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/cdefs.h>
66 #include <sys/param.h>
67 #include <sys/capsicum.h>
68 #include <sys/fcntl.h>
70 #include <sys/filedesc.h>
71 #include <sys/kernel.h>
73 #include <sys/mutex.h>
76 #include <sys/procdesc.h>
77 #include <sys/resourcevar.h>
79 #include <sys/sysproto.h>
80 #include <sys/sysctl.h>
81 #include <sys/systm.h>
82 #include <sys/ucred.h>
85 #include <security/audit/audit.h>
89 FEATURE(process_descriptors, "Process Descriptors");
91 MALLOC_DEFINE(M_PROCDESC, "procdesc", "process descriptors");
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;
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_flags = DFLAG_PASSABLE,
116 * Return a locked process given a process descriptor, or ESRCH if it has
120 procdesc_find(struct thread *td, int fd, cap_rights_t *rightsp,
127 error = fget(td, fd, rightsp, &fp);
130 if (fp->f_type != DTYPE_PROCDESC) {
135 sx_slock(&proctree_lock);
136 if (pd->pd_proc != NULL) {
141 sx_sunlock(&proctree_lock);
148 * Function to be used by procstat(1) sysctls when returning procdesc
152 procdesc_pid(struct file *fp_procdesc)
156 KASSERT(fp_procdesc->f_type == DTYPE_PROCDESC,
157 ("procdesc_pid: !procdesc"));
159 pd = fp_procdesc->f_data;
164 * Retrieve the PID associated with a process descriptor.
167 kern_pdgetpid(struct thread *td, int fd, cap_rights_t *rightsp, pid_t *pidp)
172 error = fget(td, fd, rightsp, &fp);
175 if (fp->f_type != DTYPE_PROCDESC) {
179 *pidp = procdesc_pid(fp);
186 * System call to return the pid of a process given its process descriptor.
189 sys_pdgetpid(struct thread *td, struct pdgetpid_args *uap)
194 AUDIT_ARG_FD(uap->fd);
195 error = kern_pdgetpid(td, uap->fd, &cap_pdgetpid_rights, &pid);
197 error = copyout(&pid, uap->pidp, sizeof(pid));
202 * When a new process is forked by pdfork(), a file descriptor is allocated
203 * by the fork code first, then the process is forked, and then we get a
204 * chance to set up the process descriptor. Failure is not permitted at this
205 * point, so procdesc_new() must succeed.
208 procdesc_new(struct proc *p, int flags)
212 pd = malloc(sizeof(*pd), M_PROCDESC, M_WAITOK | M_ZERO);
214 pd->pd_pid = p->p_pid;
217 if (flags & PD_DAEMON)
218 pd->pd_flags |= PDF_DAEMON;
219 PROCDESC_LOCK_INIT(pd);
220 knlist_init_mtx(&pd->pd_selinfo.si_note, &pd->pd_lock);
223 * Process descriptors start out with two references: one from their
224 * struct file, and the other from their struct proc.
226 refcount_init(&pd->pd_refcount, 2);
230 * Create a new process decriptor for the process that refers to it.
233 procdesc_falloc(struct thread *td, struct file **resultfp, int *resultfd,
234 int flags, struct filecaps *fcaps)
239 if (flags & PD_CLOEXEC)
242 return (falloc_caps(td, resultfp, resultfd, fflags, fcaps));
246 * Initialize a file with a process descriptor.
249 procdesc_finit(struct procdesc *pdp, struct file *fp)
252 finit(fp, FREAD | FWRITE, DTYPE_PROCDESC, pdp, &procdesc_ops);
256 procdesc_free(struct procdesc *pd)
260 * When the last reference is released, we assert that the descriptor
261 * has been closed, but not that the process has exited, as we will
262 * detach the descriptor before the process dies if the descript is
263 * closed, as we can't wait synchronously.
265 if (refcount_release(&pd->pd_refcount)) {
266 KASSERT(pd->pd_proc == NULL,
267 ("procdesc_free: pd_proc != NULL"));
268 KASSERT((pd->pd_flags & PDF_CLOSED),
269 ("procdesc_free: !PDF_CLOSED"));
271 knlist_destroy(&pd->pd_selinfo.si_note);
272 PROCDESC_LOCK_DESTROY(pd);
273 free(pd, M_PROCDESC);
278 * procdesc_exit() - notify a process descriptor that its process is exiting.
279 * We use the proctree_lock to ensure that process exit either happens
280 * strictly before or strictly after a concurrent call to procdesc_close().
283 procdesc_exit(struct proc *p)
287 sx_assert(&proctree_lock, SA_XLOCKED);
288 PROC_LOCK_ASSERT(p, MA_OWNED);
289 KASSERT(p->p_procdesc != NULL, ("procdesc_exit: p_procdesc NULL"));
294 KASSERT((pd->pd_flags & PDF_CLOSED) == 0 || p->p_pptr == p->p_reaper,
295 ("procdesc_exit: closed && parent not reaper"));
297 pd->pd_flags |= PDF_EXITED;
298 pd->pd_xstat = KW_EXITCODE(p->p_xexit, p->p_xsig);
301 * If the process descriptor has been closed, then we have nothing
302 * to do; return 1 so that init will get SIGCHLD and do the reaping.
303 * Clean up the procdesc now rather than letting it happen during
306 if (pd->pd_flags & PDF_CLOSED) {
309 p->p_procdesc = NULL;
313 if (pd->pd_flags & PDF_SELECTED) {
314 pd->pd_flags &= ~PDF_SELECTED;
315 selwakeup(&pd->pd_selinfo);
317 KNOTE_LOCKED(&pd->pd_selinfo.si_note, NOTE_EXIT);
323 * When a process descriptor is reaped, perhaps as a result of close(), release
324 * the process's reference on the process descriptor.
327 procdesc_reap(struct proc *p)
331 sx_assert(&proctree_lock, SA_XLOCKED);
332 KASSERT(p->p_procdesc != NULL, ("procdesc_reap: p_procdesc == NULL"));
336 p->p_procdesc = NULL;
341 * procdesc_close() - last close on a process descriptor. If the process is
342 * still running, terminate with SIGKILL (unless PDF_DAEMON is set) and let
343 * its reaper clean up the mess; if not, we have to clean up the zombie
347 procdesc_close(struct file *fp, struct thread *td)
352 KASSERT(fp->f_type == DTYPE_PROCDESC, ("procdesc_close: !procdesc"));
355 fp->f_ops = &badfileops;
358 sx_xlock(&proctree_lock);
360 pd->pd_flags |= PDF_CLOSED;
365 * This is the case where process' exit status was already
366 * collected and procdesc_reap() was already called.
368 sx_xunlock(&proctree_lock);
371 AUDIT_ARG_PROCESS(p);
372 if (p->p_state == PRS_ZOMBIE) {
374 * If the process is already dead and just awaiting
375 * reaping, do that now. This will release the
376 * process's reference to the process descriptor when it
377 * calls back into procdesc_reap().
379 proc_reap(curthread, p, NULL, 0);
382 * If the process is not yet dead, we need to kill it,
383 * but we can't wait around synchronously for it to go
384 * away, as that path leads to madness (and deadlocks).
385 * First, detach the process from its descriptor so that
386 * its exit status will be reported normally.
389 p->p_procdesc = NULL;
393 * Next, reparent it to its reaper (usually init(8)) so
394 * that there's someone to pick up the pieces; finally,
395 * terminate with prejudice.
397 p->p_sigparent = SIGCHLD;
398 if ((p->p_flag & P_TRACED) == 0) {
399 proc_reparent(p, p->p_reaper, true);
401 proc_clear_orphan(p);
402 p->p_oppid = p->p_reaper->p_pid;
403 proc_add_orphan(p, p->p_reaper);
405 if ((pd->pd_flags & PDF_DAEMON) == 0)
406 kern_psignal(p, SIGKILL);
408 sx_xunlock(&proctree_lock);
413 * Release the file descriptor's reference on the process descriptor.
420 procdesc_poll(struct file *fp, int events, struct ucred *active_cred,
429 if (pd->pd_flags & PDF_EXITED)
432 selrecord(td, &pd->pd_selinfo);
433 pd->pd_flags |= PDF_SELECTED;
440 procdesc_kqops_detach(struct knote *kn)
444 pd = kn->kn_fp->f_data;
445 knlist_remove(&pd->pd_selinfo.si_note, kn, 0);
449 procdesc_kqops_event(struct knote *kn, long hint)
454 pd = kn->kn_fp->f_data;
457 * Initial test after registration. Generate a NOTE_EXIT in
458 * case the process already terminated before registration.
460 event = pd->pd_flags & PDF_EXITED ? NOTE_EXIT : 0;
462 /* Mask off extra data. */
463 event = (u_int)hint & NOTE_PCTRLMASK;
466 /* If the user is interested in this event, record it. */
467 if (kn->kn_sfflags & event)
468 kn->kn_fflags |= event;
470 /* Process is gone, so flag the event as finished. */
471 if (event == NOTE_EXIT) {
472 kn->kn_flags |= EV_EOF | EV_ONESHOT;
473 if (kn->kn_fflags & NOTE_EXIT)
474 kn->kn_data = pd->pd_xstat;
475 if (kn->kn_fflags == 0)
476 kn->kn_flags |= EV_DROP;
480 return (kn->kn_fflags != 0);
483 static struct filterops procdesc_kqops = {
485 .f_detach = procdesc_kqops_detach,
486 .f_event = procdesc_kqops_event,
490 procdesc_kqfilter(struct file *fp, struct knote *kn)
495 switch (kn->kn_filter) {
496 case EVFILT_PROCDESC:
497 kn->kn_fop = &procdesc_kqops;
498 kn->kn_flags |= EV_CLEAR;
499 knlist_add(&pd->pd_selinfo.si_note, kn, 0);
507 procdesc_stat(struct file *fp, struct stat *sb, struct ucred *active_cred)
510 struct timeval pstart, boottime;
513 * XXXRW: Perhaps we should cache some more information from the
514 * process so that we can return it reliably here even after it has
515 * died. For example, caching its credential data.
517 bzero(sb, sizeof(*sb));
519 sx_slock(&proctree_lock);
520 if (pd->pd_proc != NULL) {
521 PROC_LOCK(pd->pd_proc);
522 AUDIT_ARG_PROCESS(pd->pd_proc);
524 /* Set birth and [acm] times to process start time. */
525 pstart = pd->pd_proc->p_stats->p_start;
526 getboottime(&boottime);
527 timevaladd(&pstart, &boottime);
528 TIMEVAL_TO_TIMESPEC(&pstart, &sb->st_birthtim);
529 sb->st_atim = sb->st_birthtim;
530 sb->st_ctim = sb->st_birthtim;
531 sb->st_mtim = sb->st_birthtim;
532 if (pd->pd_proc->p_state != PRS_ZOMBIE)
533 sb->st_mode = S_IFREG | S_IRWXU;
535 sb->st_mode = S_IFREG;
536 sb->st_uid = pd->pd_proc->p_ucred->cr_ruid;
537 sb->st_gid = pd->pd_proc->p_ucred->cr_rgid;
538 PROC_UNLOCK(pd->pd_proc);
540 sb->st_mode = S_IFREG;
541 sx_sunlock(&proctree_lock);
546 procdesc_fill_kinfo(struct file *fp, struct kinfo_file *kif,
547 struct filedesc *fdp)
549 struct procdesc *pdp;
551 kif->kf_type = KF_TYPE_PROCDESC;
553 kif->kf_un.kf_proc.kf_pid = pdp->pd_pid;