the pieces; finally, 399 * terminate with prejudice. 400 */ 401 p->p_sigparent = SIGCHLD; 402 if ((p->p_flag & P_TRACED) == 0) { 403 proc_reparent(p, p->p_reaper, true); 404 } else { 405 proc_clear_orphan(p); 406 p->p_oppid = p->p_reaper->p_pid; 407 proc_add_orphan(p, p->p_reaper); 408 } 409 if ((pd->pd_flags & PDF_DAEMON) == 0) 410 kern_psignal(p, SIGKILL); 411 PROC_UNLOCK(p); 412 sx_xunlock(&proctree_lock); 413 } 414 } 415 416 /* 417 * Release the file descriptor's reference on the process descriptor. 418 */ 419 procdesc_free(pd); 420 return (0); 421 } 422 423 static int 424 procdesc_poll(struct file *fp, int events, struct ucred *active_cred, 425 struct thread *td) 426 { 427 struct procdesc *pd; 428 int revents; 429 430 revents = 0; 431 pd = fp->f_data; 432 PROCDESC_LOCK(pd); 433 if (pd->pd_flags & PDF_EXITED) 434 revents |= POLLHUP; 435 if (revents == 0) { 436 selrecord(td, &pd->pd_selinfo); 437 pd->pd_flags |= PDF_SELECTED; 438 } 439 PROCDESC_UNLOCK(pd); 440 return (revents); 441 } 442 443 static void 444 procdesc_kqops_detach(struct knote *kn) 445 { 446 struct procdesc *pd; 447 448 pd = kn->kn_fp->f_data; 449 knlist_remove(&pd->pd_selinfo.si_note, kn, 0); 450 } 451 452 static int 453 procdesc_kqops_event(struct knote *kn, long hint) 454 { 455 struct procdesc *pd; 456 u_int event; 457 458 pd = kn->kn_fp->f_data; 459 if (hint == 0) { 460 /* 461 * Initial test after registration. Generate a NOTE_EXIT in 462 * case the process already terminated before registration. 463 */ 464 event = pd->pd_flags & PDF_EXITED ? NOTE_EXIT : 0; 465 } else { 466 /* Mask off extra data. */ 467 event = (u_int)hint & NOTE_PCTRLMASK; 468 } 469 470 /* If the user is interested in this event, record it. */ 471 if (kn->kn_sfflags & event) 472 kn->kn_fflags |= event; 473 474 /* Process is gone, so flag the event as finished. */ 475 if (event == NOTE_EXIT) { 476 kn->kn_flags |= EV_EOF | EV_ONESHOT; 477 if (kn->kn_fflags & NOTE_EXIT) 478 kn->kn_data = pd->pd_xstat; 479 if (kn->kn_fflags == 0) 480 kn->kn_flags |= EV_DROP; 481 return (1); 482 } 483 484 return (kn->kn_fflags != 0); 485 } 486 487 static struct filterops procdesc_kqops = { 488 .f_isfd = 1, 489 .f_detach = procdesc_kqops_detach, 490 .f_event = procdesc_kqops_event, 491 }; 492 493 static int 494 procdesc_kqfilter(struct file *fp, struct knote *kn) 495 { 496 struct procdesc *pd; 497 498 pd = fp->f_data; 499 switch (kn->kn_filter) { 500 case EVFILT_PROCDESC: 501 kn->kn_fop = &procdesc_kqops; 502 kn->kn_flags |= EV_CLEAR; 503 knlist_add(&pd->pd_selinfo.si_note, kn, 0); 504 return (0); 505 default: 506 return (EINVAL); 507 } 508 } 509 510 static int 511 procdesc_stat(struct file *fp, struct stat *sb, struct ucred *active_cred, 512 struct thread *td) 513 { 514 struct procdesc *pd; 515 struct timeval pstart, boottime; 516 517 /* 518 * XXXRW: Perhaps we should cache some more information from the 519 * process so that we can return it reliably here even after it has 520 * died. For example, caching its credential data. 521 */ 522 bzero(sb, sizeof(*sb)); 523 pd = fp->f_data; 524 sx_slock(&proctree_lock); 525 if (pd->pd_proc != NULL) { 526 PROC_LOCK(pd->pd_proc); 527 AUDIT_ARG_PROCESS(pd->pd_proc); 528 529 /* Set birth and [acm] times to process start time. */ 530 pstart = pd->pd_proc->p_stats->p_start; 531 getboottime(&boottime); 532 timevaladd(&pstart, &boottime); 533 TIMEVAL_TO_TIMESPEC(&pstart, &sb->st_birthtim); 534 sb->st_atim = sb->st_birthtim; 535 sb->st_ctim = sb->st_birthtim; 536 sb->st_mtim = sb->st_birthtim; 537 if (pd->pd_proc->p_state != PRS_ZOMBIE) 538 sb->st_mode = S_IFREG | S_IRWXU; 539 else 540 sb->st_mode = S_IFREG; 541 sb->st_uid = pd->pd_proc->p_ucred->cr_ruid; 542 sb->st_gid = pd->pd_proc->p_ucred->cr_rgid; 543 PROC_UNLOCK(pd->pd_proc); 544 } else 545 sb->st_mode = S_IFREG; 546 sx_sunlock(&proctree_lock); 547 return (0); 548 } 549 550 static int 551 procdesc_fill_kinfo(struct file *fp, struct kinfo_file *kif, 552 struct filedesc *fdp) 553 { 554 struct procdesc *pdp; 555 556 kif->kf_type = KF_TYPE_PROCDESC; 557 pdp = fp->f_data; 558 kif->kf_un.kf_proc.kf_pid = pdp->pd_pid; 559 return (0); 560 } 561