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
sys_fork(struct thread * td,struct fork_args * uap)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
sys_pdfork(struct thread * td,struct pdfork_args * uap)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
sys_vfork(struct thread * td,struct vfork_args * uap)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
sys_rfork(struct thread * td,struct rfork_args * uap)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
sysctl_kern_randompid(SYSCTL_HANDLER_ARGS)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
fork_findpid(int flags)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
fork_norfproc(struct thread * td,int flags)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
do_fork(struct thread * td,struct fork_req * fr,struct proc * p2,struct thread * td2,struct vmspace * vm2,struct file * fp_procdesc)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
628 /*
629 * This begins the section where we must prevent the parent
630 * from being swapped.
631 */
632 _PHOLD(p1);
633 PROC_UNLOCK(p1);
634
635 /*
636 * Attach the new process to its parent.
637 *
638 * If RFNOWAIT is set, the newly created process becomes a child
639 * of init. This effectively disassociates the child from the
640 * parent.
641 */
642 if ((fr->fr_flags & RFNOWAIT) != 0) {
643 pptr = p1->p_reaper;
644 p2->p_reaper = pptr;
645 } else {
646 p2->p_reaper = (p1->p_treeflag & P_TREE_REAPER) != 0 ?
647 p1 : p1->p_reaper;
648 pptr = p1;
649 }
650 p2->p_pptr = pptr;
651 p2->p_oppid = pptr->p_pid;
652 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling);
653 LIST_INIT(&p2->p_reaplist);
654 LIST_INSERT_HEAD(&p2->p_reaper->p_reaplist, p2, p_reapsibling);
655 if (p2->p_reaper == p1 && p1 != initproc) {
656 p2->p_reapsubtree = p2->p_pid;
657 proc_id_set_cond(PROC_ID_REAP, p2->p_pid);
658 }
659 sx_xunlock(&proctree_lock);
660
661 /* Inform accounting that we have forked. */
662 p2->p_acflag = AFORK;
663 PROC_UNLOCK(p2);
664
665 #ifdef KTRACE
666 ktrprocfork(p1, p2);
667 #endif
668
669 /*
670 * Finish creating the child process. It will return via a different
671 * execution path later. (ie: directly into user mode)
672 */
673 vm_forkproc(td, p2, td2, vm2, fr->fr_flags);
674
675 if (fr->fr_flags == (RFFDG | RFPROC)) {
676 VM_CNT_INC(v_forks);
677 VM_CNT_ADD(v_forkpages, p2->p_vmspace->vm_dsize +
678 p2->p_vmspace->vm_ssize);
679 } else if (fr->fr_flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) {
680 VM_CNT_INC(v_vforks);
681 VM_CNT_ADD(v_vforkpages, p2->p_vmspace->vm_dsize +
682 p2->p_vmspace->vm_ssize);
683 } else if (p1 == &proc0) {
684 VM_CNT_INC(v_kthreads);
685 VM_CNT_ADD(v_kthreadpages, p2->p_vmspace->vm_dsize +
686 p2->p_vmspace->vm_ssize);
687 } else {
688 VM_CNT_INC(v_rforks);
689 VM_CNT_ADD(v_rforkpages, p2->p_vmspace->vm_dsize +
690 p2->p_vmspace->vm_ssize);
691 }
692
693 /*
694 * Associate the process descriptor with the process before anything
695 * can happen that might cause that process to need the descriptor.
696 * However, don't do this until after fork(2) can no longer fail.
697 */
698 if (fr->fr_flags & RFPROCDESC)
699 procdesc_new(p2, fr->fr_pd_flags);
700
701 /*
702 * Both processes are set up, now check if any loadable modules want
703 * to adjust anything.
704 */
705 EVENTHANDLER_DIRECT_INVOKE(process_fork, p1, p2, fr->fr_flags);
706
707 /*
708 * Set the child start time and mark the process as being complete.
709 */
710 PROC_LOCK(p2);
711 PROC_LOCK(p1);
712 microuptime(&p2->p_stats->p_start);
713 PROC_SLOCK(p2);
714 p2->p_state = PRS_NORMAL;
715 PROC_SUNLOCK(p2);
716
717 #ifdef KDTRACE_HOOKS
718 /*
719 * Tell the DTrace fasttrap provider about the new process so that any
720 * tracepoints inherited from the parent can be removed. We have to do
721 * this only after p_state is PRS_NORMAL since the fasttrap module will
722 * use pfind() later on.
723 */
724 if ((fr->fr_flags & RFMEM) == 0 && dtrace_fasttrap_fork)
725 dtrace_fasttrap_fork(p1, p2);
726 #endif
727 if (fr->fr_flags & RFPPWAIT) {
728 td->td_pflags |= TDP_RFPPWAIT;
729 td->td_rfppwait_p = p2;
730 td->td_dbgflags |= TDB_VFORK;
731 }
732 PROC_UNLOCK(p2);
733
734 /*
735 * Tell any interested parties about the new process.
736 */
737 knote_fork(p1->p_klist, p2->p_pid);
738
739 /*
740 * Now can be swapped.
741 */
742 _PRELE(p1);
743 PROC_UNLOCK(p1);
744 SDT_PROBE3(proc, , , create, p2, p1, fr->fr_flags);
745
746 if (fr->fr_flags & RFPROCDESC) {
747 procdesc_finit(p2->p_procdesc, fp_procdesc);
748 fdrop(fp_procdesc, td);
749 }
750
751 /*
752 * Speculative check for PTRACE_FORK. PTRACE_FORK is not
753 * synced with forks in progress so it is OK if we miss it
754 * if being set atm.
755 */
756 if ((p1->p_ptevents & PTRACE_FORK) != 0) {
757 sx_xlock(&proctree_lock);
758 PROC_LOCK(p2);
759
760 /*
761 * p1->p_ptevents & p1->p_pptr are protected by both
762 * process and proctree locks for modifications,
763 * so owning proctree_lock allows the race-free read.
764 */
765 if ((p1->p_ptevents & PTRACE_FORK) != 0) {
766 /*
767 * Arrange for debugger to receive the fork event.
768 *
769 * We can report PL_FLAG_FORKED regardless of
770 * P_FOLLOWFORK settings, but it does not make a sense
771 * for runaway child.
772 */
773 td->td_dbgflags |= TDB_FORK;
774 td->td_dbg_forked = p2->p_pid;
775 td2->td_dbgflags |= TDB_STOPATFORK;
776 proc_set_traced(p2, true);
777 CTR2(KTR_PTRACE,
778 "do_fork: attaching to new child pid %d: oppid %d",
779 p2->p_pid, p2->p_oppid);
780 proc_reparent(p2, p1->p_pptr, false);
781 }
782 PROC_UNLOCK(p2);
783 sx_xunlock(&proctree_lock);
784 }
785
786 racct_proc_fork_done(p2);
787
788 if ((fr->fr_flags & RFSTOPPED) == 0) {
789 if (fr->fr_pidp != NULL)
790 *fr->fr_pidp = p2->p_pid;
791 /*
792 * If RFSTOPPED not requested, make child runnable and
793 * add to run queue.
794 */
795 thread_lock(td2);
796 TD_SET_CAN_RUN(td2);
797 sched_add(td2, SRQ_BORING);
798 } else {
799 *fr->fr_procp = p2;
800 }
801 }
802
803 static void
ast_vfork(struct thread * td,int tda __unused)804 ast_vfork(struct thread *td, int tda __unused)
805 {
806 struct proc *p, *p2;
807
808 MPASS(td->td_pflags & TDP_RFPPWAIT);
809
810 p = td->td_proc;
811 /*
812 * Preserve synchronization semantics of vfork. If
813 * waiting for child to exec or exit, fork set
814 * P_PPWAIT on child, and there we sleep on our proc
815 * (in case of exit).
816 *
817 * Do it after the ptracestop() above is finished, to
818 * not block our debugger until child execs or exits
819 * to finish vfork wait.
820 */
821 td->td_pflags &= ~TDP_RFPPWAIT;
822 p2 = td->td_rfppwait_p;
823 again:
824 PROC_LOCK(p2);
825 while (p2->p_flag & P_PPWAIT) {
826 PROC_LOCK(p);
827 if (thread_suspend_check_needed()) {
828 PROC_UNLOCK(p2);
829 thread_suspend_check(0);
830 PROC_UNLOCK(p);
831 goto again;
832 } else {
833 PROC_UNLOCK(p);
834 }
835 cv_timedwait(&p2->p_pwait, &p2->p_mtx, hz);
836 }
837 PROC_UNLOCK(p2);
838
839 if (td->td_dbgflags & TDB_VFORK) {
840 PROC_LOCK(p);
841 if (p->p_ptevents & PTRACE_VFORK)
842 ptracestop(td, SIGTRAP, NULL);
843 td->td_dbgflags &= ~TDB_VFORK;
844 PROC_UNLOCK(p);
845 }
846 }
847
848 int
fork1(struct thread * td,struct fork_req * fr)849 fork1(struct thread *td, struct fork_req *fr)
850 {
851 struct proc *p1, *newproc;
852 struct thread *td2;
853 struct vmspace *vm2;
854 struct ucred *cred;
855 struct file *fp_procdesc;
856 struct pgrp *pg;
857 vm_ooffset_t mem_charged;
858 int error, nprocs_new;
859 static int curfail;
860 static struct timeval lastfail;
861 int flags, pages;
862 bool killsx_locked, singlethreaded;
863
864 flags = fr->fr_flags;
865 pages = fr->fr_pages;
866
867 if ((flags & RFSTOPPED) != 0)
868 MPASS(fr->fr_procp != NULL && fr->fr_pidp == NULL);
869 else
870 MPASS(fr->fr_procp == NULL);
871
872 /* Check for the undefined or unimplemented flags. */
873 if ((flags & ~(RFFLAGS | RFTSIGFLAGS(RFTSIGMASK))) != 0)
874 return (EINVAL);
875
876 /* Signal value requires RFTSIGZMB. */
877 if ((flags & RFTSIGFLAGS(RFTSIGMASK)) != 0 && (flags & RFTSIGZMB) == 0)
878 return (EINVAL);
879
880 /* Can't copy and clear. */
881 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG))
882 return (EINVAL);
883
884 /* Check the validity of the signal number. */
885 if ((flags & RFTSIGZMB) != 0 && (u_int)RFTSIGNUM(flags) > _SIG_MAXSIG)
886 return (EINVAL);
887
888 if ((flags & RFPROCDESC) != 0) {
889 /* Can't not create a process yet get a process descriptor. */
890 if ((flags & RFPROC) == 0)
891 return (EINVAL);
892
893 /* Must provide a place to put a procdesc if creating one. */
894 if (fr->fr_pd_fd == NULL)
895 return (EINVAL);
896
897 /* Check if we are using supported flags. */
898 if ((fr->fr_pd_flags & ~PD_ALLOWED_AT_FORK) != 0)
899 return (EINVAL);
900 }
901
902 p1 = td->td_proc;
903
904 /*
905 * Here we don't create a new process, but we divorce
906 * certain parts of a process from itself.
907 */
908 if ((flags & RFPROC) == 0) {
909 if (fr->fr_procp != NULL)
910 *fr->fr_procp = NULL;
911 else if (fr->fr_pidp != NULL)
912 *fr->fr_pidp = 0;
913 return (fork_norfproc(td, flags));
914 }
915
916 fp_procdesc = NULL;
917 newproc = NULL;
918 vm2 = NULL;
919 killsx_locked = false;
920 singlethreaded = false;
921
922 /*
923 * Increment the nprocs resource before allocations occur.
924 * Although process entries are dynamically created, we still
925 * keep a global limit on the maximum number we will
926 * create. There are hard-limits as to the number of processes
927 * that can run, established by the KVA and memory usage for
928 * the process data.
929 *
930 * Don't allow a nonprivileged user to use the last ten
931 * processes; don't let root exceed the limit.
932 */
933 nprocs_new = atomic_fetchadd_int(&nprocs, 1) + 1;
934 if (nprocs_new >= maxproc - 10) {
935 if (priv_check_cred(td->td_ucred, PRIV_MAXPROC) != 0 ||
936 nprocs_new >= maxproc) {
937 error = EAGAIN;
938 sx_xlock(&allproc_lock);
939 if (ppsratecheck(&lastfail, &curfail, 1)) {
940 printf("maxproc limit exceeded by uid %u "
941 "(pid %d); see tuning(7) and "
942 "login.conf(5)\n",
943 td->td_ucred->cr_ruid, p1->p_pid);
944 }
945 sx_xunlock(&allproc_lock);
946 goto fail2;
947 }
948 }
949
950 /*
951 * If we are possibly multi-threaded, and there is a process
952 * sending a signal to our group right now, ensure that our
953 * other threads cannot be chosen for the signal queueing.
954 * Otherwise, this might delay signal action, and make the new
955 * child escape the signaling.
956 */
957 pg = p1->p_pgrp;
958 if (p1->p_numthreads > 1) {
959 if (sx_try_slock(&pg->pg_killsx) != 0) {
960 killsx_locked = true;
961 } else {
962 PROC_LOCK(p1);
963 if (thread_single(p1, SINGLE_BOUNDARY)) {
964 PROC_UNLOCK(p1);
965 error = ERESTART;
966 goto fail2;
967 }
968 PROC_UNLOCK(p1);
969 singlethreaded = true;
970 }
971 }
972
973 /*
974 * Atomically check for signals and block processes from sending
975 * a signal to our process group until the child is visible.
976 */
977 if (!killsx_locked && sx_slock_sig(&pg->pg_killsx) != 0) {
978 error = ERESTART;
979 goto fail2;
980 }
981 if (__predict_false(p1->p_pgrp != pg || sig_intr() != 0)) {
982 /*
983 * Either the process was moved to other process
984 * group, or there is pending signal. sx_slock_sig()
985 * does not check for signals if not sleeping for the
986 * lock.
987 */
988 sx_sunlock(&pg->pg_killsx);
989 killsx_locked = false;
990 error = ERESTART;
991 goto fail2;
992 } else {
993 killsx_locked = true;
994 }
995
996 /*
997 * If required, create a process descriptor in the parent first; we
998 * will abandon it if something goes wrong. We don't finit() until
999 * later.
1000 */
1001 if (flags & RFPROCDESC) {
1002 error = procdesc_falloc(td, &fp_procdesc, fr->fr_pd_fd,
1003 fr->fr_pd_flags, fr->fr_pd_fcaps);
1004 if (error != 0)
1005 goto fail2;
1006 AUDIT_ARG_FD(*fr->fr_pd_fd);
1007 }
1008
1009 mem_charged = 0;
1010 if (pages == 0)
1011 pages = kstack_pages;
1012 /* Allocate new proc. */
1013 newproc = uma_zalloc(proc_zone, M_WAITOK);
1014 td2 = FIRST_THREAD_IN_PROC(newproc);
1015 if (td2 == NULL) {
1016 td2 = thread_alloc(pages);
1017 if (td2 == NULL) {
1018 error = ENOMEM;
1019 goto fail2;
1020 }
1021 proc_linkup(newproc, td2);
1022 } else {
1023 error = thread_recycle(td2, pages);
1024 if (error != 0)
1025 goto fail2;
1026 }
1027
1028 if ((flags & RFMEM) == 0) {
1029 vm2 = vmspace_fork(p1->p_vmspace, &mem_charged);
1030 if (vm2 == NULL) {
1031 error = ENOMEM;
1032 goto fail2;
1033 }
1034 if (!swap_reserve(mem_charged)) {
1035 /*
1036 * The swap reservation failed. The accounting
1037 * from the entries of the copied vm2 will be
1038 * subtracted in vmspace_free(), so force the
1039 * reservation there.
1040 */
1041 swap_reserve_force(mem_charged);
1042 error = ENOMEM;
1043 goto fail2;
1044 }
1045 } else
1046 vm2 = NULL;
1047
1048 /*
1049 * XXX: This is ugly; when we copy resource usage, we need to bump
1050 * per-cred resource counters.
1051 */
1052 newproc->p_ucred = crcowget(td->td_ucred);
1053
1054 /*
1055 * Initialize resource accounting for the child process.
1056 */
1057 error = racct_proc_fork(p1, newproc);
1058 if (error != 0) {
1059 error = EAGAIN;
1060 goto fail1;
1061 }
1062
1063 #ifdef MAC
1064 mac_proc_init(newproc);
1065 #endif
1066 newproc->p_klist = knlist_alloc(&newproc->p_mtx);
1067 STAILQ_INIT(&newproc->p_ktr);
1068
1069 /*
1070 * Increment the count of procs running with this uid. Don't allow
1071 * a nonprivileged user to exceed their current limit.
1072 */
1073 cred = td->td_ucred;
1074 if (!chgproccnt(cred->cr_ruidinfo, 1, lim_cur(td, RLIMIT_NPROC))) {
1075 if (priv_check_cred(cred, PRIV_PROC_LIMIT) != 0)
1076 goto fail0;
1077 chgproccnt(cred->cr_ruidinfo, 1, 0);
1078 }
1079
1080 do_fork(td, fr, newproc, td2, vm2, fp_procdesc);
1081 error = 0;
1082 goto cleanup;
1083 fail0:
1084 error = EAGAIN;
1085 #ifdef MAC
1086 mac_proc_destroy(newproc);
1087 #endif
1088 racct_proc_exit(newproc);
1089 fail1:
1090 proc_unset_cred(newproc, false);
1091 fail2:
1092 if (vm2 != NULL)
1093 vmspace_free(vm2);
1094 uma_zfree(proc_zone, newproc);
1095 if ((flags & RFPROCDESC) != 0 && fp_procdesc != NULL) {
1096 fdclose(td, fp_procdesc, *fr->fr_pd_fd);
1097 fdrop(fp_procdesc, td);
1098 }
1099 atomic_add_int(&nprocs, -1);
1100 cleanup:
1101 if (killsx_locked)
1102 sx_sunlock(&pg->pg_killsx);
1103 if (singlethreaded) {
1104 PROC_LOCK(p1);
1105 thread_single_end(p1, SINGLE_BOUNDARY);
1106 PROC_UNLOCK(p1);
1107 }
1108 if (error != 0)
1109 pause("fork", hz / 2);
1110 return (error);
1111 }
1112
1113 /*
1114 * Handle the return of a child process from fork1(). This function
1115 * is called from the MD fork_trampoline() entry point.
1116 */
1117 void
fork_exit(void (* callout)(void *,struct trapframe *),void * arg,struct trapframe * frame)1118 fork_exit(void (*callout)(void *, struct trapframe *), void *arg,
1119 struct trapframe *frame)
1120 {
1121 struct proc *p;
1122 struct thread *td;
1123 struct thread *dtd;
1124
1125 kmsan_mark(frame, sizeof(*frame), KMSAN_STATE_INITED);
1126
1127 td = curthread;
1128 p = td->td_proc;
1129 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new"));
1130
1131 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)",
1132 td, td_get_sched(td), p->p_pid, td->td_name);
1133
1134 sched_fork_exit(td);
1135
1136 /*
1137 * Processes normally resume in mi_switch() after being
1138 * cpu_switch()'ed to, but when children start up they arrive here
1139 * instead, so we must do much the same things as mi_switch() would.
1140 */
1141 if ((dtd = PCPU_GET(deadthread))) {
1142 PCPU_SET(deadthread, NULL);
1143 thread_stash(dtd);
1144 }
1145 thread_unlock(td);
1146
1147 /*
1148 * cpu_fork_kthread_handler intercepts this function call to
1149 * have this call a non-return function to stay in kernel mode.
1150 * initproc has its own fork handler, but it does return.
1151 */
1152 KASSERT(callout != NULL, ("NULL callout in fork_exit"));
1153 callout(arg, frame);
1154
1155 /*
1156 * Check if a kernel thread misbehaved and returned from its main
1157 * function.
1158 */
1159 if (p->p_flag & P_KPROC) {
1160 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n",
1161 td->td_name, p->p_pid);
1162 kthread_exit();
1163 }
1164 mtx_assert(&Giant, MA_NOTOWNED);
1165
1166 if (p->p_sysent->sv_schedtail != NULL)
1167 (p->p_sysent->sv_schedtail)(td);
1168 }
1169
1170 /*
1171 * Simplified back end of syscall(), used when returning from fork()
1172 * directly into user mode. This function is passed in to fork_exit()
1173 * as the first parameter and is called when returning to a new
1174 * userland process.
1175 */
1176 void
fork_return(struct thread * td,struct trapframe * frame)1177 fork_return(struct thread *td, struct trapframe *frame)
1178 {
1179 struct proc *p;
1180
1181 p = td->td_proc;
1182 if (td->td_dbgflags & TDB_STOPATFORK) {
1183 PROC_LOCK(p);
1184 if ((p->p_flag & P_TRACED) != 0) {
1185 /*
1186 * Inform the debugger if one is still present.
1187 */
1188 td->td_dbgflags |= TDB_CHILD | TDB_SCX | TDB_FSTP;
1189 ptracestop(td, SIGSTOP, NULL);
1190 td->td_dbgflags &= ~(TDB_CHILD | TDB_SCX);
1191 } else {
1192 /*
1193 * ... otherwise clear the request.
1194 */
1195 td->td_dbgflags &= ~TDB_STOPATFORK;
1196 }
1197 PROC_UNLOCK(p);
1198 } else if (p->p_flag & P_TRACED) {
1199 /*
1200 * This is the start of a new thread in a traced
1201 * process. Report a system call exit event.
1202 */
1203 PROC_LOCK(p);
1204 td->td_dbgflags |= TDB_SCX;
1205 if ((p->p_ptevents & PTRACE_SCX) != 0 ||
1206 (td->td_dbgflags & TDB_BORN) != 0)
1207 ptracestop(td, SIGTRAP, NULL);
1208 td->td_dbgflags &= ~(TDB_SCX | TDB_BORN);
1209 PROC_UNLOCK(p);
1210 }
1211
1212 /*
1213 * If the prison was killed mid-fork, die along with it.
1214 */
1215 if (!prison_isalive(td->td_ucred->cr_prison))
1216 exit1(td, 0, SIGKILL);
1217
1218 userret(td, frame);
1219
1220 #ifdef KTRACE
1221 if (KTRPOINT(td, KTR_SYSRET))
1222 ktrsysret(td->td_sa.code, 0, 0);
1223 #endif
1224 }
1225
1226 static void
fork_init(void * arg __unused)1227 fork_init(void *arg __unused)
1228 {
1229 ast_register(TDA_VFORK, ASTR_ASTF_REQUIRED | ASTR_TDP, TDP_RFPPWAIT,
1230 ast_vfork);
1231 }
1232 SYSINIT(fork, SI_SUB_INTRINSIC, SI_ORDER_ANY, fork_init, NULL);
1233