1 /*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1982, 1986, 1989, 1991, 1993
5 * The Regents of the University of California. All rights reserved.
6 * (c) UNIX System Laboratories, Inc.
7 * All or some portions of this file are derived from material licensed
8 * to the University of California by American Telephone and Telegraph
9 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
10 * the permission of UNIX System Laboratories, Inc.
11 *
12 * Redistribution and use in source and binary forms, with or without
13 * modification, are permitted provided that the following conditions
14 * are met:
15 * 1. Redistributions of source code must retain the above copyright
16 * notice, this list of conditions and the following disclaimer.
17 * 2. Redistributions in binary form must reproduce the above copyright
18 * notice, this list of conditions and the following disclaimer in the
19 * documentation and/or other materials provided with the distribution.
20 * 3. Neither the name of the University nor the names of its contributors
21 * may be used to endorse or promote products derived from this software
22 * without specific prior written permission.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * SUCH DAMAGE.
35 */
36
37 #include <sys/cdefs.h>
38 #include "opt_ktrace.h"
39 #include "opt_kstack_pages.h"
40
41 #include <sys/param.h>
42 #include <sys/systm.h>
43 #include <sys/bitstring.h>
44 #include <sys/sysproto.h>
45 #include <sys/eventhandler.h>
46 #include <sys/fcntl.h>
47 #include <sys/filedesc.h>
48 #include <sys/jail.h>
49 #include <sys/kernel.h>
50 #include <sys/kthread.h>
51 #include <sys/sysctl.h>
52 #include <sys/lock.h>
53 #include <sys/malloc.h>
54 #include <sys/msan.h>
55 #include <sys/mutex.h>
56 #include <sys/priv.h>
57 #include <sys/proc.h>
58 #include <sys/procdesc.h>
59 #include <sys/ptrace.h>
60 #include <sys/racct.h>
61 #include <sys/resourcevar.h>
62 #include <sys/sched.h>
63 #include <sys/syscall.h>
64 #include <sys/vmmeter.h>
65 #include <sys/vnode.h>
66 #include <sys/acct.h>
67 #include <sys/ktr.h>
68 #include <sys/ktrace.h>
69 #include <sys/unistd.h>
70 #include <sys/sdt.h>
71 #include <sys/sx.h>
72 #include <sys/sysent.h>
73 #include <sys/signalvar.h>
74
75 #include <security/audit/audit.h>
76 #include <security/mac/mac_framework.h>
77
78 #include <vm/vm.h>
79 #include <vm/pmap.h>
80 #include <vm/vm_map.h>
81 #include <vm/vm_extern.h>
82 #include <vm/uma.h>
83
84 #ifdef KDTRACE_HOOKS
85 #include <sys/dtrace_bsd.h>
86 dtrace_fork_func_t dtrace_fasttrap_fork;
87 #endif
88
89 SDT_PROVIDER_DECLARE(proc);
90 SDT_PROBE_DEFINE3(proc, , , create, "struct proc *", "struct proc *", "int");
91
92 #ifndef _SYS_SYSPROTO_H_
93 struct fork_args {
94 int dummy;
95 };
96 #endif
97
98 /* ARGSUSED */
99 int
sys_fork(struct thread * td,struct fork_args * uap)100 sys_fork(struct thread *td, struct fork_args *uap)
101 {
102 struct fork_req fr;
103 int error, pid;
104
105 bzero(&fr, sizeof(fr));
106 fr.fr_flags = RFFDG | RFPROC;
107 fr.fr_pidp = &pid;
108 error = fork1(td, &fr);
109 if (error == 0) {
110 td->td_retval[0] = pid;
111 td->td_retval[1] = 0;
112 }
113 return (error);
114 }
115
116 /* ARGUSED */
117 int
sys_pdfork(struct thread * td,struct pdfork_args * uap)118 sys_pdfork(struct thread *td, struct pdfork_args *uap)
119 {
120 struct fork_req fr;
121 int error, fd, pid;
122
123 bzero(&fr, sizeof(fr));
124 fr.fr_flags = RFFDG | RFPROC | RFPROCDESC;
125 fr.fr_pidp = &pid;
126 fr.fr_pd_fd = &fd;
127 fr.fr_pd_flags = uap->flags;
128 AUDIT_ARG_FFLAGS(uap->flags);
129 /*
130 * It is necessary to return fd by reference because 0 is a valid file
131 * descriptor number, and the child needs to be able to distinguish
132 * itself from the parent using the return value.
133 */
134 error = fork1(td, &fr);
135 if (error == 0) {
136 td->td_retval[0] = pid;
137 td->td_retval[1] = 0;
138 error = copyout(&fd, uap->fdp, sizeof(fd));
139 }
140 return (error);
141 }
142
143 /* ARGSUSED */
144 int
sys_vfork(struct thread * td,struct vfork_args * uap)145 sys_vfork(struct thread *td, struct vfork_args *uap)
146 {
147 struct fork_req fr;
148 int error, pid;
149
150 bzero(&fr, sizeof(fr));
151 fr.fr_flags = RFFDG | RFPROC | RFPPWAIT | RFMEM;
152 fr.fr_pidp = &pid;
153 error = fork1(td, &fr);
154 if (error == 0) {
155 td->td_retval[0] = pid;
156 td->td_retval[1] = 0;
157 }
158 return (error);
159 }
160
161 int
sys_rfork(struct thread * td,struct rfork_args * uap)162 sys_rfork(struct thread *td, struct rfork_args *uap)
163 {
164 struct fork_req fr;
165 int error, pid;
166
167 /* Don't allow kernel-only flags. */
168 if ((uap->flags & RFKERNELONLY) != 0)
169 return (EINVAL);
170 /* RFSPAWN must not appear with others */
171 if ((uap->flags & RFSPAWN) != 0 && uap->flags != RFSPAWN)
172 return (EINVAL);
173
174 AUDIT_ARG_FFLAGS(uap->flags);
175 bzero(&fr, sizeof(fr));
176 if ((uap->flags & RFSPAWN) != 0) {
177 fr.fr_flags = RFFDG | RFPROC | RFPPWAIT | RFMEM;
178 fr.fr_flags2 = FR2_DROPSIG_CAUGHT;
179 } else {
180 fr.fr_flags = uap->flags;
181 }
182 fr.fr_pidp = &pid;
183 error = fork1(td, &fr);
184 if (error == 0) {
185 td->td_retval[0] = pid;
186 td->td_retval[1] = 0;
187 }
188 return (error);
189 }
190
191 int __exclusive_cache_line nprocs = 1; /* process 0 */
192 int lastpid = 0;
193 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0,
194 "Last used PID");
195
196 /*
197 * Random component to lastpid generation. We mix in a random factor to make
198 * it a little harder to predict. We sanity check the modulus value to avoid
199 * doing it in critical paths. Don't let it be too small or we pointlessly
200 * waste randomness entropy, and don't let it be impossibly large. Using a
201 * modulus that is too big causes a LOT more process table scans and slows
202 * down fork processing as the pidchecked caching is defeated.
203 */
204 static int randompid = 0;
205
206 static int
sysctl_kern_randompid(SYSCTL_HANDLER_ARGS)207 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS)
208 {
209 int error, pid;
210
211 error = sysctl_wire_old_buffer(req, sizeof(int));
212 if (error != 0)
213 return(error);
214 sx_xlock(&allproc_lock);
215 pid = randompid;
216 error = sysctl_handle_int(oidp, &pid, 0, req);
217 if (error == 0 && req->newptr != NULL) {
218 if (pid == 0)
219 randompid = 0;
220 else if (pid == 1)
221 /* generate a random PID modulus between 100 and 1123 */
222 randompid = 100 + arc4random() % 1024;
223 else if (pid < 0 || pid > pid_max - 100)
224 /* out of range */
225 randompid = pid_max - 100;
226 else if (pid < 100)
227 /* Make it reasonable */
228 randompid = 100;
229 else
230 randompid = pid;
231 }
232 sx_xunlock(&allproc_lock);
233 return (error);
234 }
235
236 SYSCTL_PROC(_kern, OID_AUTO, randompid,
237 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 0,
238 sysctl_kern_randompid, "I",
239 "Random PID modulus. Special values: 0: disable, 1: choose random value");
240
241 extern bitstr_t proc_id_pidmap;
242 extern bitstr_t proc_id_grpidmap;
243 extern bitstr_t proc_id_sessidmap;
244 extern bitstr_t proc_id_reapmap;
245
246 /*
247 * Find an unused process ID
248 *
249 * If RFHIGHPID is set (used during system boot), do not allocate
250 * low-numbered pids.
251 */
252 static int
fork_findpid(int flags)253 fork_findpid(int flags)
254 {
255 pid_t result;
256 int trypid, random;
257
258 /*
259 * Avoid calling arc4random with procid_lock held.
260 */
261 random = 0;
262 if (__predict_false(randompid))
263 random = arc4random() % randompid;
264
265 mtx_lock(&procid_lock);
266
267 trypid = lastpid + 1;
268 if (flags & RFHIGHPID) {
269 if (trypid < 10)
270 trypid = 10;
271 } else {
272 trypid += random;
273 }
274 retry:
275 if (trypid >= pid_max)
276 trypid = 2;
277
278 bit_ffc_at(&proc_id_pidmap, trypid, pid_max, &result);
279 if (result == -1) {
280 KASSERT(trypid != 2, ("unexpectedly ran out of IDs"));
281 trypid = 2;
282 goto retry;
283 }
284 if (bit_test(&proc_id_grpidmap, result) ||
285 bit_test(&proc_id_sessidmap, result) ||
286 bit_test(&proc_id_reapmap, result)) {
287 trypid = result + 1;
288 goto retry;
289 }
290
291 /*
292 * RFHIGHPID does not mess with the lastpid counter during boot.
293 */
294 if ((flags & RFHIGHPID) == 0)
295 lastpid = result;
296
297 bit_set(&proc_id_pidmap, result);
298 mtx_unlock(&procid_lock);
299
300 return (result);
301 }
302
303 static int
fork_norfproc(struct thread * td,int flags)304 fork_norfproc(struct thread *td, int flags)
305 {
306 struct proc *p1;
307 int error;
308
309 KASSERT((flags & RFPROC) == 0,
310 ("fork_norfproc called with RFPROC set"));
311 p1 = td->td_proc;
312
313 /*
314 * Quiesce other threads if necessary. If RFMEM is not specified we
315 * must ensure that other threads do not concurrently create a second
316 * process sharing the vmspace, see vmspace_unshare().
317 */
318 if ((p1->p_flag & (P_HADTHREADS | P_SYSTEM)) == P_HADTHREADS &&
319 ((flags & (RFCFDG | RFFDG)) != 0 || (flags & RFMEM) == 0)) {
320 PROC_LOCK(p1);
321 if (thread_single(p1, SINGLE_BOUNDARY)) {
322 PROC_UNLOCK(p1);
323 return (ERESTART);
324 }
325 PROC_UNLOCK(p1);
326 }
327
328 error = vm_forkproc(td, NULL, NULL, NULL, flags);
329 if (error != 0)
330 goto fail;
331
332 /*
333 * Close all file descriptors.
334 */
335 if ((flags & RFCFDG) != 0) {
336 struct filedesc *fdtmp;
337 struct pwddesc *pdtmp;
338
339 pdtmp = pdinit(td->td_proc->p_pd, false);
340 fdtmp = fdinit();
341 pdescfree(td);
342 fdescfree(td);
343 p1->p_fd = fdtmp;
344 p1->p_pd = pdtmp;
345 }
346
347 /*
348 * Unshare file descriptors (from parent).
349 */
350 if ((flags & RFFDG) != 0) {
351 fdunshare(td);
352 pdunshare(td);
353 }
354
355 fail:
356 if ((p1->p_flag & (P_HADTHREADS | P_SYSTEM)) == P_HADTHREADS &&
357 ((flags & (RFCFDG | RFFDG)) != 0 || (flags & RFMEM) == 0)) {
358 PROC_LOCK(p1);
359 thread_single_end(p1, SINGLE_BOUNDARY);
360 PROC_UNLOCK(p1);
361 }
362 return (error);
363 }
364
365 static void
do_fork(struct thread * td,struct fork_req * fr,struct proc * p2,struct thread * td2,struct vmspace * vm2,struct file * fp_procdesc)366 do_fork(struct thread *td, struct fork_req *fr, struct proc *p2, struct thread *td2,
367 struct vmspace *vm2, struct file *fp_procdesc)
368 {
369 struct proc *p1, *pptr;
370 struct filedesc *fd;
371 struct filedesc_to_leader *fdtol;
372 struct pwddesc *pd;
373 struct sigacts *newsigacts;
374
375 p1 = td->td_proc;
376
377 PROC_LOCK(p1);
378 bcopy(&p1->p_startcopy, &p2->p_startcopy,
379 __rangeof(struct proc, p_startcopy, p_endcopy));
380 pargs_hold(p2->p_args);
381 PROC_UNLOCK(p1);
382
383 bzero(&p2->p_startzero,
384 __rangeof(struct proc, p_startzero, p_endzero));
385
386 /* Tell the prison that we exist. */
387 prison_proc_hold(p2->p_ucred->cr_prison);
388
389 p2->p_state = PRS_NEW; /* protect against others */
390 p2->p_pid = fork_findpid(fr->fr_flags);
391 AUDIT_ARG_PID(p2->p_pid);
392 TSFORK(p2->p_pid, p1->p_pid);
393
394 sx_xlock(&allproc_lock);
395 LIST_INSERT_HEAD(&allproc, p2, p_list);
396 allproc_gen++;
397 prison_proc_link(p2->p_ucred->cr_prison, p2);
398 sx_xunlock(&allproc_lock);
399
400 sx_xlock(PIDHASHLOCK(p2->p_pid));
401 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash);
402 sx_xunlock(PIDHASHLOCK(p2->p_pid));
403
404 tidhash_add(td2);
405
406 /*
407 * Malloc things while we don't hold any locks.
408 */
409 if (fr->fr_flags & RFSIGSHARE)
410 newsigacts = NULL;
411 else
412 newsigacts = sigacts_alloc();
413
414 /*
415 * Copy filedesc.
416 */
417 if (fr->fr_flags & RFCFDG) {
418 pd = pdinit(p1->p_pd, false);
419 fd = fdinit();
420 fdtol = NULL;
421 } else if (fr->fr_flags & RFFDG) {
422 if (fr->fr_flags2 & FR2_SHARE_PATHS)
423 pd = pdshare(p1->p_pd);
424 else
425 pd = pdcopy(p1->p_pd);
426 fd = fdcopy(p1->p_fd);
427 fdtol = NULL;
428 } else {
429 if (fr->fr_flags2 & FR2_SHARE_PATHS)
430 pd = pdcopy(p1->p_pd);
431 else
432 pd = pdshare(p1->p_pd);
433 fd = fdshare(p1->p_fd);
434 if (p1->p_fdtol == NULL)
435 p1->p_fdtol = filedesc_to_leader_alloc(NULL, NULL,
436 p1->p_leader);
437 if ((fr->fr_flags & RFTHREAD) != 0) {
438 /*
439 * Shared file descriptor table, and shared
440 * process leaders.
441 */
442 fdtol = filedesc_to_leader_share(p1->p_fdtol, p1->p_fd);
443 } else {
444 /*
445 * Shared file descriptor table, and different
446 * process leaders.
447 */
448 fdtol = filedesc_to_leader_alloc(p1->p_fdtol,
449 p1->p_fd, p2);
450 }
451 }
452 /*
453 * Make a proc table entry for the new process.
454 * Start by zeroing the section of proc that is zero-initialized,
455 * then copy the section that is copied directly from the parent.
456 */
457
458 PROC_LOCK(p2);
459 PROC_LOCK(p1);
460
461 bzero(&td2->td_startzero,
462 __rangeof(struct thread, td_startzero, td_endzero));
463
464 bcopy(&td->td_startcopy, &td2->td_startcopy,
465 __rangeof(struct thread, td_startcopy, td_endcopy));
466
467 bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name));
468 td2->td_sigstk = td->td_sigstk;
469 td2->td_flags = TDF_INMEM;
470 td2->td_lend_user_pri = PRI_MAX;
471
472 #ifdef VIMAGE
473 td2->td_vnet = NULL;
474 td2->td_vnet_lpush = NULL;
475 #endif
476
477 /*
478 * Allow the scheduler to initialize the child.
479 */
480 thread_lock(td);
481 sched_fork(td, td2);
482 /*
483 * Request AST to check for TDP_RFPPWAIT. Do it here
484 * to avoid calling thread_lock() again.
485 */
486 if ((fr->fr_flags & RFPPWAIT) != 0)
487 ast_sched_locked(td, TDA_VFORK);
488 thread_unlock(td);
489
490 /*
491 * Duplicate sub-structures as needed.
492 * Increase reference counts on shared objects.
493 */
494 p2->p_flag = P_INMEM;
495 p2->p_flag2 = p1->p_flag2 & (P2_ASLR_DISABLE | P2_ASLR_ENABLE |
496 P2_ASLR_IGNSTART | P2_NOTRACE | P2_NOTRACE_EXEC |
497 P2_PROTMAX_ENABLE | P2_PROTMAX_DISABLE | P2_TRAPCAP |
498 P2_STKGAP_DISABLE | P2_STKGAP_DISABLE_EXEC | P2_NO_NEW_PRIVS |
499 P2_WXORX_DISABLE | P2_WXORX_ENABLE_EXEC | P2_LOGSIGEXIT_CTL |
500 P2_LOGSIGEXIT_ENABLE);
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
ast_vfork(struct thread * td,int tda __unused)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
fork1(struct thread * td,struct fork_req * fr)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 error = thread_recycle(td2, pages);
1023 if (error != 0)
1024 goto fail2;
1025 }
1026
1027 if ((flags & RFMEM) == 0) {
1028 vm2 = vmspace_fork(p1->p_vmspace, &mem_charged);
1029 if (vm2 == NULL) {
1030 error = ENOMEM;
1031 goto fail2;
1032 }
1033 if (!swap_reserve(mem_charged)) {
1034 /*
1035 * The swap reservation failed. The accounting
1036 * from the entries of the copied vm2 will be
1037 * subtracted in vmspace_free(), so force the
1038 * reservation there.
1039 */
1040 swap_reserve_force(mem_charged);
1041 error = ENOMEM;
1042 goto fail2;
1043 }
1044 } else
1045 vm2 = NULL;
1046
1047 /*
1048 * XXX: This is ugly; when we copy resource usage, we need to bump
1049 * per-cred resource counters.
1050 */
1051 newproc->p_ucred = crcowget(td->td_ucred);
1052
1053 /*
1054 * Initialize resource accounting for the child process.
1055 */
1056 error = racct_proc_fork(p1, newproc);
1057 if (error != 0) {
1058 error = EAGAIN;
1059 goto fail1;
1060 }
1061
1062 #ifdef MAC
1063 mac_proc_init(newproc);
1064 #endif
1065 newproc->p_klist = knlist_alloc(&newproc->p_mtx);
1066 STAILQ_INIT(&newproc->p_ktr);
1067
1068 /*
1069 * Increment the count of procs running with this uid. Don't allow
1070 * a nonprivileged user to exceed their current limit.
1071 */
1072 cred = td->td_ucred;
1073 if (!chgproccnt(cred->cr_ruidinfo, 1, lim_cur(td, RLIMIT_NPROC))) {
1074 if (priv_check_cred(cred, PRIV_PROC_LIMIT) != 0)
1075 goto fail0;
1076 chgproccnt(cred->cr_ruidinfo, 1, 0);
1077 }
1078
1079 do_fork(td, fr, newproc, td2, vm2, fp_procdesc);
1080 error = 0;
1081 goto cleanup;
1082 fail0:
1083 error = EAGAIN;
1084 #ifdef MAC
1085 mac_proc_destroy(newproc);
1086 #endif
1087 racct_proc_exit(newproc);
1088 fail1:
1089 proc_unset_cred(newproc, false);
1090 fail2:
1091 if (vm2 != NULL)
1092 vmspace_free(vm2);
1093 uma_zfree(proc_zone, newproc);
1094 if ((flags & RFPROCDESC) != 0 && fp_procdesc != NULL) {
1095 fdclose(td, fp_procdesc, *fr->fr_pd_fd);
1096 fdrop(fp_procdesc, td);
1097 }
1098 atomic_add_int(&nprocs, -1);
1099 cleanup:
1100 if (killsx_locked)
1101 sx_sunlock(&pg->pg_killsx);
1102 if (singlethreaded) {
1103 PROC_LOCK(p1);
1104 thread_single_end(p1, SINGLE_BOUNDARY);
1105 PROC_UNLOCK(p1);
1106 }
1107 if (error != 0)
1108 pause("fork", hz / 2);
1109 return (error);
1110 }
1111
1112 /*
1113 * Handle the return of a child process from fork1(). This function
1114 * is called from the MD fork_trampoline() entry point.
1115 */
1116 void
fork_exit(void (* callout)(void *,struct trapframe *),void * arg,struct trapframe * frame)1117 fork_exit(void (*callout)(void *, struct trapframe *), void *arg,
1118 struct trapframe *frame)
1119 {
1120 struct proc *p;
1121 struct thread *td;
1122 struct thread *dtd;
1123
1124 kmsan_mark(frame, sizeof(*frame), KMSAN_STATE_INITED);
1125
1126 td = curthread;
1127 p = td->td_proc;
1128 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new"));
1129
1130 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)",
1131 td, td_get_sched(td), p->p_pid, td->td_name);
1132
1133 sched_fork_exit(td);
1134
1135 /*
1136 * Processes normally resume in mi_switch() after being
1137 * cpu_switch()'ed to, but when children start up they arrive here
1138 * instead, so we must do much the same things as mi_switch() would.
1139 */
1140 if ((dtd = PCPU_GET(deadthread))) {
1141 PCPU_SET(deadthread, NULL);
1142 thread_stash(dtd);
1143 }
1144 thread_unlock(td);
1145
1146 /*
1147 * cpu_fork_kthread_handler intercepts this function call to
1148 * have this call a non-return function to stay in kernel mode.
1149 * initproc has its own fork handler, but it does return.
1150 */
1151 KASSERT(callout != NULL, ("NULL callout in fork_exit"));
1152 callout(arg, frame);
1153
1154 /*
1155 * Check if a kernel thread misbehaved and returned from its main
1156 * function.
1157 */
1158 if (p->p_flag & P_KPROC) {
1159 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n",
1160 td->td_name, p->p_pid);
1161 kthread_exit();
1162 }
1163 mtx_assert(&Giant, MA_NOTOWNED);
1164
1165 /*
1166 * Now going to return to userland.
1167 */
1168
1169 if (p->p_sysent->sv_schedtail != NULL)
1170 (p->p_sysent->sv_schedtail)(td);
1171
1172 userret(td, frame);
1173 }
1174
1175 /*
1176 * Simplified back end of syscall(), used when returning from fork()
1177 * directly into user mode. This function is passed in to fork_exit()
1178 * as the first parameter and is called when returning to a new
1179 * userland process.
1180 */
1181 void
fork_return(struct thread * td,struct trapframe * frame)1182 fork_return(struct thread *td, struct trapframe *frame)
1183 {
1184 struct proc *p;
1185
1186 p = td->td_proc;
1187 if (td->td_dbgflags & TDB_STOPATFORK) {
1188 PROC_LOCK(p);
1189 if ((p->p_flag & P_TRACED) != 0) {
1190 /*
1191 * Inform the debugger if one is still present.
1192 */
1193 td->td_dbgflags |= TDB_CHILD | TDB_SCX | TDB_FSTP;
1194 ptracestop(td, SIGSTOP, NULL);
1195 td->td_dbgflags &= ~(TDB_CHILD | TDB_SCX);
1196 } else {
1197 /*
1198 * ... otherwise clear the request.
1199 */
1200 td->td_dbgflags &= ~TDB_STOPATFORK;
1201 }
1202 PROC_UNLOCK(p);
1203 } else if (p->p_flag & P_TRACED) {
1204 /*
1205 * This is the start of a new thread in a traced
1206 * process. Report a system call exit event.
1207 */
1208 PROC_LOCK(p);
1209 td->td_dbgflags |= TDB_SCX;
1210 if ((p->p_ptevents & PTRACE_SCX) != 0 ||
1211 (td->td_dbgflags & TDB_BORN) != 0)
1212 ptracestop(td, SIGTRAP, NULL);
1213 td->td_dbgflags &= ~(TDB_SCX | TDB_BORN);
1214 PROC_UNLOCK(p);
1215 }
1216
1217 /*
1218 * If the prison was killed mid-fork, die along with it.
1219 */
1220 if (!prison_isalive(td->td_ucred->cr_prison))
1221 exit1(td, 0, SIGKILL);
1222
1223 #ifdef KTRACE
1224 if (KTRPOINT(td, KTR_SYSRET))
1225 ktrsysret(td->td_sa.code, 0, 0);
1226 #endif
1227 }
1228
1229 static void
fork_init(void * arg __unused)1230 fork_init(void *arg __unused)
1231 {
1232 ast_register(TDA_VFORK, ASTR_ASTF_REQUIRED | ASTR_TDP, TDP_RFPPWAIT,
1233 ast_vfork);
1234 }
1235 SYSINIT(fork, SI_SUB_INTRINSIC, SI_ORDER_ANY, fork_init, NULL);
1236