1 /*-
2 * Copyright (c) 2009 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 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 */
29
30 /*-
31 * FreeBSD process descriptor facility.
32 *
33 * Some processes are represented by a file descriptor, which will be used in
34 * preference to signaling and pids for the purposes of process management,
35 * and is, in effect, a form of capability. When a process descriptor is
36 * used with a process, it ceases to be visible to certain traditional UNIX
37 * process facilities, such as waitpid(2).
38 *
39 * Some semantics:
40 *
41 * - At most one process descriptor will exist for any process, although
42 * references to that descriptor may be held from many processes (or even
43 * be in flight between processes over a local domain socket).
44 * - Last close on the process descriptor will terminate the process using
45 * SIGKILL and reparent it to init so that there's a process to reap it
46 * when it's done exiting.
47 * - If the process exits before the descriptor is closed, it will not
48 * generate SIGCHLD on termination, or be picked up by waitpid().
49 * - The pdkill(2) system call may be used to deliver a signal to the process
50 * using its process descriptor.
51 * - The pdwait4(2) system call may be used to block (or not) on a process
52 * descriptor to collect termination information.
53 *
54 * Open questions:
55 *
56 * - How to handle ptrace(2)?
57 * - Will we want to add a pidtoprocdesc(2) system call to allow process
58 * descriptors to be created for processes without pdfork(2)?
59 */
60
61 #include <sys/cdefs.h>
62 __FBSDID("$FreeBSD: releng/11.1/sys/kern/sys_procdesc.c 304843 2016-08-26 10:04:10Z kib $");
63
64 #include <sys/param.h>
65 #include <sys/capsicum.h>
66 #include <sys/fcntl.h>
67 #include <sys/file.h>
68 #include <sys/filedesc.h>
69 #include <sys/kernel.h>
70 #include <sys/lock.h>
71 #include <sys/mutex.h>
72 #include <sys/poll.h>
73 #include <sys/proc.h>
74 #include <sys/procdesc.h>
75 #include <sys/resourcevar.h>
76 #include <sys/stat.h>
77 #include <sys/sysproto.h>
78 #include <sys/sysctl.h>
79 #include <sys/systm.h>
80 #include <sys/ucred.h>
81 #include <sys/user.h>
82
83 #include <security/audit/audit.h>
84
85 #include <vm/uma.h>
86
87 FEATURE(process_descriptors, "Process Descriptors");
88
89 static uma_zone_t procdesc_zone;
90
91 static fo_poll_t procdesc_poll;
92 static fo_kqfilter_t procdesc_kqfilter;
93 static fo_stat_t procdesc_stat;
94 static fo_close_t procdesc_close;
95 static fo_fill_kinfo_t procdesc_fill_kinfo;
96
97 static struct fileops procdesc_ops = {
98 .fo_read = invfo_rdwr,
99 .fo_write = invfo_rdwr,
100 .fo_truncate = invfo_truncate,
101 .fo_ioctl = invfo_ioctl,
102 .fo_poll = procdesc_poll,
103 .fo_kqfilter = procdesc_kqfilter,
104 .fo_stat = procdesc_stat,
105 .fo_close = procdesc_close,
106 .fo_chmod = invfo_chmod,
107 .fo_chown = invfo_chown,
108 .fo_sendfile = invfo_sendfile,
109 .fo_fill_kinfo = procdesc_fill_kinfo,
110 .fo_flags = DFLAG_PASSABLE,
111 };
112
113 /*
114 * Initialize with VFS so that process descriptors are available along with
115 * other file descriptor types. As long as it runs before init(8) starts,
116 * there shouldn't be a problem.
117 */
118 static void
119 procdesc_init(void *dummy __unused)
120 {
121
122 procdesc_zone = uma_zcreate("procdesc", sizeof(struct procdesc),
123 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
124 if (procdesc_zone == NULL)
125 panic("procdesc_init: procdesc_zone not initialized");
126 }
127 SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_ANY, procdesc_init, NULL);
128
129 /*
130 * Return a locked process given a process descriptor, or ESRCH if it has
131 * died.
132 */
133 int
134 procdesc_find(struct thread *td, int fd, cap_rights_t *rightsp,
135 struct proc **p)
136 {
137 struct procdesc *pd;
138 struct file *fp;
139 int error;
140
141 error = fget(td, fd, rightsp, &fp);
142 if (error)
143 return (error);
144 if (fp->f_type != DTYPE_PROCDESC) {
145 error = EBADF;
146 goto out;
147 }
148 pd = fp->f_data;
149 sx_slock(&proctree_lock);
150 if (pd->pd_proc != NULL) {
151 *p = pd->pd_proc;
152 PROC_LOCK(*p);
153 } else
154 error = ESRCH;
155 sx_sunlock(&proctree_lock);
156 out:
157 fdrop(fp, td);
158 return (error);
159 }
160
161 /*
162 * Function to be used by procstat(1) sysctls when returning procdesc
163 * information.
164 */
165 pid_t
166 procdesc_pid(struct file *fp_procdesc)
167 {
168 struct procdesc *pd;
169
170 KASSERT(fp_procdesc->f_type == DTYPE_PROCDESC,
171 ("procdesc_pid: !procdesc"));
172
173 pd = fp_procdesc->f_data;
174 return (pd->pd_pid);
175 }
176
177 /*
178 * Retrieve the PID associated with a process descriptor.
179 */
180 int
181 kern_pdgetpid(struct thread *td, int fd, cap_rights_t *rightsp, pid_t *pidp)
182 {
183 struct file *fp;
184 int error;
185
186 error = fget(td, fd, rightsp, &fp);
187 if (error)
188 return (error);
189 if (fp->f_type != DTYPE_PROCDESC) {
190 error = EBADF;
191 goto out;
192 }
193 *pidp = procdesc_pid(fp);
194 out:
195 fdrop(fp, td);
196 return (error);
197 }
198
199 /*
200 * System call to return the pid of a process given its process descriptor.
201 */
202 int
203 sys_pdgetpid(struct thread *td, struct pdgetpid_args *uap)
204 {
205 cap_rights_t rights;
206 pid_t pid;
207 int error;
208
209 AUDIT_ARG_FD(uap->fd);
210 error = kern_pdgetpid(td, uap->fd,
211 cap_rights_init(&rights, CAP_PDGETPID), &pid);
212 if (error == 0)
213 error = copyout(&pid, uap->pidp, sizeof(pid));
214 return (error);
215 }
216
217 /*
218 * When a new process is forked by pdfork(), a file descriptor is allocated
219 * by the fork code first, then the process is forked, and then we get a
220 * chance to set up the process descriptor. Failure is not permitted at this
221 * point, so procdesc_new() must succeed.
222 */
223 void
224 procdesc_new(struct proc *p, int flags)
225 {
226 struct procdesc *pd;
227
228 pd = uma_zalloc(procdesc_zone, M_WAITOK | M_ZERO);
229 pd->pd_proc = p;
230 pd->pd_pid = p->p_pid;
231 p->p_procdesc = pd;
232 pd->pd_flags = 0;
233 if (flags & PD_DAEMON)
234 pd->pd_flags |= PDF_DAEMON;
235 PROCDESC_LOCK_INIT(pd);
236 knlist_init_mtx(&pd->pd_selinfo.si_note, &pd->pd_lock);
237
238 /*
239 * Process descriptors start out with two references: one from their
240 * struct file, and the other from their struct proc.
241 */
242 refcount_init(&pd->pd_refcount, 2);
243 }
244
245 /*
246 * Create a new process decriptor for the process that refers to it.
247 */
248 int
249 procdesc_falloc(struct thread *td, struct file **resultfp, int *resultfd,
250 int flags, struct filecaps *fcaps)
251 {
252 int fflags;
253
254 fflags = 0;
255 if (flags & PD_CLOEXEC)
256 fflags = O_CLOEXEC;
257
258 return (falloc_caps(td, resultfp, resultfd, fflags, fcaps));
259 }
260
261 /*
262 * Initialize a file with a process descriptor.
263 */
264 void
265 procdesc_finit(struct procdesc *pdp, struct file *fp)
266 {
267
268 finit(fp, FREAD | FWRITE, DTYPE_PROCDESC, pdp, &procdesc_ops);
269 }
270
271 static void
272 procdesc_free(struct procdesc *pd)
273 {
274
275 /*
276 * When the last reference is released, we assert that the descriptor
277 * has been closed, but not that the process has exited, as we will
278 * detach the descriptor before the process dies if the descript is
279 * closed, as we can't wait synchronously.
280 */
281 if (refcount_release(&pd->pd_refcount)) {
282 KASSERT(pd->pd_proc == NULL,
283 ("procdesc_free: pd_proc != NULL"));
284 KASSERT((pd->pd_flags & PDF_CLOSED),
285 ("procdesc_free: !PDF_CLOSED"));
286
287 knlist_destroy(&pd->pd_selinfo.si_note);
288 PROCDESC_LOCK_DESTROY(pd);
289 uma_zfree(procdesc_zone, pd);
290 }
291 }
292
293 /*
294 * procdesc_exit() - notify a process descriptor that its process is exiting.
295 * We use the proctree_lock to ensure that process exit either happens
296 * strictly before or strictly after a concurrent call to procdesc_close().
297 */
298 int
299 procdesc_exit(struct proc *p)
300 {
301 struct procdesc *pd;
302
303 sx_assert(&proctree_lock, SA_XLOCKED);
304 PROC_LOCK_ASSERT(p, MA_OWNED);
305 KASSERT(p->p_procdesc != NULL, ("procdesc_exit: p_procdesc NULL"));
306
307 pd = p->p_procdesc;
308
309 PROCDESC_LOCK(pd);
310 KASSERT((pd->pd_flags & PDF_CLOSED) == 0 || p->p_pptr == initproc,
311 ("procdesc_exit: closed && parent not init"));
312
313 pd->pd_flags |= PDF_EXITED;
314 pd->pd_xstat = KW_EXITCODE(p->p_xexit, p->p_xsig);
315
316 /*
317 * If the process descriptor has been closed, then we have nothing
318 * to do; return 1 so that init will get SIGCHLD and do the reaping.
319 * Clean up the procdesc now rather than letting it happen during
320 * that reap.
321 */
322 if (pd->pd_flags & PDF_CLOSED) {
323 PROCDESC_UNLOCK(pd);
324 pd->pd_proc = NULL;
325 p->p_procdesc = NULL;
326 procdesc_free(pd);
327 return (1);
328 }
329 if (pd->pd_flags & PDF_SELECTED) {
330 pd->pd_flags &= ~PDF_SELECTED;
331 selwakeup(&pd->pd_selinfo);
332 }
333 KNOTE_LOCKED(&pd->pd_selinfo.si_note, NOTE_EXIT);
334 PROCDESC_UNLOCK(pd);
335 return (0);
336 }
337
338 /*
339 * When a process descriptor is reaped, perhaps as a result of close() or
340 * pdwait4(), release the process's reference on the process descriptor.
341 */
342 void
343 procdesc_reap(struct proc *p)
344 {
345 struct procdesc *pd;
346
347 sx_assert(&proctree_lock, SA_XLOCKED);
348 KASSERT(p->p_procdesc != NULL, ("procdesc_reap: p_procdesc == NULL"));
349
350 pd = p->p_procdesc;
351 pd->pd_proc = NULL;
352 p->p_procdesc = NULL;
353 procdesc_free(pd);
354 }
355
356 /*
357 * procdesc_close() - last close on a process descriptor. If the process is
358 * still running, terminate with SIGKILL (unless PDF_DAEMON is set) and let
359 * init(8) clean up the mess; if not, we have to clean up the zombie ourselves.
360 */
361 static int
362 procdesc_close(struct file *fp, struct thread *td)
363 {
364 struct procdesc *pd;
365 struct proc *p;
366
367 KASSERT(fp->f_type == DTYPE_PROCDESC, ("procdesc_close: !procdesc"));
368
369 pd = fp->f_data;
370 fp->f_ops = &badfileops;
371 fp->f_data = NULL;
372
373 sx_xlock(&proctree_lock);
374 PROCDESC_LOCK(pd);
375 pd->pd_flags |= PDF_CLOSED;
376 PROCDESC_UNLOCK(pd);
377 p = pd->pd_proc;
378 if (p == NULL) {
379 /*
380 * This is the case where process' exit status was already
381 * collected and procdesc_reap() was already called.
382 */
383 sx_xunlock(&proctree_lock);
384 } else {
385 PROC_LOCK(p);
386 if (p->p_state == PRS_ZOMBIE) {
387 /*
388 * If the process is already dead and just awaiting
389 * reaping, do that now. This will release the
390 * process's reference to the process descriptor when it
391 * calls back into procdesc_reap().
392 */
393 PROC_SLOCK(p);
394 proc_reap(curthread, p, NULL, 0);
395 } else {
396 /*
397 * If the process is not yet dead, we need to kill it,
398 * but we can't wait around synchronously for it to go
399 * away, as that path leads to madness (and deadlocks).
400 * First, detach the process from its descriptor so that
401 * its exit status will be reported normally.
402 */
403 pd->pd_proc = NULL;
404 p->p_procdesc = NULL;
405 procdesc_free(pd);
406
407 /*
408 * Next, reparent it to init(8) so that there's someone
409 * to pick up the pieces; finally, terminate with
410 * prejudice.
411 */
412 p->p_sigparent = SIGCHLD;
413 proc_reparent(p, initproc);
414 if ((pd->pd_flags & PDF_DAEMON) == 0)
415 kern_psignal(p, SIGKILL);
416 PROC_UNLOCK(p);
417 sx_xunlock(&proctree_lock);
418 }
419 }
420
421 /*
422 * Release the file descriptor's reference on the process descriptor.
423 */
424 procdesc_free(pd);
425 return (0);
426 }
427
428 static int
429 procdesc_poll(struct file *fp, int events, struct ucred *active_cred,
430 struct thread *td)
431 {
432 struct procdesc *pd;
433 int revents;
434
435 revents = 0;
436 pd = fp->f_data;
437 PROCDESC_LOCK(pd);
438 if (pd->pd_flags & PDF_EXITED)
439 revents |= POLLHUP;
440 if (revents == 0) {
441 selrecord(td, &pd->pd_selinfo);
442 pd->pd_flags |= PDF_SELECTED;
443 }
444 PROCDESC_UNLOCK(pd);
445 return (revents);
446 }
447
448 static void
449 procdesc_kqops_detach(struct knote *kn)
450 {
451 struct procdesc *pd;
452
453 pd = kn->kn_fp->f_data;
454 knlist_remove(&pd->pd_selinfo.si_note, kn, 0);
455 }
456
457 static int
458 procdesc_kqops_event(struct knote *kn, long hint)
459 {
460 struct procdesc *pd;
461 u_int event;
462
463 pd = kn->kn_fp->f_data;
464 if (hint == 0) {
465 /*
466 * Initial test after registration. Generate a NOTE_EXIT in
467 * case the process already terminated before registration.
468 */
469 event = pd->pd_flags & PDF_EXITED ? NOTE_EXIT : 0;
470 } else {
471 /* Mask off extra data. */
472 event = (u_int)hint & NOTE_PCTRLMASK;
473 }
474
475 /* If the user is interested in this event, record it. */
476 if (kn->kn_sfflags & event)
477 kn->kn_fflags |= event;
478
479 /* Process is gone, so flag the event as finished. */
480 if (event == NOTE_EXIT) {
481 kn->kn_flags |= EV_EOF | EV_ONESHOT;
482 if (kn->kn_fflags & NOTE_EXIT)
483 kn->kn_data = pd->pd_xstat;
484 if (kn->kn_fflags == 0)
485 kn->kn_flags |= EV_DROP;
486 return (1);
487 }
488
489 return (kn->kn_fflags != 0);
490 }
491
492 static struct filterops procdesc_kqops = {
493 .f_isfd = 1,
494 .f_detach = procdesc_kqops_detach,
495 .f_event = procdesc_kqops_event,
496 };
497
498 static int
499 procdesc_kqfilter(struct file *fp, struct knote *kn)
500 {
501 struct procdesc *pd;
502
503 pd = fp->f_data;
504 switch (kn->kn_filter) {
505 case EVFILT_PROCDESC:
506 kn->kn_fop = &procdesc_kqops;
507 kn->kn_flags |= EV_CLEAR;
508 knlist_add(&pd->pd_selinfo.si_note, kn, 0);
509 return (0);
510 default:
511 return (EINVAL);
512 }
513 }
514
515 static int
516 procdesc_stat(struct file *fp, struct stat *sb, struct ucred *active_cred,
517 struct thread *td)
518 {
519 struct procdesc *pd;
520 struct timeval pstart, boottime;
521
522 /*
523 * XXXRW: Perhaps we should cache some more information from the
524 * process so that we can return it reliably here even after it has
525 * died. For example, caching its credential data.
526 */
527 bzero(sb, sizeof(*sb));
528 pd = fp->f_data;
529 sx_slock(&proctree_lock);
530 if (pd->pd_proc != NULL) {
531 PROC_LOCK(pd->pd_proc);
532
533 /* Set birth and [acm] times to process start time. */
534 pstart = pd->pd_proc->p_stats->p_start;
535 getboottime(&boottime);
536 timevaladd(&pstart, &boottime);
537 TIMEVAL_TO_TIMESPEC(&pstart, &sb->st_birthtim);
538 sb->st_atim = sb->st_birthtim;
539 sb->st_ctim = sb->st_birthtim;
540 sb->st_mtim = sb->st_birthtim;
541 if (pd->pd_proc->p_state != PRS_ZOMBIE)
542 sb->st_mode = S_IFREG | S_IRWXU;
543 else
544 sb->st_mode = S_IFREG;
545 sb->st_uid = pd->pd_proc->p_ucred->cr_ruid;
546 sb->st_gid = pd->pd_proc->p_ucred->cr_rgid;
547 PROC_UNLOCK(pd->pd_proc);
548 } else
549 sb->st_mode = S_IFREG;
550 sx_sunlock(&proctree_lock);
551 return (0);
552 }
553
554 static int
555 procdesc_fill_kinfo(struct file *fp, struct kinfo_file *kif,
556 struct filedesc *fdp)
557 {
558 struct procdesc *pdp;
559
560 kif->kf_type = KF_TYPE_PROCDESC;
561 pdp = fp->f_data;
562 kif->kf_un.kf_proc.kf_pid = pdp->pd_pid;
563 return (0);
564 }
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