2 * SPDX-License-Identifier: BSD-2-Clause
4 * Copyright (c) 2009, 2016 Robert N. M. Watson
7 * This software was developed at the University of Cambridge Computer
8 * Laboratory with support from a grant from Google, Inc.
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.
15 * Redistribution and use in source and binary forms, with or without
16 * modification, are permitted provided that the following conditions
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.
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
38 * FreeBSD process descriptor facility.
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).
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.
61 * - Will we want to add a pidtoprocdesc(2) system call to allow process
62 * descriptors to be created for processes without pdfork(2)?
65 #include <sys/param.h>
66 #include <sys/capsicum.h>
67 #include <sys/fcntl.h>
69 #include <sys/filedesc.h>
70 #include <sys/kernel.h>
72 #include <sys/mutex.h>
75 #include <sys/procdesc.h>
76 #include <sys/resourcevar.h>
78 #include <sys/sysproto.h>
79 #include <sys/sysctl.h>
80 #include <sys/systm.h>
81 #include <sys/ucred.h>
84 #include <security/audit/audit.h>
88 FEATURE(process_descriptors, "Process Descriptors");
90 MALLOC_DEFINE(M_PROCDESC, "procdesc", "process descriptors");
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;
99 static 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,
117 * Return a locked process given a process descriptor, or ESRCH if it has
121 procdesc_find(struct thread *td, int fd, cap_rights_t *rightsp,
128 error = fget(td, fd, rightsp, &fp);
131 if (fp->f_type != DTYPE_PROCDESC) {
136 sx_slock(&proctree_lock);
137 if (pd->pd_proc != NULL) {
142 sx_sunlock(&proctree_lock);
149 * Function to be used by procstat(1) sysctls when returning procdesc
153 procdesc_pid(struct file *fp_procdesc)
157 KASSERT(fp_procdesc->f_type == DTYPE_PROCDESC,
158 ("procdesc_pid: !procdesc"));
160 pd = fp_procdesc->f_data;
165 * Retrieve the PID associated with a process descriptor.
168 kern_pdgetpid(struct thread *td, int fd, cap_rights_t *rightsp, pid_t *pidp)
173 error = fget(td, fd, rightsp, &fp);
176 if (fp->f_type != DTYPE_PROCDESC) {
180 *pidp = procdesc_pid(fp);
187 * System call to return the pid of a process given its process descriptor.
190 sys_pdgetpid(struct thread *td, struct pdgetpid_args *uap)
195 AUDIT_ARG_FD(uap->fd);
196 error = kern_pdgetpid(td, uap->fd, &cap_pdgetpid_rights, &pid);
198 error = copyout(&pid, uap->pidp, sizeof(pid));
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.
209 procdesc_new(struct proc *p, int flags)
213 pd = malloc(sizeof(*pd), M_PROCDESC, M_WAITOK | M_ZERO);
215 pd->pd_pid = p->p_pid;
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);
224 * Process descriptors start out with two references: one from their
225 * struct file, and the other from their struct proc.
227 refcount_init(&pd->pd_refcount, 2);
231 * Create a new process decriptor for the process that refers to it.
234 procdesc_falloc(struct thread *td, struct file **resultfp, int *resultfd,
235 int flags, struct filecaps *fcaps)
240 if (flags & PD_CLOEXEC)
243 return (falloc_caps(td, resultfp, resultfd, fflags, fcaps));
247 * Initialize a file with a process descriptor.
250 procdesc_finit(struct procdesc *pdp, struct file *fp)
253 finit(fp, FREAD | FWRITE, DTYPE_PROCDESC, pdp, &procdesc_ops);
257 procdesc_free(struct procdesc *pd)
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.
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"));
272 knlist_destroy(&pd->pd_selinfo.si_note);
273 PROCDESC_LOCK_DESTROY(pd);
274 free(pd, M_PROCDESC);
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().
284 procdesc_exit(struct proc *p)
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"));
295 KASSERT((pd->pd_flags & PDF_CLOSED) == 0 || p->p_pptr == p->p_reaper,
296 ("procdesc_exit: closed && parent not reaper"));
298 pd->pd_flags |= PDF_EXITED;
299 pd->pd_xstat = KW_EXITCODE(p->p_xexit, p->p_xsig);
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
307 if (pd->pd_flags & PDF_CLOSED) {
310 p->p_procdesc = NULL;
314 if (pd->pd_flags & PDF_SELECTED) {
315 pd->pd_flags &= ~PDF_SELECTED;
316 selwakeup(&pd->pd_selinfo);
318 KNOTE_LOCKED(&pd->pd_selinfo.si_note, NOTE_EXIT);
324 * When a process descriptor is reaped, perhaps as a result of close(), release
325 * the process's reference on the process descriptor.
328 procdesc_reap(struct proc *p)
332 sx_assert(&proctree_lock, SA_XLOCKED);
333 KASSERT(p->p_procdesc != NULL, ("procdesc_reap: p_procdesc == NULL"));
337 p->p_procdesc = NULL;
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
348 procdesc_close(struct file *fp, struct thread *td)
353 KASSERT(fp->f_type == DTYPE_PROCDESC, ("procdesc_close: !procdesc"));
356 fp->f_ops = &badfileops;
359 sx_xlock(&proctree_lock);
361 pd->pd_flags |= PDF_CLOSED;
366 * This is the case where process' exit status was already
367 * collected and procdesc_reap() was already called.
369 sx_xunlock(&proctree_lock);
372 AUDIT_ARG_PROCESS(p);
373 if (p->p_state == PRS_ZOMBIE) {
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().
380 proc_reap(curthread, p, NULL, 0);
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.
390 p->p_procdesc = NULL;
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.
398 p->p_sigparent = SIGCHLD;
399 if ((p->p_flag & P_TRACED) == 0) {
400 proc_reparent(p, p->p_reaper, true);
402 proc_clear_orphan(p);
403 p->p_oppid = p->p_reaper->p_pid;
404 proc_add_orphan(p, p->p_reaper);
406 if ((pd->pd_flags & PDF_DAEMON) == 0)
407 kern_psignal(p, SIGKILL);
409 sx_xunlock(&proctree_lock);
414 * Release the file descriptor's reference on the process descriptor.
421 procdesc_poll(struct file *fp, int events, struct ucred *active_cred,
430 if (pd->pd_flags & PDF_EXITED)
433 selrecord(td, &pd->pd_selinfo);
434 pd->pd_flags |= PDF_SELECTED;
441 procdesc_kqops_detach(struct knote *kn)
445 pd = kn->kn_fp->f_data;
446 knlist_remove(&pd->pd_selinfo.si_note, kn, 0);
450 procdesc_kqops_event(struct knote *kn, long hint)
455 pd = kn->kn_fp->f_data;
458 * Initial test after registration. Generate a NOTE_EXIT in
459 * case the process already terminated before registration.
461 event = pd->pd_flags & PDF_EXITED ? NOTE_EXIT : 0;
463 /* Mask off extra data. */
464 event = (u_int)hint & NOTE_PCTRLMASK;
467 /* If the user is interested in this event, record it. */
468 if (kn->kn_sfflags & event)
469 kn->kn_fflags |= event;
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;
481 return (kn->kn_fflags != 0);
484 static struct filterops procdesc_kqops = {
486 .f_detach = procdesc_kqops_detach,
487 .f_event = procdesc_kqops_event,
491 procdesc_kqfilter(struct file *fp, struct knote *kn)
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);
508 procdesc_stat(struct file *fp, struct stat *sb, struct ucred *active_cred)
511 struct timeval pstart, boottime;
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.
518 bzero(sb, sizeof(*sb));
520 sx_slock(&proctree_lock);
521 if (pd->pd_proc != NULL) {
522 PROC_LOCK(pd->pd_proc);
523 AUDIT_ARG_PROCESS(pd->pd_proc);
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;
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);
541 sb->st_mode = S_IFREG;
542 sx_sunlock(&proctree_lock);
547 procdesc_fill_kinfo(struct file *fp, struct kinfo_file *kif,
548 struct filedesc *fdp)
550 struct procdesc *pdp;
552 kif->kf_type = KF_TYPE_PROCDESC;
554 kif->kf_un.kf_proc.kf_pid = pdp->pd_pid;
559 procdesc_cmp(struct file *fp1, struct file *fp2, struct thread *td)
561 struct procdesc *pdp1, *pdp2;
563 if (fp2->f_type != DTYPE_PROCDESC)
567 return (kcmp_cmp((uintptr_t)pdp1->pd_pid, (uintptr_t)pdp2->pd_pid));