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 #include "opt_ktrace.h" 41 #include "opt_kstack_pages.h" 42 43 #include <sys/param.h> 44 #include <sys/systm.h> 45 #include <sys/bitstring.h> 46 #include <sys/sysproto.h> 47 #include <sys/eventhandler.h> 48 #include <sys/fcntl.h> 49 #include <sys/filedesc.h> 50 #include <sys/jail.h> 51 #include <sys/kernel.h> 52 #include <sys/kthread.h> 53 #include <sys/sysctl.h> 54 #include <sys/lock.h> 55 #include <sys/malloc.h> 56 #include <sys/msan.h> 57 #include <sys/mutex.h> 58 #include <sys/priv.h> 59 #include <sys/proc.h> 60 #include <sys/procdesc.h> 61 #include <sys/ptrace.h> 62 #include <sys/racct.h> 63 #include <sys/resourcevar.h> 64 #include <sys/sched.h> 65 #include <sys/syscall.h> 66 #include <sys/vmmeter.h> 67 #include <sys/vnode.h> 68 #include <sys/acct.h> 69 #include <sys/ktr.h> 70 #include <sys/ktrace.h> 71 #include <sys/unistd.h> 72 #include <sys/sdt.h> 73 #include <sys/sx.h> 74 #include <sys/sysent.h> 75 #include <sys/signalvar.h> 76 77 #include <security/audit/audit.h> 78 #include <security/mac/mac_framework.h> 79 80 #include <vm/vm.h> 81 #include <vm/pmap.h> 82 #include <vm/vm_map.h> 83 #include <vm/vm_extern.h> 84 #include <vm/uma.h> 85 86 #ifdef KDTRACE_HOOKS 87 #include <sys/dtrace_bsd.h> 88 dtrace_fork_func_t dtrace_fasttrap_fork; 89 #endif 90 91 SDT_PROVIDER_DECLARE(proc); 92 SDT_PROBE_DEFINE3(proc, , , create, "struct proc *", "struct proc *", "int"); 93 94 #ifndef _SYS_SYSPROTO_H_ 95 struct fork_args { 96 int dummy; 97 }; 98 #endif 99 100 /* ARGSUSED */ 101 int 102 sys_fork(struct thread *td, struct fork_args *uap) 103 { 104 struct fork_req fr; 105 int error, pid; 106 107 bzero(&fr, sizeof(fr)); 108 fr.fr_flags = RFFDG | RFPROC; 109 fr.fr_pidp = &pid; 110 error = fork1(td, &fr); 111 if (error == 0) { 112 td->td_retval[0] = pid; 113 td->td_retval[1] = 0; 114 } 115 return (error); 116 } 117 118 /* ARGUSED */ 119 int 120 sys_pdfork(struct thread *td, struct pdfork_args *uap) 121 { 122 struct fork_req fr; 123 int error, fd, pid; 124 125 bzero(&fr, sizeof(fr)); 126 fr.fr_flags = RFFDG | RFPROC | RFPROCDESC; 127 fr.fr_pidp = &pid; 128 fr.fr_pd_fd = &fd; 129 fr.fr_pd_flags = uap->flags; 130 AUDIT_ARG_FFLAGS(uap->flags); 131 /* 132 * It is necessary to return fd by reference because 0 is a valid file 133 * descriptor number, and the child needs to be able to distinguish 134 * itself from the parent using the return value. 135 */ 136 error = fork1(td, &fr); 137 if (error == 0) { 138 td->td_retval[0] = pid; 139 td->td_retval[1] = 0; 140 error = copyout(&fd, uap->fdp, sizeof(fd)); 141 } 142 return (error); 143 } 144 145 /* ARGSUSED */ 146 int 147 sys_vfork(struct thread *td, struct vfork_args *uap) 148 { 149 struct fork_req fr; 150 int error, pid; 151 152 bzero(&fr, sizeof(fr)); 153 fr.fr_flags = RFFDG | RFPROC | RFPPWAIT | RFMEM; 154 fr.fr_pidp = &pid; 155 error = fork1(td, &fr); 156 if (error == 0) { 157 td->td_retval[0] = pid; 158 td->td_retval[1] = 0; 159 } 160 return (error); 161 } 162 163 int 164 sys_rfork(struct thread *td, struct rfork_args *uap) 165 { 166 struct fork_req fr; 167 int error, pid; 168 169 /* Don't allow kernel-only flags. */ 170 if ((uap->flags & RFKERNELONLY) != 0) 171 return (EINVAL); 172 /* RFSPAWN must not appear with others */ 173 if ((uap->flags & RFSPAWN) != 0 && uap->flags != RFSPAWN) 174 return (EINVAL); 175 176 AUDIT_ARG_FFLAGS(uap->flags); 177 bzero(&fr, sizeof(fr)); 178 if ((uap->flags & RFSPAWN) != 0) { 179 fr.fr_flags = RFFDG | RFPROC | RFPPWAIT | RFMEM; 180 fr.fr_flags2 = FR2_DROPSIG_CAUGHT; 181 } else { 182 fr.fr_flags = uap->flags; 183 } 184 fr.fr_pidp = &pid; 185 error = fork1(td, &fr); 186 if (error == 0) { 187 td->td_retval[0] = pid; 188 td->td_retval[1] = 0; 189 } 190 return (error); 191 } 192 193 int __exclusive_cache_line nprocs = 1; /* process 0 */ 194 int lastpid = 0; 195 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0, 196 "Last used PID"); 197 198 /* 199 * Random component to lastpid generation. We mix in a random factor to make 200 * it a little harder to predict. We sanity check the modulus value to avoid 201 * doing it in critical paths. Don't let it be too small or we pointlessly 202 * waste randomness entropy, and don't let it be impossibly large. Using a 203 * modulus that is too big causes a LOT more process table scans and slows 204 * down fork processing as the pidchecked caching is defeated. 205 */ 206 static int randompid = 0; 207 208 static int 209 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 210 { 211 int error, pid; 212 213 error = sysctl_wire_old_buffer(req, sizeof(int)); 214 if (error != 0) 215 return(error); 216 sx_xlock(&allproc_lock); 217 pid = randompid; 218 error = sysctl_handle_int(oidp, &pid, 0, req); 219 if (error == 0 && req->newptr != NULL) { 220 if (pid == 0) 221 randompid = 0; 222 else if (pid == 1) 223 /* generate a random PID modulus between 100 and 1123 */ 224 randompid = 100 + arc4random() % 1024; 225 else if (pid < 0 || pid > pid_max - 100) 226 /* out of range */ 227 randompid = pid_max - 100; 228 else if (pid < 100) 229 /* Make it reasonable */ 230 randompid = 100; 231 else 232 randompid = pid; 233 } 234 sx_xunlock(&allproc_lock); 235 return (error); 236 } 237 238 SYSCTL_PROC(_kern, OID_AUTO, randompid, 239 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 0, 240 sysctl_kern_randompid, "I", 241 "Random PID modulus. Special values: 0: disable, 1: choose random value"); 242 243 extern bitstr_t proc_id_pidmap; 244 extern bitstr_t proc_id_grpidmap; 245 extern bitstr_t proc_id_sessidmap; 246 extern bitstr_t proc_id_reapmap; 247 248 /* 249 * Find an unused process ID 250 * 251 * If RFHIGHPID is set (used during system boot), do not allocate 252 * low-numbered pids. 253 */ 254 static int 255 fork_findpid(int flags) 256 { 257 pid_t result; 258 int trypid, random; 259 260 /* 261 * Avoid calling arc4random with procid_lock held. 262 */ 263 random = 0; 264 if (__predict_false(randompid)) 265 random = arc4random() % randompid; 266 267 mtx_lock(&procid_lock); 268 269 trypid = lastpid + 1; 270 if (flags & RFHIGHPID) { 271 if (trypid < 10) 272 trypid = 10; 273 } else { 274 trypid += random; 275 } 276 retry: 277 if (trypid >= pid_max) 278 trypid = 2; 279 280 bit_ffc_at(&proc_id_pidmap, trypid, pid_max, &result); 281 if (result == -1) { 282 KASSERT(trypid != 2, ("unexpectedly ran out of IDs")); 283 trypid = 2; 284 goto retry; 285 } 286 if (bit_test(&proc_id_grpidmap, result) || 287 bit_test(&proc_id_sessidmap, result) || 288 bit_test(&proc_id_reapmap, result)) { 289 trypid = result + 1; 290 goto retry; 291 } 292 293 /* 294 * RFHIGHPID does not mess with the lastpid counter during boot. 295 */ 296 if ((flags & RFHIGHPID) == 0) 297 lastpid = result; 298 299 bit_set(&proc_id_pidmap, result); 300 mtx_unlock(&procid_lock); 301 302 return (result); 303 } 304 305 static int 306 fork_norfproc(struct thread *td, int flags) 307 { 308 struct proc *p1; 309 int error; 310 311 KASSERT((flags & RFPROC) == 0, 312 ("fork_norfproc called with RFPROC set")); 313 p1 = td->td_proc; 314 315 /* 316 * Quiesce other threads if necessary. If RFMEM is not specified we 317 * must ensure that other threads do not concurrently create a second 318 * process sharing the vmspace, see vmspace_unshare(). 319 */ 320 if ((p1->p_flag & (P_HADTHREADS | P_SYSTEM)) == P_HADTHREADS && 321 ((flags & (RFCFDG | RFFDG)) != 0 || (flags & RFMEM) == 0)) { 322 PROC_LOCK(p1); 323 if (thread_single(p1, SINGLE_BOUNDARY)) { 324 PROC_UNLOCK(p1); 325 return (ERESTART); 326 } 327 PROC_UNLOCK(p1); 328 } 329 330 error = vm_forkproc(td, NULL, NULL, NULL, flags); 331 if (error != 0) 332 goto fail; 333 334 /* 335 * Close all file descriptors. 336 */ 337 if ((flags & RFCFDG) != 0) { 338 struct filedesc *fdtmp; 339 struct pwddesc *pdtmp; 340 341 pdtmp = pdinit(td->td_proc->p_pd, false); 342 fdtmp = fdinit(); 343 pdescfree(td); 344 fdescfree(td); 345 p1->p_fd = fdtmp; 346 p1->p_pd = pdtmp; 347 } 348 349 /* 350 * Unshare file descriptors (from parent). 351 */ 352 if ((flags & RFFDG) != 0) { 353 fdunshare(td); 354 pdunshare(td); 355 } 356 357 fail: 358 if ((p1->p_flag & (P_HADTHREADS | P_SYSTEM)) == P_HADTHREADS && 359 ((flags & (RFCFDG | RFFDG)) != 0 || (flags & RFMEM) == 0)) { 360 PROC_LOCK(p1); 361 thread_single_end(p1, SINGLE_BOUNDARY); 362 PROC_UNLOCK(p1); 363 } 364 return (error); 365 } 366 367 static void 368 do_fork(struct thread *td, struct fork_req *fr, struct proc *p2, struct thread *td2, 369 struct vmspace *vm2, struct file *fp_procdesc) 370 { 371 struct proc *p1, *pptr; 372 struct filedesc *fd; 373 struct filedesc_to_leader *fdtol; 374 struct pwddesc *pd; 375 struct sigacts *newsigacts; 376 377 p1 = td->td_proc; 378 379 PROC_LOCK(p1); 380 bcopy(&p1->p_startcopy, &p2->p_startcopy, 381 __rangeof(struct proc, p_startcopy, p_endcopy)); 382 pargs_hold(p2->p_args); 383 PROC_UNLOCK(p1); 384 385 bzero(&p2->p_startzero, 386 __rangeof(struct proc, p_startzero, p_endzero)); 387 388 /* Tell the prison that we exist. */ 389 prison_proc_hold(p2->p_ucred->cr_prison); 390 391 p2->p_state = PRS_NEW; /* protect against others */ 392 p2->p_pid = fork_findpid(fr->fr_flags); 393 AUDIT_ARG_PID(p2->p_pid); 394 TSFORK(p2->p_pid, p1->p_pid); 395 396 sx_xlock(&allproc_lock); 397 LIST_INSERT_HEAD(&allproc, p2, p_list); 398 allproc_gen++; 399 prison_proc_link(p2->p_ucred->cr_prison, p2); 400 sx_xunlock(&allproc_lock); 401 402 sx_xlock(PIDHASHLOCK(p2->p_pid)); 403 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 404 sx_xunlock(PIDHASHLOCK(p2->p_pid)); 405 406 tidhash_add(td2); 407 408 /* 409 * Malloc things while we don't hold any locks. 410 */ 411 if (fr->fr_flags & RFSIGSHARE) 412 newsigacts = NULL; 413 else 414 newsigacts = sigacts_alloc(); 415 416 /* 417 * Copy filedesc. 418 */ 419 if (fr->fr_flags & RFCFDG) { 420 pd = pdinit(p1->p_pd, false); 421 fd = fdinit(); 422 fdtol = NULL; 423 } else if (fr->fr_flags & RFFDG) { 424 if (fr->fr_flags2 & FR2_SHARE_PATHS) 425 pd = pdshare(p1->p_pd); 426 else 427 pd = pdcopy(p1->p_pd); 428 fd = fdcopy(p1->p_fd); 429 fdtol = NULL; 430 } else { 431 if (fr->fr_flags2 & FR2_SHARE_PATHS) 432 pd = pdcopy(p1->p_pd); 433 else 434 pd = pdshare(p1->p_pd); 435 fd = fdshare(p1->p_fd); 436 if (p1->p_fdtol == NULL) 437 p1->p_fdtol = filedesc_to_leader_alloc(NULL, NULL, 438 p1->p_leader); 439 if ((fr->fr_flags & RFTHREAD) != 0) { 440 /* 441 * Shared file descriptor table, and shared 442 * process leaders. 443 */ 444 fdtol = filedesc_to_leader_share(p1->p_fdtol, p1->p_fd); 445 } else { 446 /* 447 * Shared file descriptor table, and different 448 * process leaders. 449 */ 450 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, 451 p1->p_fd, p2); 452 } 453 } 454 /* 455 * Make a proc table entry for the new process. 456 * Start by zeroing the section of proc that is zero-initialized, 457 * then copy the section that is copied directly from the parent. 458 */ 459 460 PROC_LOCK(p2); 461 PROC_LOCK(p1); 462 463 bzero(&td2->td_startzero, 464 __rangeof(struct thread, td_startzero, td_endzero)); 465 466 bcopy(&td->td_startcopy, &td2->td_startcopy, 467 __rangeof(struct thread, td_startcopy, td_endcopy)); 468 469 bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name)); 470 td2->td_sigstk = td->td_sigstk; 471 td2->td_flags = TDF_INMEM; 472 td2->td_lend_user_pri = PRI_MAX; 473 474 #ifdef VIMAGE 475 td2->td_vnet = NULL; 476 td2->td_vnet_lpush = NULL; 477 #endif 478 479 /* 480 * Allow the scheduler to initialize the child. 481 */ 482 thread_lock(td); 483 sched_fork(td, td2); 484 /* 485 * Request AST to check for TDP_RFPPWAIT. Do it here 486 * to avoid calling thread_lock() again. 487 */ 488 if ((fr->fr_flags & RFPPWAIT) != 0) 489 ast_sched_locked(td, TDA_VFORK); 490 thread_unlock(td); 491 492 /* 493 * Duplicate sub-structures as needed. 494 * Increase reference counts on shared objects. 495 */ 496 p2->p_flag = P_INMEM; 497 p2->p_flag2 = p1->p_flag2 & (P2_ASLR_DISABLE | P2_ASLR_ENABLE | 498 P2_ASLR_IGNSTART | P2_NOTRACE | P2_NOTRACE_EXEC | 499 P2_PROTMAX_ENABLE | P2_PROTMAX_DISABLE | P2_TRAPCAP | 500 P2_STKGAP_DISABLE | P2_STKGAP_DISABLE_EXEC | P2_NO_NEW_PRIVS | 501 P2_WXORX_DISABLE | P2_WXORX_ENABLE_EXEC); 502 p2->p_swtick = ticks; 503 if (p1->p_flag & P_PROFIL) 504 startprofclock(p2); 505 506 if (fr->fr_flags & RFSIGSHARE) { 507 p2->p_sigacts = sigacts_hold(p1->p_sigacts); 508 } else { 509 sigacts_copy(newsigacts, p1->p_sigacts); 510 p2->p_sigacts = newsigacts; 511 if ((fr->fr_flags2 & (FR2_DROPSIG_CAUGHT | FR2_KPROC)) != 0) { 512 mtx_lock(&p2->p_sigacts->ps_mtx); 513 if ((fr->fr_flags2 & FR2_DROPSIG_CAUGHT) != 0) 514 sig_drop_caught(p2); 515 if ((fr->fr_flags2 & FR2_KPROC) != 0) 516 p2->p_sigacts->ps_flag |= PS_NOCLDWAIT; 517 mtx_unlock(&p2->p_sigacts->ps_mtx); 518 } 519 } 520 521 if (fr->fr_flags & RFTSIGZMB) 522 p2->p_sigparent = RFTSIGNUM(fr->fr_flags); 523 else if (fr->fr_flags & RFLINUXTHPN) 524 p2->p_sigparent = SIGUSR1; 525 else 526 p2->p_sigparent = SIGCHLD; 527 528 if ((fr->fr_flags2 & FR2_KPROC) != 0) { 529 p2->p_flag |= P_SYSTEM | P_KPROC; 530 td2->td_pflags |= TDP_KTHREAD; 531 } 532 533 p2->p_textvp = p1->p_textvp; 534 p2->p_textdvp = p1->p_textdvp; 535 p2->p_fd = fd; 536 p2->p_fdtol = fdtol; 537 p2->p_pd = pd; 538 539 if (p1->p_flag2 & P2_INHERIT_PROTECTED) { 540 p2->p_flag |= P_PROTECTED; 541 p2->p_flag2 |= P2_INHERIT_PROTECTED; 542 } 543 544 /* 545 * p_limit is copy-on-write. Bump its refcount. 546 */ 547 lim_fork(p1, p2); 548 549 thread_cow_get_proc(td2, p2); 550 551 pstats_fork(p1->p_stats, p2->p_stats); 552 553 PROC_UNLOCK(p1); 554 PROC_UNLOCK(p2); 555 556 /* 557 * Bump references to the text vnode and directory, and copy 558 * the hardlink name. 559 */ 560 if (p2->p_textvp != NULL) 561 vrefact(p2->p_textvp); 562 if (p2->p_textdvp != NULL) 563 vrefact(p2->p_textdvp); 564 p2->p_binname = p1->p_binname == NULL ? NULL : 565 strdup(p1->p_binname, M_PARGS); 566 567 /* 568 * Set up linkage for kernel based threading. 569 */ 570 if ((fr->fr_flags & RFTHREAD) != 0) { 571 mtx_lock(&ppeers_lock); 572 p2->p_peers = p1->p_peers; 573 p1->p_peers = p2; 574 p2->p_leader = p1->p_leader; 575 mtx_unlock(&ppeers_lock); 576 PROC_LOCK(p1->p_leader); 577 if ((p1->p_leader->p_flag & P_WEXIT) != 0) { 578 PROC_UNLOCK(p1->p_leader); 579 /* 580 * The task leader is exiting, so process p1 is 581 * going to be killed shortly. Since p1 obviously 582 * isn't dead yet, we know that the leader is either 583 * sending SIGKILL's to all the processes in this 584 * task or is sleeping waiting for all the peers to 585 * exit. We let p1 complete the fork, but we need 586 * to go ahead and kill the new process p2 since 587 * the task leader may not get a chance to send 588 * SIGKILL to it. We leave it on the list so that 589 * the task leader will wait for this new process 590 * to commit suicide. 591 */ 592 PROC_LOCK(p2); 593 kern_psignal(p2, SIGKILL); 594 PROC_UNLOCK(p2); 595 } else 596 PROC_UNLOCK(p1->p_leader); 597 } else { 598 p2->p_peers = NULL; 599 p2->p_leader = p2; 600 } 601 602 sx_xlock(&proctree_lock); 603 PGRP_LOCK(p1->p_pgrp); 604 PROC_LOCK(p2); 605 PROC_LOCK(p1); 606 607 /* 608 * Preserve some more flags in subprocess. P_PROFIL has already 609 * been preserved. 610 */ 611 p2->p_flag |= p1->p_flag & P_SUGID; 612 td2->td_pflags |= (td->td_pflags & (TDP_ALTSTACK | TDP_SIGFASTBLOCK)); 613 SESS_LOCK(p1->p_session); 614 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 615 p2->p_flag |= P_CONTROLT; 616 SESS_UNLOCK(p1->p_session); 617 if (fr->fr_flags & RFPPWAIT) 618 p2->p_flag |= P_PPWAIT; 619 620 p2->p_pgrp = p1->p_pgrp; 621 LIST_INSERT_AFTER(p1, p2, p_pglist); 622 PGRP_UNLOCK(p1->p_pgrp); 623 LIST_INIT(&p2->p_children); 624 LIST_INIT(&p2->p_orphans); 625 626 callout_init_mtx(&p2->p_itcallout, &p2->p_mtx, 0); 627 TAILQ_INIT(&p2->p_kqtim_stop); 628 629 /* 630 * This begins the section where we must prevent the parent 631 * from being swapped. 632 */ 633 _PHOLD(p1); 634 PROC_UNLOCK(p1); 635 636 /* 637 * Attach the new process to its parent. 638 * 639 * If RFNOWAIT is set, the newly created process becomes a child 640 * of init. This effectively disassociates the child from the 641 * parent. 642 */ 643 if ((fr->fr_flags & RFNOWAIT) != 0) { 644 pptr = p1->p_reaper; 645 p2->p_reaper = pptr; 646 } else { 647 p2->p_reaper = (p1->p_treeflag & P_TREE_REAPER) != 0 ? 648 p1 : p1->p_reaper; 649 pptr = p1; 650 } 651 p2->p_pptr = pptr; 652 p2->p_oppid = pptr->p_pid; 653 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 654 LIST_INIT(&p2->p_reaplist); 655 LIST_INSERT_HEAD(&p2->p_reaper->p_reaplist, p2, p_reapsibling); 656 if (p2->p_reaper == p1 && p1 != initproc) { 657 p2->p_reapsubtree = p2->p_pid; 658 proc_id_set_cond(PROC_ID_REAP, p2->p_pid); 659 } 660 sx_xunlock(&proctree_lock); 661 662 /* Inform accounting that we have forked. */ 663 p2->p_acflag = AFORK; 664 PROC_UNLOCK(p2); 665 666 #ifdef KTRACE 667 ktrprocfork(p1, p2); 668 #endif 669 670 /* 671 * Finish creating the child process. It will return via a different 672 * execution path later. (ie: directly into user mode) 673 */ 674 vm_forkproc(td, p2, td2, vm2, fr->fr_flags); 675 676 if (fr->fr_flags == (RFFDG | RFPROC)) { 677 VM_CNT_INC(v_forks); 678 VM_CNT_ADD(v_forkpages, p2->p_vmspace->vm_dsize + 679 p2->p_vmspace->vm_ssize); 680 } else if (fr->fr_flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 681 VM_CNT_INC(v_vforks); 682 VM_CNT_ADD(v_vforkpages, p2->p_vmspace->vm_dsize + 683 p2->p_vmspace->vm_ssize); 684 } else if (p1 == &proc0) { 685 VM_CNT_INC(v_kthreads); 686 VM_CNT_ADD(v_kthreadpages, p2->p_vmspace->vm_dsize + 687 p2->p_vmspace->vm_ssize); 688 } else { 689 VM_CNT_INC(v_rforks); 690 VM_CNT_ADD(v_rforkpages, p2->p_vmspace->vm_dsize + 691 p2->p_vmspace->vm_ssize); 692 } 693 694 /* 695 * Associate the process descriptor with the process before anything 696 * can happen that might cause that process to need the descriptor. 697 * However, don't do this until after fork(2) can no longer fail. 698 */ 699 if (fr->fr_flags & RFPROCDESC) 700 procdesc_new(p2, fr->fr_pd_flags); 701 702 /* 703 * Both processes are set up, now check if any loadable modules want 704 * to adjust anything. 705 */ 706 EVENTHANDLER_DIRECT_INVOKE(process_fork, p1, p2, fr->fr_flags); 707 708 /* 709 * Set the child start time and mark the process as being complete. 710 */ 711 PROC_LOCK(p2); 712 PROC_LOCK(p1); 713 microuptime(&p2->p_stats->p_start); 714 PROC_SLOCK(p2); 715 p2->p_state = PRS_NORMAL; 716 PROC_SUNLOCK(p2); 717 718 #ifdef KDTRACE_HOOKS 719 /* 720 * Tell the DTrace fasttrap provider about the new process so that any 721 * tracepoints inherited from the parent can be removed. We have to do 722 * this only after p_state is PRS_NORMAL since the fasttrap module will 723 * use pfind() later on. 724 */ 725 if ((fr->fr_flags & RFMEM) == 0 && dtrace_fasttrap_fork) 726 dtrace_fasttrap_fork(p1, p2); 727 #endif 728 if (fr->fr_flags & RFPPWAIT) { 729 td->td_pflags |= TDP_RFPPWAIT; 730 td->td_rfppwait_p = p2; 731 td->td_dbgflags |= TDB_VFORK; 732 } 733 PROC_UNLOCK(p2); 734 735 /* 736 * Tell any interested parties about the new process. 737 */ 738 knote_fork(p1->p_klist, p2->p_pid); 739 740 /* 741 * Now can be swapped. 742 */ 743 _PRELE(p1); 744 PROC_UNLOCK(p1); 745 SDT_PROBE3(proc, , , create, p2, p1, fr->fr_flags); 746 747 if (fr->fr_flags & RFPROCDESC) { 748 procdesc_finit(p2->p_procdesc, fp_procdesc); 749 fdrop(fp_procdesc, td); 750 } 751 752 /* 753 * Speculative check for PTRACE_FORK. PTRACE_FORK is not 754 * synced with forks in progress so it is OK if we miss it 755 * if being set atm. 756 */ 757 if ((p1->p_ptevents & PTRACE_FORK) != 0) { 758 sx_xlock(&proctree_lock); 759 PROC_LOCK(p2); 760 761 /* 762 * p1->p_ptevents & p1->p_pptr are protected by both 763 * process and proctree locks for modifications, 764 * so owning proctree_lock allows the race-free read. 765 */ 766 if ((p1->p_ptevents & PTRACE_FORK) != 0) { 767 /* 768 * Arrange for debugger to receive the fork event. 769 * 770 * We can report PL_FLAG_FORKED regardless of 771 * P_FOLLOWFORK settings, but it does not make a sense 772 * for runaway child. 773 */ 774 td->td_dbgflags |= TDB_FORK; 775 td->td_dbg_forked = p2->p_pid; 776 td2->td_dbgflags |= TDB_STOPATFORK; 777 proc_set_traced(p2, true); 778 CTR2(KTR_PTRACE, 779 "do_fork: attaching to new child pid %d: oppid %d", 780 p2->p_pid, p2->p_oppid); 781 proc_reparent(p2, p1->p_pptr, false); 782 } 783 PROC_UNLOCK(p2); 784 sx_xunlock(&proctree_lock); 785 } 786 787 racct_proc_fork_done(p2); 788 789 if ((fr->fr_flags & RFSTOPPED) == 0) { 790 if (fr->fr_pidp != NULL) 791 *fr->fr_pidp = p2->p_pid; 792 /* 793 * If RFSTOPPED not requested, make child runnable and 794 * add to run queue. 795 */ 796 thread_lock(td2); 797 TD_SET_CAN_RUN(td2); 798 sched_add(td2, SRQ_BORING); 799 } else { 800 *fr->fr_procp = p2; 801 } 802 } 803 804 static void 805 ast_vfork(struct thread *td, int tda __unused) 806 { 807 struct proc *p, *p2; 808 809 MPASS(td->td_pflags & TDP_RFPPWAIT); 810 811 p = td->td_proc; 812 /* 813 * Preserve synchronization semantics of vfork. If 814 * waiting for child to exec or exit, fork set 815 * P_PPWAIT on child, and there we sleep on our proc 816 * (in case of exit). 817 * 818 * Do it after the ptracestop() above is finished, to 819 * not block our debugger until child execs or exits 820 * to finish vfork wait. 821 */ 822 td->td_pflags &= ~TDP_RFPPWAIT; 823 p2 = td->td_rfppwait_p; 824 again: 825 PROC_LOCK(p2); 826 while (p2->p_flag & P_PPWAIT) { 827 PROC_LOCK(p); 828 if (thread_suspend_check_needed()) { 829 PROC_UNLOCK(p2); 830 thread_suspend_check(0); 831 PROC_UNLOCK(p); 832 goto again; 833 } else { 834 PROC_UNLOCK(p); 835 } 836 cv_timedwait(&p2->p_pwait, &p2->p_mtx, hz); 837 } 838 PROC_UNLOCK(p2); 839 840 if (td->td_dbgflags & TDB_VFORK) { 841 PROC_LOCK(p); 842 if (p->p_ptevents & PTRACE_VFORK) 843 ptracestop(td, SIGTRAP, NULL); 844 td->td_dbgflags &= ~TDB_VFORK; 845 PROC_UNLOCK(p); 846 } 847 } 848 849 int 850 fork1(struct thread *td, struct fork_req *fr) 851 { 852 struct proc *p1, *newproc; 853 struct thread *td2; 854 struct vmspace *vm2; 855 struct ucred *cred; 856 struct file *fp_procdesc; 857 struct pgrp *pg; 858 vm_ooffset_t mem_charged; 859 int error, nprocs_new; 860 static int curfail; 861 static struct timeval lastfail; 862 int flags, pages; 863 bool killsx_locked, singlethreaded; 864 865 flags = fr->fr_flags; 866 pages = fr->fr_pages; 867 868 if ((flags & RFSTOPPED) != 0) 869 MPASS(fr->fr_procp != NULL && fr->fr_pidp == NULL); 870 else 871 MPASS(fr->fr_procp == NULL); 872 873 /* Check for the undefined or unimplemented flags. */ 874 if ((flags & ~(RFFLAGS | RFTSIGFLAGS(RFTSIGMASK))) != 0) 875 return (EINVAL); 876 877 /* Signal value requires RFTSIGZMB. */ 878 if ((flags & RFTSIGFLAGS(RFTSIGMASK)) != 0 && (flags & RFTSIGZMB) == 0) 879 return (EINVAL); 880 881 /* Can't copy and clear. */ 882 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 883 return (EINVAL); 884 885 /* Check the validity of the signal number. */ 886 if ((flags & RFTSIGZMB) != 0 && (u_int)RFTSIGNUM(flags) > _SIG_MAXSIG) 887 return (EINVAL); 888 889 if ((flags & RFPROCDESC) != 0) { 890 /* Can't not create a process yet get a process descriptor. */ 891 if ((flags & RFPROC) == 0) 892 return (EINVAL); 893 894 /* Must provide a place to put a procdesc if creating one. */ 895 if (fr->fr_pd_fd == NULL) 896 return (EINVAL); 897 898 /* Check if we are using supported flags. */ 899 if ((fr->fr_pd_flags & ~PD_ALLOWED_AT_FORK) != 0) 900 return (EINVAL); 901 } 902 903 p1 = td->td_proc; 904 905 /* 906 * Here we don't create a new process, but we divorce 907 * certain parts of a process from itself. 908 */ 909 if ((flags & RFPROC) == 0) { 910 if (fr->fr_procp != NULL) 911 *fr->fr_procp = NULL; 912 else if (fr->fr_pidp != NULL) 913 *fr->fr_pidp = 0; 914 return (fork_norfproc(td, flags)); 915 } 916 917 fp_procdesc = NULL; 918 newproc = NULL; 919 vm2 = NULL; 920 killsx_locked = false; 921 singlethreaded = false; 922 923 /* 924 * Increment the nprocs resource before allocations occur. 925 * Although process entries are dynamically created, we still 926 * keep a global limit on the maximum number we will 927 * create. There are hard-limits as to the number of processes 928 * that can run, established by the KVA and memory usage for 929 * the process data. 930 * 931 * Don't allow a nonprivileged user to use the last ten 932 * processes; don't let root exceed the limit. 933 */ 934 nprocs_new = atomic_fetchadd_int(&nprocs, 1) + 1; 935 if (nprocs_new >= maxproc - 10) { 936 if (priv_check_cred(td->td_ucred, PRIV_MAXPROC) != 0 || 937 nprocs_new >= maxproc) { 938 error = EAGAIN; 939 sx_xlock(&allproc_lock); 940 if (ppsratecheck(&lastfail, &curfail, 1)) { 941 printf("maxproc limit exceeded by uid %u " 942 "(pid %d); see tuning(7) and " 943 "login.conf(5)\n", 944 td->td_ucred->cr_ruid, p1->p_pid); 945 } 946 sx_xunlock(&allproc_lock); 947 goto fail2; 948 } 949 } 950 951 /* 952 * If we are possibly multi-threaded, and there is a process 953 * sending a signal to our group right now, ensure that our 954 * other threads cannot be chosen for the signal queueing. 955 * Otherwise, this might delay signal action, and make the new 956 * child escape the signaling. 957 */ 958 pg = p1->p_pgrp; 959 if (p1->p_numthreads > 1) { 960 if (sx_try_slock(&pg->pg_killsx) != 0) { 961 killsx_locked = true; 962 } else { 963 PROC_LOCK(p1); 964 if (thread_single(p1, SINGLE_BOUNDARY)) { 965 PROC_UNLOCK(p1); 966 error = ERESTART; 967 goto fail2; 968 } 969 PROC_UNLOCK(p1); 970 singlethreaded = true; 971 } 972 } 973 974 /* 975 * Atomically check for signals and block processes from sending 976 * a signal to our process group until the child is visible. 977 */ 978 if (!killsx_locked && sx_slock_sig(&pg->pg_killsx) != 0) { 979 error = ERESTART; 980 goto fail2; 981 } 982 if (__predict_false(p1->p_pgrp != pg || sig_intr() != 0)) { 983 /* 984 * Either the process was moved to other process 985 * group, or there is pending signal. sx_slock_sig() 986 * does not check for signals if not sleeping for the 987 * lock. 988 */ 989 sx_sunlock(&pg->pg_killsx); 990 killsx_locked = false; 991 error = ERESTART; 992 goto fail2; 993 } else { 994 killsx_locked = true; 995 } 996 997 /* 998 * If required, create a process descriptor in the parent first; we 999 * will abandon it if something goes wrong. We don't finit() until 1000 * later. 1001 */ 1002 if (flags & RFPROCDESC) { 1003 error = procdesc_falloc(td, &fp_procdesc, fr->fr_pd_fd, 1004 fr->fr_pd_flags, fr->fr_pd_fcaps); 1005 if (error != 0) 1006 goto fail2; 1007 AUDIT_ARG_FD(*fr->fr_pd_fd); 1008 } 1009 1010 mem_charged = 0; 1011 if (pages == 0) 1012 pages = kstack_pages; 1013 /* Allocate new proc. */ 1014 newproc = uma_zalloc(proc_zone, M_WAITOK); 1015 td2 = FIRST_THREAD_IN_PROC(newproc); 1016 if (td2 == NULL) { 1017 td2 = thread_alloc(pages); 1018 if (td2 == NULL) { 1019 error = ENOMEM; 1020 goto fail2; 1021 } 1022 proc_linkup(newproc, td2); 1023 } else { 1024 kmsan_thread_alloc(td2); 1025 if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) { 1026 if (td2->td_kstack != 0) 1027 vm_thread_dispose(td2); 1028 if (!thread_alloc_stack(td2, pages)) { 1029 error = ENOMEM; 1030 goto fail2; 1031 } 1032 } 1033 } 1034 1035 if ((flags & RFMEM) == 0) { 1036 vm2 = vmspace_fork(p1->p_vmspace, &mem_charged); 1037 if (vm2 == NULL) { 1038 error = ENOMEM; 1039 goto fail2; 1040 } 1041 if (!swap_reserve(mem_charged)) { 1042 /* 1043 * The swap reservation failed. The accounting 1044 * from the entries of the copied vm2 will be 1045 * subtracted in vmspace_free(), so force the 1046 * reservation there. 1047 */ 1048 swap_reserve_force(mem_charged); 1049 error = ENOMEM; 1050 goto fail2; 1051 } 1052 } else 1053 vm2 = NULL; 1054 1055 /* 1056 * XXX: This is ugly; when we copy resource usage, we need to bump 1057 * per-cred resource counters. 1058 */ 1059 proc_set_cred_init(newproc, td->td_ucred); 1060 1061 /* 1062 * Initialize resource accounting for the child process. 1063 */ 1064 error = racct_proc_fork(p1, newproc); 1065 if (error != 0) { 1066 error = EAGAIN; 1067 goto fail1; 1068 } 1069 1070 #ifdef MAC 1071 mac_proc_init(newproc); 1072 #endif 1073 newproc->p_klist = knlist_alloc(&newproc->p_mtx); 1074 STAILQ_INIT(&newproc->p_ktr); 1075 1076 /* 1077 * Increment the count of procs running with this uid. Don't allow 1078 * a nonprivileged user to exceed their current limit. 1079 */ 1080 cred = td->td_ucred; 1081 if (!chgproccnt(cred->cr_ruidinfo, 1, lim_cur(td, RLIMIT_NPROC))) { 1082 if (priv_check_cred(cred, PRIV_PROC_LIMIT) != 0) 1083 goto fail0; 1084 chgproccnt(cred->cr_ruidinfo, 1, 0); 1085 } 1086 1087 do_fork(td, fr, newproc, td2, vm2, fp_procdesc); 1088 error = 0; 1089 goto cleanup; 1090 fail0: 1091 error = EAGAIN; 1092 #ifdef MAC 1093 mac_proc_destroy(newproc); 1094 #endif 1095 racct_proc_exit(newproc); 1096 fail1: 1097 proc_unset_cred(newproc); 1098 fail2: 1099 if (vm2 != NULL) 1100 vmspace_free(vm2); 1101 uma_zfree(proc_zone, newproc); 1102 if ((flags & RFPROCDESC) != 0 && fp_procdesc != NULL) { 1103 fdclose(td, fp_procdesc, *fr->fr_pd_fd); 1104 fdrop(fp_procdesc, td); 1105 } 1106 atomic_add_int(&nprocs, -1); 1107 cleanup: 1108 if (killsx_locked) 1109 sx_sunlock(&pg->pg_killsx); 1110 if (singlethreaded) { 1111 PROC_LOCK(p1); 1112 thread_single_end(p1, SINGLE_BOUNDARY); 1113 PROC_UNLOCK(p1); 1114 } 1115 if (error != 0) 1116 pause("fork", hz / 2); 1117 return (error); 1118 } 1119 1120 /* 1121 * Handle the return of a child process from fork1(). This function 1122 * is called from the MD fork_trampoline() entry point. 1123 */ 1124 void 1125 fork_exit(void (*callout)(void *, struct trapframe *), void *arg, 1126 struct trapframe *frame) 1127 { 1128 struct proc *p; 1129 struct thread *td; 1130 struct thread *dtd; 1131 1132 kmsan_mark(frame, sizeof(*frame), KMSAN_STATE_INITED); 1133 1134 td = curthread; 1135 p = td->td_proc; 1136 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new")); 1137 1138 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)", 1139 td, td_get_sched(td), p->p_pid, td->td_name); 1140 1141 sched_fork_exit(td); 1142 1143 /* 1144 * Processes normally resume in mi_switch() after being 1145 * cpu_switch()'ed to, but when children start up they arrive here 1146 * instead, so we must do much the same things as mi_switch() would. 1147 */ 1148 if ((dtd = PCPU_GET(deadthread))) { 1149 PCPU_SET(deadthread, NULL); 1150 thread_stash(dtd); 1151 } 1152 thread_unlock(td); 1153 1154 /* 1155 * cpu_fork_kthread_handler intercepts this function call to 1156 * have this call a non-return function to stay in kernel mode. 1157 * initproc has its own fork handler, but it does return. 1158 */ 1159 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 1160 callout(arg, frame); 1161 1162 /* 1163 * Check if a kernel thread misbehaved and returned from its main 1164 * function. 1165 */ 1166 if (p->p_flag & P_KPROC) { 1167 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 1168 td->td_name, p->p_pid); 1169 kthread_exit(); 1170 } 1171 mtx_assert(&Giant, MA_NOTOWNED); 1172 1173 if (p->p_sysent->sv_schedtail != NULL) 1174 (p->p_sysent->sv_schedtail)(td); 1175 } 1176 1177 /* 1178 * Simplified back end of syscall(), used when returning from fork() 1179 * directly into user mode. This function is passed in to fork_exit() 1180 * as the first parameter and is called when returning to a new 1181 * userland process. 1182 */ 1183 void 1184 fork_return(struct thread *td, struct trapframe *frame) 1185 { 1186 struct proc *p; 1187 1188 p = td->td_proc; 1189 if (td->td_dbgflags & TDB_STOPATFORK) { 1190 PROC_LOCK(p); 1191 if ((p->p_flag & P_TRACED) != 0) { 1192 /* 1193 * Inform the debugger if one is still present. 1194 */ 1195 td->td_dbgflags |= TDB_CHILD | TDB_SCX | TDB_FSTP; 1196 ptracestop(td, SIGSTOP, NULL); 1197 td->td_dbgflags &= ~(TDB_CHILD | TDB_SCX); 1198 } else { 1199 /* 1200 * ... otherwise clear the request. 1201 */ 1202 td->td_dbgflags &= ~TDB_STOPATFORK; 1203 } 1204 PROC_UNLOCK(p); 1205 } else if (p->p_flag & P_TRACED) { 1206 /* 1207 * This is the start of a new thread in a traced 1208 * process. Report a system call exit event. 1209 */ 1210 PROC_LOCK(p); 1211 td->td_dbgflags |= TDB_SCX; 1212 if ((p->p_ptevents & PTRACE_SCX) != 0 || 1213 (td->td_dbgflags & TDB_BORN) != 0) 1214 ptracestop(td, SIGTRAP, NULL); 1215 td->td_dbgflags &= ~(TDB_SCX | TDB_BORN); 1216 PROC_UNLOCK(p); 1217 } 1218 1219 /* 1220 * If the prison was killed mid-fork, die along with it. 1221 */ 1222 if (!prison_isalive(td->td_ucred->cr_prison)) 1223 exit1(td, 0, SIGKILL); 1224 1225 userret(td, frame); 1226 1227 #ifdef KTRACE 1228 if (KTRPOINT(td, KTR_SYSRET)) 1229 ktrsysret(td->td_sa.code, 0, 0); 1230 #endif 1231 } 1232 1233 static void 1234 fork_init(void *arg __unused) 1235 { 1236 ast_register(TDA_VFORK, ASTR_ASTF_REQUIRED | ASTR_TDP, TDP_RFPPWAIT, 1237 ast_vfork); 1238 } 1239 SYSINIT(fork, SI_SUB_INTRINSIC, SI_ORDER_ANY, fork_init, NULL); 1240