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,const cap_rights_t * rightsp,struct proc ** p)121 procdesc_find(struct thread *td, int fd, const 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,const cap_rights_t * rightsp,pid_t * pidp)168 kern_pdgetpid(struct thread *td, int fd, const cap_rights_t *rightsp,
169 pid_t *pidp)
170 {
171 struct file *fp;
172 int error;
173
174 error = fget(td, fd, rightsp, &fp);
175 if (error)
176 return (error);
177 if (fp->f_type != DTYPE_PROCDESC) {
178 error = EBADF;
179 goto out;
180 }
181 *pidp = procdesc_pid(fp);
182 out:
183 fdrop(fp, td);
184 return (error);
185 }
186
187 /*
188 * System call to return the pid of a process given its process descriptor.
189 */
190 int
sys_pdgetpid(struct thread * td,struct pdgetpid_args * uap)191 sys_pdgetpid(struct thread *td, struct pdgetpid_args *uap)
192 {
193 pid_t pid;
194 int error;
195
196 AUDIT_ARG_FD(uap->fd);
197 error = kern_pdgetpid(td, uap->fd, &cap_pdgetpid_rights, &pid);
198 if (error == 0)
199 error = copyout(&pid, uap->pidp, sizeof(pid));
200 return (error);
201 }
202
203 /*
204 * When a new process is forked by pdfork(), a file descriptor is allocated
205 * by the fork code first, then the process is forked, and then we get a
206 * chance to set up the process descriptor. Failure is not permitted at this
207 * point, so procdesc_new() must succeed.
208 */
209 void
procdesc_new(struct proc * p,int flags)210 procdesc_new(struct proc *p, int flags)
211 {
212 struct procdesc *pd;
213
214 pd = malloc(sizeof(*pd), M_PROCDESC, M_WAITOK | M_ZERO);
215 pd->pd_proc = p;
216 pd->pd_pid = p->p_pid;
217 p->p_procdesc = pd;
218 pd->pd_flags = 0;
219 if (flags & PD_DAEMON)
220 pd->pd_flags |= PDF_DAEMON;
221 PROCDESC_LOCK_INIT(pd);
222 knlist_init_mtx(&pd->pd_selinfo.si_note, &pd->pd_lock);
223
224 /*
225 * Process descriptors start out with two references: one from their
226 * struct file, and the other from their struct proc.
227 */
228 refcount_init(&pd->pd_refcount, 2);
229 }
230
231 /*
232 * Create a new process decriptor for the process that refers to it.
233 */
234 int
procdesc_falloc(struct thread * td,struct file ** resultfp,int * resultfd,int flags,struct filecaps * fcaps)235 procdesc_falloc(struct thread *td, struct file **resultfp, int *resultfd,
236 int flags, struct filecaps *fcaps)
237 {
238 int fflags;
239
240 fflags = 0;
241 if (flags & PD_CLOEXEC)
242 fflags = O_CLOEXEC;
243
244 return (falloc_caps(td, resultfp, resultfd, fflags, fcaps));
245 }
246
247 /*
248 * Initialize a file with a process descriptor.
249 */
250 void
procdesc_finit(struct procdesc * pdp,struct file * fp)251 procdesc_finit(struct procdesc *pdp, struct file *fp)
252 {
253
254 finit(fp, FREAD | FWRITE, DTYPE_PROCDESC, pdp, &procdesc_ops);
255 }
256
257 static void
procdesc_free(struct procdesc * pd)258 procdesc_free(struct procdesc *pd)
259 {
260
261 /*
262 * When the last reference is released, we assert that the descriptor
263 * has been closed, but not that the process has exited, as we will
264 * detach the descriptor before the process dies if the descript is
265 * closed, as we can't wait synchronously.
266 */
267 if (refcount_release(&pd->pd_refcount)) {
268 KASSERT(pd->pd_proc == NULL,
269 ("procdesc_free: pd_proc != NULL"));
270 KASSERT((pd->pd_flags & PDF_CLOSED),
271 ("procdesc_free: !PDF_CLOSED"));
272
273 knlist_destroy(&pd->pd_selinfo.si_note);
274 PROCDESC_LOCK_DESTROY(pd);
275 free(pd, M_PROCDESC);
276 }
277 }
278
279 /*
280 * procdesc_exit() - notify a process descriptor that its process is exiting.
281 * We use the proctree_lock to ensure that process exit either happens
282 * strictly before or strictly after a concurrent call to procdesc_close().
283 */
284 int
procdesc_exit(struct proc * p)285 procdesc_exit(struct proc *p)
286 {
287 struct procdesc *pd;
288
289 sx_assert(&proctree_lock, SA_XLOCKED);
290 PROC_LOCK_ASSERT(p, MA_OWNED);
291 KASSERT(p->p_procdesc != NULL, ("procdesc_exit: p_procdesc NULL"));
292
293 pd = p->p_procdesc;
294
295 PROCDESC_LOCK(pd);
296 KASSERT((pd->pd_flags & PDF_CLOSED) == 0 || p->p_pptr == p->p_reaper,
297 ("procdesc_exit: closed && parent not reaper"));
298
299 pd->pd_flags |= PDF_EXITED;
300 pd->pd_xstat = KW_EXITCODE(p->p_xexit, p->p_xsig);
301
302 /*
303 * If the process descriptor has been closed, then we have nothing
304 * to do; return 1 so that init will get SIGCHLD and do the reaping.
305 * Clean up the procdesc now rather than letting it happen during
306 * that reap.
307 */
308 if (pd->pd_flags & PDF_CLOSED) {
309 PROCDESC_UNLOCK(pd);
310 pd->pd_proc = NULL;
311 p->p_procdesc = NULL;
312 procdesc_free(pd);
313 return (1);
314 }
315 if (pd->pd_flags & PDF_SELECTED) {
316 pd->pd_flags &= ~PDF_SELECTED;
317 selwakeup(&pd->pd_selinfo);
318 }
319 KNOTE_LOCKED(&pd->pd_selinfo.si_note, NOTE_EXIT);
320 PROCDESC_UNLOCK(pd);
321 return (0);
322 }
323
324 /*
325 * When a process descriptor is reaped, perhaps as a result of close(), release
326 * the process's reference on the process descriptor.
327 */
328 void
procdesc_reap(struct proc * p)329 procdesc_reap(struct proc *p)
330 {
331 struct procdesc *pd;
332
333 sx_assert(&proctree_lock, SA_XLOCKED);
334 KASSERT(p->p_procdesc != NULL, ("procdesc_reap: p_procdesc == NULL"));
335
336 pd = p->p_procdesc;
337 pd->pd_proc = NULL;
338 p->p_procdesc = NULL;
339 procdesc_free(pd);
340 }
341
342 /*
343 * procdesc_close() - last close on a process descriptor. If the process is
344 * still running, terminate with SIGKILL (unless PDF_DAEMON is set) and let
345 * its reaper clean up the mess; if not, we have to clean up the zombie
346 * ourselves.
347 */
348 static int
procdesc_close(struct file * fp,struct thread * td)349 procdesc_close(struct file *fp, struct thread *td)
350 {
351 struct procdesc *pd;
352 struct proc *p;
353
354 KASSERT(fp->f_type == DTYPE_PROCDESC, ("procdesc_close: !procdesc"));
355
356 pd = fp->f_data;
357 fp->f_ops = &badfileops;
358 fp->f_data = NULL;
359
360 sx_xlock(&proctree_lock);
361 PROCDESC_LOCK(pd);
362 pd->pd_flags |= PDF_CLOSED;
363 PROCDESC_UNLOCK(pd);
364 p = pd->pd_proc;
365 if (p == NULL) {
366 /*
367 * This is the case where process' exit status was already
368 * collected and procdesc_reap() was already called.
369 */
370 sx_xunlock(&proctree_lock);
371 } else {
372 PROC_LOCK(p);
373 AUDIT_ARG_PROCESS(p);
374 if (p->p_state == PRS_ZOMBIE) {
375 /*
376 * If the process is already dead and just awaiting
377 * reaping, do that now. This will release the
378 * process's reference to the process descriptor when it
379 * calls back into procdesc_reap().
380 */
381 proc_reap(curthread, p, NULL, 0);
382 } else {
383 /*
384 * If the process is not yet dead, we need to kill it,
385 * but we can't wait around synchronously for it to go
386 * away, as that path leads to madness (and deadlocks).
387 * First, detach the process from its descriptor so that
388 * its exit status will be reported normally.
389 */
390 pd->pd_proc = NULL;
391 p->p_procdesc = NULL;
392 procdesc_free(pd);
393
394 /*
395 * Next, reparent it to its reaper (usually init(8)) so
396 * that there's someone to pick up the pieces; finally,
397 * terminate with prejudice.
398 */
399 p->p_sigparent = SIGCHLD;
400 if ((p->p_flag & P_TRACED) == 0) {
401 proc_reparent(p, p->p_reaper, true);
402 } else {
403 proc_clear_orphan(p);
404 p->p_oppid = p->p_reaper->p_pid;
405 proc_add_orphan(p, p->p_reaper);
406 }
407 if ((pd->pd_flags & PDF_DAEMON) == 0)
408 kern_psignal(p, SIGKILL);
409 PROC_UNLOCK(p);
410 sx_xunlock(&proctree_lock);
411 }
412 }
413
414 /*
415 * Release the file descriptor's reference on the process descriptor.
416 */
417 procdesc_free(pd);
418 return (0);
419 }
420
421 static int
procdesc_poll(struct file * fp,int events,struct ucred * active_cred,struct thread * td)422 procdesc_poll(struct file *fp, int events, struct ucred *active_cred,
423 struct thread *td)
424 {
425 struct procdesc *pd;
426 int revents;
427
428 revents = 0;
429 pd = fp->f_data;
430 PROCDESC_LOCK(pd);
431 if (pd->pd_flags & PDF_EXITED)
432 revents |= POLLHUP;
433 if (revents == 0) {
434 selrecord(td, &pd->pd_selinfo);
435 pd->pd_flags |= PDF_SELECTED;
436 }
437 PROCDESC_UNLOCK(pd);
438 return (revents);
439 }
440
441 static void
procdesc_kqops_detach(struct knote * kn)442 procdesc_kqops_detach(struct knote *kn)
443 {
444 struct procdesc *pd;
445
446 pd = kn->kn_fp->f_data;
447 knlist_remove(&pd->pd_selinfo.si_note, kn, 0);
448 }
449
450 static int
procdesc_kqops_event(struct knote * kn,long hint)451 procdesc_kqops_event(struct knote *kn, long hint)
452 {
453 struct procdesc *pd;
454 u_int event;
455
456 pd = kn->kn_fp->f_data;
457 if (hint == 0) {
458 /*
459 * Initial test after registration. Generate a NOTE_EXIT in
460 * case the process already terminated before registration.
461 */
462 event = pd->pd_flags & PDF_EXITED ? NOTE_EXIT : 0;
463 } else {
464 /* Mask off extra data. */
465 event = (u_int)hint & NOTE_PCTRLMASK;
466 }
467
468 /* If the user is interested in this event, record it. */
469 if (kn->kn_sfflags & event)
470 kn->kn_fflags |= event;
471
472 /* Process is gone, so flag the event as finished. */
473 if (event == NOTE_EXIT) {
474 kn->kn_flags |= EV_EOF | EV_ONESHOT;
475 if (kn->kn_fflags & NOTE_EXIT)
476 kn->kn_data = pd->pd_xstat;
477 if (kn->kn_fflags == 0)
478 kn->kn_flags |= EV_DROP;
479 return (1);
480 }
481
482 return (kn->kn_fflags != 0);
483 }
484
485 static const struct filterops procdesc_kqops = {
486 .f_isfd = 1,
487 .f_detach = procdesc_kqops_detach,
488 .f_event = procdesc_kqops_event,
489 };
490
491 static int
procdesc_kqfilter(struct file * fp,struct knote * kn)492 procdesc_kqfilter(struct file *fp, struct knote *kn)
493 {
494 struct procdesc *pd;
495
496 pd = fp->f_data;
497 switch (kn->kn_filter) {
498 case EVFILT_PROCDESC:
499 kn->kn_fop = &procdesc_kqops;
500 kn->kn_flags |= EV_CLEAR;
501 knlist_add(&pd->pd_selinfo.si_note, kn, 0);
502 return (0);
503 default:
504 return (EINVAL);
505 }
506 }
507
508 static int
procdesc_stat(struct file * fp,struct stat * sb,struct ucred * active_cred)509 procdesc_stat(struct file *fp, struct stat *sb, struct ucred *active_cred)
510 {
511 struct procdesc *pd;
512 struct timeval pstart, boottime;
513
514 /*
515 * XXXRW: Perhaps we should cache some more information from the
516 * process so that we can return it reliably here even after it has
517 * died. For example, caching its credential data.
518 */
519 bzero(sb, sizeof(*sb));
520 pd = fp->f_data;
521 sx_slock(&proctree_lock);
522 if (pd->pd_proc != NULL) {
523 PROC_LOCK(pd->pd_proc);
524 AUDIT_ARG_PROCESS(pd->pd_proc);
525
526 /* Set birth and [acm] times to process start time. */
527 pstart = pd->pd_proc->p_stats->p_start;
528 getboottime(&boottime);
529 timevaladd(&pstart, &boottime);
530 TIMEVAL_TO_TIMESPEC(&pstart, &sb->st_birthtim);
531 sb->st_atim = sb->st_birthtim;
532 sb->st_ctim = sb->st_birthtim;
533 sb->st_mtim = sb->st_birthtim;
534 if (pd->pd_proc->p_state != PRS_ZOMBIE)
535 sb->st_mode = S_IFREG | S_IRWXU;
536 else
537 sb->st_mode = S_IFREG;
538 sb->st_uid = pd->pd_proc->p_ucred->cr_ruid;
539 sb->st_gid = pd->pd_proc->p_ucred->cr_rgid;
540 PROC_UNLOCK(pd->pd_proc);
541 } else
542 sb->st_mode = S_IFREG;
543 sx_sunlock(&proctree_lock);
544 return (0);
545 }
546
547 static int
procdesc_fill_kinfo(struct file * fp,struct kinfo_file * kif,struct filedesc * fdp)548 procdesc_fill_kinfo(struct file *fp, struct kinfo_file *kif,
549 struct filedesc *fdp)
550 {
551 struct procdesc *pdp;
552
553 kif->kf_type = KF_TYPE_PROCDESC;
554 pdp = fp->f_data;
555 kif->kf_un.kf_proc.kf_pid = pdp->pd_pid;
556 return (0);
557 }
558
559 static int
procdesc_cmp(struct file * fp1,struct file * fp2,struct thread * td)560 procdesc_cmp(struct file *fp1, struct file *fp2, struct thread *td)
561 {
562 struct procdesc *pdp1, *pdp2;
563
564 if (fp2->f_type != DTYPE_PROCDESC)
565 return (3);
566 pdp1 = fp1->f_data;
567 pdp2 = fp2->f_data;
568 return (kcmp_cmp((uintptr_t)pdp1->pd_pid, (uintptr_t)pdp2->pd_pid));
569 }
570