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/syscallsubr.h>
79 #include <sys/sysproto.h>
80 #include <sys/sysctl.h>
81 #include <sys/systm.h>
82 #include <sys/ucred.h>
83 #include <sys/user.h>
84
85 #include <security/audit/audit.h>
86
87 #include <vm/uma.h>
88
89 FEATURE(process_descriptors, "Process Descriptors");
90
91 MALLOC_DEFINE(M_PROCDESC, "procdesc", "process descriptors");
92
93 static fo_poll_t procdesc_poll;
94 static fo_kqfilter_t procdesc_kqfilter;
95 static fo_stat_t procdesc_stat;
96 static fo_close_t procdesc_close;
97 static fo_fill_kinfo_t procdesc_fill_kinfo;
98 static fo_cmp_t procdesc_cmp;
99
100 static const struct fileops procdesc_ops = {
101 .fo_read = invfo_rdwr,
102 .fo_write = invfo_rdwr,
103 .fo_truncate = invfo_truncate,
104 .fo_ioctl = invfo_ioctl,
105 .fo_poll = procdesc_poll,
106 .fo_kqfilter = procdesc_kqfilter,
107 .fo_stat = procdesc_stat,
108 .fo_close = procdesc_close,
109 .fo_chmod = invfo_chmod,
110 .fo_chown = invfo_chown,
111 .fo_sendfile = invfo_sendfile,
112 .fo_fill_kinfo = procdesc_fill_kinfo,
113 .fo_cmp = procdesc_cmp,
114 .fo_flags = DFLAG_PASSABLE,
115 };
116
117 /*
118 * Return a locked process given a process descriptor, or ESRCH if it has
119 * died.
120 */
121 int
procdesc_find(struct thread * td,int fd,const cap_rights_t * rightsp,struct proc ** p)122 procdesc_find(struct thread *td, int fd, const cap_rights_t *rightsp,
123 struct proc **p)
124 {
125 struct procdesc *pd;
126 struct file *fp;
127 int error;
128
129 error = fget(td, fd, rightsp, &fp);
130 if (error)
131 return (error);
132 if (fp->f_type != DTYPE_PROCDESC) {
133 error = EINVAL;
134 goto out;
135 }
136 pd = fp->f_data;
137 sx_slock(&proctree_lock);
138 if (pd->pd_proc != NULL) {
139 *p = pd->pd_proc;
140 PROC_LOCK(*p);
141 } else
142 error = ESRCH;
143 sx_sunlock(&proctree_lock);
144 out:
145 fdrop(fp, td);
146 return (error);
147 }
148
149 /*
150 * Function to be used by procstat(1) sysctls when returning procdesc
151 * information.
152 */
153 pid_t
procdesc_pid(struct file * fp_procdesc)154 procdesc_pid(struct file *fp_procdesc)
155 {
156 struct procdesc *pd;
157
158 KASSERT(fp_procdesc->f_type == DTYPE_PROCDESC,
159 ("procdesc_pid: !procdesc"));
160
161 pd = fp_procdesc->f_data;
162 return (pd->pd_pid);
163 }
164
165 /*
166 * Retrieve the PID associated with a process descriptor.
167 */
168 int
kern_pdgetpid(struct thread * td,int fd,const cap_rights_t * rightsp,pid_t * pidp)169 kern_pdgetpid(struct thread *td, int fd, const cap_rights_t *rightsp,
170 pid_t *pidp)
171 {
172 struct file *fp;
173 int error;
174
175 error = fget(td, fd, rightsp, &fp);
176 if (error)
177 return (error);
178 if (fp->f_type != DTYPE_PROCDESC) {
179 error = EBADF;
180 goto out;
181 }
182 *pidp = procdesc_pid(fp);
183 out:
184 fdrop(fp, td);
185 return (error);
186 }
187
188 /*
189 * System call to return the pid of a process given its process descriptor.
190 */
191 int
sys_pdgetpid(struct thread * td,struct pdgetpid_args * uap)192 sys_pdgetpid(struct thread *td, struct pdgetpid_args *uap)
193 {
194 pid_t pid;
195 int error;
196
197 AUDIT_ARG_FD(uap->fd);
198 error = kern_pdgetpid(td, uap->fd, &cap_pdgetpid_rights, &pid);
199 if (error == 0)
200 error = copyout(&pid, uap->pidp, sizeof(pid));
201 return (error);
202 }
203
204 /*
205 * When a new process is forked by pdfork(), a file descriptor is allocated
206 * by the fork code first, then the process is forked, and then we get a
207 * chance to set up the process descriptor. Failure is not permitted at this
208 * point, so procdesc_new() must succeed.
209 */
210 void
procdesc_new(struct proc * p,int flags)211 procdesc_new(struct proc *p, int flags)
212 {
213 struct procdesc *pd;
214
215 pd = malloc(sizeof(*pd), M_PROCDESC, M_WAITOK | M_ZERO);
216 pd->pd_proc = p;
217 pd->pd_pid = p->p_pid;
218 p->p_procdesc = pd;
219 pd->pd_flags = 0;
220 if (flags & PD_DAEMON)
221 pd->pd_flags |= PDF_DAEMON;
222 PROCDESC_LOCK_INIT(pd);
223 knlist_init_mtx(&pd->pd_selinfo.si_note, &pd->pd_lock);
224
225 /*
226 * Process descriptors start out with two references: one from their
227 * struct file, and the other from their struct proc.
228 */
229 refcount_init(&pd->pd_refcount, 2);
230 }
231
232 /*
233 * Create a new process decriptor for the process that refers to it.
234 */
235 int
procdesc_falloc(struct thread * td,struct file ** resultfp,int * resultfd,int flags,struct filecaps * fcaps)236 procdesc_falloc(struct thread *td, struct file **resultfp, int *resultfd,
237 int flags, struct filecaps *fcaps)
238 {
239 int fflags;
240
241 fflags = 0;
242 if (flags & PD_CLOEXEC)
243 fflags = O_CLOEXEC;
244
245 return (falloc_caps(td, resultfp, resultfd, fflags, fcaps));
246 }
247
248 /*
249 * Initialize a file with a process descriptor.
250 */
251 void
procdesc_finit(struct procdesc * pdp,struct file * fp)252 procdesc_finit(struct procdesc *pdp, struct file *fp)
253 {
254
255 finit(fp, FREAD | FWRITE, DTYPE_PROCDESC, pdp, &procdesc_ops);
256 }
257
258 static void
procdesc_free(struct procdesc * pd)259 procdesc_free(struct procdesc *pd)
260 {
261
262 /*
263 * When the last reference is released, we assert that the descriptor
264 * has been closed, but not that the process has exited, as we will
265 * detach the descriptor before the process dies if the descript is
266 * closed, as we can't wait synchronously.
267 */
268 if (refcount_release(&pd->pd_refcount)) {
269 KASSERT(pd->pd_proc == NULL,
270 ("procdesc_free: pd_proc != NULL"));
271 KASSERT((pd->pd_flags & PDF_CLOSED),
272 ("procdesc_free: !PDF_CLOSED"));
273
274 if (pd->pd_pid != -1)
275 proc_id_clear(PROC_ID_PID, pd->pd_pid);
276
277 seldrain(&pd->pd_selinfo);
278 knlist_destroy(&pd->pd_selinfo.si_note);
279 PROCDESC_LOCK_DESTROY(pd);
280 free(pd, M_PROCDESC);
281 }
282 }
283
284 /*
285 * procdesc_exit() - notify a process descriptor that its process is exiting.
286 * We use the proctree_lock to ensure that process exit either happens
287 * strictly before or strictly after a concurrent call to procdesc_close().
288 */
289 int
procdesc_exit(struct proc * p)290 procdesc_exit(struct proc *p)
291 {
292 struct procdesc *pd;
293
294 sx_assert(&proctree_lock, SA_XLOCKED);
295 PROC_LOCK_ASSERT(p, MA_OWNED);
296 KASSERT(p->p_procdesc != NULL, ("procdesc_exit: p_procdesc NULL"));
297
298 pd = p->p_procdesc;
299
300 PROCDESC_LOCK(pd);
301 KASSERT((pd->pd_flags & PDF_CLOSED) == 0 || p->p_pptr == p->p_reaper,
302 ("procdesc_exit: closed && parent not reaper"));
303
304 pd->pd_flags |= PDF_EXITED;
305 pd->pd_xstat = KW_EXITCODE(p->p_xexit, p->p_xsig);
306
307 /*
308 * If the process descriptor has been closed, then we have nothing
309 * to do; return 1 so that init will get SIGCHLD and do the reaping.
310 * Clean up the procdesc now rather than letting it happen during
311 * that reap.
312 */
313 if (pd->pd_flags & PDF_CLOSED) {
314 PROCDESC_UNLOCK(pd);
315 pd->pd_proc = NULL;
316 p->p_procdesc = NULL;
317 procdesc_free(pd);
318 return (1);
319 }
320 selwakeup(&pd->pd_selinfo);
321 KNOTE_LOCKED(&pd->pd_selinfo.si_note, NOTE_EXIT);
322 PROCDESC_UNLOCK(pd);
323
324 /* Wakeup all waiters for this procdesc' process exit. */
325 wakeup(&p->p_procdesc);
326 return (0);
327 }
328
329 /*
330 * When a process descriptor is reaped, perhaps as a result of close(), release
331 * the process's reference on the process descriptor.
332 */
333 void
procdesc_reap(struct proc * p)334 procdesc_reap(struct proc *p)
335 {
336 struct procdesc *pd;
337
338 sx_assert(&proctree_lock, SA_XLOCKED);
339 KASSERT(p->p_procdesc != NULL, ("procdesc_reap: p_procdesc == NULL"));
340
341 pd = p->p_procdesc;
342 pd->pd_proc = NULL;
343 p->p_procdesc = NULL;
344 procdesc_free(pd);
345 }
346
347 /*
348 * procdesc_close() - last close on a process descriptor. If the process is
349 * still running, terminate with SIGKILL (unless PDF_DAEMON is set) and let
350 * its reaper clean up the mess; if not, we have to clean up the zombie
351 * ourselves.
352 */
353 static int
procdesc_close(struct file * fp,struct thread * td)354 procdesc_close(struct file *fp, struct thread *td)
355 {
356 struct procdesc *pd;
357 struct proc *p;
358
359 KASSERT(fp->f_type == DTYPE_PROCDESC, ("procdesc_close: !procdesc"));
360
361 pd = fp->f_data;
362 fp->f_ops = &badfileops;
363 fp->f_data = NULL;
364
365 sx_xlock(&proctree_lock);
366 PROCDESC_LOCK(pd);
367 pd->pd_flags |= PDF_CLOSED;
368 PROCDESC_UNLOCK(pd);
369 p = pd->pd_proc;
370 if (p == NULL) {
371 /*
372 * This is the case where process' exit status was already
373 * collected and procdesc_reap() was already called.
374 */
375 sx_xunlock(&proctree_lock);
376 } else {
377 PROC_LOCK(p);
378 AUDIT_ARG_PROCESS(p);
379 if (p->p_state == PRS_ZOMBIE) {
380 /*
381 * If the process is already dead and just awaiting
382 * reaping, do that now. This will release the
383 * process's reference to the process descriptor when it
384 * calls back into procdesc_reap().
385 */
386 proc_reap(curthread, p, NULL, 0);
387 } else {
388 /*
389 * If the process is not yet dead, we need to kill it,
390 * but we can't wait around synchronously for it to go
391 * away, as that path leads to madness (and deadlocks).
392 * First, detach the process from its descriptor so that
393 * its exit status will be reported normally.
394 */
395 pd->pd_proc = NULL;
396 p->p_procdesc = NULL;
397 pd->pd_pid = -1;
398 procdesc_free(pd);
399
400 /*
401 * Next, reparent it to its reaper (usually init(8)) so
402 * that there's someone to pick up the pieces; finally,
403 * terminate with prejudice.
404 */
405 p->p_sigparent = SIGCHLD;
406 if ((p->p_flag & P_TRACED) == 0) {
407 proc_reparent(p, p->p_reaper, true);
408 } else {
409 proc_clear_orphan(p);
410 p->p_oppid = p->p_reaper->p_pid;
411 proc_add_orphan(p, p->p_reaper);
412 }
413 if ((pd->pd_flags & PDF_DAEMON) == 0)
414 kern_psignal(p, SIGKILL);
415 PROC_UNLOCK(p);
416 sx_xunlock(&proctree_lock);
417 }
418 }
419
420 /*
421 * Release the file descriptor's reference on the process descriptor.
422 */
423 procdesc_free(pd);
424 return (0);
425 }
426
427 static int
procdesc_poll(struct file * fp,int events,struct ucred * active_cred,struct thread * td)428 procdesc_poll(struct file *fp, int events, struct ucred *active_cred,
429 struct thread *td)
430 {
431 struct procdesc *pd;
432 int revents;
433
434 revents = 0;
435 pd = fp->f_data;
436 PROCDESC_LOCK(pd);
437 if (pd->pd_flags & PDF_EXITED)
438 revents |= POLLHUP;
439 else
440 selrecord(td, &pd->pd_selinfo);
441 PROCDESC_UNLOCK(pd);
442 return (revents);
443 }
444
445 static void
procdesc_kqops_detach(struct knote * kn)446 procdesc_kqops_detach(struct knote *kn)
447 {
448 struct procdesc *pd;
449
450 pd = kn->kn_fp->f_data;
451 knlist_remove(&pd->pd_selinfo.si_note, kn, 0);
452 }
453
454 static int
procdesc_kqops_event(struct knote * kn,long hint)455 procdesc_kqops_event(struct knote *kn, long hint)
456 {
457 struct procdesc *pd;
458 u_int event;
459
460 pd = kn->kn_fp->f_data;
461 if (hint == 0) {
462 /*
463 * Initial test after registration. Generate a NOTE_EXIT in
464 * case the process already terminated before registration.
465 */
466 event = pd->pd_flags & PDF_EXITED ? NOTE_EXIT : 0;
467 } else {
468 /* Mask off extra data. */
469 event = (u_int)hint & NOTE_PCTRLMASK;
470 }
471
472 /* If the user is interested in this event, record it. */
473 if (kn->kn_sfflags & event)
474 kn->kn_fflags |= event;
475
476 /* Process is gone, so flag the event as finished. */
477 if (event == NOTE_EXIT) {
478 kn->kn_flags |= EV_EOF | EV_ONESHOT;
479 if (kn->kn_fflags & NOTE_EXIT)
480 kn->kn_data = pd->pd_xstat;
481 if (kn->kn_fflags == 0)
482 kn->kn_flags |= EV_DROP;
483 return (1);
484 }
485
486 return (kn->kn_fflags != 0);
487 }
488
489 static const struct filterops procdesc_kqops = {
490 .f_isfd = 1,
491 .f_detach = procdesc_kqops_detach,
492 .f_event = procdesc_kqops_event,
493 .f_copy = knote_triv_copy,
494 };
495
496 static int
procdesc_kqfilter(struct file * fp,struct knote * kn)497 procdesc_kqfilter(struct file *fp, struct knote *kn)
498 {
499 struct procdesc *pd;
500
501 pd = fp->f_data;
502 switch (kn->kn_filter) {
503 case EVFILT_PROCDESC:
504 kn->kn_fop = &procdesc_kqops;
505 kn->kn_flags |= EV_CLEAR;
506 knlist_add(&pd->pd_selinfo.si_note, kn, 0);
507 return (0);
508 default:
509 return (EINVAL);
510 }
511 }
512
513 static int
procdesc_stat(struct file * fp,struct stat * sb,struct ucred * active_cred)514 procdesc_stat(struct file *fp, struct stat *sb, struct ucred *active_cred)
515 {
516 struct procdesc *pd;
517 struct timeval pstart, boottime;
518
519 /*
520 * XXXRW: Perhaps we should cache some more information from the
521 * process so that we can return it reliably here even after it has
522 * died. For example, caching its credential data.
523 */
524 bzero(sb, sizeof(*sb));
525 pd = fp->f_data;
526 sx_slock(&proctree_lock);
527 if (pd->pd_proc != NULL) {
528 PROC_LOCK(pd->pd_proc);
529 AUDIT_ARG_PROCESS(pd->pd_proc);
530
531 /* Set birth and [acm] times to process start time. */
532 pstart = pd->pd_proc->p_stats->p_start;
533 getboottime(&boottime);
534 timevaladd(&pstart, &boottime);
535 TIMEVAL_TO_TIMESPEC(&pstart, &sb->st_birthtim);
536 sb->st_atim = sb->st_birthtim;
537 sb->st_ctim = sb->st_birthtim;
538 sb->st_mtim = sb->st_birthtim;
539 if (pd->pd_proc->p_state != PRS_ZOMBIE)
540 sb->st_mode = S_IFREG | S_IRWXU;
541 else
542 sb->st_mode = S_IFREG;
543 sb->st_uid = pd->pd_proc->p_ucred->cr_ruid;
544 sb->st_gid = pd->pd_proc->p_ucred->cr_rgid;
545 PROC_UNLOCK(pd->pd_proc);
546 } else
547 sb->st_mode = S_IFREG;
548 sx_sunlock(&proctree_lock);
549 return (0);
550 }
551
552 static int
procdesc_fill_kinfo(struct file * fp,struct kinfo_file * kif,struct filedesc * fdp)553 procdesc_fill_kinfo(struct file *fp, struct kinfo_file *kif,
554 struct filedesc *fdp)
555 {
556 struct procdesc *pdp;
557
558 kif->kf_type = KF_TYPE_PROCDESC;
559 pdp = fp->f_data;
560 kif->kf_un.kf_proc.kf_pid = pdp->pd_pid;
561 return (0);
562 }
563
564 static int
procdesc_cmp(struct file * fp1,struct file * fp2,struct thread * td)565 procdesc_cmp(struct file *fp1, struct file *fp2, struct thread *td)
566 {
567 struct procdesc *pdp1, *pdp2;
568
569 if (fp2->f_type != DTYPE_PROCDESC)
570 return (3);
571 pdp1 = fp1->f_data;
572 pdp2 = fp2->f_data;
573 return (kcmp_cmp((uintptr_t)pdp1->pd_pid, (uintptr_t)pdp2->pd_pid));
574 }
575