1 /*-
2 * Copyright (c) 2009, 2016 Robert N. M. Watson
3 * All rights reserved.
4 *
5 * This software was developed at the University of Cambridge Computer
6 * Laboratory with support from a grant from Google, Inc.
7 *
8 * Portions of this software were developed by BAE Systems, the University of
9 * Cambridge Computer Laboratory, and Memorial University under DARPA/AFRL
10 * contract FA8650-15-C-7558 ("CADETS"), as part of the DARPA Transparent
11 * Computing (TC) research program.
12 *
13 * Redistribution and use in source and binary forms, with or without
14 * modification, are permitted provided that the following conditions
15 * are met:
16 * 1. Redistributions of source code must retain the above copyright
17 * notice, this list of conditions and the following disclaimer.
18 * 2. Redistributions in binary form must reproduce the above copyright
19 * notice, this list of conditions and the following disclaimer in the
20 * documentation and/or other materials provided with the distribution.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 */
34
35 /*-
36 * FreeBSD process descriptor facility.
37 *
38 * Some processes are represented by a file descriptor, which will be used in
39 * preference to signaling and pids for the purposes of process management,
40 * and is, in effect, a form of capability. When a process descriptor is
41 * used with a process, it ceases to be visible to certain traditional UNIX
42 * process facilities, such as waitpid(2).
43 *
44 * Some semantics:
45 *
46 * - At most one process descriptor will exist for any process, although
47 * references to that descriptor may be held from many processes (or even
48 * be in flight between processes over a local domain socket).
49 * - Last close on the process descriptor will terminate the process using
50 * SIGKILL and reparent it to init so that there's a process to reap it
51 * when it's done exiting.
52 * - If the process exits before the descriptor is closed, it will not
53 * generate SIGCHLD on termination, or be picked up by waitpid().
54 * - The pdkill(2) system call may be used to deliver a signal to the process
55 * using its process descriptor.
56 * - The pdwait4(2) system call may be used to block (or not) on a process
57 * descriptor to collect termination information.
58 *
59 * Open questions:
60 *
61 * - How to handle ptrace(2)?
62 * - Will we want to add a pidtoprocdesc(2) system call to allow process
63 * descriptors to be created for processes without pdfork(2)?
64 */
65
66 #include <sys/cdefs.h>
67 __FBSDID("$FreeBSD: releng/11.2/sys/kern/sys_procdesc.c 330964 2018-03-15 02:20:06Z eadler $");
68
69 #include <sys/param.h>
70 #include <sys/capsicum.h>
71 #include <sys/fcntl.h>
72 #include <sys/file.h>
73 #include <sys/filedesc.h>
74 #include <sys/kernel.h>
75 #include <sys/lock.h>
76 #include <sys/mutex.h>
77 #include <sys/poll.h>
78 #include <sys/proc.h>
79 #include <sys/procdesc.h>
80 #include <sys/resourcevar.h>
81 #include <sys/stat.h>
82 #include <sys/sysproto.h>
83 #include <sys/sysctl.h>
84 #include <sys/systm.h>
85 #include <sys/ucred.h>
86 #include <sys/user.h>
87
88 #include <security/audit/audit.h>
89
90 #include <vm/uma.h>
91
92 FEATURE(process_descriptors, "Process Descriptors");
93
94 static uma_zone_t procdesc_zone;
95
96 static fo_poll_t procdesc_poll;
97 static fo_kqfilter_t procdesc_kqfilter;
98 static fo_stat_t procdesc_stat;
99 static fo_close_t procdesc_close;
100 static fo_fill_kinfo_t procdesc_fill_kinfo;
101
102 static struct fileops procdesc_ops = {
103 .fo_read = invfo_rdwr,
104 .fo_write = invfo_rdwr,
105 .fo_truncate = invfo_truncate,
106 .fo_ioctl = invfo_ioctl,
107 .fo_poll = procdesc_poll,
108 .fo_kqfilter = procdesc_kqfilter,
109 .fo_stat = procdesc_stat,
110 .fo_close = procdesc_close,
111 .fo_chmod = invfo_chmod,
112 .fo_chown = invfo_chown,
113 .fo_sendfile = invfo_sendfile,
114 .fo_fill_kinfo = procdesc_fill_kinfo,
115 .fo_flags = DFLAG_PASSABLE,
116 };
117
118 /*
119 * Initialize with VFS so that process descriptors are available along with
120 * other file descriptor types. As long as it runs before init(8) starts,
121 * there shouldn't be a problem.
122 */
123 static void
124 procdesc_init(void *dummy __unused)
125 {
126
127 procdesc_zone = uma_zcreate("procdesc", sizeof(struct procdesc),
128 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
129 if (procdesc_zone == NULL)
130 panic("procdesc_init: procdesc_zone not initialized");
131 }
132 SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_ANY, procdesc_init, NULL);
133
134 /*
135 * Return a locked process given a process descriptor, or ESRCH if it has
136 * died.
137 */
138 int
139 procdesc_find(struct thread *td, int fd, cap_rights_t *rightsp,
140 struct proc **p)
141 {
142 struct procdesc *pd;
143 struct file *fp;
144 int error;
145
146 error = fget(td, fd, rightsp, &fp);
147 if (error)
148 return (error);
149 if (fp->f_type != DTYPE_PROCDESC) {
150 error = EBADF;
151 goto out;
152 }
153 pd = fp->f_data;
154 sx_slock(&proctree_lock);
155 if (pd->pd_proc != NULL) {
156 *p = pd->pd_proc;
157 PROC_LOCK(*p);
158 } else
159 error = ESRCH;
160 sx_sunlock(&proctree_lock);
161 out:
162 fdrop(fp, td);
163 return (error);
164 }
165
166 /*
167 * Function to be used by procstat(1) sysctls when returning procdesc
168 * information.
169 */
170 pid_t
171 procdesc_pid(struct file *fp_procdesc)
172 {
173 struct procdesc *pd;
174
175 KASSERT(fp_procdesc->f_type == DTYPE_PROCDESC,
176 ("procdesc_pid: !procdesc"));
177
178 pd = fp_procdesc->f_data;
179 return (pd->pd_pid);
180 }
181
182 /*
183 * Retrieve the PID associated with a process descriptor.
184 */
185 int
186 kern_pdgetpid(struct thread *td, int fd, cap_rights_t *rightsp, pid_t *pidp)
187 {
188 struct file *fp;
189 int error;
190
191 error = fget(td, fd, rightsp, &fp);
192 if (error)
193 return (error);
194 if (fp->f_type != DTYPE_PROCDESC) {
195 error = EBADF;
196 goto out;
197 }
198 *pidp = procdesc_pid(fp);
199 out:
200 fdrop(fp, td);
201 return (error);
202 }
203
204 /*
205 * System call to return the pid of a process given its process descriptor.
206 */
207 int
208 sys_pdgetpid(struct thread *td, struct pdgetpid_args *uap)
209 {
210 cap_rights_t rights;
211 pid_t pid;
212 int error;
213
214 AUDIT_ARG_FD(uap->fd);
215 error = kern_pdgetpid(td, uap->fd,
216 cap_rights_init(&rights, CAP_PDGETPID), &pid);
217 if (error == 0)
218 error = copyout(&pid, uap->pidp, sizeof(pid));
219 return (error);
220 }
221
222 /*
223 * When a new process is forked by pdfork(), a file descriptor is allocated
224 * by the fork code first, then the process is forked, and then we get a
225 * chance to set up the process descriptor. Failure is not permitted at this
226 * point, so procdesc_new() must succeed.
227 */
228 void
229 procdesc_new(struct proc *p, int flags)
230 {
231 struct procdesc *pd;
232
233 pd = uma_zalloc(procdesc_zone, M_WAITOK | M_ZERO);
234 pd->pd_proc = p;
235 pd->pd_pid = p->p_pid;
236 p->p_procdesc = pd;
237 pd->pd_flags = 0;
238 if (flags & PD_DAEMON)
239 pd->pd_flags |= PDF_DAEMON;
240 PROCDESC_LOCK_INIT(pd);
241 knlist_init_mtx(&pd->pd_selinfo.si_note, &pd->pd_lock);
242
243 /*
244 * Process descriptors start out with two references: one from their
245 * struct file, and the other from their struct proc.
246 */
247 refcount_init(&pd->pd_refcount, 2);
248 }
249
250 /*
251 * Create a new process decriptor for the process that refers to it.
252 */
253 int
254 procdesc_falloc(struct thread *td, struct file **resultfp, int *resultfd,
255 int flags, struct filecaps *fcaps)
256 {
257 int fflags;
258
259 fflags = 0;
260 if (flags & PD_CLOEXEC)
261 fflags = O_CLOEXEC;
262
263 return (falloc_caps(td, resultfp, resultfd, fflags, fcaps));
264 }
265
266 /*
267 * Initialize a file with a process descriptor.
268 */
269 void
270 procdesc_finit(struct procdesc *pdp, struct file *fp)
271 {
272
273 finit(fp, FREAD | FWRITE, DTYPE_PROCDESC, pdp, &procdesc_ops);
274 }
275
276 static void
277 procdesc_free(struct procdesc *pd)
278 {
279
280 /*
281 * When the last reference is released, we assert that the descriptor
282 * has been closed, but not that the process has exited, as we will
283 * detach the descriptor before the process dies if the descript is
284 * closed, as we can't wait synchronously.
285 */
286 if (refcount_release(&pd->pd_refcount)) {
287 KASSERT(pd->pd_proc == NULL,
288 ("procdesc_free: pd_proc != NULL"));
289 KASSERT((pd->pd_flags & PDF_CLOSED),
290 ("procdesc_free: !PDF_CLOSED"));
291
292 knlist_destroy(&pd->pd_selinfo.si_note);
293 PROCDESC_LOCK_DESTROY(pd);
294 uma_zfree(procdesc_zone, pd);
295 }
296 }
297
298 /*
299 * procdesc_exit() - notify a process descriptor that its process is exiting.
300 * We use the proctree_lock to ensure that process exit either happens
301 * strictly before or strictly after a concurrent call to procdesc_close().
302 */
303 int
304 procdesc_exit(struct proc *p)
305 {
306 struct procdesc *pd;
307
308 sx_assert(&proctree_lock, SA_XLOCKED);
309 PROC_LOCK_ASSERT(p, MA_OWNED);
310 KASSERT(p->p_procdesc != NULL, ("procdesc_exit: p_procdesc NULL"));
311
312 pd = p->p_procdesc;
313
314 PROCDESC_LOCK(pd);
315 KASSERT((pd->pd_flags & PDF_CLOSED) == 0 || p->p_pptr == initproc,
316 ("procdesc_exit: closed && parent not init"));
317
318 pd->pd_flags |= PDF_EXITED;
319 pd->pd_xstat = KW_EXITCODE(p->p_xexit, p->p_xsig);
320
321 /*
322 * If the process descriptor has been closed, then we have nothing
323 * to do; return 1 so that init will get SIGCHLD and do the reaping.
324 * Clean up the procdesc now rather than letting it happen during
325 * that reap.
326 */
327 if (pd->pd_flags & PDF_CLOSED) {
328 PROCDESC_UNLOCK(pd);
329 pd->pd_proc = NULL;
330 p->p_procdesc = NULL;
331 procdesc_free(pd);
332 return (1);
333 }
334 if (pd->pd_flags & PDF_SELECTED) {
335 pd->pd_flags &= ~PDF_SELECTED;
336 selwakeup(&pd->pd_selinfo);
337 }
338 KNOTE_LOCKED(&pd->pd_selinfo.si_note, NOTE_EXIT);
339 PROCDESC_UNLOCK(pd);
340 return (0);
341 }
342
343 /*
344 * When a process descriptor is reaped, perhaps as a result of close() or
345 * pdwait4(), release the process's reference on the process descriptor.
346 */
347 void
348 procdesc_reap(struct proc *p)
349 {
350 struct procdesc *pd;
351
352 sx_assert(&proctree_lock, SA_XLOCKED);
353 KASSERT(p->p_procdesc != NULL, ("procdesc_reap: p_procdesc == NULL"));
354
355 pd = p->p_procdesc;
356 pd->pd_proc = NULL;
357 p->p_procdesc = NULL;
358 procdesc_free(pd);
359 }
360
361 /*
362 * procdesc_close() - last close on a process descriptor. If the process is
363 * still running, terminate with SIGKILL (unless PDF_DAEMON is set) and let
364 * init(8) clean up the mess; if not, we have to clean up the zombie ourselves.
365 */
366 static int
367 procdesc_close(struct file *fp, struct thread *td)
368 {
369 struct procdesc *pd;
370 struct proc *p;
371
372 KASSERT(fp->f_type == DTYPE_PROCDESC, ("procdesc_close: !procdesc"));
373
374 pd = fp->f_data;
375 fp->f_ops = &badfileops;
376 fp->f_data = NULL;
377
378 sx_xlock(&proctree_lock);
379 PROCDESC_LOCK(pd);
380 pd->pd_flags |= PDF_CLOSED;
381 PROCDESC_UNLOCK(pd);
382 p = pd->pd_proc;
383 if (p == NULL) {
384 /*
385 * This is the case where process' exit status was already
386 * collected and procdesc_reap() was already called.
387 */
388 sx_xunlock(&proctree_lock);
389 } else {
390 PROC_LOCK(p);
391 AUDIT_ARG_PROCESS(p);
392 if (p->p_state == PRS_ZOMBIE) {
393 /*
394 * If the process is already dead and just awaiting
395 * reaping, do that now. This will release the
396 * process's reference to the process descriptor when it
397 * calls back into procdesc_reap().
398 */
399 PROC_SLOCK(p);
400 proc_reap(curthread, p, NULL, 0);
401 } else {
402 /*
403 * If the process is not yet dead, we need to kill it,
404 * but we can't wait around synchronously for it to go
405 * away, as that path leads to madness (and deadlocks).
406 * First, detach the process from its descriptor so that
407 * its exit status will be reported normally.
408 */
409 pd->pd_proc = NULL;
410 p->p_procdesc = NULL;
411 procdesc_free(pd);
412
413 /*
414 * Next, reparent it to init(8) so that there's someone
415 * to pick up the pieces; finally, terminate with
416 * prejudice.
417 */
418 p->p_sigparent = SIGCHLD;
419 proc_reparent(p, initproc);
420 if ((pd->pd_flags & PDF_DAEMON) == 0)
421 kern_psignal(p, SIGKILL);
422 PROC_UNLOCK(p);
423 sx_xunlock(&proctree_lock);
424 }
425 }
426
427 /*
428 * Release the file descriptor's reference on the process descriptor.
429 */
430 procdesc_free(pd);
431 return (0);
432 }
433
434 static int
435 procdesc_poll(struct file *fp, int events, struct ucred *active_cred,
436 struct thread *td)
437 {
438 struct procdesc *pd;
439 int revents;
440
441 revents = 0;
442 pd = fp->f_data;
443 PROCDESC_LOCK(pd);
444 if (pd->pd_flags & PDF_EXITED)
445 revents |= POLLHUP;
446 if (revents == 0) {
447 selrecord(td, &pd->pd_selinfo);
448 pd->pd_flags |= PDF_SELECTED;
449 }
450 PROCDESC_UNLOCK(pd);
451 return (revents);
452 }
453
454 static void
455 procdesc_kqops_detach(struct knote *kn)
456 {
457 struct procdesc *pd;
458
459 pd = kn->kn_fp->f_data;
460 knlist_remove(&pd->pd_selinfo.si_note, kn, 0);
461 }
462
463 static int
464 procdesc_kqops_event(struct knote *kn, long hint)
465 {
466 struct procdesc *pd;
467 u_int event;
468
469 pd = kn->kn_fp->f_data;
470 if (hint == 0) {
471 /*
472 * Initial test after registration. Generate a NOTE_EXIT in
473 * case the process already terminated before registration.
474 */
475 event = pd->pd_flags & PDF_EXITED ? NOTE_EXIT : 0;
476 } else {
477 /* Mask off extra data. */
478 event = (u_int)hint & NOTE_PCTRLMASK;
479 }
480
481 /* If the user is interested in this event, record it. */
482 if (kn->kn_sfflags & event)
483 kn->kn_fflags |= event;
484
485 /* Process is gone, so flag the event as finished. */
486 if (event == NOTE_EXIT) {
487 kn->kn_flags |= EV_EOF | EV_ONESHOT;
488 if (kn->kn_fflags & NOTE_EXIT)
489 kn->kn_data = pd->pd_xstat;
490 if (kn->kn_fflags == 0)
491 kn->kn_flags |= EV_DROP;
492 return (1);
493 }
494
495 return (kn->kn_fflags != 0);
496 }
497
498 static struct filterops procdesc_kqops = {
499 .f_isfd = 1,
500 .f_detach = procdesc_kqops_detach,
501 .f_event = procdesc_kqops_event,
502 };
503
504 static int
505 procdesc_kqfilter(struct file *fp, struct knote *kn)
506 {
507 struct procdesc *pd;
508
509 pd = fp->f_data;
510 switch (kn->kn_filter) {
511 case EVFILT_PROCDESC:
512 kn->kn_fop = &procdesc_kqops;
513 kn->kn_flags |= EV_CLEAR;
514 knlist_add(&pd->pd_selinfo.si_note, kn, 0);
515 return (0);
516 default:
517 return (EINVAL);
518 }
519 }
520
521 static int
522 procdesc_stat(struct file *fp, struct stat *sb, struct ucred *active_cred,
523 struct thread *td)
524 {
525 struct procdesc *pd;
526 struct timeval pstart, boottime;
527
528 /*
529 * XXXRW: Perhaps we should cache some more information from the
530 * process so that we can return it reliably here even after it has
531 * died. For example, caching its credential data.
532 */
533 bzero(sb, sizeof(*sb));
534 pd = fp->f_data;
535 sx_slock(&proctree_lock);
536 if (pd->pd_proc != NULL) {
537 PROC_LOCK(pd->pd_proc);
538 AUDIT_ARG_PROCESS(pd->pd_proc);
539
540 /* Set birth and [acm] times to process start time. */
541 pstart = pd->pd_proc->p_stats->p_start;
542 getboottime(&boottime);
543 timevaladd(&pstart, &boottime);
544 TIMEVAL_TO_TIMESPEC(&pstart, &sb->st_birthtim);
545 sb->st_atim = sb->st_birthtim;
546 sb->st_ctim = sb->st_birthtim;
547 sb->st_mtim = sb->st_birthtim;
548 if (pd->pd_proc->p_state != PRS_ZOMBIE)
549 sb->st_mode = S_IFREG | S_IRWXU;
550 else
551 sb->st_mode = S_IFREG;
552 sb->st_uid = pd->pd_proc->p_ucred->cr_ruid;
553 sb->st_gid = pd->pd_proc->p_ucred->cr_rgid;
554 PROC_UNLOCK(pd->pd_proc);
555 } else
556 sb->st_mode = S_IFREG;
557 sx_sunlock(&proctree_lock);
558 return (0);
559 }
560
561 static int
562 procdesc_fill_kinfo(struct file *fp, struct kinfo_file *kif,
563 struct filedesc *fdp)
564 {
565 struct procdesc *pdp;
566
567 kif->kf_type = KF_TYPE_PROCDESC;
568 pdp = fp->f_data;
569 kif->kf_un.kf_proc.kf_pid = pdp->pd_pid;
570 return (0);
571 }
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