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 * @(#)kern_fork.c 8.6 (Berkeley) 4/8/94 37 */ 38 39 #include <sys/cdefs.h> 40 __FBSDID("$FreeBSD$"); 41 42 #include "opt_ktrace.h" 43 #include "opt_kstack_pages.h" 44 45 #include <sys/param.h> 46 #include <sys/systm.h> 47 #include <sys/bitstring.h> 48 #include <sys/sysproto.h> 49 #include <sys/eventhandler.h> 50 #include <sys/fcntl.h> 51 #include <sys/filedesc.h> 52 #include <sys/jail.h> 53 #include <sys/kernel.h> 54 #include <sys/kthread.h> 55 #include <sys/sysctl.h> 56 #include <sys/lock.h> 57 #include <sys/malloc.h> 58 #include <sys/msan.h> 59 #include <sys/mutex.h> 60 #include <sys/priv.h> 61 #include <sys/proc.h> 62 #include <sys/procdesc.h> 63 #include <sys/ptrace.h> 64 #include <sys/racct.h> 65 #include <sys/resourcevar.h> 66 #include <sys/sched.h> 67 #include <sys/syscall.h> 68 #include <sys/vmmeter.h> 69 #include <sys/vnode.h> 70 #include <sys/acct.h> 71 #include <sys/ktr.h> 72 #include <sys/ktrace.h> 73 #include <sys/unistd.h> 74 #include <sys/sdt.h> 75 #include <sys/sx.h> 76 #include <sys/sysent.h> 77 #include <sys/signalvar.h> 78 79 #include <security/audit/audit.h> 80 #include <security/mac/mac_framework.h> 81 82 #include <vm/vm.h> 83 #include <vm/pmap.h> 84 #include <vm/vm_map.h> 85 #include <vm/vm_extern.h> 86 #include <vm/uma.h> 87 88 #ifdef KDTRACE_HOOKS 89 #include <sys/dtrace_bsd.h> 90 dtrace_fork_func_t dtrace_fasttrap_fork; 91 #endif 92 93 SDT_PROVIDER_DECLARE(proc); 94 SDT_PROBE_DEFINE3(proc, , , create, "struct proc *", "struct proc *", "int"); 95 96 #ifndef _SYS_SYSPROTO_H_ 97 struct fork_args { 98 int dummy; 99 }; 100 #endif 101 102 /* ARGSUSED */ 103 int 104 sys_fork(struct thread *td, struct fork_args *uap) 105 { 106 struct fork_req fr; 107 int error, pid; 108 109 bzero(&fr, sizeof(fr)); 110 fr.fr_flags = RFFDG | RFPROC; 111 fr.fr_pidp = &pid; 112 error = fork1(td, &fr); 113 if (error == 0) { 114 td->td_retval[0] = pid; 115 td->td_retval[1] = 0; 116 } 117 return (error); 118 } 119 120 /* ARGUSED */ 121 int 122 sys_pdfork(struct thread *td, struct pdfork_args *uap) 123 { 124 struct fork_req fr; 125 int error, fd, pid; 126 127 bzero(&fr, sizeof(fr)); 128 fr.fr_flags = RFFDG | RFPROC | RFPROCDESC; 129 fr.fr_pidp = &pid; 130 fr.fr_pd_fd = &fd; 131 fr.fr_pd_flags = uap->flags; 132 AUDIT_ARG_FFLAGS(uap->flags); 133 /* 134 * It is necessary to return fd by reference because 0 is a valid file 135 * descriptor number, and the child needs to be able to distinguish 136 * itself from the parent using the return value. 137 */ 138 error = fork1(td, &fr); 139 if (error == 0) { 140 td->td_retval[0] = pid; 141 td->td_retval[1] = 0; 142 error = copyout(&fd, uap->fdp, sizeof(fd)); 143 } 144 return (error); 145 } 146 147 /* ARGSUSED */ 148 int 149 sys_vfork(struct thread *td, struct vfork_args *uap) 150 { 151 struct fork_req fr; 152 int error, pid; 153 154 bzero(&fr, sizeof(fr)); 155 fr.fr_flags = RFFDG | RFPROC | RFPPWAIT | RFMEM; 156 fr.fr_pidp = &pid; 157 error = fork1(td, &fr); 158 if (error == 0) { 159 td->td_retval[0] = pid; 160 td->td_retval[1] = 0; 161 } 162 return (error); 163 } 164 165 int 166 sys_rfork(struct thread *td, struct rfork_args *uap) 167 { 168 struct fork_req fr; 169 int error, pid; 170 171 /* Don't allow kernel-only flags. */ 172 if ((uap->flags & RFKERNELONLY) != 0) 173 return (EINVAL); 174 /* RFSPAWN must not appear with others */ 175 if ((uap->flags & RFSPAWN) != 0 && uap->flags != RFSPAWN) 176 return (EINVAL); 177 178 AUDIT_ARG_FFLAGS(uap->flags); 179 bzero(&fr, sizeof(fr)); 180 if ((uap->flags & RFSPAWN) != 0) { 181 fr.fr_flags = RFFDG | RFPROC | RFPPWAIT | RFMEM; 182 fr.fr_flags2 = FR2_DROPSIG_CAUGHT; 183 } else { 184 fr.fr_flags = uap->flags; 185 } 186 fr.fr_pidp = &pid; 187 error = fork1(td, &fr); 188 if (error == 0) { 189 td->td_retval[0] = pid; 190 td->td_retval[1] = 0; 191 } 192 return (error); 193 } 194 195 int __exclusive_cache_line nprocs = 1; /* process 0 */ 196 int lastpid = 0; 197 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0, 198 "Last used PID"); 199 200 /* 201 * Random component to lastpid generation. We mix in a random factor to make 202 * it a little harder to predict. We sanity check the modulus value to avoid 203 * doing it in critical paths. Don't let it be too small or we pointlessly 204 * waste randomness entropy, and don't let it be impossibly large. Using a 205 * modulus that is too big causes a LOT more process table scans and slows 206 * down fork processing as the pidchecked caching is defeated. 207 */ 208 static int randompid = 0; 209 210 static int 211 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 212 { 213 int error, pid; 214 215 error = sysctl_wire_old_buffer(req, sizeof(int)); 216 if (error != 0) 217 return(error); 218 sx_xlock(&allproc_lock); 219 pid = randompid; 220 error = sysctl_handle_int(oidp, &pid, 0, req); 221 if (error == 0 && req->newptr != NULL) { 222 if (pid == 0) 223 randompid = 0; 224 else if (pid == 1) 225 /* generate a random PID modulus between 100 and 1123 */ 226 randompid = 100 + arc4random() % 1024; 227 else if (pid < 0 || pid > pid_max - 100) 228 /* out of range */ 229 randompid = pid_max - 100; 230 else if (pid < 100) 231 /* Make it reasonable */ 232 randompid = 100; 233 else 234 randompid = pid; 235 } 236 sx_xunlock(&allproc_lock); 237 return (error); 238 } 239 240 SYSCTL_PROC(_kern, OID_AUTO, randompid, 241 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 0, 242 sysctl_kern_randompid, "I", 243 "Random PID modulus. Special values: 0: disable, 1: choose random value"); 244 245 extern bitstr_t proc_id_pidmap; 246 extern bitstr_t proc_id_grpidmap; 247 extern bitstr_t proc_id_sessidmap; 248 extern bitstr_t proc_id_reapmap; 249 250 /* 251 * Find an unused process ID 252 * 253 * If RFHIGHPID is set (used during system boot), do not allocate 254 * low-numbered pids. 255 */ 256 static int 257 fork_findpid(int flags) 258 { 259 pid_t result; 260 int trypid, random; 261 262 /* 263 * Avoid calling arc4random with procid_lock held. 264 */ 265 random = 0; 266 if (__predict_false(randompid)) 267 random = arc4random() % randompid; 268 269 mtx_lock(&procid_lock); 270 271 trypid = lastpid + 1; 272 if (flags & RFHIGHPID) { 273 if (trypid < 10) 274 trypid = 10; 275 } else { 276 trypid += random; 277 } 278 retry: 279 if (trypid >= pid_max) 280 trypid = 2; 281 282 bit_ffc_at(&proc_id_pidmap, trypid, pid_max, &result); 283 if (result == -1) { 284 KASSERT(trypid != 2, ("unexpectedly ran out of IDs")); 285 trypid = 2; 286 goto retry; 287 } 288 if (bit_test(&proc_id_grpidmap, result) || 289 bit_test(&proc_id_sessidmap, result) || 290 bit_test(&proc_id_reapmap, result)) { 291 trypid = result + 1; 292 goto retry; 293 } 294 295 /* 296 * RFHIGHPID does not mess with the lastpid counter during boot. 297 */ 298 if ((flags & RFHIGHPID) == 0) 299 lastpid = result; 300 301 bit_set(&proc_id_pidmap, result); 302 mtx_unlock(&procid_lock); 303 304 return (result); 305 } 306 307 static int 308 fork_norfproc(struct thread *td, int flags) 309 { 310 int error; 311 struct proc *p1; 312 313 KASSERT((flags & RFPROC) == 0, 314 ("fork_norfproc called with RFPROC set")); 315 p1 = td->td_proc; 316 317 /* 318 * Quiesce other threads if necessary. If RFMEM is not specified we 319 * must ensure that other threads do not concurrently create a second 320 * process sharing the vmspace, see vmspace_unshare(). 321 */ 322 if ((p1->p_flag & (P_HADTHREADS | P_SYSTEM)) == P_HADTHREADS && 323 ((flags & (RFCFDG | RFFDG)) != 0 || (flags & RFMEM) == 0)) { 324 PROC_LOCK(p1); 325 if (thread_single(p1, SINGLE_BOUNDARY)) { 326 PROC_UNLOCK(p1); 327 return (ERESTART); 328 } 329 PROC_UNLOCK(p1); 330 } 331 332 error = vm_forkproc(td, NULL, NULL, NULL, flags); 333 if (error) 334 goto fail; 335 336 /* 337 * Close all file descriptors. 338 */ 339 if (flags & RFCFDG) { 340 struct filedesc *fdtmp; 341 struct pwddesc *pdtmp; 342 pdtmp = pdinit(td->td_proc->p_pd, false); 343 fdtmp = fdinit(td->td_proc->p_fd, false, NULL); 344 pdescfree(td); 345 fdescfree(td); 346 p1->p_fd = fdtmp; 347 p1->p_pd = pdtmp; 348 } 349 350 /* 351 * Unshare file descriptors (from parent). 352 */ 353 if (flags & RFFDG) { 354 fdunshare(td); 355 pdunshare(td); 356 } 357 358 fail: 359 if ((p1->p_flag & (P_HADTHREADS | P_SYSTEM)) == P_HADTHREADS && 360 ((flags & (RFCFDG | RFFDG)) != 0 || (flags & RFMEM) == 0)) { 361 PROC_LOCK(p1); 362 thread_single_end(p1, SINGLE_BOUNDARY); 363 PROC_UNLOCK(p1); 364 } 365 return (error); 366 } 367 368 static void 369 do_fork(struct thread *td, struct fork_req *fr, struct proc *p2, struct thread *td2, 370 struct vmspace *vm2, struct file *fp_procdesc) 371 { 372 struct proc *p1, *pptr; 373 struct filedesc *fd; 374 struct filedesc_to_leader *fdtol; 375 struct pwddesc *pd; 376 struct sigacts *newsigacts; 377 378 p1 = td->td_proc; 379 380 PROC_LOCK(p1); 381 bcopy(&p1->p_startcopy, &p2->p_startcopy, 382 __rangeof(struct proc, p_startcopy, p_endcopy)); 383 pargs_hold(p2->p_args); 384 PROC_UNLOCK(p1); 385 386 bzero(&p2->p_startzero, 387 __rangeof(struct proc, p_startzero, p_endzero)); 388 389 /* Tell the prison that we exist. */ 390 prison_proc_hold(p2->p_ucred->cr_prison); 391 392 p2->p_state = PRS_NEW; /* protect against others */ 393 p2->p_pid = fork_findpid(fr->fr_flags); 394 AUDIT_ARG_PID(p2->p_pid); 395 396 sx_xlock(&allproc_lock); 397 LIST_INSERT_HEAD(&allproc, p2, p_list); 398 allproc_gen++; 399 sx_xunlock(&allproc_lock); 400 401 sx_xlock(PIDHASHLOCK(p2->p_pid)); 402 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 403 sx_xunlock(PIDHASHLOCK(p2->p_pid)); 404 405 tidhash_add(td2); 406 407 /* 408 * Malloc things while we don't hold any locks. 409 */ 410 if (fr->fr_flags & RFSIGSHARE) 411 newsigacts = NULL; 412 else 413 newsigacts = sigacts_alloc(); 414 415 /* 416 * Copy filedesc. 417 */ 418 if (fr->fr_flags & RFCFDG) { 419 pd = pdinit(p1->p_pd, false); 420 fd = fdinit(p1->p_fd, false, NULL); 421 fdtol = NULL; 422 } else if (fr->fr_flags & RFFDG) { 423 if (fr->fr_flags2 & FR2_SHARE_PATHS) 424 pd = pdshare(p1->p_pd); 425 else 426 pd = pdcopy(p1->p_pd); 427 fd = fdcopy(p1->p_fd); 428 fdtol = NULL; 429 } else { 430 if (fr->fr_flags2 & FR2_SHARE_PATHS) 431 pd = pdcopy(p1->p_pd); 432 else 433 pd = pdshare(p1->p_pd); 434 fd = fdshare(p1->p_fd); 435 if (p1->p_fdtol == NULL) 436 p1->p_fdtol = filedesc_to_leader_alloc(NULL, NULL, 437 p1->p_leader); 438 if ((fr->fr_flags & RFTHREAD) != 0) { 439 /* 440 * Shared file descriptor table, and shared 441 * process leaders. 442 */ 443 fdtol = p1->p_fdtol; 444 FILEDESC_XLOCK(p1->p_fd); 445 fdtol->fdl_refcount++; 446 FILEDESC_XUNLOCK(p1->p_fd); 447 } else { 448 /* 449 * Shared file descriptor table, and different 450 * process leaders. 451 */ 452 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, 453 p1->p_fd, p2); 454 } 455 } 456 /* 457 * Make a proc table entry for the new process. 458 * Start by zeroing the section of proc that is zero-initialized, 459 * then copy the section that is copied directly from the parent. 460 */ 461 462 PROC_LOCK(p2); 463 PROC_LOCK(p1); 464 465 bzero(&td2->td_startzero, 466 __rangeof(struct thread, td_startzero, td_endzero)); 467 468 bcopy(&td->td_startcopy, &td2->td_startcopy, 469 __rangeof(struct thread, td_startcopy, td_endcopy)); 470 471 bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name)); 472 td2->td_sigstk = td->td_sigstk; 473 td2->td_flags = TDF_INMEM; 474 td2->td_lend_user_pri = PRI_MAX; 475 476 #ifdef VIMAGE 477 td2->td_vnet = NULL; 478 td2->td_vnet_lpush = NULL; 479 #endif 480 481 /* 482 * Allow the scheduler to initialize the child. 483 */ 484 thread_lock(td); 485 sched_fork(td, td2); 486 thread_unlock(td); 487 488 /* 489 * Duplicate sub-structures as needed. 490 * Increase reference counts on shared objects. 491 */ 492 p2->p_flag = P_INMEM; 493 p2->p_flag2 = p1->p_flag2 & (P2_ASLR_DISABLE | P2_ASLR_ENABLE | 494 P2_ASLR_IGNSTART | P2_NOTRACE | P2_NOTRACE_EXEC | 495 P2_PROTMAX_ENABLE | P2_PROTMAX_DISABLE | P2_TRAPCAP | 496 P2_STKGAP_DISABLE | P2_STKGAP_DISABLE_EXEC | P2_NO_NEW_PRIVS); 497 p2->p_swtick = ticks; 498 if (p1->p_flag & P_PROFIL) 499 startprofclock(p2); 500 501 if (fr->fr_flags & RFSIGSHARE) { 502 p2->p_sigacts = sigacts_hold(p1->p_sigacts); 503 } else { 504 sigacts_copy(newsigacts, p1->p_sigacts); 505 p2->p_sigacts = newsigacts; 506 if ((fr->fr_flags2 & (FR2_DROPSIG_CAUGHT | FR2_KPROC)) != 0) { 507 mtx_lock(&p2->p_sigacts->ps_mtx); 508 if ((fr->fr_flags2 & FR2_DROPSIG_CAUGHT) != 0) 509 sig_drop_caught(p2); 510 if ((fr->fr_flags2 & FR2_KPROC) != 0) 511 p2->p_sigacts->ps_flag |= PS_NOCLDWAIT; 512 mtx_unlock(&p2->p_sigacts->ps_mtx); 513 } 514 } 515 516 if (fr->fr_flags & RFTSIGZMB) 517 p2->p_sigparent = RFTSIGNUM(fr->fr_flags); 518 else if (fr->fr_flags & RFLINUXTHPN) 519 p2->p_sigparent = SIGUSR1; 520 else 521 p2->p_sigparent = SIGCHLD; 522 523 if ((fr->fr_flags2 & FR2_KPROC) != 0) { 524 p2->p_flag |= P_SYSTEM | P_KPROC; 525 td2->td_pflags |= TDP_KTHREAD; 526 } 527 528 p2->p_textvp = p1->p_textvp; 529 p2->p_fd = fd; 530 p2->p_fdtol = fdtol; 531 p2->p_pd = pd; 532 533 if (p1->p_flag2 & P2_INHERIT_PROTECTED) { 534 p2->p_flag |= P_PROTECTED; 535 p2->p_flag2 |= P2_INHERIT_PROTECTED; 536 } 537 538 /* 539 * p_limit is copy-on-write. Bump its refcount. 540 */ 541 lim_fork(p1, p2); 542 543 thread_cow_get_proc(td2, p2); 544 545 pstats_fork(p1->p_stats, p2->p_stats); 546 547 PROC_UNLOCK(p1); 548 PROC_UNLOCK(p2); 549 550 /* Bump references to the text vnode (for procfs). */ 551 if (p2->p_textvp) 552 vrefact(p2->p_textvp); 553 554 /* 555 * Set up linkage for kernel based threading. 556 */ 557 if ((fr->fr_flags & RFTHREAD) != 0) { 558 mtx_lock(&ppeers_lock); 559 p2->p_peers = p1->p_peers; 560 p1->p_peers = p2; 561 p2->p_leader = p1->p_leader; 562 mtx_unlock(&ppeers_lock); 563 PROC_LOCK(p1->p_leader); 564 if ((p1->p_leader->p_flag & P_WEXIT) != 0) { 565 PROC_UNLOCK(p1->p_leader); 566 /* 567 * The task leader is exiting, so process p1 is 568 * going to be killed shortly. Since p1 obviously 569 * isn't dead yet, we know that the leader is either 570 * sending SIGKILL's to all the processes in this 571 * task or is sleeping waiting for all the peers to 572 * exit. We let p1 complete the fork, but we need 573 * to go ahead and kill the new process p2 since 574 * the task leader may not get a chance to send 575 * SIGKILL to it. We leave it on the list so that 576 * the task leader will wait for this new process 577 * to commit suicide. 578 */ 579 PROC_LOCK(p2); 580 kern_psignal(p2, SIGKILL); 581 PROC_UNLOCK(p2); 582 } else 583 PROC_UNLOCK(p1->p_leader); 584 } else { 585 p2->p_peers = NULL; 586 p2->p_leader = p2; 587 } 588 589 sx_xlock(&proctree_lock); 590 PGRP_LOCK(p1->p_pgrp); 591 PROC_LOCK(p2); 592 PROC_LOCK(p1); 593 594 /* 595 * Preserve some more flags in subprocess. P_PROFIL has already 596 * been preserved. 597 */ 598 p2->p_flag |= p1->p_flag & P_SUGID; 599 td2->td_pflags |= (td->td_pflags & (TDP_ALTSTACK | 600 TDP_SIGFASTBLOCK)) | TDP_FORKING; 601 SESS_LOCK(p1->p_session); 602 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 603 p2->p_flag |= P_CONTROLT; 604 SESS_UNLOCK(p1->p_session); 605 if (fr->fr_flags & RFPPWAIT) 606 p2->p_flag |= P_PPWAIT; 607 608 p2->p_pgrp = p1->p_pgrp; 609 LIST_INSERT_AFTER(p1, p2, p_pglist); 610 PGRP_UNLOCK(p1->p_pgrp); 611 LIST_INIT(&p2->p_children); 612 LIST_INIT(&p2->p_orphans); 613 614 callout_init_mtx(&p2->p_itcallout, &p2->p_mtx, 0); 615 TAILQ_INIT(&p2->p_kqtim_stop); 616 617 /* 618 * This begins the section where we must prevent the parent 619 * from being swapped. 620 */ 621 _PHOLD(p1); 622 PROC_UNLOCK(p1); 623 624 /* 625 * Attach the new process to its parent. 626 * 627 * If RFNOWAIT is set, the newly created process becomes a child 628 * of init. This effectively disassociates the child from the 629 * parent. 630 */ 631 if ((fr->fr_flags & RFNOWAIT) != 0) { 632 pptr = p1->p_reaper; 633 p2->p_reaper = pptr; 634 } else { 635 p2->p_reaper = (p1->p_treeflag & P_TREE_REAPER) != 0 ? 636 p1 : p1->p_reaper; 637 pptr = p1; 638 } 639 p2->p_pptr = pptr; 640 p2->p_oppid = pptr->p_pid; 641 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 642 LIST_INIT(&p2->p_reaplist); 643 LIST_INSERT_HEAD(&p2->p_reaper->p_reaplist, p2, p_reapsibling); 644 if (p2->p_reaper == p1 && p1 != initproc) { 645 p2->p_reapsubtree = p2->p_pid; 646 proc_id_set_cond(PROC_ID_REAP, p2->p_pid); 647 } 648 sx_xunlock(&proctree_lock); 649 650 /* Inform accounting that we have forked. */ 651 p2->p_acflag = AFORK; 652 PROC_UNLOCK(p2); 653 654 #ifdef KTRACE 655 ktrprocfork(p1, p2); 656 #endif 657 658 /* 659 * Finish creating the child process. It will return via a different 660 * execution path later. (ie: directly into user mode) 661 */ 662 vm_forkproc(td, p2, td2, vm2, fr->fr_flags); 663 664 if (fr->fr_flags == (RFFDG | RFPROC)) { 665 VM_CNT_INC(v_forks); 666 VM_CNT_ADD(v_forkpages, p2->p_vmspace->vm_dsize + 667 p2->p_vmspace->vm_ssize); 668 } else if (fr->fr_flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 669 VM_CNT_INC(v_vforks); 670 VM_CNT_ADD(v_vforkpages, p2->p_vmspace->vm_dsize + 671 p2->p_vmspace->vm_ssize); 672 } else if (p1 == &proc0) { 673 VM_CNT_INC(v_kthreads); 674 VM_CNT_ADD(v_kthreadpages, p2->p_vmspace->vm_dsize + 675 p2->p_vmspace->vm_ssize); 676 } else { 677 VM_CNT_INC(v_rforks); 678 VM_CNT_ADD(v_rforkpages, p2->p_vmspace->vm_dsize + 679 p2->p_vmspace->vm_ssize); 680 } 681 682 /* 683 * Associate the process descriptor with the process before anything 684 * can happen that might cause that process to need the descriptor. 685 * However, don't do this until after fork(2) can no longer fail. 686 */ 687 if (fr->fr_flags & RFPROCDESC) 688 procdesc_new(p2, fr->fr_pd_flags); 689 690 /* 691 * Both processes are set up, now check if any loadable modules want 692 * to adjust anything. 693 */ 694 EVENTHANDLER_DIRECT_INVOKE(process_fork, p1, p2, fr->fr_flags); 695 696 /* 697 * Set the child start time and mark the process as being complete. 698 */ 699 PROC_LOCK(p2); 700 PROC_LOCK(p1); 701 microuptime(&p2->p_stats->p_start); 702 PROC_SLOCK(p2); 703 p2->p_state = PRS_NORMAL; 704 PROC_SUNLOCK(p2); 705 706 #ifdef KDTRACE_HOOKS 707 /* 708 * Tell the DTrace fasttrap provider about the new process so that any 709 * tracepoints inherited from the parent can be removed. We have to do 710 * this only after p_state is PRS_NORMAL since the fasttrap module will 711 * use pfind() later on. 712 */ 713 if ((fr->fr_flags & RFMEM) == 0 && dtrace_fasttrap_fork) 714 dtrace_fasttrap_fork(p1, p2); 715 #endif 716 if (fr->fr_flags & RFPPWAIT) { 717 td->td_pflags |= TDP_RFPPWAIT; 718 td->td_rfppwait_p = p2; 719 td->td_dbgflags |= TDB_VFORK; 720 } 721 PROC_UNLOCK(p2); 722 723 /* 724 * Tell any interested parties about the new process. 725 */ 726 knote_fork(p1->p_klist, p2->p_pid); 727 728 /* 729 * Now can be swapped. 730 */ 731 _PRELE(p1); 732 PROC_UNLOCK(p1); 733 SDT_PROBE3(proc, , , create, p2, p1, fr->fr_flags); 734 735 if (fr->fr_flags & RFPROCDESC) { 736 procdesc_finit(p2->p_procdesc, fp_procdesc); 737 fdrop(fp_procdesc, td); 738 } 739 740 /* 741 * Speculative check for PTRACE_FORK. PTRACE_FORK is not 742 * synced with forks in progress so it is OK if we miss it 743 * if being set atm. 744 */ 745 if ((p1->p_ptevents & PTRACE_FORK) != 0) { 746 sx_xlock(&proctree_lock); 747 PROC_LOCK(p2); 748 749 /* 750 * p1->p_ptevents & p1->p_pptr are protected by both 751 * process and proctree locks for modifications, 752 * so owning proctree_lock allows the race-free read. 753 */ 754 if ((p1->p_ptevents & PTRACE_FORK) != 0) { 755 /* 756 * Arrange for debugger to receive the fork event. 757 * 758 * We can report PL_FLAG_FORKED regardless of 759 * P_FOLLOWFORK settings, but it does not make a sense 760 * for runaway child. 761 */ 762 td->td_dbgflags |= TDB_FORK; 763 td->td_dbg_forked = p2->p_pid; 764 td2->td_dbgflags |= TDB_STOPATFORK; 765 proc_set_traced(p2, true); 766 CTR2(KTR_PTRACE, 767 "do_fork: attaching to new child pid %d: oppid %d", 768 p2->p_pid, p2->p_oppid); 769 proc_reparent(p2, p1->p_pptr, false); 770 } 771 PROC_UNLOCK(p2); 772 sx_xunlock(&proctree_lock); 773 } 774 775 racct_proc_fork_done(p2); 776 777 if ((fr->fr_flags & RFSTOPPED) == 0) { 778 if (fr->fr_pidp != NULL) 779 *fr->fr_pidp = p2->p_pid; 780 /* 781 * If RFSTOPPED not requested, make child runnable and 782 * add to run queue. 783 */ 784 thread_lock(td2); 785 TD_SET_CAN_RUN(td2); 786 sched_add(td2, SRQ_BORING); 787 } else { 788 *fr->fr_procp = p2; 789 } 790 } 791 792 void 793 fork_rfppwait(struct thread *td) 794 { 795 struct proc *p, *p2; 796 797 MPASS(td->td_pflags & TDP_RFPPWAIT); 798 799 p = td->td_proc; 800 /* 801 * Preserve synchronization semantics of vfork. If 802 * waiting for child to exec or exit, fork set 803 * P_PPWAIT on child, and there we sleep on our proc 804 * (in case of exit). 805 * 806 * Do it after the ptracestop() above is finished, to 807 * not block our debugger until child execs or exits 808 * to finish vfork wait. 809 */ 810 td->td_pflags &= ~TDP_RFPPWAIT; 811 p2 = td->td_rfppwait_p; 812 again: 813 PROC_LOCK(p2); 814 while (p2->p_flag & P_PPWAIT) { 815 PROC_LOCK(p); 816 if (thread_suspend_check_needed()) { 817 PROC_UNLOCK(p2); 818 thread_suspend_check(0); 819 PROC_UNLOCK(p); 820 goto again; 821 } else { 822 PROC_UNLOCK(p); 823 } 824 cv_timedwait(&p2->p_pwait, &p2->p_mtx, hz); 825 } 826 PROC_UNLOCK(p2); 827 828 if (td->td_dbgflags & TDB_VFORK) { 829 PROC_LOCK(p); 830 if (p->p_ptevents & PTRACE_VFORK) 831 ptracestop(td, SIGTRAP, NULL); 832 td->td_dbgflags &= ~TDB_VFORK; 833 PROC_UNLOCK(p); 834 } 835 } 836 837 int 838 fork1(struct thread *td, struct fork_req *fr) 839 { 840 struct proc *p1, *newproc; 841 struct thread *td2; 842 struct vmspace *vm2; 843 struct ucred *cred; 844 struct file *fp_procdesc; 845 vm_ooffset_t mem_charged; 846 int error, nprocs_new; 847 static int curfail; 848 static struct timeval lastfail; 849 int flags, pages; 850 851 flags = fr->fr_flags; 852 pages = fr->fr_pages; 853 854 if ((flags & RFSTOPPED) != 0) 855 MPASS(fr->fr_procp != NULL && fr->fr_pidp == NULL); 856 else 857 MPASS(fr->fr_procp == NULL); 858 859 /* Check for the undefined or unimplemented flags. */ 860 if ((flags & ~(RFFLAGS | RFTSIGFLAGS(RFTSIGMASK))) != 0) 861 return (EINVAL); 862 863 /* Signal value requires RFTSIGZMB. */ 864 if ((flags & RFTSIGFLAGS(RFTSIGMASK)) != 0 && (flags & RFTSIGZMB) == 0) 865 return (EINVAL); 866 867 /* Can't copy and clear. */ 868 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 869 return (EINVAL); 870 871 /* Check the validity of the signal number. */ 872 if ((flags & RFTSIGZMB) != 0 && (u_int)RFTSIGNUM(flags) > _SIG_MAXSIG) 873 return (EINVAL); 874 875 if ((flags & RFPROCDESC) != 0) { 876 /* Can't not create a process yet get a process descriptor. */ 877 if ((flags & RFPROC) == 0) 878 return (EINVAL); 879 880 /* Must provide a place to put a procdesc if creating one. */ 881 if (fr->fr_pd_fd == NULL) 882 return (EINVAL); 883 884 /* Check if we are using supported flags. */ 885 if ((fr->fr_pd_flags & ~PD_ALLOWED_AT_FORK) != 0) 886 return (EINVAL); 887 } 888 889 p1 = td->td_proc; 890 891 /* 892 * Here we don't create a new process, but we divorce 893 * certain parts of a process from itself. 894 */ 895 if ((flags & RFPROC) == 0) { 896 if (fr->fr_procp != NULL) 897 *fr->fr_procp = NULL; 898 else if (fr->fr_pidp != NULL) 899 *fr->fr_pidp = 0; 900 return (fork_norfproc(td, flags)); 901 } 902 903 fp_procdesc = NULL; 904 newproc = NULL; 905 vm2 = NULL; 906 907 /* 908 * Increment the nprocs resource before allocations occur. 909 * Although process entries are dynamically created, we still 910 * keep a global limit on the maximum number we will 911 * create. There are hard-limits as to the number of processes 912 * that can run, established by the KVA and memory usage for 913 * the process data. 914 * 915 * Don't allow a nonprivileged user to use the last ten 916 * processes; don't let root exceed the limit. 917 */ 918 nprocs_new = atomic_fetchadd_int(&nprocs, 1) + 1; 919 if (nprocs_new >= maxproc - 10) { 920 if (priv_check_cred(td->td_ucred, PRIV_MAXPROC) != 0 || 921 nprocs_new >= maxproc) { 922 error = EAGAIN; 923 sx_xlock(&allproc_lock); 924 if (ppsratecheck(&lastfail, &curfail, 1)) { 925 printf("maxproc limit exceeded by uid %u " 926 "(pid %d); see tuning(7) and " 927 "login.conf(5)\n", 928 td->td_ucred->cr_ruid, p1->p_pid); 929 } 930 sx_xunlock(&allproc_lock); 931 goto fail2; 932 } 933 } 934 935 /* 936 * If required, create a process descriptor in the parent first; we 937 * will abandon it if something goes wrong. We don't finit() until 938 * later. 939 */ 940 if (flags & RFPROCDESC) { 941 error = procdesc_falloc(td, &fp_procdesc, fr->fr_pd_fd, 942 fr->fr_pd_flags, fr->fr_pd_fcaps); 943 if (error != 0) 944 goto fail2; 945 AUDIT_ARG_FD(*fr->fr_pd_fd); 946 } 947 948 mem_charged = 0; 949 if (pages == 0) 950 pages = kstack_pages; 951 /* Allocate new proc. */ 952 newproc = uma_zalloc(proc_zone, M_WAITOK); 953 td2 = FIRST_THREAD_IN_PROC(newproc); 954 if (td2 == NULL) { 955 td2 = thread_alloc(pages); 956 if (td2 == NULL) { 957 error = ENOMEM; 958 goto fail2; 959 } 960 proc_linkup(newproc, td2); 961 } else { 962 kmsan_thread_alloc(td2); 963 if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) { 964 if (td2->td_kstack != 0) 965 vm_thread_dispose(td2); 966 if (!thread_alloc_stack(td2, pages)) { 967 error = ENOMEM; 968 goto fail2; 969 } 970 } 971 } 972 973 if ((flags & RFMEM) == 0) { 974 vm2 = vmspace_fork(p1->p_vmspace, &mem_charged); 975 if (vm2 == NULL) { 976 error = ENOMEM; 977 goto fail2; 978 } 979 if (!swap_reserve(mem_charged)) { 980 /* 981 * The swap reservation failed. The accounting 982 * from the entries of the copied vm2 will be 983 * subtracted in vmspace_free(), so force the 984 * reservation there. 985 */ 986 swap_reserve_force(mem_charged); 987 error = ENOMEM; 988 goto fail2; 989 } 990 } else 991 vm2 = NULL; 992 993 /* 994 * XXX: This is ugly; when we copy resource usage, we need to bump 995 * per-cred resource counters. 996 */ 997 proc_set_cred_init(newproc, td->td_ucred); 998 999 /* 1000 * Initialize resource accounting for the child process. 1001 */ 1002 error = racct_proc_fork(p1, newproc); 1003 if (error != 0) { 1004 error = EAGAIN; 1005 goto fail1; 1006 } 1007 1008 #ifdef MAC 1009 mac_proc_init(newproc); 1010 #endif 1011 newproc->p_klist = knlist_alloc(&newproc->p_mtx); 1012 STAILQ_INIT(&newproc->p_ktr); 1013 1014 /* 1015 * Increment the count of procs running with this uid. Don't allow 1016 * a nonprivileged user to exceed their current limit. 1017 */ 1018 cred = td->td_ucred; 1019 if (!chgproccnt(cred->cr_ruidinfo, 1, lim_cur(td, RLIMIT_NPROC))) { 1020 if (priv_check_cred(cred, PRIV_PROC_LIMIT) != 0) 1021 goto fail0; 1022 chgproccnt(cred->cr_ruidinfo, 1, 0); 1023 } 1024 1025 do_fork(td, fr, newproc, td2, vm2, fp_procdesc); 1026 return (0); 1027 fail0: 1028 error = EAGAIN; 1029 #ifdef MAC 1030 mac_proc_destroy(newproc); 1031 #endif 1032 racct_proc_exit(newproc); 1033 fail1: 1034 proc_unset_cred(newproc); 1035 fail2: 1036 if (vm2 != NULL) 1037 vmspace_free(vm2); 1038 uma_zfree(proc_zone, newproc); 1039 if ((flags & RFPROCDESC) != 0 && fp_procdesc != NULL) { 1040 fdclose(td, fp_procdesc, *fr->fr_pd_fd); 1041 fdrop(fp_procdesc, td); 1042 } 1043 atomic_add_int(&nprocs, -1); 1044 pause("fork", hz / 2); 1045 return (error); 1046 } 1047 1048 /* 1049 * Handle the return of a child process from fork1(). This function 1050 * is called from the MD fork_trampoline() entry point. 1051 */ 1052 void 1053 fork_exit(void (*callout)(void *, struct trapframe *), void *arg, 1054 struct trapframe *frame) 1055 { 1056 struct proc *p; 1057 struct thread *td; 1058 struct thread *dtd; 1059 1060 kmsan_mark(frame, sizeof(*frame), KMSAN_STATE_INITED); 1061 1062 td = curthread; 1063 p = td->td_proc; 1064 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new")); 1065 1066 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)", 1067 td, td_get_sched(td), p->p_pid, td->td_name); 1068 1069 sched_fork_exit(td); 1070 /* 1071 * Processes normally resume in mi_switch() after being 1072 * cpu_switch()'ed to, but when children start up they arrive here 1073 * instead, so we must do much the same things as mi_switch() would. 1074 */ 1075 if ((dtd = PCPU_GET(deadthread))) { 1076 PCPU_SET(deadthread, NULL); 1077 thread_stash(dtd); 1078 } 1079 thread_unlock(td); 1080 1081 /* 1082 * cpu_fork_kthread_handler intercepts this function call to 1083 * have this call a non-return function to stay in kernel mode. 1084 * initproc has its own fork handler, but it does return. 1085 */ 1086 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 1087 callout(arg, frame); 1088 1089 /* 1090 * Check if a kernel thread misbehaved and returned from its main 1091 * function. 1092 */ 1093 if (p->p_flag & P_KPROC) { 1094 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 1095 td->td_name, p->p_pid); 1096 kthread_exit(); 1097 } 1098 mtx_assert(&Giant, MA_NOTOWNED); 1099 1100 if (p->p_sysent->sv_schedtail != NULL) 1101 (p->p_sysent->sv_schedtail)(td); 1102 td->td_pflags &= ~TDP_FORKING; 1103 } 1104 1105 /* 1106 * Simplified back end of syscall(), used when returning from fork() 1107 * directly into user mode. This function is passed in to fork_exit() 1108 * as the first parameter and is called when returning to a new 1109 * userland process. 1110 */ 1111 void 1112 fork_return(struct thread *td, struct trapframe *frame) 1113 { 1114 struct proc *p; 1115 1116 p = td->td_proc; 1117 if (td->td_dbgflags & TDB_STOPATFORK) { 1118 PROC_LOCK(p); 1119 if ((p->p_flag & P_TRACED) != 0) { 1120 /* 1121 * Inform the debugger if one is still present. 1122 */ 1123 td->td_dbgflags |= TDB_CHILD | TDB_SCX | TDB_FSTP; 1124 ptracestop(td, SIGSTOP, NULL); 1125 td->td_dbgflags &= ~(TDB_CHILD | TDB_SCX); 1126 } else { 1127 /* 1128 * ... otherwise clear the request. 1129 */ 1130 td->td_dbgflags &= ~TDB_STOPATFORK; 1131 } 1132 PROC_UNLOCK(p); 1133 } else if (p->p_flag & P_TRACED || td->td_dbgflags & TDB_BORN) { 1134 /* 1135 * This is the start of a new thread in a traced 1136 * process. Report a system call exit event. 1137 */ 1138 PROC_LOCK(p); 1139 td->td_dbgflags |= TDB_SCX; 1140 if ((p->p_ptevents & PTRACE_SCX) != 0 || 1141 (td->td_dbgflags & TDB_BORN) != 0) 1142 ptracestop(td, SIGTRAP, NULL); 1143 td->td_dbgflags &= ~(TDB_SCX | TDB_BORN); 1144 PROC_UNLOCK(p); 1145 } 1146 1147 /* 1148 * If the prison was killed mid-fork, die along with it. 1149 */ 1150 if (!prison_isalive(td->td_ucred->cr_prison)) 1151 exit1(td, 0, SIGKILL); 1152 1153 userret(td, frame); 1154 1155 #ifdef KTRACE 1156 if (KTRPOINT(td, KTR_SYSRET)) 1157 ktrsysret(SYS_fork, 0, 0); 1158 #endif 1159 } 1160