1/*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1982, 1986, 1989, 1991, 1993 5 * The Regents of the University of California. All rights reserved. 6 * (c) UNIX System Laboratories, Inc. 7 * All or some portions of this file are derived from material licensed 8 * to the University of California by American Telephone and Telegraph 9 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 10 * the permission of UNIX System Laboratories, Inc. 11 * 12 * Redistribution and use in source and binary forms, with or without 13 * modification, are permitted provided that the following conditions 14 * are met: 15 * 1. Redistributions of source code must retain the above copyright 16 * notice, this list of conditions and the following disclaimer. 17 * 2. Redistributions in binary form must reproduce the above copyright 18 * notice, this list of conditions and the following disclaimer in the 19 * documentation and/or other materials provided with the distribution. 20 * 3. Neither the name of the University nor the names of its contributors 21 * may be used to endorse or promote products derived from this software 22 * without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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#include <sys/cdefs.h> 38#include "opt_ktrace.h" 39#include "opt_kstack_pages.h" 40 41#include <sys/param.h> 42#include <sys/systm.h> 43#include <sys/bitstring.h> 44#include <sys/sysproto.h> 45#include <sys/eventhandler.h> 46#include <sys/fcntl.h> 47#include <sys/filedesc.h> 48#include <sys/jail.h> 49#include <sys/kernel.h> 50#include <sys/kthread.h> 51#include <sys/sysctl.h> 52#include <sys/lock.h> 53#include <sys/malloc.h> 54#include <sys/msan.h> 55#include <sys/mutex.h> 56#include <sys/priv.h> 57#include <sys/proc.h> 58#include <sys/procdesc.h> 59#include <sys/ptrace.h> 60#include <sys/racct.h> 61#include <sys/resourcevar.h> 62#include <sys/sched.h> 63#include <sys/syscall.h> 64#include <sys/vmmeter.h> 65#include <sys/vnode.h> 66#include <sys/acct.h> 67#include <sys/ktr.h> 68#include <sys/ktrace.h> 69#include <sys/unistd.h> 70#include <sys/sdt.h> 71#include <sys/sx.h> 72#include <sys/sysent.h> 73#include <sys/signalvar.h> 74 75#include <security/audit/audit.h> 76#include <security/mac/mac_framework.h> 77 78#include <vm/vm.h> 79#include <vm/pmap.h> 80#include <vm/vm_map.h> 81#include <vm/vm_extern.h> 82#include <vm/uma.h> 83 84#ifdef KDTRACE_HOOKS 85#include <sys/dtrace_bsd.h> 86dtrace_fork_func_t dtrace_fasttrap_fork; 87#endif 88 89SDT_PROVIDER_DECLARE(proc); 90SDT_PROBE_DEFINE3(proc, , , create, "struct proc *", "struct proc *", "int"); 91 92#ifndef _SYS_SYSPROTO_H_ 93struct fork_args { 94 int dummy; 95}; 96#endif 97 98/* ARGSUSED */ 99int 100sys_fork(struct thread *td, struct fork_args *uap) 101{ 102 struct fork_req fr; 103 int error, pid; 104 105 bzero(&fr, sizeof(fr)); 106 fr.fr_flags = RFFDG | RFPROC; 107 fr.fr_pidp = &pid; 108 error = fork1(td, &fr); 109 if (error == 0) { 110 td->td_retval[0] = pid; 111 td->td_retval[1] = 0; 112 } 113 return (error); 114} 115 116/* ARGUSED */ 117int 118sys_pdfork(struct thread *td, struct pdfork_args *uap) 119{ 120 struct fork_req fr; 121 int error, fd, pid; 122 123 bzero(&fr, sizeof(fr)); 124 fr.fr_flags = RFFDG | RFPROC | RFPROCDESC; 125 fr.fr_pidp = &pid; 126 fr.fr_pd_fd = &fd; 127 fr.fr_pd_flags = uap->flags; 128 AUDIT_ARG_FFLAGS(uap->flags); 129 /* 130 * It is necessary to return fd by reference because 0 is a valid file 131 * descriptor number, and the child needs to be able to distinguish 132 * itself from the parent using the return value. 133 */ 134 error = fork1(td, &fr); 135 if (error == 0) { 136 td->td_retval[0] = pid; 137 td->td_retval[1] = 0; 138 error = copyout(&fd, uap->fdp, sizeof(fd)); 139 } 140 return (error); 141} 142 143/* ARGSUSED */ 144int 145sys_vfork(struct thread *td, struct vfork_args *uap) 146{ 147 struct fork_req fr; 148 int error, pid; 149 150 bzero(&fr, sizeof(fr)); 151 fr.fr_flags = RFFDG | RFPROC | RFPPWAIT | RFMEM; 152 fr.fr_pidp = &pid; 153 error = fork1(td, &fr); 154 if (error == 0) { 155 td->td_retval[0] = pid; 156 td->td_retval[1] = 0; 157 } 158 return (error); 159} 160 161int 162sys_rfork(struct thread *td, struct rfork_args *uap) 163{ 164 struct fork_req fr; 165 int error, pid; 166 167 /* Don't allow kernel-only flags. */ 168 if ((uap->flags & RFKERNELONLY) != 0) 169 return (EINVAL); 170 /* RFSPAWN must not appear with others */ 171 if ((uap->flags & RFSPAWN) != 0 && uap->flags != RFSPAWN) 172 return (EINVAL); 173 174 AUDIT_ARG_FFLAGS(uap->flags); 175 bzero(&fr, sizeof(fr)); 176 if ((uap->flags & RFSPAWN) != 0) { 177 fr.fr_flags = RFFDG | RFPROC | RFPPWAIT | RFMEM; 178 fr.fr_flags2 = FR2_DROPSIG_CAUGHT; 179 } else { 180 fr.fr_flags = uap->flags; 181 } 182 fr.fr_pidp = &pid; 183 error = fork1(td, &fr); 184 if (error == 0) { 185 td->td_retval[0] = pid; 186 td->td_retval[1] = 0; 187 } 188 return (error); 189} 190 191int __exclusive_cache_line nprocs = 1; /* process 0 */ 192int lastpid = 0; 193SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0, 194 "Last used PID"); 195 196/* 197 * Random component to lastpid generation. We mix in a random factor to make 198 * it a little harder to predict. We sanity check the modulus value to avoid 199 * doing it in critical paths. Don't let it be too small or we pointlessly 200 * waste randomness entropy, and don't let it be impossibly large. Using a 201 * modulus that is too big causes a LOT more process table scans and slows 202 * down fork processing as the pidchecked caching is defeated. 203 */ 204static int randompid = 0; 205 206static int 207sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 208{ 209 int error, pid; 210 211 error = sysctl_wire_old_buffer(req, sizeof(int)); 212 if (error != 0) 213 return(error); 214 sx_xlock(&allproc_lock); 215 pid = randompid; 216 error = sysctl_handle_int(oidp, &pid, 0, req); 217 if (error == 0 && req->newptr != NULL) { 218 if (pid == 0) 219 randompid = 0; 220 else if (pid == 1) 221 /* generate a random PID modulus between 100 and 1123 */ 222 randompid = 100 + arc4random() % 1024; 223 else if (pid < 0 || pid > pid_max - 100) 224 /* out of range */ 225 randompid = pid_max - 100; 226 else if (pid < 100) 227 /* Make it reasonable */ 228 randompid = 100; 229 else 230 randompid = pid; 231 } 232 sx_xunlock(&allproc_lock); 233 return (error); 234} 235 236SYSCTL_PROC(_kern, OID_AUTO, randompid, 237 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 0, 238 sysctl_kern_randompid, "I", 239 "Random PID modulus. Special values: 0: disable, 1: choose random value"); 240 241extern bitstr_t proc_id_pidmap; 242extern bitstr_t proc_id_grpidmap; 243extern bitstr_t proc_id_sessidmap; 244extern bitstr_t proc_id_reapmap; 245 246/* 247 * Find an unused process ID 248 * 249 * If RFHIGHPID is set (used during system boot), do not allocate 250 * low-numbered pids. 251 */ 252static int 253fork_findpid(int flags) 254{ 255 pid_t result; 256 int trypid, random; 257 258 /* 259 * Avoid calling arc4random with procid_lock held. 260 */ 261 random = 0; 262 if (__predict_false(randompid)) 263 random = arc4random() % randompid; 264 265 mtx_lock(&procid_lock); 266 267 trypid = lastpid + 1; 268 if (flags & RFHIGHPID) { 269 if (trypid < 10) 270 trypid = 10; 271 } else { 272 trypid += random; 273 } 274retry: 275 if (trypid >= pid_max) 276 trypid = 2; 277 278 bit_ffc_at(&proc_id_pidmap, trypid, pid_max, &result); 279 if (result == -1) { 280 KASSERT(trypid != 2, ("unexpectedly ran out of IDs")); 281 trypid = 2; 282 goto retry; 283 } 284 if (bit_test(&proc_id_grpidmap, result) || 285 bit_test(&proc_id_sessidmap, result) || 286 bit_test(&proc_id_reapmap, result)) { 287 trypid = result + 1; 288 goto retry; 289 } 290 291 /* 292 * RFHIGHPID does not mess with the lastpid counter during boot. 293 */ 294 if ((flags & RFHIGHPID) == 0) 295 lastpid = result; 296 297 bit_set(&proc_id_pidmap, result); 298 mtx_unlock(&procid_lock); 299 300 return (result); 301} 302 303static int 304fork_norfproc(struct thread *td, int flags) 305{ 306 struct proc *p1; 307 int error; 308 309 KASSERT((flags & RFPROC) == 0, 310 ("fork_norfproc called with RFPROC set")); 311 p1 = td->td_proc; 312 313 /* 314 * Quiesce other threads if necessary. If RFMEM is not specified we 315 * must ensure that other threads do not concurrently create a second 316 * process sharing the vmspace, see vmspace_unshare(). 317 */ 318 if ((p1->p_flag & (P_HADTHREADS | P_SYSTEM)) == P_HADTHREADS && 319 ((flags & (RFCFDG | RFFDG)) != 0 || (flags & RFMEM) == 0)) { 320 PROC_LOCK(p1); 321 if (thread_single(p1, SINGLE_BOUNDARY)) { 322 PROC_UNLOCK(p1); 323 return (ERESTART); 324 } 325 PROC_UNLOCK(p1); 326 } 327 328 error = vm_forkproc(td, NULL, NULL, NULL, flags); 329 if (error != 0) 330 goto fail; 331 332 /* 333 * Close all file descriptors. 334 */ 335 if ((flags & RFCFDG) != 0) { 336 struct filedesc *fdtmp; 337 struct pwddesc *pdtmp; 338 339 pdtmp = pdinit(td->td_proc->p_pd, false); 340 fdtmp = fdinit(); 341 pdescfree(td); 342 fdescfree(td); 343 p1->p_fd = fdtmp; 344 p1->p_pd = pdtmp; 345 } 346 347 /* 348 * Unshare file descriptors (from parent). 349 */ 350 if ((flags & RFFDG) != 0) { 351 fdunshare(td); 352 pdunshare(td); 353 } 354 355fail: 356 if ((p1->p_flag & (P_HADTHREADS | P_SYSTEM)) == P_HADTHREADS && 357 ((flags & (RFCFDG | RFFDG)) != 0 || (flags & RFMEM) == 0)) { 358 PROC_LOCK(p1); 359 thread_single_end(p1, SINGLE_BOUNDARY); 360 PROC_UNLOCK(p1); 361 } 362 return (error); 363} 364 365static void 366do_fork(struct thread *td, struct fork_req *fr, struct proc *p2, struct thread *td2, 367 struct vmspace *vm2, struct file *fp_procdesc) 368{ 369 struct proc *p1, *pptr; 370 struct filedesc *fd; 371 struct filedesc_to_leader *fdtol; 372 struct pwddesc *pd; 373 struct sigacts *newsigacts; 374 375 p1 = td->td_proc; 376 377 PROC_LOCK(p1); 378 bcopy(&p1->p_startcopy, &p2->p_startcopy, 379 __rangeof(struct proc, p_startcopy, p_endcopy)); 380 pargs_hold(p2->p_args); 381 PROC_UNLOCK(p1); 382 383 bzero(&p2->p_startzero, 384 __rangeof(struct proc, p_startzero, p_endzero)); 385 386 /* Tell the prison that we exist. */ 387 prison_proc_hold(p2->p_ucred->cr_prison); 388 389 p2->p_state = PRS_NEW; /* protect against others */ 390 p2->p_pid = fork_findpid(fr->fr_flags); 391 AUDIT_ARG_PID(p2->p_pid); 392 TSFORK(p2->p_pid, p1->p_pid); 393 394 sx_xlock(&allproc_lock); 395 LIST_INSERT_HEAD(&allproc, p2, p_list); 396 allproc_gen++; 397 prison_proc_link(p2->p_ucred->cr_prison, p2); 398 sx_xunlock(&allproc_lock); 399 400 sx_xlock(PIDHASHLOCK(p2->p_pid)); 401 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 402 sx_xunlock(PIDHASHLOCK(p2->p_pid)); 403 404 tidhash_add(td2); 405 406 /* 407 * Malloc things while we don't hold any locks. 408 */ 409 if (fr->fr_flags & RFSIGSHARE) 410 newsigacts = NULL; 411 else 412 newsigacts = sigacts_alloc(); 413 414 /* 415 * Copy filedesc. 416 */ 417 if (fr->fr_flags & RFCFDG) { 418 pd = pdinit(p1->p_pd, false); 419 fd = fdinit(); 420 fdtol = NULL; 421 } else if (fr->fr_flags & RFFDG) { 422 if (fr->fr_flags2 & FR2_SHARE_PATHS) 423 pd = pdshare(p1->p_pd); 424 else 425 pd = pdcopy(p1->p_pd); 426 fd = fdcopy(p1->p_fd); 427 fdtol = NULL; 428 } else { 429 if (fr->fr_flags2 & FR2_SHARE_PATHS) 430 pd = pdcopy(p1->p_pd); 431 else 432 pd = pdshare(p1->p_pd); 433 fd = fdshare(p1->p_fd); 434 if (p1->p_fdtol == NULL) 435 p1->p_fdtol = filedesc_to_leader_alloc(NULL, NULL, 436 p1->p_leader); 437 if ((fr->fr_flags & RFTHREAD) != 0) { 438 /* 439 * Shared file descriptor table, and shared 440 * process leaders. 441 */ 442 fdtol = filedesc_to_leader_share(p1->p_fdtol, p1->p_fd); 443 } else { 444 /* 445 * Shared file descriptor table, and different 446 * process leaders. 447 */ 448 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, 449 p1->p_fd, p2); 450 } 451 } 452 /* 453 * Make a proc table entry for the new process. 454 * Start by zeroing the section of proc that is zero-initialized, 455 * then copy the section that is copied directly from the parent. 456 */ 457 458 PROC_LOCK(p2); 459 PROC_LOCK(p1); 460 461 bzero(&td2->td_startzero, 462 __rangeof(struct thread, td_startzero, td_endzero)); 463 464 bcopy(&td->td_startcopy, &td2->td_startcopy, 465 __rangeof(struct thread, td_startcopy, td_endcopy)); 466 467 bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name)); 468 td2->td_sigstk = td->td_sigstk; 469 td2->td_flags = TDF_INMEM; 470 td2->td_lend_user_pri = PRI_MAX; 471 472#ifdef VIMAGE 473 td2->td_vnet = NULL; 474 td2->td_vnet_lpush = NULL; 475#endif 476 477 /* 478 * Allow the scheduler to initialize the child. 479 */ 480 thread_lock(td); 481 sched_fork(td, td2); 482 /* 483 * Request AST to check for TDP_RFPPWAIT. Do it here 484 * to avoid calling thread_lock() again. 485 */ 486 if ((fr->fr_flags & RFPPWAIT) != 0) 487 ast_sched_locked(td, TDA_VFORK); 488 thread_unlock(td); 489 490 /* 491 * Duplicate sub-structures as needed. 492 * Increase reference counts on shared objects. 493 */ 494 p2->p_flag = P_INMEM; 495 p2->p_flag2 = p1->p_flag2 & (P2_ASLR_DISABLE | P2_ASLR_ENABLE | 496 P2_ASLR_IGNSTART | P2_NOTRACE | P2_NOTRACE_EXEC | 497 P2_PROTMAX_ENABLE | P2_PROTMAX_DISABLE | P2_TRAPCAP | 498 P2_STKGAP_DISABLE | P2_STKGAP_DISABLE_EXEC | P2_NO_NEW_PRIVS | 499 P2_WXORX_DISABLE | P2_WXORX_ENABLE_EXEC); 500 p2->p_swtick = ticks; 501 if (p1->p_flag & P_PROFIL) 502 startprofclock(p2); 503 504 if (fr->fr_flags & RFSIGSHARE) { 505 p2->p_sigacts = sigacts_hold(p1->p_sigacts); 506 } else { 507 sigacts_copy(newsigacts, p1->p_sigacts); 508 p2->p_sigacts = newsigacts; 509 if ((fr->fr_flags2 & (FR2_DROPSIG_CAUGHT | FR2_KPROC)) != 0) { 510 mtx_lock(&p2->p_sigacts->ps_mtx); 511 if ((fr->fr_flags2 & FR2_DROPSIG_CAUGHT) != 0) 512 sig_drop_caught(p2); 513 if ((fr->fr_flags2 & FR2_KPROC) != 0) 514 p2->p_sigacts->ps_flag |= PS_NOCLDWAIT; 515 mtx_unlock(&p2->p_sigacts->ps_mtx); 516 } 517 } 518 519 if (fr->fr_flags & RFTSIGZMB) 520 p2->p_sigparent = RFTSIGNUM(fr->fr_flags); 521 else if (fr->fr_flags & RFLINUXTHPN) 522 p2->p_sigparent = SIGUSR1; 523 else 524 p2->p_sigparent = SIGCHLD; 525 526 if ((fr->fr_flags2 & FR2_KPROC) != 0) { 527 p2->p_flag |= P_SYSTEM | P_KPROC; 528 td2->td_pflags |= TDP_KTHREAD; 529 } 530 531 p2->p_textvp = p1->p_textvp; 532 p2->p_textdvp = p1->p_textdvp; 533 p2->p_fd = fd; 534 p2->p_fdtol = fdtol; 535 p2->p_pd = pd; 536 537 if (p1->p_flag2 & P2_INHERIT_PROTECTED) { 538 p2->p_flag |= P_PROTECTED; 539 p2->p_flag2 |= P2_INHERIT_PROTECTED; 540 } 541 542 /* 543 * p_limit is copy-on-write. Bump its refcount. 544 */ 545 lim_fork(p1, p2); 546 547 thread_cow_get_proc(td2, p2); 548 549 pstats_fork(p1->p_stats, p2->p_stats); 550 551 PROC_UNLOCK(p1); 552 PROC_UNLOCK(p2); 553 554 /* 555 * Bump references to the text vnode and directory, and copy 556 * the hardlink name. 557 */ 558 if (p2->p_textvp != NULL) 559 vrefact(p2->p_textvp); 560 if (p2->p_textdvp != NULL) 561 vrefact(p2->p_textdvp); 562 p2->p_binname = p1->p_binname == NULL ? NULL : 563 strdup(p1->p_binname, M_PARGS); 564 565 /* 566 * Set up linkage for kernel based threading. 567 */ 568 if ((fr->fr_flags & RFTHREAD) != 0) { 569 mtx_lock(&ppeers_lock); 570 p2->p_peers = p1->p_peers; 571 p1->p_peers = p2; 572 p2->p_leader = p1->p_leader; 573 mtx_unlock(&ppeers_lock); 574 PROC_LOCK(p1->p_leader); 575 if ((p1->p_leader->p_flag & P_WEXIT) != 0) { 576 PROC_UNLOCK(p1->p_leader); 577 /* 578 * The task leader is exiting, so process p1 is 579 * going to be killed shortly. Since p1 obviously 580 * isn't dead yet, we know that the leader is either 581 * sending SIGKILL's to all the processes in this 582 * task or is sleeping waiting for all the peers to 583 * exit. We let p1 complete the fork, but we need 584 * to go ahead and kill the new process p2 since 585 * the task leader may not get a chance to send 586 * SIGKILL to it. We leave it on the list so that 587 * the task leader will wait for this new process 588 * to commit suicide. 589 */ 590 PROC_LOCK(p2); 591 kern_psignal(p2, SIGKILL); 592 PROC_UNLOCK(p2); 593 } else 594 PROC_UNLOCK(p1->p_leader); 595 } else { 596 p2->p_peers = NULL; 597 p2->p_leader = p2; 598 } 599 600 sx_xlock(&proctree_lock); 601 PGRP_LOCK(p1->p_pgrp); 602 PROC_LOCK(p2); 603 PROC_LOCK(p1); 604 605 /* 606 * Preserve some more flags in subprocess. P_PROFIL has already 607 * been preserved. 608 */ 609 p2->p_flag |= p1->p_flag & P_SUGID; 610 td2->td_pflags |= (td->td_pflags & (TDP_ALTSTACK | TDP_SIGFASTBLOCK)); 611 SESS_LOCK(p1->p_session); 612 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 613 p2->p_flag |= P_CONTROLT; 614 SESS_UNLOCK(p1->p_session); 615 if (fr->fr_flags & RFPPWAIT) 616 p2->p_flag |= P_PPWAIT; 617 618 p2->p_pgrp = p1->p_pgrp; 619 LIST_INSERT_AFTER(p1, p2, p_pglist); 620 PGRP_UNLOCK(p1->p_pgrp); 621 LIST_INIT(&p2->p_children); 622 LIST_INIT(&p2->p_orphans); 623 624 callout_init_mtx(&p2->p_itcallout, &p2->p_mtx, 0); 625 626 /* 627 * This begins the section where we must prevent the parent 628 * from being swapped. 629 */ 630 _PHOLD(p1); 631 PROC_UNLOCK(p1); 632 633 /* 634 * Attach the new process to its parent. 635 * 636 * If RFNOWAIT is set, the newly created process becomes a child 637 * of init. This effectively disassociates the child from the 638 * parent. 639 */ 640 if ((fr->fr_flags & RFNOWAIT) != 0) { 641 pptr = p1->p_reaper; 642 p2->p_reaper = pptr; 643 } else { 644 p2->p_reaper = (p1->p_treeflag & P_TREE_REAPER) != 0 ? 645 p1 : p1->p_reaper; 646 pptr = p1; 647 } 648 p2->p_pptr = pptr; 649 p2->p_oppid = pptr->p_pid; 650 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 651 LIST_INIT(&p2->p_reaplist); 652 LIST_INSERT_HEAD(&p2->p_reaper->p_reaplist, p2, p_reapsibling); 653 if (p2->p_reaper == p1 && p1 != initproc) { 654 p2->p_reapsubtree = p2->p_pid; 655 proc_id_set_cond(PROC_ID_REAP, p2->p_pid); 656 } 657 sx_xunlock(&proctree_lock); 658 659 /* Inform accounting that we have forked. */ 660 p2->p_acflag = AFORK; 661 PROC_UNLOCK(p2); 662 663#ifdef KTRACE 664 ktrprocfork(p1, p2); 665#endif 666 667 /* 668 * Finish creating the child process. It will return via a different 669 * execution path later. (ie: directly into user mode) 670 */ 671 vm_forkproc(td, p2, td2, vm2, fr->fr_flags); 672 673 if (fr->fr_flags == (RFFDG | RFPROC)) { 674 VM_CNT_INC(v_forks); 675 VM_CNT_ADD(v_forkpages, p2->p_vmspace->vm_dsize + 676 p2->p_vmspace->vm_ssize); 677 } else if (fr->fr_flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 678 VM_CNT_INC(v_vforks); 679 VM_CNT_ADD(v_vforkpages, p2->p_vmspace->vm_dsize + 680 p2->p_vmspace->vm_ssize); 681 } else if (p1 == &proc0) { 682 VM_CNT_INC(v_kthreads); 683 VM_CNT_ADD(v_kthreadpages, p2->p_vmspace->vm_dsize + 684 p2->p_vmspace->vm_ssize); 685 } else { 686 VM_CNT_INC(v_rforks); 687 VM_CNT_ADD(v_rforkpages, p2->p_vmspace->vm_dsize + 688 p2->p_vmspace->vm_ssize); 689 } 690 691 /* 692 * Associate the process descriptor with the process before anything 693 * can happen that might cause that process to need the descriptor. 694 * However, don't do this until after fork(2) can no longer fail. 695 */ 696 if (fr->fr_flags & RFPROCDESC) 697 procdesc_new(p2, fr->fr_pd_flags); 698 699 /* 700 * Both processes are set up, now check if any loadable modules want 701 * to adjust anything. 702 */ 703 EVENTHANDLER_DIRECT_INVOKE(process_fork, p1, p2, fr->fr_flags); 704 705 /* 706 * Set the child start time and mark the process as being complete. 707 */ 708 PROC_LOCK(p2); 709 PROC_LOCK(p1); 710 microuptime(&p2->p_stats->p_start); 711 PROC_SLOCK(p2); 712 p2->p_state = PRS_NORMAL; 713 PROC_SUNLOCK(p2); 714 715#ifdef KDTRACE_HOOKS 716 /* 717 * Tell the DTrace fasttrap provider about the new process so that any 718 * tracepoints inherited from the parent can be removed. We have to do 719 * this only after p_state is PRS_NORMAL since the fasttrap module will 720 * use pfind() later on. 721 */ 722 if ((fr->fr_flags & RFMEM) == 0 && dtrace_fasttrap_fork) 723 dtrace_fasttrap_fork(p1, p2); 724#endif 725 if (fr->fr_flags & RFPPWAIT) { 726 td->td_pflags |= TDP_RFPPWAIT; 727 td->td_rfppwait_p = p2; 728 td->td_dbgflags |= TDB_VFORK; 729 } 730 PROC_UNLOCK(p2); 731 732 /* 733 * Tell any interested parties about the new process. 734 */ 735 knote_fork(p1->p_klist, p2->p_pid); 736 737 /* 738 * Now can be swapped. 739 */ 740 _PRELE(p1); 741 PROC_UNLOCK(p1); 742 SDT_PROBE3(proc, , , create, p2, p1, fr->fr_flags); 743 744 if (fr->fr_flags & RFPROCDESC) { 745 procdesc_finit(p2->p_procdesc, fp_procdesc); 746 fdrop(fp_procdesc, td); 747 } 748 749 /* 750 * Speculative check for PTRACE_FORK. PTRACE_FORK is not 751 * synced with forks in progress so it is OK if we miss it 752 * if being set atm. 753 */ 754 if ((p1->p_ptevents & PTRACE_FORK) != 0) { 755 sx_xlock(&proctree_lock); 756 PROC_LOCK(p2); 757 758 /* 759 * p1->p_ptevents & p1->p_pptr are protected by both 760 * process and proctree locks for modifications, 761 * so owning proctree_lock allows the race-free read. 762 */ 763 if ((p1->p_ptevents & PTRACE_FORK) != 0) { 764 /* 765 * Arrange for debugger to receive the fork event. 766 * 767 * We can report PL_FLAG_FORKED regardless of 768 * P_FOLLOWFORK settings, but it does not make a sense 769 * for runaway child. 770 */ 771 td->td_dbgflags |= TDB_FORK; 772 td->td_dbg_forked = p2->p_pid; 773 td2->td_dbgflags |= TDB_STOPATFORK; 774 proc_set_traced(p2, true); 775 CTR2(KTR_PTRACE, 776 "do_fork: attaching to new child pid %d: oppid %d", 777 p2->p_pid, p2->p_oppid); 778 proc_reparent(p2, p1->p_pptr, false); 779 } 780 PROC_UNLOCK(p2); 781 sx_xunlock(&proctree_lock); 782 } 783 784 racct_proc_fork_done(p2); 785 786 if ((fr->fr_flags & RFSTOPPED) == 0) { 787 if (fr->fr_pidp != NULL) 788 *fr->fr_pidp = p2->p_pid; 789 /* 790 * If RFSTOPPED not requested, make child runnable and 791 * add to run queue. 792 */ 793 thread_lock(td2); 794 TD_SET_CAN_RUN(td2); 795 sched_add(td2, SRQ_BORING); 796 } else { 797 *fr->fr_procp = p2; 798 } 799} 800 801static void 802ast_vfork(struct thread *td, int tda __unused) 803{ 804 struct proc *p, *p2; 805 806 MPASS(td->td_pflags & TDP_RFPPWAIT); 807 808 p = td->td_proc; 809 /* 810 * Preserve synchronization semantics of vfork. If 811 * waiting for child to exec or exit, fork set 812 * P_PPWAIT on child, and there we sleep on our proc 813 * (in case of exit). 814 * 815 * Do it after the ptracestop() above is finished, to 816 * not block our debugger until child execs or exits 817 * to finish vfork wait. 818 */ 819 td->td_pflags &= ~TDP_RFPPWAIT; 820 p2 = td->td_rfppwait_p; 821again: 822 PROC_LOCK(p2); 823 while (p2->p_flag & P_PPWAIT) { 824 PROC_LOCK(p); 825 if (thread_suspend_check_needed()) { 826 PROC_UNLOCK(p2); 827 thread_suspend_check(0); 828 PROC_UNLOCK(p); 829 goto again; 830 } else { 831 PROC_UNLOCK(p); 832 } 833 cv_timedwait(&p2->p_pwait, &p2->p_mtx, hz); 834 } 835 PROC_UNLOCK(p2); 836 837 if (td->td_dbgflags & TDB_VFORK) { 838 PROC_LOCK(p); 839 if (p->p_ptevents & PTRACE_VFORK) 840 ptracestop(td, SIGTRAP, NULL); 841 td->td_dbgflags &= ~TDB_VFORK; 842 PROC_UNLOCK(p); 843 } 844} 845 846int 847fork1(struct thread *td, struct fork_req *fr) 848{ 849 struct proc *p1, *newproc; 850 struct thread *td2; 851 struct vmspace *vm2; 852 struct ucred *cred; 853 struct file *fp_procdesc; 854 struct pgrp *pg; 855 vm_ooffset_t mem_charged; 856 int error, nprocs_new; 857 static int curfail; 858 static struct timeval lastfail; 859 int flags, pages; 860 bool killsx_locked, singlethreaded; 861 862 flags = fr->fr_flags; 863 pages = fr->fr_pages; 864 865 if ((flags & RFSTOPPED) != 0) 866 MPASS(fr->fr_procp != NULL && fr->fr_pidp == NULL); 867 else 868 MPASS(fr->fr_procp == NULL); 869 870 /* Check for the undefined or unimplemented flags. */ 871 if ((flags & ~(RFFLAGS | RFTSIGFLAGS(RFTSIGMASK))) != 0) 872 return (EINVAL); 873 874 /* Signal value requires RFTSIGZMB. */ 875 if ((flags & RFTSIGFLAGS(RFTSIGMASK)) != 0 && (flags & RFTSIGZMB) == 0) 876 return (EINVAL); 877 878 /* Can't copy and clear. */ 879 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 880 return (EINVAL); 881 882 /* Check the validity of the signal number. */ 883 if ((flags & RFTSIGZMB) != 0 && (u_int)RFTSIGNUM(flags) > _SIG_MAXSIG) 884 return (EINVAL); 885 886 if ((flags & RFPROCDESC) != 0) { 887 /* Can't not create a process yet get a process descriptor. */ 888 if ((flags & RFPROC) == 0) 889 return (EINVAL); 890 891 /* Must provide a place to put a procdesc if creating one. */ 892 if (fr->fr_pd_fd == NULL) 893 return (EINVAL); 894 895 /* Check if we are using supported flags. */ 896 if ((fr->fr_pd_flags & ~PD_ALLOWED_AT_FORK) != 0) 897 return (EINVAL); 898 } 899 900 p1 = td->td_proc; 901 902 /* 903 * Here we don't create a new process, but we divorce 904 * certain parts of a process from itself. 905 */ 906 if ((flags & RFPROC) == 0) { 907 if (fr->fr_procp != NULL) 908 *fr->fr_procp = NULL; 909 else if (fr->fr_pidp != NULL) 910 *fr->fr_pidp = 0; 911 return (fork_norfproc(td, flags)); 912 } 913 914 fp_procdesc = NULL; 915 newproc = NULL; 916 vm2 = NULL; 917 killsx_locked = false; 918 singlethreaded = false; 919 920 /* 921 * Increment the nprocs resource before allocations occur. 922 * Although process entries are dynamically created, we still 923 * keep a global limit on the maximum number we will 924 * create. There are hard-limits as to the number of processes 925 * that can run, established by the KVA and memory usage for 926 * the process data. 927 * 928 * Don't allow a nonprivileged user to use the last ten 929 * processes; don't let root exceed the limit. 930 */ 931 nprocs_new = atomic_fetchadd_int(&nprocs, 1) + 1; 932 if (nprocs_new >= maxproc - 10) { 933 if (priv_check_cred(td->td_ucred, PRIV_MAXPROC) != 0 || 934 nprocs_new >= maxproc) { 935 error = EAGAIN; 936 sx_xlock(&allproc_lock); 937 if (ppsratecheck(&lastfail, &curfail, 1)) { 938 printf("maxproc limit exceeded by uid %u " 939 "(pid %d); see tuning(7) and " 940 "login.conf(5)\n", 941 td->td_ucred->cr_ruid, p1->p_pid); 942 } 943 sx_xunlock(&allproc_lock); 944 goto fail2; 945 } 946 } 947 948 /* 949 * If we are possibly multi-threaded, and there is a process 950 * sending a signal to our group right now, ensure that our 951 * other threads cannot be chosen for the signal queueing. 952 * Otherwise, this might delay signal action, and make the new 953 * child escape the signaling. 954 */ 955 pg = p1->p_pgrp; 956 if (p1->p_numthreads > 1) { 957 if (sx_try_slock(&pg->pg_killsx) != 0) { 958 killsx_locked = true; 959 } else { 960 PROC_LOCK(p1); 961 if (thread_single(p1, SINGLE_BOUNDARY)) { 962 PROC_UNLOCK(p1); 963 error = ERESTART; 964 goto fail2; 965 } 966 PROC_UNLOCK(p1); 967 singlethreaded = true; 968 } 969 } 970 971 /* 972 * Atomically check for signals and block processes from sending 973 * a signal to our process group until the child is visible. 974 */ 975 if (!killsx_locked && sx_slock_sig(&pg->pg_killsx) != 0) { 976 error = ERESTART; 977 goto fail2; 978 } 979 if (__predict_false(p1->p_pgrp != pg || sig_intr() != 0)) { 980 /* 981 * Either the process was moved to other process 982 * group, or there is pending signal. sx_slock_sig() 983 * does not check for signals if not sleeping for the 984 * lock. 985 */ 986 sx_sunlock(&pg->pg_killsx); 987 killsx_locked = false; 988 error = ERESTART; 989 goto fail2; 990 } else { 991 killsx_locked = true; 992 } 993 994 /* 995 * If required, create a process descriptor in the parent first; we 996 * will abandon it if something goes wrong. We don't finit() until 997 * later. 998 */ 999 if (flags & RFPROCDESC) { 1000 error = procdesc_falloc(td, &fp_procdesc, fr->fr_pd_fd, 1001 fr->fr_pd_flags, fr->fr_pd_fcaps); 1002 if (error != 0) 1003 goto fail2; 1004 AUDIT_ARG_FD(*fr->fr_pd_fd); 1005 } 1006 1007 mem_charged = 0; 1008 if (pages == 0) 1009 pages = kstack_pages; 1010 /* Allocate new proc. */ 1011 newproc = uma_zalloc(proc_zone, M_WAITOK); 1012 td2 = FIRST_THREAD_IN_PROC(newproc); 1013 if (td2 == NULL) { 1014 td2 = thread_alloc(pages); 1015 if (td2 == NULL) { 1016 error = ENOMEM; 1017 goto fail2; 1018 } 1019 proc_linkup(newproc, td2); 1020 } else { 1021 error = thread_recycle(td2, pages); 1022 if (error != 0) 1023 goto fail2; 1024 } 1025 1026 if ((flags & RFMEM) == 0) { 1027 vm2 = vmspace_fork(p1->p_vmspace, &mem_charged); 1028 if (vm2 == NULL) { 1029 error = ENOMEM; 1030 goto fail2; 1031 } 1032 if (!swap_reserve(mem_charged)) { 1033 /* 1034 * The swap reservation failed. The accounting 1035 * from the entries of the copied vm2 will be 1036 * subtracted in vmspace_free(), so force the 1037 * reservation there. 1038 */ 1039 swap_reserve_force(mem_charged); 1040 error = ENOMEM; 1041 goto fail2; 1042 } 1043 } else 1044 vm2 = NULL; 1045 1046 /* 1047 * XXX: This is ugly; when we copy resource usage, we need to bump 1048 * per-cred resource counters. 1049 */ 1050 newproc->p_ucred = crcowget(td->td_ucred); 1051 1052 /* 1053 * Initialize resource accounting for the child process. 1054 */ 1055 error = racct_proc_fork(p1, newproc); 1056 if (error != 0) { 1057 error = EAGAIN; 1058 goto fail1; 1059 } 1060 1061#ifdef MAC 1062 mac_proc_init(newproc); 1063#endif 1064 newproc->p_klist = knlist_alloc(&newproc->p_mtx); 1065 STAILQ_INIT(&newproc->p_ktr); 1066 1067 /* 1068 * Increment the count of procs running with this uid. Don't allow 1069 * a nonprivileged user to exceed their current limit. 1070 */ 1071 cred = td->td_ucred; 1072 if (!chgproccnt(cred->cr_ruidinfo, 1, lim_cur(td, RLIMIT_NPROC))) { 1073 if (priv_check_cred(cred, PRIV_PROC_LIMIT) != 0) 1074 goto fail0; 1075 chgproccnt(cred->cr_ruidinfo, 1, 0); 1076 } 1077 1078 do_fork(td, fr, newproc, td2, vm2, fp_procdesc); 1079 error = 0; 1080 goto cleanup; 1081fail0: 1082 error = EAGAIN; 1083#ifdef MAC 1084 mac_proc_destroy(newproc); 1085#endif 1086 racct_proc_exit(newproc); 1087fail1: 1088 proc_unset_cred(newproc); 1089fail2: 1090 if (vm2 != NULL) 1091 vmspace_free(vm2); 1092 uma_zfree(proc_zone, newproc); 1093 if ((flags & RFPROCDESC) != 0 && fp_procdesc != NULL) { 1094 fdclose(td, fp_procdesc, *fr->fr_pd_fd); 1095 fdrop(fp_procdesc, td); 1096 } 1097 atomic_add_int(&nprocs, -1); 1098cleanup: 1099 if (killsx_locked) 1100 sx_sunlock(&pg->pg_killsx); 1101 if (singlethreaded) { 1102 PROC_LOCK(p1); 1103 thread_single_end(p1, SINGLE_BOUNDARY); 1104 PROC_UNLOCK(p1); 1105 } 1106 if (error != 0) 1107 pause("fork", hz / 2); 1108 return (error); 1109} 1110 1111/* 1112 * Handle the return of a child process from fork1(). This function 1113 * is called from the MD fork_trampoline() entry point. 1114 */ 1115void 1116fork_exit(void (*callout)(void *, struct trapframe *), void *arg, 1117 struct trapframe *frame) 1118{ 1119 struct proc *p; 1120 struct thread *td; 1121 struct thread *dtd; 1122 1123 kmsan_mark(frame, sizeof(*frame), KMSAN_STATE_INITED); 1124 1125 td = curthread; 1126 p = td->td_proc; 1127 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new")); 1128 1129 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)", 1130 td, td_get_sched(td), p->p_pid, td->td_name); 1131 1132 sched_fork_exit(td); 1133 1134 /* 1135 * Processes normally resume in mi_switch() after being 1136 * cpu_switch()'ed to, but when children start up they arrive here 1137 * instead, so we must do much the same things as mi_switch() would. 1138 */ 1139 if ((dtd = PCPU_GET(deadthread))) { 1140 PCPU_SET(deadthread, NULL); 1141 thread_stash(dtd); 1142 } 1143 thread_unlock(td); 1144 1145 /* 1146 * cpu_fork_kthread_handler intercepts this function call to 1147 * have this call a non-return function to stay in kernel mode. 1148 * initproc has its own fork handler, but it does return. 1149 */ 1150 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 1151 callout(arg, frame); 1152 1153 /* 1154 * Check if a kernel thread misbehaved and returned from its main 1155 * function. 1156 */ 1157 if (p->p_flag & P_KPROC) { 1158 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 1159 td->td_name, p->p_pid); 1160 kthread_exit(); 1161 } 1162 mtx_assert(&Giant, MA_NOTOWNED); 1163 1164 /* 1165 * Now going to return to userland. 1166 */ 1167 1168 if (p->p_sysent->sv_schedtail != NULL) 1169 (p->p_sysent->sv_schedtail)(td); 1170 1171 userret(td, frame); 1172} 1173 1174/* 1175 * Simplified back end of syscall(), used when returning from fork() 1176 * directly into user mode. This function is passed in to fork_exit() 1177 * as the first parameter and is called when returning to a new 1178 * userland process. 1179 */ 1180void 1181fork_return(struct thread *td, struct trapframe *frame) 1182{ 1183 struct proc *p; 1184 1185 p = td->td_proc; 1186 if (td->td_dbgflags & TDB_STOPATFORK) { 1187 PROC_LOCK(p); 1188 if ((p->p_flag & P_TRACED) != 0) { 1189 /* 1190 * Inform the debugger if one is still present. 1191 */ 1192 td->td_dbgflags |= TDB_CHILD | TDB_SCX | TDB_FSTP; 1193 ptracestop(td, SIGSTOP, NULL); 1194 td->td_dbgflags &= ~(TDB_CHILD | TDB_SCX); 1195 } else { 1196 /* 1197 * ... otherwise clear the request. 1198 */ 1199 td->td_dbgflags &= ~TDB_STOPATFORK; 1200 } 1201 PROC_UNLOCK(p); 1202 } else if (p->p_flag & P_TRACED) { 1203 /* 1204 * This is the start of a new thread in a traced 1205 * process. Report a system call exit event. 1206 */ 1207 PROC_LOCK(p); 1208 td->td_dbgflags |= TDB_SCX; 1209 if ((p->p_ptevents & PTRACE_SCX) != 0 || 1210 (td->td_dbgflags & TDB_BORN) != 0) 1211 ptracestop(td, SIGTRAP, NULL); 1212 td->td_dbgflags &= ~(TDB_SCX | TDB_BORN); 1213 PROC_UNLOCK(p); 1214 } 1215 1216 /* 1217 * If the prison was killed mid-fork, die along with it. 1218 */ 1219 if (!prison_isalive(td->td_ucred->cr_prison)) 1220 exit1(td, 0, SIGKILL); 1221 1222#ifdef KTRACE 1223 if (KTRPOINT(td, KTR_SYSRET)) 1224 ktrsysret(td->td_sa.code, 0, 0); 1225#endif 1226} 1227 1228static void 1229fork_init(void *arg __unused) 1230{ 1231 ast_register(TDA_VFORK, ASTR_ASTF_REQUIRED | ASTR_TDP, TDP_RFPPWAIT, 1232 ast_vfork); 1233} 1234SYSINIT(fork, SI_SUB_INTRINSIC, SI_ORDER_ANY, fork_init, NULL); 1235