1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause 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 #include <sys/param.h> 69 #include <sys/capsicum.h> 70 #include <sys/fcntl.h> 71 #include <sys/file.h> 72 #include <sys/filedesc.h> 73 #include <sys/kernel.h> 74 #include <sys/lock.h> 75 #include <sys/mutex.h> 76 #include <sys/poll.h> 77 #include <sys/proc.h> 78 #include <sys/procdesc.h> 79 #include <sys/resourcevar.h> 80 #include <sys/stat.h> 81 #include <sys/sysproto.h> 82 #include <sys/sysctl.h> 83 #include <sys/systm.h> 84 #include <sys/ucred.h> 85 #include <sys/user.h> 86 87 #include <security/audit/audit.h> 88 89 #include <vm/uma.h> 90 91 FEATURE(process_descriptors, "Process Descriptors"); 92 93 MALLOC_DEFINE(M_PROCDESC, "procdesc", "process descriptors"); 94 95 static fo_poll_t procdesc_poll; 96 static fo_kqfilter_t procdesc_kqfilter; 97 static fo_stat_t procdesc_stat; 98 static fo_close_t procdesc_close; 99 static fo_fill_kinfo_t procdesc_fill_kinfo; 100 101 static struct fileops procdesc_ops = { 102 .fo_read = invfo_rdwr, 103 .fo_write = invfo_rdwr, 104 .fo_truncate = invfo_truncate, 105 .fo_ioctl = invfo_ioctl, 106 .fo_poll = procdesc_poll, 107 .fo_kqfilter = procdesc_kqfilter, 108 .fo_stat = procdesc_stat, 109 .fo_close = procdesc_close, 110 .fo_chmod = invfo_chmod, 111 .fo_chown = invfo_chown, 112 .fo_sendfile = invfo_sendfile, 113 .fo_fill_kinfo = procdesc_fill_kinfo, 114 .fo_flags = DFLAG_PASSABLE, 115 }; 116 117 /* 118 * Return a locked process given a process descriptor, or ESRCH if it has 119 * died. 120 */ 121 int 122 procdesc_find(struct thread *td, int fd, cap_rights_t *rightsp, 123 struct proc **p) 124 { 125 struct procdesc *pd; 126 struct file *fp; 127 int error; 128 129 error = fget(td, fd, rightsp, &fp); 130 if (error) 131 return (error); 132 if (fp->f_type != DTYPE_PROCDESC) { 133 error = EBADF; 134 goto out; 135 } 136 pd = fp->f_data; 137 sx_slock(&proctree_lock); 138 if (pd->pd_proc != NULL) { 139 *p = pd->pd_proc; 140 PROC_LOCK(*p); 141 } else 142 error = ESRCH; 143 sx_sunlock(&proctree_lock); 144 out: 145 fdrop(fp, td); 146 return (error); 147 } 148 149 /* 150 * Function to be used by procstat(1) sysctls when returning procdesc 151 * information. 152 */ 153 pid_t 154 procdesc_pid(struct file *fp_procdesc) 155 { 156 struct procdesc *pd; 157 158 KASSERT(fp_procdesc->f_type == DTYPE_PROCDESC, 159 ("procdesc_pid: !procdesc")); 160 161 pd = fp_procdesc->f_data; 162 return (pd->pd_pid); 163 } 164 165 /* 166 * Retrieve the PID associated with a process descriptor. 167 */ 168 int 169 kern_pdgetpid(struct thread *td, int fd, cap_rights_t *rightsp, pid_t *pidp) 170 { 171 struct file *fp; 172 int error; 173 174 error = fget(td, fd, rightsp, &fp); 175 if (error) 176 return (error); 177 if (fp->f_type != DTYPE_PROCDESC) { 178 error = EBADF; 179 goto out; 180 } 181 *pidp = procdesc_pid(fp); 182 out: 183 fdrop(fp, td); 184 return (error); 185 } 186 187 /* 188 * System call to return the pid of a process given its process descriptor. 189 */ 190 int 191 sys_pdgetpid(struct thread *td, struct pdgetpid_args *uap) 192 { 193 pid_t pid; 194 int error; 195 196 AUDIT_ARG_FD(uap->fd); 197 error = kern_pdgetpid(td, uap->fd, &cap_pdgetpid_rights, &pid); 198 if (error == 0) 199 error = copyout(&pid, uap->pidp, sizeof(pid)); 200 return (error); 201 } 202 203 /* 204 * When a new process is forked by pdfork(), a file descriptor is allocated 205 * by the fork code first, then the process is forked, and then we get a 206 * chance to set up the process descriptor. Failure is not permitted at this 207 * point, so procdesc_new() must succeed. 208 */ 209 void 210 procdesc_new(struct proc *p, int flags) 211 { 212 struct procdesc *pd; 213 214 pd = malloc(sizeof(*pd), M_PROCDESC, M_WAITOK | M_ZERO); 215 pd->pd_proc = p; 216 pd->pd_pid = p->p_pid; 217 p->p_procdesc = pd; 218 pd->pd_flags = 0; 219 if (flags & PD_DAEMON) 220 pd->pd_flags |= PDF_DAEMON; 221 PROCDESC_LOCK_INIT(pd); 222 knlist_init_mtx(&pd->pd_selinfo.si_note, &pd->pd_lock); 223 224 /* 225 * Process descriptors start out with two references: one from their 226 * struct file, and the other from their struct proc. 227 */ 228 refcount_init(&pd->pd_refcount, 2); 229 } 230 231 /* 232 * Create a new process decriptor for the process that refers to it. 233 */ 234 int 235 procdesc_falloc(struct thread *td, struct file **resultfp, int *resultfd, 236 int flags, struct filecaps *fcaps) 237 { 238 int fflags; 239 240 fflags = 0; 241 if (flags & PD_CLOEXEC) 242 fflags = O_CLOEXEC; 243 244 return (falloc_caps(td, resultfp, resultfd, fflags, fcaps)); 245 } 246 247 /* 248 * Initialize a file with a process descriptor. 249 */ 250 void 251 procdesc_finit(struct procdesc *pdp, struct file *fp) 252 { 253 254 finit(fp, FREAD | FWRITE, DTYPE_PROCDESC, pdp, &procdesc_ops); 255 } 256 257 static void 258 procdesc_free(struct procdesc *pd) 259 { 260 261 /* 262 * When the last reference is released, we assert that the descriptor 263 * has been closed, but not that the process has exited, as we will 264 * detach the descriptor before the process dies if the descript is 265 * closed, as we can't wait synchronously. 266 */ 267 if (refcount_release(&pd->pd_refcount)) { 268 KASSERT(pd->pd_proc == NULL, 269 ("procdesc_free: pd_proc != NULL")); 270 KASSERT((pd->pd_flags & PDF_CLOSED), 271 ("procdesc_free: !PDF_CLOSED")); 272 273 knlist_destroy(&pd->pd_selinfo.si_note); 274 PROCDESC_LOCK_DESTROY(pd); 275 free(pd, M_PROCDESC); 276 } 277 } 278 279 /* 280 * procdesc_exit() - notify a process descriptor that its process is exiting. 281 * We use the proctree_lock to ensure that process exit either happens 282 * strictly before or strictly after a concurrent call to procdesc_close(). 283 */ 284 int 285 procdesc_exit(struct proc *p) 286 { 287 struct procdesc *pd; 288 289 sx_assert(&proctree_lock, SA_XLOCKED); 290 PROC_LOCK_ASSERT(p, MA_OWNED); 291 KASSERT(p->p_procdesc != NULL, ("procdesc_exit: p_procdesc NULL")); 292 293 pd = p->p_procdesc; 294 295 PROCDESC_LOCK(pd); 296 KASSERT((pd->pd_flags & PDF_CLOSED) == 0 || p->p_pptr == p->p_reaper, 297 ("procdesc_exit: closed && parent not reaper")); 298 299 pd->pd_flags |= PDF_EXITED; 300 pd->pd_xstat = KW_EXITCODE(p->p_xexit, p->p_xsig); 301 302 /* 303 * If the process descriptor has been closed, then we have nothing 304 * to do; return 1 so that init will get SIGCHLD and do the reaping. 305 * Clean up the procdesc now rather than letting it happen during 306 * that reap. 307 */ 308 if (pd->pd_flags & PDF_CLOSED) { 309 PROCDESC_UNLOCK(pd); 310 pd->pd_proc = NULL; 311 p->p_procdesc = NULL; 312 procdesc_free(pd); 313 return (1); 314 } 315 if (pd->pd_flags & PDF_SELECTED) { 316 pd->pd_flags &= ~PDF_SELECTED; 317 selwakeup(&pd->pd_selinfo); 318 } 319 KNOTE_LOCKED(&pd->pd_selinfo.si_note, NOTE_EXIT); 320 PROCDESC_UNLOCK(pd); 321 return (0); 322 } 323 324 /* 325 * When a process descriptor is reaped, perhaps as a result of close() or 326 * pdwait4(), release the process's reference on the process descriptor. 327 */ 328 void 329 procdesc_reap(struct proc *p) 330 { 331 struct procdesc *pd; 332 333 sx_assert(&proctree_lock, SA_XLOCKED); 334 KASSERT(p->p_procdesc != NULL, ("procdesc_reap: p_procdesc == NULL")); 335 336 pd = p->p_procdesc; 337 pd->pd_proc = NULL; 338 p->p_procdesc = NULL; 339 procdesc_free(pd); 340 } 341 342 /* 343 * procdesc_close() - last close on a process descriptor. If the process is 344 * still running, terminate with SIGKILL (unless PDF_DAEMON is set) and let 345 * its reaper clean up the mess; if not, we have to clean up the zombie 346 * ourselves. 347 */ 348 static int 349 procdesc_close(struct file *fp, struct thread *td) 350 { 351 struct procdesc *pd; 352 struct proc *p; 353 354 KASSERT(fp->f_type == DTYPE_PROCDESC, ("procdesc_close: !procdesc")); 355 356 pd = fp->f_data; 357 fp->f_ops = &badfileops; 358 fp->f_data = NULL; 359 360 sx_xlock(&proctree_lock); 361 PROCDESC_LOCK(pd); 362 pd->pd_flags |= PDF_CLOSED; 363 PROCDESC_UNLOCK(pd); 364 p = pd->pd_proc; 365 if (p == NULL) { 366 /* 367 * This is the case where process' exit status was already 368 * collected and procdesc_reap() was already called. 369 */ 370 sx_xunlock(&proctree_lock); 371 } else { 372 PROC_LOCK(p); 373 AUDIT_ARG_PROCESS(p); 374 if (p->p_state == PRS_ZOMBIE) { 375 /* 376 * If the process is already dead and just awaiting 377 * reaping, do that now. This will release the 378 * process's reference to the process descriptor when it 379 * calls back into procdesc_reap(). 380 */ 381 proc_reap(curthread, p, NULL, 0); 382 } else { 383 /* 384 * If the process is not yet dead, we need to kill it, 385 * but we can't wait around synchronously for it to go 386 * away, as that path leads to madness (and deadlocks). 387 * First, detach the process from its descriptor so that 388 * its exit status will be reported normally. 389 */ 390 pd->pd_proc = NULL; 391 p->p_procdesc = NULL; 392 procdesc_free(pd); 393 394 /* 395 * Next, reparent it to its reaper (usually init(8)) so 396 * that there's someone to pick up the pieces; finally, 397 * terminate with prejudice. 398 */ 399 p->p_sigparent = SIGCHLD; 400 if ((p->p_flag & P_TRACED) == 0) { 401 proc_reparent(p, p->p_reaper, true); 402 } else { 403 proc_clear_orphan(p); 404 p->p_oppid = p->p_reaper->p_pid; 405 proc_add_orphan(p, p->p_reaper); 406 } 407 if ((pd->pd_flags & PDF_DAEMON) == 0) 408 kern_psignal(p, SIGKILL); 409 PROC_UNLOCK(p); 410 sx_xunlock(&proctree_lock); 411 } 412 } 413 414 /* 415 * Release the file descriptor's reference on the process descriptor. 416 */ 417 procdesc_free(pd); 418 return (0); 419 } 420 421 static int 422 procdesc_poll(struct file *fp, int events, struct ucred *active_cred, 423 struct thread *td) 424 { 425 struct procdesc *pd; 426 int revents; 427 428 revents = 0; 429 pd = fp->f_data; 430 PROCDESC_LOCK(pd); 431 if (pd->pd_flags & PDF_EXITED) 432 revents |= POLLHUP; 433 if (revents == 0) { 434 selrecord(td, &pd->pd_selinfo); 435 pd->pd_flags |= PDF_SELECTED; 436 } 437 PROCDESC_UNLOCK(pd); 438 return (revents); 439 } 440 441 static void 442 procdesc_kqops_detach(struct knote *kn) 443 { 444 struct procdesc *pd; 445 446 pd = kn->kn_fp->f_data; 447 knlist_remove(&pd->pd_selinfo.si_note, kn, 0); 448 } 449 450 static int 451 procdesc_kqops_event(struct knote *kn, long hint) 452 { 453 struct procdesc *pd; 454 u_int event; 455 456 pd = kn->kn_fp->f_data; 457 if (hint == 0) { 458 /* 459 * Initial test after registration. Generate a NOTE_EXIT in 460 * case the process already terminated before registration. 461 */ 462 event = pd->pd_flags & PDF_EXITED ? NOTE_EXIT : 0; 463 } else { 464 /* Mask off extra data. */ 465 event = (u_int)hint & NOTE_PCTRLMASK; 466 } 467 468 /* If the user is interested in this event, record it. */ 469 if (kn->kn_sfflags & event) 470 kn->kn_fflags |= event; 471 472 /* Process is gone, so flag the event as finished. */ 473 if (event == NOTE_EXIT) { 474 kn->kn_flags |= EV_EOF | EV_ONESHOT; 475 if (kn->kn_fflags & NOTE_EXIT) 476 kn->kn_data = pd->pd_xstat; 477 if (kn->kn_fflags == 0) 478 kn->kn_flags |= EV_DROP; 479 return (1); 480 } 481 482 return (kn->kn_fflags != 0); 483 } 484 485 static struct filterops procdesc_kqops = { 486 .f_isfd = 1, 487 .f_detach = procdesc_kqops_detach, 488 .f_event = procdesc_kqops_event, 489 }; 490 491 static int 492 procdesc_kqfilter(struct file *fp, struct knote *kn) 493 { 494 struct procdesc *pd; 495 496 pd = fp->f_data; 497 switch (kn->kn_filter) { 498 case EVFILT_PROCDESC: 499 kn->kn_fop = &procdesc_kqops; 500 kn->kn_flags |= EV_CLEAR; 501 knlist_add(&pd->pd_selinfo.si_note, kn, 0); 502 return (0); 503 default: 504 return (EINVAL); 505 } 506 } 507 508 static int 509 procdesc_stat(struct file *fp, struct stat *sb, struct ucred *active_cred) 510 { 511 struct procdesc *pd; 512 struct timeval pstart, boottime; 513 514 /* 515 * XXXRW: Perhaps we should cache some more information from the 516 * process so that we can return it reliably here even after it has 517 * died. For example, caching its credential data. 518 */ 519 bzero(sb, sizeof(*sb)); 520 pd = fp->f_data; 521 sx_slock(&proctree_lock); 522 if (pd->pd_proc != NULL) { 523 PROC_LOCK(pd->pd_proc); 524 AUDIT_ARG_PROCESS(pd->pd_proc); 525 526 /* Set birth and [acm] times to process start time. */ 527 pstart = pd->pd_proc->p_stats->p_start; 528 getboottime(&boottime); 529 timevaladd(&pstart, &boottime); 530 TIMEVAL_TO_TIMESPEC(&pstart, &sb->st_birthtim); 531 sb->st_atim = sb->st_birthtim; 532 sb->st_ctim = sb->st_birthtim; 533 sb->st_mtim = sb->st_birthtim; 534 if (pd->pd_proc->p_state != PRS_ZOMBIE) 535 sb->st_mode = S_IFREG | S_IRWXU; 536 else 537 sb->st_mode = S_IFREG; 538 sb->st_uid = pd->pd_proc->p_ucred->cr_ruid; 539 sb->st_gid = pd->pd_proc->p_ucred->cr_rgid; 540 PROC_UNLOCK(pd->pd_proc); 541 } else 542 sb->st_mode = S_IFREG; 543 sx_sunlock(&proctree_lock); 544 return (0); 545 } 546 547 static int 548 procdesc_fill_kinfo(struct file *fp, struct kinfo_file *kif, 549 struct filedesc *fdp) 550 { 551 struct procdesc *pdp; 552 553 kif->kf_type = KF_TYPE_PROCDESC; 554 pdp = fp->f_data; 555 kif->kf_un.kf_proc.kf_pid = pdp->pd_pid; 556 return (0); 557 } 558