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 88FEATURE(process_descriptors, "Process Descriptors"); 89 90MALLOC_DEFINE(M_PROCDESC, "procdesc", "process descriptors"); 91 92static fo_poll_t procdesc_poll; 93static fo_kqfilter_t procdesc_kqfilter; 94static fo_stat_t procdesc_stat; 95static fo_close_t procdesc_close; 96static fo_fill_kinfo_t procdesc_fill_kinfo; 97static fo_cmp_t procdesc_cmp; 98 99static struct fileops procdesc_ops = { 100 .fo_read = invfo_rdwr, 101 .fo_write = invfo_rdwr, 102 .fo_truncate = invfo_truncate, 103 .fo_ioctl = invfo_ioctl, 104 .fo_poll = procdesc_poll, 105 .fo_kqfilter = procdesc_kqfilter, 106 .fo_stat = procdesc_stat, 107 .fo_close = procdesc_close, 108 .fo_chmod = invfo_chmod, 109 .fo_chown = invfo_chown, 110 .fo_sendfile = invfo_sendfile, 111 .fo_fill_kinfo = procdesc_fill_kinfo, 112 .fo_cmp = procdesc_cmp, 113 .fo_flags = DFLAG_PASSABLE, 114}; 115 116/* 117 * Return a locked process given a process descriptor, or ESRCH if it has 118 * died. 119 */ 120int 121procdesc_find(struct thread *td, int fd, cap_rights_t *rightsp, 122 struct proc **p) 123{ 124 struct procdesc *pd; 125 struct file *fp; 126 int error; 127 128 error = fget(td, fd, rightsp, &fp); 129 if (error) 130 return (error); 131 if (fp->f_type != DTYPE_PROCDESC) { 132 error = EBADF; 133 goto out; 134 } 135 pd = fp->f_data; 136 sx_slock(&proctree_lock); 137 if (pd->pd_proc != NULL) { 138 *p = pd->pd_proc; 139 PROC_LOCK(*p); 140 } else 141 error = ESRCH; 142 sx_sunlock(&proctree_lock); 143out: 144 fdrop(fp, td); 145 return (error); 146} 147 148/* 149 * Function to be used by procstat(1) sysctls when returning procdesc 150 * information. 151 */ 152pid_t 153procdesc_pid(struct file *fp_procdesc) 154{ 155 struct procdesc *pd; 156 157 KASSERT(fp_procdesc->f_type == DTYPE_PROCDESC, 158 ("procdesc_pid: !procdesc")); 159 160 pd = fp_procdesc->f_data; 161 return (pd->pd_pid); 162} 163 164/* 165 * Retrieve the PID associated with a process descriptor. 166 */ 167int 168kern_pdgetpid(struct thread *td, int fd, cap_rights_t *rightsp, pid_t *pidp) 169{ 170 struct file *fp; 171 int error; 172 173 error = fget(td, fd, rightsp, &fp); 174 if (error) 175 return (error); 176 if (fp->f_type != DTYPE_PROCDESC) { 177 error = EBADF; 178 goto out; 179 } 180 *pidp = procdesc_pid(fp); 181out: 182 fdrop(fp, td); 183 return (error); 184} 185 186/* 187 * System call to return the pid of a process given its process descriptor. 188 */ 189int 190sys_pdgetpid(struct thread *td, struct pdgetpid_args *uap) 191{ 192 pid_t pid; 193 int error; 194 195 AUDIT_ARG_FD(uap->fd); 196 error = kern_pdgetpid(td, uap->fd, &cap_pdgetpid_rights, &pid); 197 if (error == 0) 198 error = copyout(&pid, uap->pidp, sizeof(pid)); 199 return (error); 200} 201 202/* 203 * When a new process is forked by pdfork(), a file descriptor is allocated 204 * by the fork code first, then the process is forked, and then we get a 205 * chance to set up the process descriptor. Failure is not permitted at this 206 * point, so procdesc_new() must succeed. 207 */ 208void 209procdesc_new(struct proc *p, int flags) 210{ 211 struct procdesc *pd; 212 213 pd = malloc(sizeof(*pd), M_PROCDESC, M_WAITOK | M_ZERO); 214 pd->pd_proc = p; 215 pd->pd_pid = p->p_pid; 216 p->p_procdesc = pd; 217 pd->pd_flags = 0; 218 if (flags & PD_DAEMON) 219 pd->pd_flags |= PDF_DAEMON; 220 PROCDESC_LOCK_INIT(pd); 221 knlist_init_mtx(&pd->pd_selinfo.si_note, &pd->pd_lock); 222 223 /* 224 * Process descriptors start out with two references: one from their 225 * struct file, and the other from their struct proc. 226 */ 227 refcount_init(&pd->pd_refcount, 2); 228} 229 230/* 231 * Create a new process decriptor for the process that refers to it. 232 */ 233int 234procdesc_falloc(struct thread *td, struct file **resultfp, int *resultfd, 235 int flags, struct filecaps *fcaps) 236{ 237 int fflags; 238 239 fflags = 0; 240 if (flags & PD_CLOEXEC) 241 fflags = O_CLOEXEC; 242 243 return (falloc_caps(td, resultfp, resultfd, fflags, fcaps)); 244} 245 246/* 247 * Initialize a file with a process descriptor. 248 */ 249void 250procdesc_finit(struct procdesc *pdp, struct file *fp) 251{ 252 253 finit(fp, FREAD | FWRITE, DTYPE_PROCDESC, pdp, &procdesc_ops); 254} 255 256static void 257procdesc_free(struct procdesc *pd) 258{ 259 260 /* 261 * When the last reference is released, we assert that the descriptor 262 * has been closed, but not that the process has exited, as we will 263 * detach the descriptor before the process dies if the descript is 264 * closed, as we can't wait synchronously. 265 */ 266 if (refcount_release(&pd->pd_refcount)) { 267 KASSERT(pd->pd_proc == NULL, 268 ("procdesc_free: pd_proc != NULL")); 269 KASSERT((pd->pd_flags & PDF_CLOSED), 270 ("procdesc_free: !PDF_CLOSED")); 271 272 knlist_destroy(&pd->pd_selinfo.si_note); 273 PROCDESC_LOCK_DESTROY(pd); 274 free(pd, M_PROCDESC); 275 } 276} 277 278/* 279 * procdesc_exit() - notify a process descriptor that its process is exiting. 280 * We use the proctree_lock to ensure that process exit either happens 281 * strictly before or strictly after a concurrent call to procdesc_close(). 282 */ 283int 284procdesc_exit(struct proc *p) 285{ 286 struct procdesc *pd; 287 288 sx_assert(&proctree_lock, SA_XLOCKED); 289 PROC_LOCK_ASSERT(p, MA_OWNED); 290 KASSERT(p->p_procdesc != NULL, ("procdesc_exit: p_procdesc NULL")); 291 292 pd = p->p_procdesc; 293 294 PROCDESC_LOCK(pd); 295 KASSERT((pd->pd_flags & PDF_CLOSED) == 0 || p->p_pptr == p->p_reaper, 296 ("procdesc_exit: closed && parent not reaper")); 297 298 pd->pd_flags |= PDF_EXITED; 299 pd->pd_xstat = KW_EXITCODE(p->p_xexit, p->p_xsig); 300 301 /* 302 * If the process descriptor has been closed, then we have nothing 303 * to do; return 1 so that init will get SIGCHLD and do the reaping. 304 * Clean up the procdesc now rather than letting it happen during 305 * that reap. 306 */ 307 if (pd->pd_flags & PDF_CLOSED) { 308 PROCDESC_UNLOCK(pd); 309 pd->pd_proc = NULL; 310 p->p_procdesc = NULL; 311 procdesc_free(pd); 312 return (1); 313 } 314 if (pd->pd_flags & PDF_SELECTED) { 315 pd->pd_flags &= ~PDF_SELECTED; 316 selwakeup(&pd->pd_selinfo); 317 } 318 KNOTE_LOCKED(&pd->pd_selinfo.si_note, NOTE_EXIT); 319 PROCDESC_UNLOCK(pd); 320 return (0); 321} 322 323/* 324 * When a process descriptor is reaped, perhaps as a result of close(), release 325 * the process's reference on the process descriptor. 326 */ 327void 328procdesc_reap(struct proc *p) 329{ 330 struct procdesc *pd; 331 332 sx_assert(&proctree_lock, SA_XLOCKED); 333 KASSERT(p->p_procdesc != NULL, ("procdesc_reap: p_procdesc == NULL")); 334 335 pd = p->p_procdesc; 336 pd->pd_proc = NULL; 337 p->p_procdesc = NULL; 338 procdesc_free(pd); 339} 340 341/* 342 * procdesc_close() - last close on a process descriptor. If the process is 343 * still running, terminate with SIGKILL (unless PDF_DAEMON is set) and let 344 * its reaper clean up the mess; if not, we have to clean up the zombie 345 * ourselves. 346 */ 347static int 348procdesc_close(struct file *fp, struct thread *td) 349{ 350 struct procdesc *pd; 351 struct proc *p; 352 353 KASSERT(fp->f_type == DTYPE_PROCDESC, ("procdesc_close: !procdesc")); 354 355 pd = fp->f_data; 356 fp->f_ops = &badfileops; 357 fp->f_data = NULL; 358 359 sx_xlock(&proctree_lock); 360 PROCDESC_LOCK(pd); 361 pd->pd_flags |= PDF_CLOSED; 362 PROCDESC_UNLOCK(pd); 363 p = pd->pd_proc; 364 if (p == NULL) { 365 /* 366 * This is the case where process' exit status was already 367 * collected and procdesc_reap() was already called. 368 */ 369 sx_xunlock(&proctree_lock); 370 } else { 371 PROC_LOCK(p); 372 AUDIT_ARG_PROCESS(p); 373 if (p->p_state == PRS_ZOMBIE) { 374 /* 375 * If the process is already dead and just awaiting 376 * reaping, do that now. This will release the 377 * process's reference to the process descriptor when it 378 * calls back into procdesc_reap(). 379 */ 380 proc_reap(curthread, p, NULL, 0); 381 } else { 382 /* 383 * If the process is not yet dead, we need to kill it, 384 * but we can't wait around synchronously for it to go 385 * away, as that path leads to madness (and deadlocks). 386 * First, detach the process from its descriptor so that 387 * its exit status will be reported normally. 388 */ 389 pd->pd_proc = NULL; 390 p->p_procdesc = NULL; 391 procdesc_free(pd); 392 393 /* 394 * Next, reparent it to its reaper (usually init(8)) so 395 * that there's someone to pick up the pieces; finally, 396 * terminate with prejudice. 397 */ 398 p->p_sigparent = SIGCHLD; 399 if ((p->p_flag & P_TRACED) == 0) { 400 proc_reparent(p, p->p_reaper, true); 401 } else { 402 proc_clear_orphan(p); 403 p->p_oppid = p->p_reaper->p_pid; 404 proc_add_orphan(p, p->p_reaper); 405 } 406 if ((pd->pd_flags & PDF_DAEMON) == 0) 407 kern_psignal(p, SIGKILL); 408 PROC_UNLOCK(p); 409 sx_xunlock(&proctree_lock); 410 } 411 } 412 413 /* 414 * Release the file descriptor's reference on the process descriptor. 415 */ 416 procdesc_free(pd); 417 return (0); 418} 419 420static int 421procdesc_poll(struct file *fp, int events, struct ucred *active_cred, 422 struct thread *td) 423{ 424 struct procdesc *pd; 425 int revents; 426 427 revents = 0; 428 pd = fp->f_data; 429 PROCDESC_LOCK(pd); 430 if (pd->pd_flags & PDF_EXITED) 431 revents |= POLLHUP; 432 if (revents == 0) { 433 selrecord(td, &pd->pd_selinfo); 434 pd->pd_flags |= PDF_SELECTED; 435 } 436 PROCDESC_UNLOCK(pd); 437 return (revents); 438} 439 440static void 441procdesc_kqops_detach(struct knote *kn) 442{ 443 struct procdesc *pd; 444 445 pd = kn->kn_fp->f_data; 446 knlist_remove(&pd->pd_selinfo.si_note, kn, 0); 447} 448 449static int 450procdesc_kqops_event(struct knote *kn, long hint) 451{ 452 struct procdesc *pd; 453 u_int event; 454 455 pd = kn->kn_fp->f_data; 456 if (hint == 0) { 457 /* 458 * Initial test after registration. Generate a NOTE_EXIT in 459 * case the process already terminated before registration. 460 */ 461 event = pd->pd_flags & PDF_EXITED ? NOTE_EXIT : 0; 462 } else { 463 /* Mask off extra data. */ 464 event = (u_int)hint & NOTE_PCTRLMASK; 465 } 466 467 /* If the user is interested in this event, record it. */ 468 if (kn->kn_sfflags & event) 469 kn->kn_fflags |= event; 470 471 /* Process is gone, so flag the event as finished. */ 472 if (event == NOTE_EXIT) { 473 kn->kn_flags |= EV_EOF | EV_ONESHOT; 474 if (kn->kn_fflags & NOTE_EXIT) 475 kn->kn_data = pd->pd_xstat; 476 if (kn->kn_fflags == 0) 477 kn->kn_flags |= EV_DROP; 478 return (1); 479 } 480 481 return (kn->kn_fflags != 0); 482} 483 484static struct filterops procdesc_kqops = { 485 .f_isfd = 1, 486 .f_detach = procdesc_kqops_detach, 487 .f_event = procdesc_kqops_event, 488}; 489 490static int 491procdesc_kqfilter(struct file *fp, struct knote *kn) 492{ 493 struct procdesc *pd; 494 495 pd = fp->f_data; 496 switch (kn->kn_filter) { 497 case EVFILT_PROCDESC: 498 kn->kn_fop = &procdesc_kqops; 499 kn->kn_flags |= EV_CLEAR; 500 knlist_add(&pd->pd_selinfo.si_note, kn, 0); 501 return (0); 502 default: 503 return (EINVAL); 504 } 505} 506 507static int 508procdesc_stat(struct file *fp, struct stat *sb, struct ucred *active_cred) 509{ 510 struct procdesc *pd; 511 struct timeval pstart, boottime; 512 513 /* 514 * XXXRW: Perhaps we should cache some more information from the 515 * process so that we can return it reliably here even after it has 516 * died. For example, caching its credential data. 517 */ 518 bzero(sb, sizeof(*sb)); 519 pd = fp->f_data; 520 sx_slock(&proctree_lock); 521 if (pd->pd_proc != NULL) { 522 PROC_LOCK(pd->pd_proc); 523 AUDIT_ARG_PROCESS(pd->pd_proc); 524 525 /* Set birth and [acm] times to process start time. */ 526 pstart = pd->pd_proc->p_stats->p_start; 527 getboottime(&boottime); 528 timevaladd(&pstart, &boottime); 529 TIMEVAL_TO_TIMESPEC(&pstart, &sb->st_birthtim); 530 sb->st_atim = sb->st_birthtim; 531 sb->st_ctim = sb->st_birthtim; 532 sb->st_mtim = sb->st_birthtim; 533 if (pd->pd_proc->p_state != PRS_ZOMBIE) 534 sb->st_mode = S_IFREG | S_IRWXU; 535 else 536 sb->st_mode = S_IFREG; 537 sb->st_uid = pd->pd_proc->p_ucred->cr_ruid; 538 sb->st_gid = pd->pd_proc->p_ucred->cr_rgid; 539 PROC_UNLOCK(pd->pd_proc); 540 } else 541 sb->st_mode = S_IFREG; 542 sx_sunlock(&proctree_lock); 543 return (0); 544} 545 546static int 547procdesc_fill_kinfo(struct file *fp, struct kinfo_file *kif, 548 struct filedesc *fdp) 549{ 550 struct procdesc *pdp; 551 552 kif->kf_type = KF_TYPE_PROCDESC; 553 pdp = fp->f_data; 554 kif->kf_un.kf_proc.kf_pid = pdp->pd_pid; 555 return (0); 556} 557 558static int 559procdesc_cmp(struct file *fp1, struct file *fp2, struct thread *td) 560{ 561 struct procdesc *pdp1, *pdp2; 562 563 if (fp2->f_type != DTYPE_PROCDESC) 564 return (3); 565 pdp1 = fp1->f_data; 566 pdp2 = fp2->f_data; 567 return (kcmp_cmp((uintptr_t)pdp1->pd_pid, (uintptr_t)pdp2->pd_pid)); 568} 569