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 * 59 * Open questions: 60 * 61 * - Will we want to add a pidtoprocdesc(2) system call to allow process 62 * descriptors to be created for processes without pdfork(2)? 63 */ 64 65 #include <sys/param.h> 66 #include <sys/capsicum.h> 67 #include <sys/fcntl.h> 68 #include <sys/file.h> 69 #include <sys/filedesc.h> 70 #include <sys/kernel.h> 71 #include <sys/lock.h> 72 #include <sys/mutex.h> 73 #include <sys/poll.h> 74 #include <sys/proc.h> 75 #include <sys/procdesc.h> 76 #include <sys/resourcevar.h> 77 #include <sys/stat.h> 78 #include <sys/sysproto.h> 79 #include <sys/sysctl.h> 80 #include <sys/systm.h> 81 #include <sys/ucred.h> 82 #include <sys/user.h> 83 84 #include <security/audit/audit.h> 85 86 #include <vm/uma.h> 87 88 FEATURE(process_descriptors, "Process Descriptors"); 89 90 MALLOC_DEFINE(M_PROCDESC, "procdesc", "process descriptors"); 91 92 static fo_poll_t procdesc_poll; 93 static fo_kqfilter_t procdesc_kqfilter; 94 static fo_stat_t procdesc_stat; 95 static fo_close_t procdesc_close; 96 static fo_fill_kinfo_t procdesc_fill_kinfo; 97 98 static struct fileops procdesc_ops = { 99 .fo_read = invfo_rdwr, 100 .fo_write = invfo_rdwr, 101 .fo_truncate = invfo_truncate, 102 .fo_ioctl = invfo_ioctl, 103 .fo_poll = procdesc_poll, 104 .fo_kqfilter = procdesc_kqfilter, 105 .fo_stat = procdesc_stat, 106 .fo_close = procdesc_close, 107 .fo_chmod = invfo_chmod, 108 .fo_chown = invfo_chown, 109 .fo_sendfile = invfo_sendfile, 110 .fo_fill_kinfo = procdesc_fill_kinfo, 111 .fo_flags = DFLAG_PASSABLE, 112 }; 113 114 /* 115 * Return a locked process given a process descriptor, or ESRCH if it has 116 * died. 117 */ 118 int 119 procdesc_find(struct thread *td, int fd, cap_rights_t *rightsp, 120 struct proc **p) 121 { 122 struct procdesc *pd; 123 struct file *fp; 124 int error; 125 126 error = fget(td, fd, rightsp, &fp); 127 if (error) 128 return (error); 129 if (fp->f_type != DTYPE_PROCDESC) { 130 error = EBADF; 131 goto out; 132 } 133 pd = fp->f_data; 134 sx_slock(&proctree_lock); 135 if (pd->pd_proc != NULL) { 136 *p = pd->pd_proc; 137 PROC_LOCK(*p); 138 } else 139 error = ESRCH; 140 sx_sunlock(&proctree_lock); 141 out: 142 fdrop(fp, td); 143 return (error); 144 } 145 146 /* 147 * Function to be used by procstat(1) sysctls when returning procdesc 148 * information. 149 */ 150 pid_t 151 procdesc_pid(struct file *fp_procdesc) 152 { 153 struct procdesc *pd; 154 155 KASSERT(fp_procdesc->f_type == DTYPE_PROCDESC, 156 ("procdesc_pid: !procdesc")); 157 158 pd = fp_procdesc->f_data; 159 return (pd->pd_pid); 160 } 161 162 /* 163 * Retrieve the PID associated with a process descriptor. 164 */ 165 int 166 kern_pdgetpid(struct thread *td, int fd, cap_rights_t *rightsp, pid_t *pidp) 167 { 168 struct file *fp; 169 int error; 170 171 error = fget(td, fd, rightsp, &fp); 172 if (error) 173 return (error); 174 if (fp->f_type != DTYPE_PROCDESC) { 175 error = EBADF; 176 goto out; 177 } 178 *pidp = procdesc_pid(fp); 179 out: 180 fdrop(fp, td); 181 return (error); 182 } 183 184 /* 185 * System call to return the pid of a process given its process descriptor. 186 */ 187 int 188 sys_pdgetpid(struct thread *td, struct pdgetpid_args *uap) 189 { 190 pid_t pid; 191 int error; 192 193 AUDIT_ARG_FD(uap->fd); 194 error = kern_pdgetpid(td, uap->fd, &cap_pdgetpid_rights, &pid); 195 if (error == 0) 196 error = copyout(&pid, uap->pidp, sizeof(pid)); 197 return (error); 198 } 199 200 /* 201 * When a new process is forked by pdfork(), a file descriptor is allocated 202 * by the fork code first, then the process is forked, and then we get a 203 * chance to set up the process descriptor. Failure is not permitted at this 204 * point, so procdesc_new() must succeed. 205 */ 206 void 207 procdesc_new(struct proc *p, int flags) 208 { 209 struct procdesc *pd; 210 211 pd = malloc(sizeof(*pd), M_PROCDESC, M_WAITOK | M_ZERO); 212 pd->pd_proc = p; 213 pd->pd_pid = p->p_pid; 214 p->p_procdesc = pd; 215 pd->pd_flags = 0; 216 if (flags & PD_DAEMON) 217 pd->pd_flags |= PDF_DAEMON; 218 PROCDESC_LOCK_INIT(pd); 219 knlist_init_mtx(&pd->pd_selinfo.si_note, &pd->pd_lock); 220 221 /* 222 * Process descriptors start out with two references: one from their 223 * struct file, and the other from their struct proc. 224 */ 225 refcount_init(&pd->pd_refcount, 2); 226 } 227 228 /* 229 * Create a new process decriptor for the process that refers to it. 230 */ 231 int 232 procdesc_falloc(struct thread *td, struct file **resultfp, int *resultfd, 233 int flags, struct filecaps *fcaps) 234 { 235 int fflags; 236 237 fflags = 0; 238 if (flags & PD_CLOEXEC) 239 fflags = O_CLOEXEC; 240 241 return (falloc_caps(td, resultfp, resultfd, fflags, fcaps)); 242 } 243 244 /* 245 * Initialize a file with a process descriptor. 246 */ 247 void 248 procdesc_finit(struct procdesc *pdp, struct file *fp) 249 { 250 251 finit(fp, FREAD | FWRITE, DTYPE_PROCDESC, pdp, &procdesc_ops); 252 } 253 254 static void 255 procdesc_free(struct procdesc *pd) 256 { 257 258 /* 259 * When the last reference is released, we assert that the descriptor 260 * has been closed, but not that the process has exited, as we will 261 * detach the descriptor before the process dies if the descript is 262 * closed, as we can't wait synchronously. 263 */ 264 if (refcount_release(&pd->pd_refcount)) { 265 KASSERT(pd->pd_proc == NULL, 266 ("procdesc_free: pd_proc != NULL")); 267 KASSERT((pd->pd_flags & PDF_CLOSED), 268 ("procdesc_free: !PDF_CLOSED")); 269 270 knlist_destroy(&pd->pd_selinfo.si_note); 271 PROCDESC_LOCK_DESTROY(pd); 272 free(pd, M_PROCDESC); 273 } 274 } 275 276 /* 277 * procdesc_exit() - notify a process descriptor that its process is exiting. 278 * We use the proctree_lock to ensure that process exit either happens 279 * strictly before or strictly after a concurrent call to procdesc_close(). 280 */ 281 int 282 procdesc_exit(struct proc *p) 283 { 284 struct procdesc *pd; 285 286 sx_assert(&proctree_lock, SA_XLOCKED); 287 PROC_LOCK_ASSERT(p, MA_OWNED); 288 KASSERT(p->p_procdesc != NULL, ("procdesc_exit: p_procdesc NULL")); 289 290 pd = p->p_procdesc; 291 292 PROCDESC_LOCK(pd); 293 KASSERT((pd->pd_flags & PDF_CLOSED) == 0 || p->p_pptr == p->p_reaper, 294 ("procdesc_exit: closed && parent not reaper")); 295 296 pd->pd_flags |= PDF_EXITED; 297 pd->pd_xstat = KW_EXITCODE(p->p_xexit, p->p_xsig); 298 299 /* 300 * If the process descriptor has been closed, then we have nothing 301 * to do; return 1 so that init will get SIGCHLD and do the reaping. 302 * Clean up the procdesc now rather than letting it happen during 303 * that reap. 304 */ 305 if (pd->pd_flags & PDF_CLOSED) { 306 PROCDESC_UNLOCK(pd); 307 pd->pd_proc = NULL; 308 p->p_procdesc = NULL; 309 procdesc_free(pd); 310 return (1); 311 } 312 if (pd->pd_flags & PDF_SELECTED) { 313 pd->pd_flags &= ~PDF_SELECTED; 314 selwakeup(&pd->pd_selinfo); 315 } 316 KNOTE_LOCKED(&pd->pd_selinfo.si_note, NOTE_EXIT); 317 PROCDESC_UNLOCK(pd); 318 return (0); 319 } 320 321 /* 322 * When a process descriptor is reaped, perhaps as a result of close(), release 323 * the process's reference on the process descriptor. 324 */ 325 void 326 procdesc_reap(struct proc *p) 327 { 328 struct procdesc *pd; 329 330 sx_assert(&proctree_lock, SA_XLOCKED); 331 KASSERT(p->p_procdesc != NULL, ("procdesc_reap: p_procdesc == NULL")); 332 333 pd = p->p_procdesc; 334 pd->pd_proc = NULL; 335 p->p_procdesc = NULL; 336 procdesc_free(pd); 337 } 338 339 /* 340 * procdesc_close() - last close on a process descriptor. If the process is 341 * still running, terminate with SIGKILL (unless PDF_DAEMON is set) and let 342 * its reaper clean up the mess; if not, we have to clean up the zombie 343 * 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 AUDIT_ARG_PROCESS(p); 371 if (p->p_state == PRS_ZOMBIE) { 372 /* 373 * If the process is already dead and just awaiting 374 * reaping, do that now. This will release the 375 * process's reference to the process descriptor when it 376 * calls back into procdesc_reap(). 377 */ 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 its reaper (usually init(8)) so 393 * that there's someone to pick up the pieces; finally, 394 * terminate with prejudice. 395 */ 396 p->p_sigparent = SIGCHLD; 397 if ((p->p_flag & P_TRACED) == 0) { 398 proc_reparent(p, p->p_reaper, true); 399 } else { 400 proc_clear_orphan(p); 401 p->p_oppid = p->p_reaper->p_pid; 402 proc_add_orphan(p, p->p_reaper); 403 } 404 if ((pd->pd_flags & PDF_DAEMON) == 0) 405 kern_psignal(p, SIGKILL); 406 PROC_UNLOCK(p); 407 sx_xunlock(&proctree_lock); 408 } 409 } 410 411 /* 412 * Release the file descriptor's reference on the process descriptor. 413 */ 414 procdesc_free(pd); 415 return (0); 416 } 417 418 static int 419 procdesc_poll(struct file *fp, int events, struct ucred *active_cred, 420 struct thread *td) 421 { 422 struct procdesc *pd; 423 int revents; 424 425 revents = 0; 426 pd = fp->f_data; 427 PROCDESC_LOCK(pd); 428 if (pd->pd_flags & PDF_EXITED) 429 revents |= POLLHUP; 430 if (revents == 0) { 431 selrecord(td, &pd->pd_selinfo); 432 pd->pd_flags |= PDF_SELECTED; 433 } 434 PROCDESC_UNLOCK(pd); 435 return (revents); 436 } 437 438 static void 439 procdesc_kqops_detach(struct knote *kn) 440 { 441 struct procdesc *pd; 442 443 pd = kn->kn_fp->f_data; 444 knlist_remove(&pd->pd_selinfo.si_note, kn, 0); 445 } 446 447 static int 448 procdesc_kqops_event(struct knote *kn, long hint) 449 { 450 struct procdesc *pd; 451 u_int event; 452 453 pd = kn->kn_fp->f_data; 454 if (hint == 0) { 455 /* 456 * Initial test after registration. Generate a NOTE_EXIT in 457 * case the process already terminated before registration. 458 */ 459 event = pd->pd_flags & PDF_EXITED ? NOTE_EXIT : 0; 460 } else { 461 /* Mask off extra data. */ 462 event = (u_int)hint & NOTE_PCTRLMASK; 463 } 464 465 /* If the user is interested in this event, record it. */ 466 if (kn->kn_sfflags & event) 467 kn->kn_fflags |= event; 468 469 /* Process is gone, so flag the event as finished. */ 470 if (event == NOTE_EXIT) { 471 kn->kn_flags |= EV_EOF | EV_ONESHOT; 472 if (kn->kn_fflags & NOTE_EXIT) 473 kn->kn_data = pd->pd_xstat; 474 if (kn->kn_fflags == 0) 475 kn->kn_flags |= EV_DROP; 476 return (1); 477 } 478 479 return (kn->kn_fflags != 0); 480 } 481 482 static struct filterops procdesc_kqops = { 483 .f_isfd = 1, 484 .f_detach = procdesc_kqops_detach, 485 .f_event = procdesc_kqops_event, 486 }; 487 488 static int 489 procdesc_kqfilter(struct file *fp, struct knote *kn) 490 { 491 struct procdesc *pd; 492 493 pd = fp->f_data; 494 switch (kn->kn_filter) { 495 case EVFILT_PROCDESC: 496 kn->kn_fop = &procdesc_kqops; 497 kn->kn_flags |= EV_CLEAR; 498 knlist_add(&pd->pd_selinfo.si_note, kn, 0); 499 return (0); 500 default: 501 return (EINVAL); 502 } 503 } 504 505 static int 506 procdesc_stat(struct file *fp, struct stat *sb, struct ucred *active_cred) 507 { 508 struct procdesc *pd; 509 struct timeval pstart, boottime; 510 511 /* 512 * XXXRW: Perhaps we should cache some more information from the 513 * process so that we can return it reliably here even after it has 514 * died. For example, caching its credential data. 515 */ 516 bzero(sb, sizeof(*sb)); 517 pd = fp->f_data; 518 sx_slock(&proctree_lock); 519 if (pd->pd_proc != NULL) { 520 PROC_LOCK(pd->pd_proc); 521 AUDIT_ARG_PROCESS(pd->pd_proc); 522 523 /* Set birth and [acm] times to process start time. */ 524 pstart = pd->pd_proc->p_stats->p_start; 525 getboottime(&boottime); 526 timevaladd(&pstart, &boottime); 527 TIMEVAL_TO_TIMESPEC(&pstart, &sb->st_birthtim); 528 sb->st_atim = sb->st_birthtim; 529 sb->st_ctim = sb->st_birthtim; 530 sb->st_mtim = sb->st_birthtim; 531 if (pd->pd_proc->p_state != PRS_ZOMBIE) 532 sb->st_mode = S_IFREG | S_IRWXU; 533 else 534 sb->st_mode = S_IFREG; 535 sb->st_uid = pd->pd_proc->p_ucred->cr_ruid; 536 sb->st_gid = pd->pd_proc->p_ucred->cr_rgid; 537 PROC_UNLOCK(pd->pd_proc); 538 } else 539 sb->st_mode = S_IFREG; 540 sx_sunlock(&proctree_lock); 541 return (0); 542 } 543 544 static int 545 procdesc_fill_kinfo(struct file *fp, struct kinfo_file *kif, 546 struct filedesc *fdp) 547 { 548 struct procdesc *pdp; 549 550 kif->kf_type = KF_TYPE_PROCDESC; 551 pdp = fp->f_data; 552 kif->kf_un.kf_proc.kf_pid = pdp->pd_pid; 553 return (0); 554 } 555