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 * - How to handle ptrace(2)? 64 * - Will we want to add a pidtoprocdesc(2) system call to allow process 65 * descriptors to be created for processes without pdfork(2)? 66 */ 67 68#include <sys/cdefs.h> 69__FBSDID("$FreeBSD$"); 70 71#include <sys/param.h> 72#include <sys/capsicum.h> 73#include <sys/fcntl.h> 74#include <sys/file.h> 75#include <sys/filedesc.h> 76#include <sys/kernel.h> 77#include <sys/lock.h> 78#include <sys/mutex.h> 79#include <sys/poll.h> 80#include <sys/proc.h> 81#include <sys/procdesc.h> 82#include <sys/resourcevar.h> 83#include <sys/stat.h> 84#include <sys/sysproto.h> 85#include <sys/sysctl.h> 86#include <sys/systm.h> 87#include <sys/ucred.h> 88#include <sys/user.h> 89 90#include <security/audit/audit.h> 91 92#include <vm/uma.h> 93 94FEATURE(process_descriptors, "Process Descriptors"); 95 96static uma_zone_t procdesc_zone; 97 98static fo_poll_t procdesc_poll; 99static fo_kqfilter_t procdesc_kqfilter; 100static fo_stat_t procdesc_stat; 101static fo_close_t procdesc_close; 102static fo_fill_kinfo_t procdesc_fill_kinfo; 103 104static struct fileops procdesc_ops = { 105 .fo_read = invfo_rdwr, 106 .fo_write = invfo_rdwr, 107 .fo_truncate = invfo_truncate, 108 .fo_ioctl = invfo_ioctl, 109 .fo_poll = procdesc_poll, 110 .fo_kqfilter = procdesc_kqfilter, 111 .fo_stat = procdesc_stat, 112 .fo_close = procdesc_close, 113 .fo_chmod = invfo_chmod, 114 .fo_chown = invfo_chown, 115 .fo_sendfile = invfo_sendfile, 116 .fo_fill_kinfo = procdesc_fill_kinfo, 117 .fo_flags = DFLAG_PASSABLE, 118}; 119 120/* 121 * Initialize with VFS so that process descriptors are available along with 122 * other file descriptor types. As long as it runs before init(8) starts, 123 * there shouldn't be a problem. 124 */ 125static void 126procdesc_init(void *dummy __unused) 127{ 128 129 procdesc_zone = uma_zcreate("procdesc", sizeof(struct procdesc), 130 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0); 131 if (procdesc_zone == NULL) 132 panic("procdesc_init: procdesc_zone not initialized"); 133} 134SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_ANY, procdesc_init, NULL); 135 136/* 137 * Return a locked process given a process descriptor, or ESRCH if it has 138 * died. 139 */ 140int 141procdesc_find(struct thread *td, int fd, cap_rights_t *rightsp, 142 struct proc **p) 143{ 144 struct procdesc *pd; 145 struct file *fp; 146 int error; 147 148 error = fget(td, fd, rightsp, &fp); 149 if (error) 150 return (error); 151 if (fp->f_type != DTYPE_PROCDESC) { 152 error = EBADF; 153 goto out; 154 } 155 pd = fp->f_data; 156 sx_slock(&proctree_lock); 157 if (pd->pd_proc != NULL) { 158 *p = pd->pd_proc; 159 PROC_LOCK(*p); 160 } else 161 error = ESRCH; 162 sx_sunlock(&proctree_lock); 163out: 164 fdrop(fp, td); 165 return (error); 166} 167 168/* 169 * Function to be used by procstat(1) sysctls when returning procdesc 170 * information. 171 */ 172pid_t 173procdesc_pid(struct file *fp_procdesc) 174{ 175 struct procdesc *pd; 176 177 KASSERT(fp_procdesc->f_type == DTYPE_PROCDESC, 178 ("procdesc_pid: !procdesc")); 179 180 pd = fp_procdesc->f_data; 181 return (pd->pd_pid); 182} 183 184/* 185 * Retrieve the PID associated with a process descriptor. 186 */ 187int 188kern_pdgetpid(struct thread *td, int fd, cap_rights_t *rightsp, pid_t *pidp) 189{ 190 struct file *fp; 191 int error; 192 193 error = fget(td, fd, rightsp, &fp); 194 if (error) 195 return (error); 196 if (fp->f_type != DTYPE_PROCDESC) { 197 error = EBADF; 198 goto out; 199 } 200 *pidp = procdesc_pid(fp); 201out: 202 fdrop(fp, td); 203 return (error); 204} 205 206/* 207 * System call to return the pid of a process given its process descriptor. 208 */ 209int 210sys_pdgetpid(struct thread *td, struct pdgetpid_args *uap) 211{ 212 pid_t pid; 213 int error; 214 215 AUDIT_ARG_FD(uap->fd); 216 error = kern_pdgetpid(td, uap->fd, &cap_pdgetpid_rights, &pid); 217 if (error == 0) 218 error = copyout(&pid, uap->pidp, sizeof(pid)); 219 return (error); 220} 221 222/* 223 * When a new process is forked by pdfork(), a file descriptor is allocated 224 * by the fork code first, then the process is forked, and then we get a 225 * chance to set up the process descriptor. Failure is not permitted at this 226 * point, so procdesc_new() must succeed. 227 */ 228void 229procdesc_new(struct proc *p, int flags) 230{ 231 struct procdesc *pd; 232 233 pd = uma_zalloc(procdesc_zone, M_WAITOK | M_ZERO); 234 pd->pd_proc = p; 235 pd->pd_pid = p->p_pid; 236 p->p_procdesc = pd; 237 pd->pd_flags = 0; 238 if (flags & PD_DAEMON) 239 pd->pd_flags |= PDF_DAEMON; 240 PROCDESC_LOCK_INIT(pd); 241 knlist_init_mtx(&pd->pd_selinfo.si_note, &pd->pd_lock); 242 243 /* 244 * Process descriptors start out with two references: one from their 245 * struct file, and the other from their struct proc. 246 */ 247 refcount_init(&pd->pd_refcount, 2); 248} 249 250/* 251 * Create a new process decriptor for the process that refers to it. 252 */ 253int 254procdesc_falloc(struct thread *td, struct file **resultfp, int *resultfd, 255 int flags, struct filecaps *fcaps) 256{ 257 int fflags; 258 259 fflags = 0; 260 if (flags & PD_CLOEXEC) 261 fflags = O_CLOEXEC; 262 263 return (falloc_caps(td, resultfp, resultfd, fflags, fcaps)); 264} 265 266/* 267 * Initialize a file with a process descriptor. 268 */ 269void 270procdesc_finit(struct procdesc *pdp, struct file *fp) 271{ 272 273 finit(fp, FREAD | FWRITE, DTYPE_PROCDESC, pdp, &procdesc_ops); 274} 275 276static void 277procdesc_free(struct procdesc *pd) 278{ 279 280 /* 281 * When the last reference is released, we assert that the descriptor 282 * has been closed, but not that the process has exited, as we will 283 * detach the descriptor before the process dies if the descript is 284 * closed, as we can't wait synchronously. 285 */ 286 if (refcount_release(&pd->pd_refcount)) { 287 KASSERT(pd->pd_proc == NULL, 288 ("procdesc_free: pd_proc != NULL")); 289 KASSERT((pd->pd_flags & PDF_CLOSED), 290 ("procdesc_free: !PDF_CLOSED")); 291 292 knlist_destroy(&pd->pd_selinfo.si_note); 293 PROCDESC_LOCK_DESTROY(pd); 294 uma_zfree(procdesc_zone, pd); 295 } 296} 297 298/* 299 * procdesc_exit() - notify a process descriptor that its process is exiting. 300 * We use the proctree_lock to ensure that process exit either happens 301 * strictly before or strictly after a concurrent call to procdesc_close(). 302 */ 303int 304procdesc_exit(struct proc *p) 305{ 306 struct procdesc *pd; 307 308 sx_assert(&proctree_lock, SA_XLOCKED); 309 PROC_LOCK_ASSERT(p, MA_OWNED); 310 KASSERT(p->p_procdesc != NULL, ("procdesc_exit: p_procdesc NULL")); 311 312 pd = p->p_procdesc; 313 314 PROCDESC_LOCK(pd); 315 KASSERT((pd->pd_flags & PDF_CLOSED) == 0 || p->p_pptr == p->p_reaper, 316 ("procdesc_exit: closed && parent not reaper")); 317 318 pd->pd_flags |= PDF_EXITED; 319 pd->pd_xstat = KW_EXITCODE(p->p_xexit, p->p_xsig); 320 321 /* 322 * If the process descriptor has been closed, then we have nothing 323 * to do; return 1 so that init will get SIGCHLD and do the reaping. 324 * Clean up the procdesc now rather than letting it happen during 325 * that reap. 326 */ 327 if (pd->pd_flags & PDF_CLOSED) { 328 PROCDESC_UNLOCK(pd); 329 pd->pd_proc = NULL; 330 p->p_procdesc = NULL; 331 procdesc_free(pd); 332 return (1); 333 } 334 if (pd->pd_flags & PDF_SELECTED) { 335 pd->pd_flags &= ~PDF_SELECTED; 336 selwakeup(&pd->pd_selinfo); 337 } 338 KNOTE_LOCKED(&pd->pd_selinfo.si_note, NOTE_EXIT); 339 PROCDESC_UNLOCK(pd); 340 return (0); 341} 342 343/* 344 * When a process descriptor is reaped, perhaps as a result of close() or 345 * pdwait4(), release the process's reference on the process descriptor. 346 */ 347void 348procdesc_reap(struct proc *p) 349{ 350 struct procdesc *pd; 351 352 sx_assert(&proctree_lock, SA_XLOCKED); 353 KASSERT(p->p_procdesc != NULL, ("procdesc_reap: p_procdesc == NULL")); 354 355 pd = p->p_procdesc; 356 pd->pd_proc = NULL; 357 p->p_procdesc = NULL; 358 procdesc_free(pd); 359} 360 361/* 362 * procdesc_close() - last close on a process descriptor. If the process is 363 * still running, terminate with SIGKILL (unless PDF_DAEMON is set) and let 364 * its reaper clean up the mess; if not, we have to clean up the zombie 365 * ourselves. 366 */ 367static int 368procdesc_close(struct file *fp, struct thread *td) 369{ 370 struct procdesc *pd; 371 struct proc *p; 372 373 KASSERT(fp->f_type == DTYPE_PROCDESC, ("procdesc_close: !procdesc")); 374 375 pd = fp->f_data; 376 fp->f_ops = &badfileops; 377 fp->f_data = NULL; 378 379 sx_xlock(&proctree_lock); 380 PROCDESC_LOCK(pd); 381 pd->pd_flags |= PDF_CLOSED; 382 PROCDESC_UNLOCK(pd); 383 p = pd->pd_proc; 384 if (p == NULL) { 385 /* 386 * This is the case where process' exit status was already 387 * collected and procdesc_reap() was already called. 388 */ 389 sx_xunlock(&proctree_lock); 390 } else { 391 PROC_LOCK(p); 392 AUDIT_ARG_PROCESS(p); 393 if (p->p_state == PRS_ZOMBIE) { 394 /* 395 * If the process is already dead and just awaiting 396 * reaping, do that now. This will release the 397 * process's reference to the process descriptor when it 398 * calls back into procdesc_reap(). 399 */ 400 proc_reap(curthread, p, NULL, 0); 401 } else { 402 /* 403 * If the process is not yet dead, we need to kill it, 404 * but we can't wait around synchronously for it to go 405 * away, as that path leads to madness (and deadlocks). 406 * First, detach the process from its descriptor so that 407 * its exit status will be reported normally. 408 */ 409 pd->pd_proc = NULL; 410 p->p_procdesc = NULL; 411 procdesc_free(pd); 412 413 /* 414 * Next, reparent it to its reaper (usually init(8)) so 415 * that there's someone to pick up the pieces; finally, 416 * terminate with prejudice. 417 */ 418 p->p_sigparent = SIGCHLD; 419 if ((p->p_flag & P_TRACED) == 0) { 420 proc_reparent(p, p->p_reaper, true); 421 } else { 422 proc_clear_orphan(p); 423 p->p_oppid = p->p_reaper->p_pid; 424 proc_add_orphan(p, p->p_reaper); 425 } 426 if ((pd->pd_flags & PDF_DAEMON) == 0) 427 kern_psignal(p, SIGKILL); 428 PROC_UNLOCK(p); 429 sx_xunlock(&proctree_lock); 430 } 431 } 432 433 /* 434 * Release the file descriptor's reference on the process descriptor. 435 */ 436 procdesc_free(pd); 437 return (0); 438} 439 440static int 441procdesc_poll(struct file *fp, int events, struct ucred *active_cred, 442 struct thread *td) 443{ 444 struct procdesc *pd; 445 int revents; 446 447 revents = 0; 448 pd = fp->f_data; 449 PROCDESC_LOCK(pd); 450 if (pd->pd_flags & PDF_EXITED) 451 revents |= POLLHUP; 452 if (revents == 0) { 453 selrecord(td, &pd->pd_selinfo); 454 pd->pd_flags |= PDF_SELECTED; 455 } 456 PROCDESC_UNLOCK(pd); 457 return (revents); 458} 459 460static void 461procdesc_kqops_detach(struct knote *kn) 462{ 463 struct procdesc *pd; 464 465 pd = kn->kn_fp->f_data; 466 knlist_remove(&pd->pd_selinfo.si_note, kn, 0); 467} 468 469static int 470procdesc_kqops_event(struct knote *kn, long hint) 471{ 472 struct procdesc *pd; 473 u_int event; 474 475 pd = kn->kn_fp->f_data; 476 if (hint == 0) { 477 /* 478 * Initial test after registration. Generate a NOTE_EXIT in 479 * case the process already terminated before registration. 480 */ 481 event = pd->pd_flags & PDF_EXITED ? NOTE_EXIT : 0; 482 } else { 483 /* Mask off extra data. */ 484 event = (u_int)hint & NOTE_PCTRLMASK; 485 } 486 487 /* If the user is interested in this event, record it. */ 488 if (kn->kn_sfflags & event) 489 kn->kn_fflags |= event; 490 491 /* Process is gone, so flag the event as finished. */ 492 if (event == NOTE_EXIT) { 493 kn->kn_flags |= EV_EOF | EV_ONESHOT; 494 if (kn->kn_fflags & NOTE_EXIT) 495 kn->kn_data = pd->pd_xstat; 496 if (kn->kn_fflags == 0) 497 kn->kn_flags |= EV_DROP; 498 return (1); 499 } 500 501 return (kn->kn_fflags != 0); 502} 503 504static struct filterops procdesc_kqops = { 505 .f_isfd = 1, 506 .f_detach = procdesc_kqops_detach, 507 .f_event = procdesc_kqops_event, 508}; 509 510static int 511procdesc_kqfilter(struct file *fp, struct knote *kn) 512{ 513 struct procdesc *pd; 514 515 pd = fp->f_data; 516 switch (kn->kn_filter) { 517 case EVFILT_PROCDESC: 518 kn->kn_fop = &procdesc_kqops; 519 kn->kn_flags |= EV_CLEAR; 520 knlist_add(&pd->pd_selinfo.si_note, kn, 0); 521 return (0); 522 default: 523 return (EINVAL); 524 } 525} 526 527static int 528procdesc_stat(struct file *fp, struct stat *sb, struct ucred *active_cred, 529 struct thread *td) 530{ 531 struct procdesc *pd; 532 struct timeval pstart, boottime; 533 534 /* 535 * XXXRW: Perhaps we should cache some more information from the 536 * process so that we can return it reliably here even after it has 537 * died. For example, caching its credential data. 538 */ 539 bzero(sb, sizeof(*sb)); 540 pd = fp->f_data; 541 sx_slock(&proctree_lock); 542 if (pd->pd_proc != NULL) { 543 PROC_LOCK(pd->pd_proc); 544 AUDIT_ARG_PROCESS(pd->pd_proc); 545 546 /* Set birth and [acm] times to process start time. */ 547 pstart = pd->pd_proc->p_stats->p_start; 548 getboottime(&boottime); 549 timevaladd(&pstart, &boottime); 550 TIMEVAL_TO_TIMESPEC(&pstart, &sb->st_birthtim); 551 sb->st_atim = sb->st_birthtim; 552 sb->st_ctim = sb->st_birthtim; 553 sb->st_mtim = sb->st_birthtim; 554 if (pd->pd_proc->p_state != PRS_ZOMBIE) 555 sb->st_mode = S_IFREG | S_IRWXU; 556 else 557 sb->st_mode = S_IFREG; 558 sb->st_uid = pd->pd_proc->p_ucred->cr_ruid; 559 sb->st_gid = pd->pd_proc->p_ucred->cr_rgid; 560 PROC_UNLOCK(pd->pd_proc); 561 } else 562 sb->st_mode = S_IFREG; 563 sx_sunlock(&proctree_lock); 564 return (0); 565} 566 567static int 568procdesc_fill_kinfo(struct file *fp, struct kinfo_file *kif, 569 struct filedesc *fdp) 570{ 571 struct procdesc *pdp; 572 573 kif->kf_type = KF_TYPE_PROCDESC; 574 pdp = fp->f_data; 575 kif->kf_un.kf_proc.kf_pid = pdp->pd_pid; 576 return (0); 577} 578