1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause
3 *
4 * Copyright (c) 2009, 2016 Robert N. M. Watson
5 * All rights reserved.
6 *
7 * This software was developed at the University of Cambridge Computer
8 * Laboratory with support from a grant from Google, Inc.
9 *
10 * Portions of this software were developed by BAE Systems, the University of
11 * Cambridge Computer Laboratory, and Memorial University under DARPA/AFRL
12 * contract FA8650-15-C-7558 ("CADETS"), as part of the DARPA Transparent
13 * Computing (TC) research program.
14 *
15 * Redistribution and use in source and binary forms, with or without
16 * modification, are permitted provided that the following conditions
17 * are met:
18 * 1. Redistributions of source code must retain the above copyright
19 * notice, this list of conditions and the following disclaimer.
20 * 2. Redistributions in binary form must reproduce the above copyright
21 * notice, this list of conditions and the following disclaimer in the
22 * documentation and/or other materials provided with the distribution.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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 /*-
38 * FreeBSD process descriptor facility.
39 *
40 * Some processes are represented by a file descriptor, which will be used in
41 * preference to signaling and pids for the purposes of process management,
42 * and is, in effect, a form of capability. When a process descriptor is
43 * used with a process, it ceases to be visible to certain traditional UNIX
44 * process facilities, such as waitpid(2).
45 *
46 * Some semantics:
47 *
48 * - At most one process descriptor will exist for any process, although
49 * references to that descriptor may be held from many processes (or even
50 * be in flight between processes over a local domain socket).
51 * - Last close on the process descriptor will terminate the process using
52 * SIGKILL and reparent it to init so that there's a process to reap it
53 * when it's done exiting.
54 * - If the process exits before the descriptor is closed, it will not
55 * generate SIGCHLD on termination, or be picked up by waitpid().
56 * - The pdkill(2) system call may be used to deliver a signal to the process
57 * using its process descriptor.
58 *
59 * Open questions:
60 *
61 * - Will we want to add a pidtoprocdesc(2) system call to allow process
62 * descriptors to be created for processes without pdfork(2)?
63 */
64
65 #include <sys/param.h>
66 #include <sys/capsicum.h>
67 #include <sys/fcntl.h>
68 #include <sys/file.h>
69 #include <sys/filedesc.h>
70 #include <sys/kernel.h>
71 #include <sys/lock.h>
72 #include <sys/mutex.h>
73 #include <sys/poll.h>
74 #include <sys/proc.h>
75 #include <sys/procdesc.h>
76 #include <sys/resourcevar.h>
77 #include <sys/stat.h>
78 #include <sys/sysproto.h>
79 #include <sys/sysctl.h>
80 #include <sys/systm.h>
81 #include <sys/ucred.h>
82 #include <sys/user.h>
83
84 #include <security/audit/audit.h>
85
86 #include <vm/uma.h>
87
88 FEATURE(process_descriptors, "Process Descriptors");
89
90 MALLOC_DEFINE(M_PROCDESC, "procdesc", "process descriptors");
91
92 static fo_poll_t procdesc_poll;
93 static fo_kqfilter_t procdesc_kqfilter;
94 static fo_stat_t procdesc_stat;
95 static fo_close_t procdesc_close;
96 static fo_fill_kinfo_t procdesc_fill_kinfo;
97 static fo_cmp_t procdesc_cmp;
98
99 static const struct fileops procdesc_ops = {
100 .fo_read = invfo_rdwr,
101 .fo_write = invfo_rdwr,
102 .fo_truncate = invfo_truncate,
103 .fo_ioctl = invfo_ioctl,
104 .fo_poll = procdesc_poll,
105 .fo_kqfilter = procdesc_kqfilter,
106 .fo_stat = procdesc_stat,
107 .fo_close = procdesc_close,
108 .fo_chmod = invfo_chmod,
109 .fo_chown = invfo_chown,
110 .fo_sendfile = invfo_sendfile,
111 .fo_fill_kinfo = procdesc_fill_kinfo,
112 .fo_cmp = procdesc_cmp,
113 .fo_flags = DFLAG_PASSABLE,
114 };
115
116 /*
117 * Return a locked process given a process descriptor, or ESRCH if it has
118 * died.
119 */
120 int
procdesc_find(struct thread * td,int fd,cap_rights_t * rightsp,struct proc ** p)121 procdesc_find(struct thread *td, int fd, cap_rights_t *rightsp,
122 struct proc **p)
123 {
124 struct procdesc *pd;
125 struct file *fp;
126 int error;
127
128 error = fget(td, fd, rightsp, &fp);
129 if (error)
130 return (error);
131 if (fp->f_type != DTYPE_PROCDESC) {
132 error = EBADF;
133 goto out;
134 }
135 pd = fp->f_data;
136 sx_slock(&proctree_lock);
137 if (pd->pd_proc != NULL) {
138 *p = pd->pd_proc;
139 PROC_LOCK(*p);
140 } else
141 error = ESRCH;
142 sx_sunlock(&proctree_lock);
143 out:
144 fdrop(fp, td);
145 return (error);
146 }
147
148 /*
149 * Function to be used by procstat(1) sysctls when returning procdesc
150 * information.
151 */
152 pid_t
procdesc_pid(struct file * fp_procdesc)153 procdesc_pid(struct file *fp_procdesc)
154 {
155 struct procdesc *pd;
156
157 KASSERT(fp_procdesc->f_type == DTYPE_PROCDESC,
158 ("procdesc_pid: !procdesc"));
159
160 pd = fp_procdesc->f_data;
161 return (pd->pd_pid);
162 }
163
164 /*
165 * Retrieve the PID associated with a process descriptor.
166 */
167 int
kern_pdgetpid(struct thread * td,int fd,cap_rights_t * rightsp,pid_t * pidp)168 kern_pdgetpid(struct thread *td, int fd, cap_rights_t *rightsp, pid_t *pidp)
169 {
170 struct file *fp;
171 int error;
172
173 error = fget(td, fd, rightsp, &fp);
174 if (error)
175 return (error);
176 if (fp->f_type != DTYPE_PROCDESC) {
177 error = EBADF;
178 goto out;
179 }
180 *pidp = procdesc_pid(fp);
181 out:
182 fdrop(fp, td);
183 return (error);
184 }
185
186 /*
187 * System call to return the pid of a process given its process descriptor.
188 */
189 int
sys_pdgetpid(struct thread * td,struct pdgetpid_args * uap)190 sys_pdgetpid(struct thread *td, struct pdgetpid_args *uap)
191 {
192 pid_t pid;
193 int error;
194
195 AUDIT_ARG_FD(uap->fd);
196 error = kern_pdgetpid(td, uap->fd, &cap_pdgetpid_rights, &pid);
197 if (error == 0)
198 error = copyout(&pid, uap->pidp, sizeof(pid));
199 return (error);
200 }
201
202 /*
203 * When a new process is forked by pdfork(), a file descriptor is allocated
204 * by the fork code first, then the process is forked, and then we get a
205 * chance to set up the process descriptor. Failure is not permitted at this
206 * point, so procdesc_new() must succeed.
207 */
208 void
procdesc_new(struct proc * p,int flags)209 procdesc_new(struct proc *p, int flags)
210 {
211 struct procdesc *pd;
212
213 pd = malloc(sizeof(*pd), M_PROCDESC, M_WAITOK | M_ZERO);
214 pd->pd_proc = p;
215 pd->pd_pid = p->p_pid;
216 p->p_procdesc = pd;
217 pd->pd_flags = 0;
218 if (flags & PD_DAEMON)
219 pd->pd_flags |= PDF_DAEMON;
220 PROCDESC_LOCK_INIT(pd);
221 knlist_init_mtx(&pd->pd_selinfo.si_note, &pd->pd_lock);
222
223 /*
224 * Process descriptors start out with two references: one from their
225 * struct file, and the other from their struct proc.
226 */
227 refcount_init(&pd->pd_refcount, 2);
228 }
229
230 /*
231 * Create a new process decriptor for the process that refers to it.
232 */
233 int
procdesc_falloc(struct thread * td,struct file ** resultfp,int * resultfd,int flags,struct filecaps * fcaps)234 procdesc_falloc(struct thread *td, struct file **resultfp, int *resultfd,
235 int flags, struct filecaps *fcaps)
236 {
237 int fflags;
238
239 fflags = 0;
240 if (flags & PD_CLOEXEC)
241 fflags = O_CLOEXEC;
242
243 return (falloc_caps(td, resultfp, resultfd, fflags, fcaps));
244 }
245
246 /*
247 * Initialize a file with a process descriptor.
248 */
249 void
procdesc_finit(struct procdesc * pdp,struct file * fp)250 procdesc_finit(struct procdesc *pdp, struct file *fp)
251 {
252
253 finit(fp, FREAD | FWRITE, DTYPE_PROCDESC, pdp, &procdesc_ops);
254 }
255
256 static void
procdesc_free(struct procdesc * pd)257 procdesc_free(struct procdesc *pd)
258 {
259
260 /*
261 * When the last reference is released, we assert that the descriptor
262 * has been closed, but not that the process has exited, as we will
263 * detach the descriptor before the process dies if the descript is
264 * closed, as we can't wait synchronously.
265 */
266 if (refcount_release(&pd->pd_refcount)) {
267 KASSERT(pd->pd_proc == NULL,
268 ("procdesc_free: pd_proc != NULL"));
269 KASSERT((pd->pd_flags & PDF_CLOSED),
270 ("procdesc_free: !PDF_CLOSED"));
271
272 knlist_destroy(&pd->pd_selinfo.si_note);
273 PROCDESC_LOCK_DESTROY(pd);
274 free(pd, M_PROCDESC);
275 }
276 }
277
278 /*
279 * procdesc_exit() - notify a process descriptor that its process is exiting.
280 * We use the proctree_lock to ensure that process exit either happens
281 * strictly before or strictly after a concurrent call to procdesc_close().
282 */
283 int
procdesc_exit(struct proc * p)284 procdesc_exit(struct proc *p)
285 {
286 struct procdesc *pd;
287
288 sx_assert(&proctree_lock, SA_XLOCKED);
289 PROC_LOCK_ASSERT(p, MA_OWNED);
290 KASSERT(p->p_procdesc != NULL, ("procdesc_exit: p_procdesc NULL"));
291
292 pd = p->p_procdesc;
293
294 PROCDESC_LOCK(pd);
295 KASSERT((pd->pd_flags & PDF_CLOSED) == 0 || p->p_pptr == p->p_reaper,
296 ("procdesc_exit: closed && parent not reaper"));
297
298 pd->pd_flags |= PDF_EXITED;
299 pd->pd_xstat = KW_EXITCODE(p->p_xexit, p->p_xsig);
300
301 /*
302 * If the process descriptor has been closed, then we have nothing
303 * to do; return 1 so that init will get SIGCHLD and do the reaping.
304 * Clean up the procdesc now rather than letting it happen during
305 * that reap.
306 */
307 if (pd->pd_flags & PDF_CLOSED) {
308 PROCDESC_UNLOCK(pd);
309 pd->pd_proc = NULL;
310 p->p_procdesc = NULL;
311 procdesc_free(pd);
312 return (1);
313 }
314 if (pd->pd_flags & PDF_SELECTED) {
315 pd->pd_flags &= ~PDF_SELECTED;
316 selwakeup(&pd->pd_selinfo);
317 }
318 KNOTE_LOCKED(&pd->pd_selinfo.si_note, NOTE_EXIT);
319 PROCDESC_UNLOCK(pd);
320 return (0);
321 }
322
323 /*
324 * When a process descriptor is reaped, perhaps as a result of close(), release
325 * the process's reference on the process descriptor.
326 */
327 void
procdesc_reap(struct proc * p)328 procdesc_reap(struct proc *p)
329 {
330 struct procdesc *pd;
331
332 sx_assert(&proctree_lock, SA_XLOCKED);
333 KASSERT(p->p_procdesc != NULL, ("procdesc_reap: p_procdesc == NULL"));
334
335 pd = p->p_procdesc;
336 pd->pd_proc = NULL;
337 p->p_procdesc = NULL;
338 procdesc_free(pd);
339 }
340
341 /*
342 * procdesc_close() - last close on a process descriptor. If the process is
343 * still running, terminate with SIGKILL (unless PDF_DAEMON is set) and let
344 * its reaper clean up the mess; if not, we have to clean up the zombie
345 * ourselves.
346 */
347 static int
procdesc_close(struct file * fp,struct thread * td)348 procdesc_close(struct file *fp, struct thread *td)
349 {
350 struct procdesc *pd;
351 struct proc *p;
352
353 KASSERT(fp->f_type == DTYPE_PROCDESC, ("procdesc_close: !procdesc"));
354
355 pd = fp->f_data;
356 fp->f_ops = &badfileops;
357 fp->f_data = NULL;
358
359 sx_xlock(&proctree_lock);
360 PROCDESC_LOCK(pd);
361 pd->pd_flags |= PDF_CLOSED;
362 PROCDESC_UNLOCK(pd);
363 p = pd->pd_proc;
364 if (p == NULL) {
365 /*
366 * This is the case where process' exit status was already
367 * collected and procdesc_reap() was already called.
368 */
369 sx_xunlock(&proctree_lock);
370 } else {
371 PROC_LOCK(p);
372 AUDIT_ARG_PROCESS(p);
373 if (p->p_state == PRS_ZOMBIE) {
374 /*
375 * If the process is already dead and just awaiting
376 * reaping, do that now. This will release the
377 * process's reference to the process descriptor when it
378 * calls back into procdesc_reap().
379 */
380 proc_reap(curthread, p, NULL, 0);
381 } else {
382 /*
383 * If the process is not yet dead, we need to kill it,
384 * but we can't wait around synchronously for it to go
385 * away, as that path leads to madness (and deadlocks).
386 * First, detach the process from its descriptor so that
387 * its exit status will be reported normally.
388 */
389 pd->pd_proc = NULL;
390 p->p_procdesc = NULL;
391 procdesc_free(pd);
392
393 /*
394 * Next, reparent it to its reaper (usually init(8)) so
395 * that there's someone to pick up the pieces; finally,
396 * terminate with prejudice.
397 */
398 p->p_sigparent = SIGCHLD;
399 if ((p->p_flag & P_TRACED) == 0) {
400 proc_reparent(p, p->p_reaper, true);
401 } else {
402 proc_clear_orphan(p);
403 p->p_oppid = p->p_reaper->p_pid;
404 proc_add_orphan(p, p->p_reaper);
405 }
406 if ((pd->pd_flags & PDF_DAEMON) == 0)
407 kern_psignal(p, SIGKILL);
408 PROC_UNLOCK(p);
409 sx_xunlock(&proctree_lock);
410 }
411 }
412
413 /*
414 * Release the file descriptor's reference on the process descriptor.
415 */
416 procdesc_free(pd);
417 return (0);
418 }
419
420 static int
procdesc_poll(struct file * fp,int events,struct ucred * active_cred,struct thread * td)421 procdesc_poll(struct file *fp, int events, struct ucred *active_cred,
422 struct thread *td)
423 {
424 struct procdesc *pd;
425 int revents;
426
427 revents = 0;
428 pd = fp->f_data;
429 PROCDESC_LOCK(pd);
430 if (pd->pd_flags & PDF_EXITED)
431 revents |= POLLHUP;
432 if (revents == 0) {
433 selrecord(td, &pd->pd_selinfo);
434 pd->pd_flags |= PDF_SELECTED;
435 }
436 PROCDESC_UNLOCK(pd);
437 return (revents);
438 }
439
440 static void
procdesc_kqops_detach(struct knote * kn)441 procdesc_kqops_detach(struct knote *kn)
442 {
443 struct procdesc *pd;
444
445 pd = kn->kn_fp->f_data;
446 knlist_remove(&pd->pd_selinfo.si_note, kn, 0);
447 }
448
449 static int
procdesc_kqops_event(struct knote * kn,long hint)450 procdesc_kqops_event(struct knote *kn, long hint)
451 {
452 struct procdesc *pd;
453 u_int event;
454
455 pd = kn->kn_fp->f_data;
456 if (hint == 0) {
457 /*
458 * Initial test after registration. Generate a NOTE_EXIT in
459 * case the process already terminated before registration.
460 */
461 event = pd->pd_flags & PDF_EXITED ? NOTE_EXIT : 0;
462 } else {
463 /* Mask off extra data. */
464 event = (u_int)hint & NOTE_PCTRLMASK;
465 }
466
467 /* If the user is interested in this event, record it. */
468 if (kn->kn_sfflags & event)
469 kn->kn_fflags |= event;
470
471 /* Process is gone, so flag the event as finished. */
472 if (event == NOTE_EXIT) {
473 kn->kn_flags |= EV_EOF | EV_ONESHOT;
474 if (kn->kn_fflags & NOTE_EXIT)
475 kn->kn_data = pd->pd_xstat;
476 if (kn->kn_fflags == 0)
477 kn->kn_flags |= EV_DROP;
478 return (1);
479 }
480
481 return (kn->kn_fflags != 0);
482 }
483
484 static const struct filterops procdesc_kqops = {
485 .f_isfd = 1,
486 .f_detach = procdesc_kqops_detach,
487 .f_event = procdesc_kqops_event,
488 };
489
490 static int
procdesc_kqfilter(struct file * fp,struct knote * kn)491 procdesc_kqfilter(struct file *fp, struct knote *kn)
492 {
493 struct procdesc *pd;
494
495 pd = fp->f_data;
496 switch (kn->kn_filter) {
497 case EVFILT_PROCDESC:
498 kn->kn_fop = &procdesc_kqops;
499 kn->kn_flags |= EV_CLEAR;
500 knlist_add(&pd->pd_selinfo.si_note, kn, 0);
501 return (0);
502 default:
503 return (EINVAL);
504 }
505 }
506
507 static int
procdesc_stat(struct file * fp,struct stat * sb,struct ucred * active_cred)508 procdesc_stat(struct file *fp, struct stat *sb, struct ucred *active_cred)
509 {
510 struct procdesc *pd;
511 struct timeval pstart, boottime;
512
513 /*
514 * XXXRW: Perhaps we should cache some more information from the
515 * process so that we can return it reliably here even after it has
516 * died. For example, caching its credential data.
517 */
518 bzero(sb, sizeof(*sb));
519 pd = fp->f_data;
520 sx_slock(&proctree_lock);
521 if (pd->pd_proc != NULL) {
522 PROC_LOCK(pd->pd_proc);
523 AUDIT_ARG_PROCESS(pd->pd_proc);
524
525 /* Set birth and [acm] times to process start time. */
526 pstart = pd->pd_proc->p_stats->p_start;
527 getboottime(&boottime);
528 timevaladd(&pstart, &boottime);
529 TIMEVAL_TO_TIMESPEC(&pstart, &sb->st_birthtim);
530 sb->st_atim = sb->st_birthtim;
531 sb->st_ctim = sb->st_birthtim;
532 sb->st_mtim = sb->st_birthtim;
533 if (pd->pd_proc->p_state != PRS_ZOMBIE)
534 sb->st_mode = S_IFREG | S_IRWXU;
535 else
536 sb->st_mode = S_IFREG;
537 sb->st_uid = pd->pd_proc->p_ucred->cr_ruid;
538 sb->st_gid = pd->pd_proc->p_ucred->cr_rgid;
539 PROC_UNLOCK(pd->pd_proc);
540 } else
541 sb->st_mode = S_IFREG;
542 sx_sunlock(&proctree_lock);
543 return (0);
544 }
545
546 static int
procdesc_fill_kinfo(struct file * fp,struct kinfo_file * kif,struct filedesc * fdp)547 procdesc_fill_kinfo(struct file *fp, struct kinfo_file *kif,
548 struct filedesc *fdp)
549 {
550 struct procdesc *pdp;
551
552 kif->kf_type = KF_TYPE_PROCDESC;
553 pdp = fp->f_data;
554 kif->kf_un.kf_proc.kf_pid = pdp->pd_pid;
555 return (0);
556 }
557
558 static int
procdesc_cmp(struct file * fp1,struct file * fp2,struct thread * td)559 procdesc_cmp(struct file *fp1, struct file *fp2, struct thread *td)
560 {
561 struct procdesc *pdp1, *pdp2;
562
563 if (fp2->f_type != DTYPE_PROCDESC)
564 return (3);
565 pdp1 = fp1->f_data;
566 pdp2 = fp2->f_data;
567 return (kcmp_cmp((uintptr_t)pdp1->pd_pid, (uintptr_t)pdp2->pd_pid));
568 }
569