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/asan.h> 44 #include <sys/bitstring.h> 45 #include <sys/sysproto.h> 46 #include <sys/eventhandler.h> 47 #include <sys/fcntl.h> 48 #include <sys/filedesc.h> 49 #include <sys/jail.h> 50 #include <sys/kernel.h> 51 #include <sys/kthread.h> 52 #include <sys/sysctl.h> 53 #include <sys/lock.h> 54 #include <sys/malloc.h> 55 #include <sys/msan.h> 56 #include <sys/mutex.h> 57 #include <sys/priv.h> 58 #include <sys/proc.h> 59 #include <sys/procdesc.h> 60 #include <sys/ptrace.h> 61 #include <sys/racct.h> 62 #include <sys/resourcevar.h> 63 #include <sys/sched.h> 64 #include <sys/syscall.h> 65 #include <sys/vmmeter.h> 66 #include <sys/vnode.h> 67 #include <sys/acct.h> 68 #include <sys/ktr.h> 69 #include <sys/ktrace.h> 70 #include <sys/unistd.h> 71 #include <sys/sdt.h> 72 #include <sys/sx.h> 73 #include <sys/sysent.h> 74 #include <sys/signalvar.h> 75 76 #include <security/audit/audit.h> 77 #include <security/mac/mac_framework.h> 78 79 #include <vm/vm.h> 80 #include <vm/pmap.h> 81 #include <vm/vm_map.h> 82 #include <vm/vm_extern.h> 83 #include <vm/uma.h> 84 85 #ifdef KDTRACE_HOOKS 86 #include <sys/dtrace_bsd.h> 87 dtrace_fork_func_t dtrace_fasttrap_fork; 88 #endif 89 90 SDT_PROVIDER_DECLARE(proc); 91 SDT_PROBE_DEFINE3(proc, , , create, "struct proc *", "struct proc *", "int"); 92 93 #ifndef _SYS_SYSPROTO_H_ 94 struct fork_args { 95 int dummy; 96 }; 97 #endif 98 99 /* ARGSUSED */ 100 int 101 sys_fork(struct thread *td, struct fork_args *uap) 102 { 103 struct fork_req fr; 104 int error, pid; 105 106 bzero(&fr, sizeof(fr)); 107 fr.fr_flags = RFFDG | RFPROC; 108 fr.fr_pidp = &pid; 109 error = fork1(td, &fr); 110 if (error == 0) { 111 td->td_retval[0] = pid; 112 td->td_retval[1] = 0; 113 } 114 return (error); 115 } 116 117 /* ARGUSED */ 118 int 119 sys_pdfork(struct thread *td, struct pdfork_args *uap) 120 { 121 struct fork_req fr; 122 int error, fd, pid; 123 124 bzero(&fr, sizeof(fr)); 125 fr.fr_flags = RFFDG | RFPROC | RFPROCDESC; 126 fr.fr_pidp = &pid; 127 fr.fr_pd_fd = &fd; 128 fr.fr_pd_flags = uap->flags; 129 AUDIT_ARG_FFLAGS(uap->flags); 130 /* 131 * It is necessary to return fd by reference because 0 is a valid file 132 * descriptor number, and the child needs to be able to distinguish 133 * itself from the parent using the return value. 134 */ 135 error = fork1(td, &fr); 136 if (error == 0) { 137 td->td_retval[0] = pid; 138 td->td_retval[1] = 0; 139 error = copyout(&fd, uap->fdp, sizeof(fd)); 140 } 141 return (error); 142 } 143 144 /* ARGSUSED */ 145 int 146 sys_vfork(struct thread *td, struct vfork_args *uap) 147 { 148 struct fork_req fr; 149 int error, pid; 150 151 bzero(&fr, sizeof(fr)); 152 fr.fr_flags = RFFDG | RFPROC | RFPPWAIT | RFMEM; 153 fr.fr_pidp = &pid; 154 error = fork1(td, &fr); 155 if (error == 0) { 156 td->td_retval[0] = pid; 157 td->td_retval[1] = 0; 158 } 159 return (error); 160 } 161 162 int 163 sys_rfork(struct thread *td, struct rfork_args *uap) 164 { 165 struct fork_req fr; 166 int error, pid; 167 168 /* Don't allow kernel-only flags. */ 169 if ((uap->flags & RFKERNELONLY) != 0) 170 return (EINVAL); 171 /* RFSPAWN must not appear with others */ 172 if ((uap->flags & RFSPAWN) != 0 && uap->flags != RFSPAWN) 173 return (EINVAL); 174 175 AUDIT_ARG_FFLAGS(uap->flags); 176 bzero(&fr, sizeof(fr)); 177 if ((uap->flags & RFSPAWN) != 0) { 178 fr.fr_flags = RFFDG | RFPROC | RFPPWAIT | RFMEM; 179 fr.fr_flags2 = FR2_DROPSIG_CAUGHT; 180 } else { 181 fr.fr_flags = uap->flags; 182 } 183 fr.fr_pidp = &pid; 184 error = fork1(td, &fr); 185 if (error == 0) { 186 td->td_retval[0] = pid; 187 td->td_retval[1] = 0; 188 } 189 return (error); 190 } 191 192 int __exclusive_cache_line nprocs = 1; /* process 0 */ 193 int lastpid = 0; 194 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0, 195 "Last used PID"); 196 197 /* 198 * Random component to lastpid generation. We mix in a random factor to make 199 * it a little harder to predict. We sanity check the modulus value to avoid 200 * doing it in critical paths. Don't let it be too small or we pointlessly 201 * waste randomness entropy, and don't let it be impossibly large. Using a 202 * modulus that is too big causes a LOT more process table scans and slows 203 * down fork processing as the pidchecked caching is defeated. 204 */ 205 static int randompid = 0; 206 207 static int 208 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 209 { 210 int error, pid; 211 212 error = sysctl_wire_old_buffer(req, sizeof(int)); 213 if (error != 0) 214 return(error); 215 sx_xlock(&allproc_lock); 216 pid = randompid; 217 error = sysctl_handle_int(oidp, &pid, 0, req); 218 if (error == 0 && req->newptr != NULL) { 219 if (pid == 0) 220 randompid = 0; 221 else if (pid == 1) 222 /* generate a random PID modulus between 100 and 1123 */ 223 randompid = 100 + arc4random() % 1024; 224 else if (pid < 0 || pid > pid_max - 100) 225 /* out of range */ 226 randompid = pid_max - 100; 227 else if (pid < 100) 228 /* Make it reasonable */ 229 randompid = 100; 230 else 231 randompid = pid; 232 } 233 sx_xunlock(&allproc_lock); 234 return (error); 235 } 236 237 SYSCTL_PROC(_kern, OID_AUTO, randompid, 238 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 0, 239 sysctl_kern_randompid, "I", 240 "Random PID modulus. Special values: 0: disable, 1: choose random value"); 241 242 extern bitstr_t proc_id_pidmap; 243 extern bitstr_t proc_id_grpidmap; 244 extern bitstr_t proc_id_sessidmap; 245 extern bitstr_t proc_id_reapmap; 246 247 /* 248 * Find an unused process ID 249 * 250 * If RFHIGHPID is set (used during system boot), do not allocate 251 * low-numbered pids. 252 */ 253 static int 254 fork_findpid(int flags) 255 { 256 pid_t result; 257 int trypid, random; 258 259 /* 260 * Avoid calling arc4random with procid_lock held. 261 */ 262 random = 0; 263 if (__predict_false(randompid)) 264 random = arc4random() % randompid; 265 266 mtx_lock(&procid_lock); 267 268 trypid = lastpid + 1; 269 if (flags & RFHIGHPID) { 270 if (trypid < 10) 271 trypid = 10; 272 } else { 273 trypid += random; 274 } 275 retry: 276 if (trypid >= pid_max) 277 trypid = 2; 278 279 bit_ffc_at(&proc_id_pidmap, trypid, pid_max, &result); 280 if (result == -1) { 281 KASSERT(trypid != 2, ("unexpectedly ran out of IDs")); 282 trypid = 2; 283 goto retry; 284 } 285 if (bit_test(&proc_id_grpidmap, result) || 286 bit_test(&proc_id_sessidmap, result) || 287 bit_test(&proc_id_reapmap, result)) { 288 trypid = result + 1; 289 goto retry; 290 } 291 292 /* 293 * RFHIGHPID does not mess with the lastpid counter during boot. 294 */ 295 if ((flags & RFHIGHPID) == 0) 296 lastpid = result; 297 298 bit_set(&proc_id_pidmap, result); 299 mtx_unlock(&procid_lock); 300 301 return (result); 302 } 303 304 static int 305 fork_norfproc(struct thread *td, int flags) 306 { 307 struct proc *p1; 308 int error; 309 310 KASSERT((flags & RFPROC) == 0, 311 ("fork_norfproc called with RFPROC set")); 312 p1 = td->td_proc; 313 314 /* 315 * Quiesce other threads if necessary. If RFMEM is not specified we 316 * must ensure that other threads do not concurrently create a second 317 * process sharing the vmspace, see vmspace_unshare(). 318 */ 319 if ((p1->p_flag & (P_HADTHREADS | P_SYSTEM)) == P_HADTHREADS && 320 ((flags & (RFCFDG | RFFDG)) != 0 || (flags & RFMEM) == 0)) { 321 PROC_LOCK(p1); 322 if (thread_single(p1, SINGLE_BOUNDARY)) { 323 PROC_UNLOCK(p1); 324 return (ERESTART); 325 } 326 PROC_UNLOCK(p1); 327 } 328 329 error = vm_forkproc(td, NULL, NULL, NULL, flags); 330 if (error != 0) 331 goto fail; 332 333 /* 334 * Close all file descriptors. 335 */ 336 if ((flags & RFCFDG) != 0) { 337 struct filedesc *fdtmp; 338 struct pwddesc *pdtmp; 339 340 pdtmp = pdinit(td->td_proc->p_pd, false); 341 fdtmp = fdinit(); 342 pdescfree(td); 343 fdescfree(td); 344 p1->p_fd = fdtmp; 345 p1->p_pd = pdtmp; 346 } 347 348 /* 349 * Unshare file descriptors (from parent). 350 */ 351 if ((flags & RFFDG) != 0) { 352 fdunshare(td); 353 pdunshare(td); 354 } 355 356 fail: 357 if ((p1->p_flag & (P_HADTHREADS | P_SYSTEM)) == P_HADTHREADS && 358 ((flags & (RFCFDG | RFFDG)) != 0 || (flags & RFMEM) == 0)) { 359 PROC_LOCK(p1); 360 thread_single_end(p1, SINGLE_BOUNDARY); 361 PROC_UNLOCK(p1); 362 } 363 return (error); 364 } 365 366 static void 367 do_fork(struct thread *td, struct fork_req *fr, struct proc *p2, struct thread *td2, 368 struct vmspace *vm2, struct file *fp_procdesc) 369 { 370 struct proc *p1, *pptr; 371 struct filedesc *fd; 372 struct filedesc_to_leader *fdtol; 373 struct pwddesc *pd; 374 struct sigacts *newsigacts; 375 376 p1 = td->td_proc; 377 378 PROC_LOCK(p1); 379 bcopy(&p1->p_startcopy, &p2->p_startcopy, 380 __rangeof(struct proc, p_startcopy, p_endcopy)); 381 pargs_hold(p2->p_args); 382 PROC_UNLOCK(p1); 383 384 bzero(&p2->p_startzero, 385 __rangeof(struct proc, p_startzero, p_endzero)); 386 387 /* Tell the prison that we exist. */ 388 prison_proc_hold(p2->p_ucred->cr_prison); 389 390 p2->p_state = PRS_NEW; /* protect against others */ 391 p2->p_pid = fork_findpid(fr->fr_flags); 392 AUDIT_ARG_PID(p2->p_pid); 393 TSFORK(p2->p_pid, p1->p_pid); 394 395 sx_xlock(&allproc_lock); 396 LIST_INSERT_HEAD(&allproc, p2, p_list); 397 allproc_gen++; 398 prison_proc_link(p2->p_ucred->cr_prison, p2); 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(); 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 = filedesc_to_leader_share(p1->p_fdtol, p1->p_fd); 444 } else { 445 /* 446 * Shared file descriptor table, and different 447 * process leaders. 448 */ 449 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, 450 p1->p_fd, p2); 451 } 452 } 453 /* 454 * Make a proc table entry for the new process. 455 * Start by zeroing the section of proc that is zero-initialized, 456 * then copy the section that is copied directly from the parent. 457 */ 458 459 PROC_LOCK(p2); 460 PROC_LOCK(p1); 461 462 bzero(&td2->td_startzero, 463 __rangeof(struct thread, td_startzero, td_endzero)); 464 465 bcopy(&td->td_startcopy, &td2->td_startcopy, 466 __rangeof(struct thread, td_startcopy, td_endcopy)); 467 468 bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name)); 469 td2->td_sigstk = td->td_sigstk; 470 td2->td_flags = TDF_INMEM; 471 td2->td_lend_user_pri = PRI_MAX; 472 473 #ifdef VIMAGE 474 td2->td_vnet = NULL; 475 td2->td_vnet_lpush = NULL; 476 #endif 477 478 /* 479 * Allow the scheduler to initialize the child. 480 */ 481 thread_lock(td); 482 sched_fork(td, td2); 483 /* 484 * Request AST to check for TDP_RFPPWAIT. Do it here 485 * to avoid calling thread_lock() again. 486 */ 487 if ((fr->fr_flags & RFPPWAIT) != 0) 488 ast_sched_locked(td, TDA_VFORK); 489 thread_unlock(td); 490 491 /* 492 * Duplicate sub-structures as needed. 493 * Increase reference counts on shared objects. 494 */ 495 p2->p_flag = P_INMEM; 496 p2->p_flag2 = p1->p_flag2 & (P2_ASLR_DISABLE | P2_ASLR_ENABLE | 497 P2_ASLR_IGNSTART | P2_NOTRACE | P2_NOTRACE_EXEC | 498 P2_PROTMAX_ENABLE | P2_PROTMAX_DISABLE | P2_TRAPCAP | 499 P2_STKGAP_DISABLE | P2_STKGAP_DISABLE_EXEC | P2_NO_NEW_PRIVS | 500 P2_WXORX_DISABLE | P2_WXORX_ENABLE_EXEC); 501 p2->p_swtick = ticks; 502 if (p1->p_flag & P_PROFIL) 503 startprofclock(p2); 504 505 if (fr->fr_flags & RFSIGSHARE) { 506 p2->p_sigacts = sigacts_hold(p1->p_sigacts); 507 } else { 508 sigacts_copy(newsigacts, p1->p_sigacts); 509 p2->p_sigacts = newsigacts; 510 if ((fr->fr_flags2 & (FR2_DROPSIG_CAUGHT | FR2_KPROC)) != 0) { 511 mtx_lock(&p2->p_sigacts->ps_mtx); 512 if ((fr->fr_flags2 & FR2_DROPSIG_CAUGHT) != 0) 513 sig_drop_caught(p2); 514 if ((fr->fr_flags2 & FR2_KPROC) != 0) 515 p2->p_sigacts->ps_flag |= PS_NOCLDWAIT; 516 mtx_unlock(&p2->p_sigacts->ps_mtx); 517 } 518 } 519 520 if (fr->fr_flags & RFTSIGZMB) 521 p2->p_sigparent = RFTSIGNUM(fr->fr_flags); 522 else if (fr->fr_flags & RFLINUXTHPN) 523 p2->p_sigparent = SIGUSR1; 524 else 525 p2->p_sigparent = SIGCHLD; 526 527 if ((fr->fr_flags2 & FR2_KPROC) != 0) { 528 p2->p_flag |= P_SYSTEM | P_KPROC; 529 td2->td_pflags |= TDP_KTHREAD; 530 } 531 532 p2->p_textvp = p1->p_textvp; 533 p2->p_textdvp = p1->p_textdvp; 534 p2->p_fd = fd; 535 p2->p_fdtol = fdtol; 536 p2->p_pd = pd; 537 538 if (p1->p_flag2 & P2_INHERIT_PROTECTED) { 539 p2->p_flag |= P_PROTECTED; 540 p2->p_flag2 |= P2_INHERIT_PROTECTED; 541 } 542 543 /* 544 * p_limit is copy-on-write. Bump its refcount. 545 */ 546 lim_fork(p1, p2); 547 548 thread_cow_get_proc(td2, p2); 549 550 pstats_fork(p1->p_stats, p2->p_stats); 551 552 PROC_UNLOCK(p1); 553 PROC_UNLOCK(p2); 554 555 /* 556 * Bump references to the text vnode and directory, and copy 557 * the hardlink name. 558 */ 559 if (p2->p_textvp != NULL) 560 vrefact(p2->p_textvp); 561 if (p2->p_textdvp != NULL) 562 vrefact(p2->p_textdvp); 563 p2->p_binname = p1->p_binname == NULL ? NULL : 564 strdup(p1->p_binname, M_PARGS); 565 566 /* 567 * Set up linkage for kernel based threading. 568 */ 569 if ((fr->fr_flags & RFTHREAD) != 0) { 570 mtx_lock(&ppeers_lock); 571 p2->p_peers = p1->p_peers; 572 p1->p_peers = p2; 573 p2->p_leader = p1->p_leader; 574 mtx_unlock(&ppeers_lock); 575 PROC_LOCK(p1->p_leader); 576 if ((p1->p_leader->p_flag & P_WEXIT) != 0) { 577 PROC_UNLOCK(p1->p_leader); 578 /* 579 * The task leader is exiting, so process p1 is 580 * going to be killed shortly. Since p1 obviously 581 * isn't dead yet, we know that the leader is either 582 * sending SIGKILL's to all the processes in this 583 * task or is sleeping waiting for all the peers to 584 * exit. We let p1 complete the fork, but we need 585 * to go ahead and kill the new process p2 since 586 * the task leader may not get a chance to send 587 * SIGKILL to it. We leave it on the list so that 588 * the task leader will wait for this new process 589 * to commit suicide. 590 */ 591 PROC_LOCK(p2); 592 kern_psignal(p2, SIGKILL); 593 PROC_UNLOCK(p2); 594 } else 595 PROC_UNLOCK(p1->p_leader); 596 } else { 597 p2->p_peers = NULL; 598 p2->p_leader = p2; 599 } 600 601 sx_xlock(&proctree_lock); 602 PGRP_LOCK(p1->p_pgrp); 603 PROC_LOCK(p2); 604 PROC_LOCK(p1); 605 606 /* 607 * Preserve some more flags in subprocess. P_PROFIL has already 608 * been preserved. 609 */ 610 p2->p_flag |= p1->p_flag & P_SUGID; 611 td2->td_pflags |= (td->td_pflags & (TDP_ALTSTACK | TDP_SIGFASTBLOCK)); 612 SESS_LOCK(p1->p_session); 613 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 614 p2->p_flag |= P_CONTROLT; 615 SESS_UNLOCK(p1->p_session); 616 if (fr->fr_flags & RFPPWAIT) 617 p2->p_flag |= P_PPWAIT; 618 619 p2->p_pgrp = p1->p_pgrp; 620 LIST_INSERT_AFTER(p1, p2, p_pglist); 621 PGRP_UNLOCK(p1->p_pgrp); 622 LIST_INIT(&p2->p_children); 623 LIST_INIT(&p2->p_orphans); 624 625 callout_init_mtx(&p2->p_itcallout, &p2->p_mtx, 0); 626 627 /* 628 * This begins the section where we must prevent the parent 629 * from being swapped. 630 */ 631 _PHOLD(p1); 632 PROC_UNLOCK(p1); 633 634 /* 635 * Attach the new process to its parent. 636 * 637 * If RFNOWAIT is set, the newly created process becomes a child 638 * of init. This effectively disassociates the child from the 639 * parent. 640 */ 641 if ((fr->fr_flags & RFNOWAIT) != 0) { 642 pptr = p1->p_reaper; 643 p2->p_reaper = pptr; 644 } else { 645 p2->p_reaper = (p1->p_treeflag & P_TREE_REAPER) != 0 ? 646 p1 : p1->p_reaper; 647 pptr = p1; 648 } 649 p2->p_pptr = pptr; 650 p2->p_oppid = pptr->p_pid; 651 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 652 LIST_INIT(&p2->p_reaplist); 653 LIST_INSERT_HEAD(&p2->p_reaper->p_reaplist, p2, p_reapsibling); 654 if (p2->p_reaper == p1 && p1 != initproc) { 655 p2->p_reapsubtree = p2->p_pid; 656 proc_id_set_cond(PROC_ID_REAP, p2->p_pid); 657 } 658 sx_xunlock(&proctree_lock); 659 660 /* Inform accounting that we have forked. */ 661 p2->p_acflag = AFORK; 662 PROC_UNLOCK(p2); 663 664 #ifdef KTRACE 665 ktrprocfork(p1, p2); 666 #endif 667 668 /* 669 * Finish creating the child process. It will return via a different 670 * execution path later. (ie: directly into user mode) 671 */ 672 vm_forkproc(td, p2, td2, vm2, fr->fr_flags); 673 674 if (fr->fr_flags == (RFFDG | RFPROC)) { 675 VM_CNT_INC(v_forks); 676 VM_CNT_ADD(v_forkpages, p2->p_vmspace->vm_dsize + 677 p2->p_vmspace->vm_ssize); 678 } else if (fr->fr_flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 679 VM_CNT_INC(v_vforks); 680 VM_CNT_ADD(v_vforkpages, p2->p_vmspace->vm_dsize + 681 p2->p_vmspace->vm_ssize); 682 } else if (p1 == &proc0) { 683 VM_CNT_INC(v_kthreads); 684 VM_CNT_ADD(v_kthreadpages, p2->p_vmspace->vm_dsize + 685 p2->p_vmspace->vm_ssize); 686 } else { 687 VM_CNT_INC(v_rforks); 688 VM_CNT_ADD(v_rforkpages, p2->p_vmspace->vm_dsize + 689 p2->p_vmspace->vm_ssize); 690 } 691 692 /* 693 * Associate the process descriptor with the process before anything 694 * can happen that might cause that process to need the descriptor. 695 * However, don't do this until after fork(2) can no longer fail. 696 */ 697 if (fr->fr_flags & RFPROCDESC) 698 procdesc_new(p2, fr->fr_pd_flags); 699 700 /* 701 * Both processes are set up, now check if any loadable modules want 702 * to adjust anything. 703 */ 704 EVENTHANDLER_DIRECT_INVOKE(process_fork, p1, p2, fr->fr_flags); 705 706 /* 707 * Set the child start time and mark the process as being complete. 708 */ 709 PROC_LOCK(p2); 710 PROC_LOCK(p1); 711 microuptime(&p2->p_stats->p_start); 712 PROC_SLOCK(p2); 713 p2->p_state = PRS_NORMAL; 714 PROC_SUNLOCK(p2); 715 716 #ifdef KDTRACE_HOOKS 717 /* 718 * Tell the DTrace fasttrap provider about the new process so that any 719 * tracepoints inherited from the parent can be removed. We have to do 720 * this only after p_state is PRS_NORMAL since the fasttrap module will 721 * use pfind() later on. 722 */ 723 if ((fr->fr_flags & RFMEM) == 0 && dtrace_fasttrap_fork) 724 dtrace_fasttrap_fork(p1, p2); 725 #endif 726 if (fr->fr_flags & RFPPWAIT) { 727 td->td_pflags |= TDP_RFPPWAIT; 728 td->td_rfppwait_p = p2; 729 td->td_dbgflags |= TDB_VFORK; 730 } 731 PROC_UNLOCK(p2); 732 733 /* 734 * Tell any interested parties about the new process. 735 */ 736 knote_fork(p1->p_klist, p2->p_pid); 737 738 /* 739 * Now can be swapped. 740 */ 741 _PRELE(p1); 742 PROC_UNLOCK(p1); 743 SDT_PROBE3(proc, , , create, p2, p1, fr->fr_flags); 744 745 if (fr->fr_flags & RFPROCDESC) { 746 procdesc_finit(p2->p_procdesc, fp_procdesc); 747 fdrop(fp_procdesc, td); 748 } 749 750 /* 751 * Speculative check for PTRACE_FORK. PTRACE_FORK is not 752 * synced with forks in progress so it is OK if we miss it 753 * if being set atm. 754 */ 755 if ((p1->p_ptevents & PTRACE_FORK) != 0) { 756 sx_xlock(&proctree_lock); 757 PROC_LOCK(p2); 758 759 /* 760 * p1->p_ptevents & p1->p_pptr are protected by both 761 * process and proctree locks for modifications, 762 * so owning proctree_lock allows the race-free read. 763 */ 764 if ((p1->p_ptevents & PTRACE_FORK) != 0) { 765 /* 766 * Arrange for debugger to receive the fork event. 767 * 768 * We can report PL_FLAG_FORKED regardless of 769 * P_FOLLOWFORK settings, but it does not make a sense 770 * for runaway child. 771 */ 772 td->td_dbgflags |= TDB_FORK; 773 td->td_dbg_forked = p2->p_pid; 774 td2->td_dbgflags |= TDB_STOPATFORK; 775 proc_set_traced(p2, true); 776 CTR2(KTR_PTRACE, 777 "do_fork: attaching to new child pid %d: oppid %d", 778 p2->p_pid, p2->p_oppid); 779 proc_reparent(p2, p1->p_pptr, false); 780 } 781 PROC_UNLOCK(p2); 782 sx_xunlock(&proctree_lock); 783 } 784 785 racct_proc_fork_done(p2); 786 787 if ((fr->fr_flags & RFSTOPPED) == 0) { 788 if (fr->fr_pidp != NULL) 789 *fr->fr_pidp = p2->p_pid; 790 /* 791 * If RFSTOPPED not requested, make child runnable and 792 * add to run queue. 793 */ 794 thread_lock(td2); 795 TD_SET_CAN_RUN(td2); 796 sched_add(td2, SRQ_BORING); 797 } else { 798 *fr->fr_procp = p2; 799 } 800 } 801 802 static void 803 ast_vfork(struct thread *td, int tda __unused) 804 { 805 struct proc *p, *p2; 806 807 MPASS(td->td_pflags & TDP_RFPPWAIT); 808 809 p = td->td_proc; 810 /* 811 * Preserve synchronization semantics of vfork. If 812 * waiting for child to exec or exit, fork set 813 * P_PPWAIT on child, and there we sleep on our proc 814 * (in case of exit). 815 * 816 * Do it after the ptracestop() above is finished, to 817 * not block our debugger until child execs or exits 818 * to finish vfork wait. 819 */ 820 td->td_pflags &= ~TDP_RFPPWAIT; 821 p2 = td->td_rfppwait_p; 822 again: 823 PROC_LOCK(p2); 824 while (p2->p_flag & P_PPWAIT) { 825 PROC_LOCK(p); 826 if (thread_suspend_check_needed()) { 827 PROC_UNLOCK(p2); 828 thread_suspend_check(0); 829 PROC_UNLOCK(p); 830 goto again; 831 } else { 832 PROC_UNLOCK(p); 833 } 834 cv_timedwait(&p2->p_pwait, &p2->p_mtx, hz); 835 } 836 PROC_UNLOCK(p2); 837 838 if (td->td_dbgflags & TDB_VFORK) { 839 PROC_LOCK(p); 840 if (p->p_ptevents & PTRACE_VFORK) 841 ptracestop(td, SIGTRAP, NULL); 842 td->td_dbgflags &= ~TDB_VFORK; 843 PROC_UNLOCK(p); 844 } 845 } 846 847 int 848 fork1(struct thread *td, struct fork_req *fr) 849 { 850 struct proc *p1, *newproc; 851 struct thread *td2; 852 struct vmspace *vm2; 853 struct ucred *cred; 854 struct file *fp_procdesc; 855 struct pgrp *pg; 856 vm_ooffset_t mem_charged; 857 int error, nprocs_new; 858 static int curfail; 859 static struct timeval lastfail; 860 int flags, pages; 861 bool killsx_locked, singlethreaded; 862 863 flags = fr->fr_flags; 864 pages = fr->fr_pages; 865 866 if ((flags & RFSTOPPED) != 0) 867 MPASS(fr->fr_procp != NULL && fr->fr_pidp == NULL); 868 else 869 MPASS(fr->fr_procp == NULL); 870 871 /* Check for the undefined or unimplemented flags. */ 872 if ((flags & ~(RFFLAGS | RFTSIGFLAGS(RFTSIGMASK))) != 0) 873 return (EINVAL); 874 875 /* Signal value requires RFTSIGZMB. */ 876 if ((flags & RFTSIGFLAGS(RFTSIGMASK)) != 0 && (flags & RFTSIGZMB) == 0) 877 return (EINVAL); 878 879 /* Can't copy and clear. */ 880 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 881 return (EINVAL); 882 883 /* Check the validity of the signal number. */ 884 if ((flags & RFTSIGZMB) != 0 && (u_int)RFTSIGNUM(flags) > _SIG_MAXSIG) 885 return (EINVAL); 886 887 if ((flags & RFPROCDESC) != 0) { 888 /* Can't not create a process yet get a process descriptor. */ 889 if ((flags & RFPROC) == 0) 890 return (EINVAL); 891 892 /* Must provide a place to put a procdesc if creating one. */ 893 if (fr->fr_pd_fd == NULL) 894 return (EINVAL); 895 896 /* Check if we are using supported flags. */ 897 if ((fr->fr_pd_flags & ~PD_ALLOWED_AT_FORK) != 0) 898 return (EINVAL); 899 } 900 901 p1 = td->td_proc; 902 903 /* 904 * Here we don't create a new process, but we divorce 905 * certain parts of a process from itself. 906 */ 907 if ((flags & RFPROC) == 0) { 908 if (fr->fr_procp != NULL) 909 *fr->fr_procp = NULL; 910 else if (fr->fr_pidp != NULL) 911 *fr->fr_pidp = 0; 912 return (fork_norfproc(td, flags)); 913 } 914 915 fp_procdesc = NULL; 916 newproc = NULL; 917 vm2 = NULL; 918 killsx_locked = false; 919 singlethreaded = false; 920 921 /* 922 * Increment the nprocs resource before allocations occur. 923 * Although process entries are dynamically created, we still 924 * keep a global limit on the maximum number we will 925 * create. There are hard-limits as to the number of processes 926 * that can run, established by the KVA and memory usage for 927 * the process data. 928 * 929 * Don't allow a nonprivileged user to use the last ten 930 * processes; don't let root exceed the limit. 931 */ 932 nprocs_new = atomic_fetchadd_int(&nprocs, 1) + 1; 933 if (nprocs_new >= maxproc - 10) { 934 if (priv_check_cred(td->td_ucred, PRIV_MAXPROC) != 0 || 935 nprocs_new >= maxproc) { 936 error = EAGAIN; 937 sx_xlock(&allproc_lock); 938 if (ppsratecheck(&lastfail, &curfail, 1)) { 939 printf("maxproc limit exceeded by uid %u " 940 "(pid %d); see tuning(7) and " 941 "login.conf(5)\n", 942 td->td_ucred->cr_ruid, p1->p_pid); 943 } 944 sx_xunlock(&allproc_lock); 945 goto fail2; 946 } 947 } 948 949 /* 950 * If we are possibly multi-threaded, and there is a process 951 * sending a signal to our group right now, ensure that our 952 * other threads cannot be chosen for the signal queueing. 953 * Otherwise, this might delay signal action, and make the new 954 * child escape the signaling. 955 */ 956 pg = p1->p_pgrp; 957 if (p1->p_numthreads > 1) { 958 if (sx_try_slock(&pg->pg_killsx) != 0) { 959 killsx_locked = true; 960 } else { 961 PROC_LOCK(p1); 962 if (thread_single(p1, SINGLE_BOUNDARY)) { 963 PROC_UNLOCK(p1); 964 error = ERESTART; 965 goto fail2; 966 } 967 PROC_UNLOCK(p1); 968 singlethreaded = true; 969 } 970 } 971 972 /* 973 * Atomically check for signals and block processes from sending 974 * a signal to our process group until the child is visible. 975 */ 976 if (!killsx_locked && sx_slock_sig(&pg->pg_killsx) != 0) { 977 error = ERESTART; 978 goto fail2; 979 } 980 if (__predict_false(p1->p_pgrp != pg || sig_intr() != 0)) { 981 /* 982 * Either the process was moved to other process 983 * group, or there is pending signal. sx_slock_sig() 984 * does not check for signals if not sleeping for the 985 * lock. 986 */ 987 sx_sunlock(&pg->pg_killsx); 988 killsx_locked = false; 989 error = ERESTART; 990 goto fail2; 991 } else { 992 killsx_locked = true; 993 } 994 995 /* 996 * If required, create a process descriptor in the parent first; we 997 * will abandon it if something goes wrong. We don't finit() until 998 * later. 999 */ 1000 if (flags & RFPROCDESC) { 1001 error = procdesc_falloc(td, &fp_procdesc, fr->fr_pd_fd, 1002 fr->fr_pd_flags, fr->fr_pd_fcaps); 1003 if (error != 0) 1004 goto fail2; 1005 AUDIT_ARG_FD(*fr->fr_pd_fd); 1006 } 1007 1008 mem_charged = 0; 1009 if (pages == 0) 1010 pages = kstack_pages; 1011 /* Allocate new proc. */ 1012 newproc = uma_zalloc(proc_zone, M_WAITOK); 1013 td2 = FIRST_THREAD_IN_PROC(newproc); 1014 if (td2 == NULL) { 1015 td2 = thread_alloc(pages); 1016 if (td2 == NULL) { 1017 error = ENOMEM; 1018 goto fail2; 1019 } 1020 proc_linkup(newproc, td2); 1021 } else { 1022 kmsan_thread_alloc(td2); 1023 if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) { 1024 if (td2->td_kstack != 0) 1025 vm_thread_dispose(td2); 1026 if (!thread_alloc_stack(td2, pages)) { 1027 error = ENOMEM; 1028 goto fail2; 1029 } 1030 } else { 1031 kasan_mark((void *)td2->td_kstack, 1032 ptoa(td2->td_kstack_pages), 1033 ptoa(td2->td_kstack_pages), 0); 1034 } 1035 } 1036 1037 if ((flags & RFMEM) == 0) { 1038 vm2 = vmspace_fork(p1->p_vmspace, &mem_charged); 1039 if (vm2 == NULL) { 1040 error = ENOMEM; 1041 goto fail2; 1042 } 1043 if (!swap_reserve(mem_charged)) { 1044 /* 1045 * The swap reservation failed. The accounting 1046 * from the entries of the copied vm2 will be 1047 * subtracted in vmspace_free(), so force the 1048 * reservation there. 1049 */ 1050 swap_reserve_force(mem_charged); 1051 error = ENOMEM; 1052 goto fail2; 1053 } 1054 } else 1055 vm2 = NULL; 1056 1057 /* 1058 * XXX: This is ugly; when we copy resource usage, we need to bump 1059 * per-cred resource counters. 1060 */ 1061 newproc->p_ucred = crcowget(td->td_ucred); 1062 1063 /* 1064 * Initialize resource accounting for the child process. 1065 */ 1066 error = racct_proc_fork(p1, newproc); 1067 if (error != 0) { 1068 error = EAGAIN; 1069 goto fail1; 1070 } 1071 1072 #ifdef MAC 1073 mac_proc_init(newproc); 1074 #endif 1075 newproc->p_klist = knlist_alloc(&newproc->p_mtx); 1076 STAILQ_INIT(&newproc->p_ktr); 1077 1078 /* 1079 * Increment the count of procs running with this uid. Don't allow 1080 * a nonprivileged user to exceed their current limit. 1081 */ 1082 cred = td->td_ucred; 1083 if (!chgproccnt(cred->cr_ruidinfo, 1, lim_cur(td, RLIMIT_NPROC))) { 1084 if (priv_check_cred(cred, PRIV_PROC_LIMIT) != 0) 1085 goto fail0; 1086 chgproccnt(cred->cr_ruidinfo, 1, 0); 1087 } 1088 1089 do_fork(td, fr, newproc, td2, vm2, fp_procdesc); 1090 error = 0; 1091 goto cleanup; 1092 fail0: 1093 error = EAGAIN; 1094 #ifdef MAC 1095 mac_proc_destroy(newproc); 1096 #endif 1097 racct_proc_exit(newproc); 1098 fail1: 1099 proc_unset_cred(newproc); 1100 fail2: 1101 if (vm2 != NULL) 1102 vmspace_free(vm2); 1103 uma_zfree(proc_zone, newproc); 1104 if ((flags & RFPROCDESC) != 0 && fp_procdesc != NULL) { 1105 fdclose(td, fp_procdesc, *fr->fr_pd_fd); 1106 fdrop(fp_procdesc, td); 1107 } 1108 atomic_add_int(&nprocs, -1); 1109 cleanup: 1110 if (killsx_locked) 1111 sx_sunlock(&pg->pg_killsx); 1112 if (singlethreaded) { 1113 PROC_LOCK(p1); 1114 thread_single_end(p1, SINGLE_BOUNDARY); 1115 PROC_UNLOCK(p1); 1116 } 1117 if (error != 0) 1118 pause("fork", hz / 2); 1119 return (error); 1120 } 1121 1122 /* 1123 * Handle the return of a child process from fork1(). This function 1124 * is called from the MD fork_trampoline() entry point. 1125 */ 1126 void 1127 fork_exit(void (*callout)(void *, struct trapframe *), void *arg, 1128 struct trapframe *frame) 1129 { 1130 struct proc *p; 1131 struct thread *td; 1132 struct thread *dtd; 1133 1134 kmsan_mark(frame, sizeof(*frame), KMSAN_STATE_INITED); 1135 1136 td = curthread; 1137 p = td->td_proc; 1138 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new")); 1139 1140 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)", 1141 td, td_get_sched(td), p->p_pid, td->td_name); 1142 1143 sched_fork_exit(td); 1144 1145 /* 1146 * Processes normally resume in mi_switch() after being 1147 * cpu_switch()'ed to, but when children start up they arrive here 1148 * instead, so we must do much the same things as mi_switch() would. 1149 */ 1150 if ((dtd = PCPU_GET(deadthread))) { 1151 PCPU_SET(deadthread, NULL); 1152 thread_stash(dtd); 1153 } 1154 thread_unlock(td); 1155 1156 /* 1157 * cpu_fork_kthread_handler intercepts this function call to 1158 * have this call a non-return function to stay in kernel mode. 1159 * initproc has its own fork handler, but it does return. 1160 */ 1161 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 1162 callout(arg, frame); 1163 1164 /* 1165 * Check if a kernel thread misbehaved and returned from its main 1166 * function. 1167 */ 1168 if (p->p_flag & P_KPROC) { 1169 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 1170 td->td_name, p->p_pid); 1171 kthread_exit(); 1172 } 1173 mtx_assert(&Giant, MA_NOTOWNED); 1174 1175 /* 1176 * Now going to return to userland. 1177 */ 1178 1179 if (p->p_sysent->sv_schedtail != NULL) 1180 (p->p_sysent->sv_schedtail)(td); 1181 1182 userret(td, frame); 1183 } 1184 1185 /* 1186 * Simplified back end of syscall(), used when returning from fork() 1187 * directly into user mode. This function is passed in to fork_exit() 1188 * as the first parameter and is called when returning to a new 1189 * userland process. 1190 */ 1191 void 1192 fork_return(struct thread *td, struct trapframe *frame) 1193 { 1194 struct proc *p; 1195 1196 p = td->td_proc; 1197 if (td->td_dbgflags & TDB_STOPATFORK) { 1198 PROC_LOCK(p); 1199 if ((p->p_flag & P_TRACED) != 0) { 1200 /* 1201 * Inform the debugger if one is still present. 1202 */ 1203 td->td_dbgflags |= TDB_CHILD | TDB_SCX | TDB_FSTP; 1204 ptracestop(td, SIGSTOP, NULL); 1205 td->td_dbgflags &= ~(TDB_CHILD | TDB_SCX); 1206 } else { 1207 /* 1208 * ... otherwise clear the request. 1209 */ 1210 td->td_dbgflags &= ~TDB_STOPATFORK; 1211 } 1212 PROC_UNLOCK(p); 1213 } else if (p->p_flag & P_TRACED) { 1214 /* 1215 * This is the start of a new thread in a traced 1216 * process. Report a system call exit event. 1217 */ 1218 PROC_LOCK(p); 1219 td->td_dbgflags |= TDB_SCX; 1220 if ((p->p_ptevents & PTRACE_SCX) != 0 || 1221 (td->td_dbgflags & TDB_BORN) != 0) 1222 ptracestop(td, SIGTRAP, NULL); 1223 td->td_dbgflags &= ~(TDB_SCX | TDB_BORN); 1224 PROC_UNLOCK(p); 1225 } 1226 1227 /* 1228 * If the prison was killed mid-fork, die along with it. 1229 */ 1230 if (!prison_isalive(td->td_ucred->cr_prison)) 1231 exit1(td, 0, SIGKILL); 1232 1233 #ifdef KTRACE 1234 if (KTRPOINT(td, KTR_SYSRET)) 1235 ktrsysret(td->td_sa.code, 0, 0); 1236 #endif 1237 } 1238 1239 static void 1240 fork_init(void *arg __unused) 1241 { 1242 ast_register(TDA_VFORK, ASTR_ASTF_REQUIRED | ASTR_TDP, TDP_RFPPWAIT, 1243 ast_vfork); 1244 } 1245 SYSINIT(fork, SI_SUB_INTRINSIC, SI_ORDER_ANY, fork_init, NULL); 1246