/*-
* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
*
* Copyright (c) 2009, 2016 Robert N. M. Watson
* All rights reserved.
*
* This software was developed at the University of Cambridge Computer
* Laboratory with support from a grant from Google, Inc.
*
* Portions of this software were developed by BAE Systems, the University of
* Cambridge Computer Laboratory, and Memorial University under DARPA/AFRL
* contract FA8650-15-C-7558 ("CADETS"), as part of the DARPA Transparent
* Computing (TC) research program.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
/*-
* FreeBSD process descriptor facility.
*
* Some processes are represented by a file descriptor, which will be used in
* preference to signaling and pids for the purposes of process management,
* and is, in effect, a form of capability. When a process descriptor is
* used with a process, it ceases to be visible to certain traditional UNIX
* process facilities, such as waitpid(2).
*
* Some semantics:
*
* - At most one process descriptor will exist for any process, although
* references to that descriptor may be held from many processes (or even
* be in flight between processes over a local domain socket).
* - Last close on the process descriptor will terminate the process using
* SIGKILL and reparent it to init so that there's a process to reap it
* when it's done exiting.
* - If the process exits before the descriptor is closed, it will not
* generate SIGCHLD on termination, or be picked up by waitpid().
* - The pdkill(2) system call may be used to deliver a signal to the process
* using its process descriptor.
* - The pdwait4(2) system call may be used to block (or not) on a process
* descriptor to collect termination information.
*
* Open questions:
*
* - Will we want to add a pidtoprocdesc(2) system call to allow process
* descriptors to be created for processes without pdfork(2)?
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/capsicum.h>
#include <sys/fcntl.h>
#include <sys/file.h>
#include <sys/filedesc.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/poll.h>
#include <sys/proc.h>
#include <sys/procdesc.h>
#include <sys/resourcevar.h>
#include <sys/stat.h>
#include <sys/sysproto.h>
#include <sys/sysctl.h>
#include <sys/systm.h>
#include <sys/ucred.h>
#include <sys/user.h>
#include <security/audit/audit.h>
#include <vm/uma.h>
FEATURE(process_descriptors, "Process Descriptors");
MALLOC_DEFINE(M_PROCDESC, "procdesc", "process descriptors");
static fo_poll_t procdesc_poll;
static fo_kqfilter_t procdesc_kqfilter;
static fo_stat_t procdesc_stat;
static fo_close_t procdesc_close;
static fo_fill_kinfo_t procdesc_fill_kinfo;
static struct fileops procdesc_ops = {
.fo_read = invfo_rdwr,
.fo_write = invfo_rdwr,
.fo_truncate = invfo_truncate,
.fo_ioctl = invfo_ioctl,
.fo_poll = procdesc_poll,
.fo_kqfilter = procdesc_kqfilter,
.fo_stat = procdesc_stat,
.fo_close = procdesc_close,
.fo_chmod = invfo_chmod,
.fo_chown = invfo_chown,
.fo_sendfile = invfo_sendfile,
.fo_fill_kinfo = procdesc_fill_kinfo,
.fo_flags = DFLAG_PASSABLE,
};
/*
* Return a locked process given a process descriptor, or ESRCH if it has
* died.
*/
int
procdesc_find(struct thread *td, int fd, cap_rights_t *rightsp,
struct proc **p)
{
struct procdesc *pd;
struct file *fp;
int error;
error = fget(td, fd, rightsp, &fp);
if (error)
return (error);
if (fp->f_type != DTYPE_PROCDESC) {
error = EBADF;
goto out;
}
pd = fp->f_data;
sx_slock(&proctree_lock);
if (pd->pd_proc != NULL) {
*p = pd->pd_proc;
PROC_LOCK(*p);
} else
error = ESRCH;
sx_sunlock(&proctree_lock);
out:
fdrop(fp, td);
return (error);
}
/*
* Function to be used by procstat(1) sysctls when returning procdesc
* information.
*/
pid_t
procdesc_pid(struct file *fp_procdesc)
{
struct procdesc *pd;
KASSERT(fp_procdesc->f_type == DTYPE_PROCDESC,
("procdesc_pid: !procdesc"));
pd = fp_procdesc->f_data;
return (pd->pd_pid);
}
/*
* Retrieve the PID associated with a process descriptor.
*/
int
kern_pdgetpid(struct thread *td, int fd, cap_rights_t *rightsp, pid_t *pidp)
{
struct file *fp;
int error;
error = fget(td, fd, rightsp, &fp);
if (error)
return (error);
if (fp->f_type != DTYPE_PROCDESC) {
error = EBADF;
goto out;
}
*pidp = procdesc_pid(fp);
out:
fdrop(fp, td);
return (error);
}
/*
* System call to return the pid of a process given its process descriptor.
*/
int
sys_pdgetpid(struct thread *td, struct pdgetpid_args *uap)
{
pid_t pid;
int error;
AUDIT_ARG_FD(uap->fd);
error = kern_pdgetpid(td, uap->fd, &cap_pdgetpid_rights, &pid);
if (error == 0)
error = copyout(&pid, uap->pidp, sizeof(pid));
return (error);
}
/*
* When a new process is forked by pdfork(), a file descriptor is allocated
* by the fork code first, then the process is forked, and then we get a
* chance to set up the process descriptor. Failure is not permitted at this
* point, so procdesc_new() must succeed.
*/
void
procdesc_new(struct proc *p, int flags)
{
struct procdesc *pd;
pd = malloc(sizeof(*pd), M_PROCDESC, M_WAITOK | M_ZERO);
pd->pd_proc = p;
pd->pd_pid = p->p_pid;
p->p_procdesc = pd;
pd->pd_flags = 0;
if (flags & PD_DAEMON)
pd->pd_flags |= PDF_DAEMON;
PROCDESC_LOCK_INIT(pd);
knlist_init_mtx(&pd->pd_selinfo.si_note, &pd->pd_lock);
/*
* Process descriptors start out with two references: one from their
* struct file, and the other from their struct proc.
*/
refcount_init(&pd->pd_refcount, 2);
}
/*
* Create a new process decriptor for the process that refers to it.
*/
int
procdesc_falloc(struct thread *td, struct file **resultfp, int *resultfd,
int flags, struct filecaps *fcaps)
{
int fflags;
fflags = 0;
if (flags & PD_CLOEXEC)
fflags = O_CLOEXEC;
return (falloc_caps(td, resultfp, resultfd, fflags, fcaps));
}
/*
* Initialize a file with a process descriptor.
*/
void
procdesc_finit(struct procdesc *pdp, struct file *fp)
{
finit(fp, FREAD | FWRITE, DTYPE_PROCDESC, pdp, &procdesc_ops);
}
static void
procdesc_free(struct procdesc *pd)
{
/*
* When the last reference is released, we assert that the descriptor
* has been closed, but not that the process has exited, as we will
* detach the descriptor before the process dies if the descript is
* closed, as we can't wait synchronously.
*/
if (refcount_release(&pd->pd_refcount)) {
KASSERT(pd->pd_proc == NULL,
("procdesc_free: pd_proc != NULL"));
KASSERT((pd->pd_flags & PDF_CLOSED),
("procdesc_free: !PDF_CLOSED"));
knlist_destroy(&pd->pd_selinfo.si_note);
PROCDESC_LOCK_DESTROY(pd);
free(pd, M_PROCDESC);
}
}
/*
* procdesc_exit() - notify a process descriptor that its process is exiting.
* We use the proctree_lock to ensure that process exit either happens
* strictly before or strictly after a concurrent call to procdesc_close().
*/
int
procdesc_exit(struct proc *p)
{
struct procdesc *pd;
sx_assert(&proctree_lock, SA_XLOCKED);
PROC_LOCK_ASSERT(p, MA_OWNED);
KASSERT(p->p_procdesc != NULL, ("procdesc_exit: p_procdesc NULL"));
pd = p->p_procdesc;
PROCDESC_LOCK(pd);
KASSERT((pd->pd_flags & PDF_CLOSED) == 0 || p->p_pptr == p->p_reaper,
("procdesc_exit: closed && parent not reaper"));
pd->pd_flags |= PDF_EXITED;
pd->pd_xstat = KW_EXITCODE(p->p_xexit, p->p_xsig);
/*
* If the process descriptor has been closed, then we have nothing
* to do; return 1 so that init will get SIGCHLD and do the reaping.
* Clean up the procdesc now rather than letting it happen during
* that reap.
*/
if (pd->pd_flags & PDF_CLOSED) {
PROCDESC_UNLOCK(pd);
pd->pd_proc = NULL;
p->p_procdesc = NULL;
procdesc_free(pd);
return (1);
}
if (pd->pd_flags & PDF_SELECTED) {
pd->pd_flags &= ~PDF_SELECTED;
selwakeup(&pd->pd_selinfo);
}
KNOTE_LOCKED(&pd->pd_selinfo.si_note, NOTE_EXIT);
PROCDESC_UNLOCK(pd);
return (0);
}
/*
* When a process descriptor is reaped, perhaps as a result of close() or
* pdwait4(), release the process's reference on the process descriptor.
*/
void
procdesc_reap(struct proc *p)
{
struct procdesc *pd;
sx_assert(&proctree_lock, SA_XLOCKED);
KASSERT(p->p_procdesc != NULL, ("procdesc_reap: p_procdesc == NULL"));
pd = p->p_procdesc;
pd->pd_proc = NULL;
p->p_procdesc = NULL;
procdesc_free(pd);
}
/*
* procdesc_close() - last close on a process descriptor. If the process is
* still running, terminate with SIGKILL (unless PDF_DAEMON is set) and let
* its reaper clean up the mess; if not, we have to clean up the zombie
* ourselves.
*/
static int
procdesc_close(struct file *fp, struct thread *td)
{
struct procdesc *pd;
struct proc *p;
KASSERT(fp->f_type == DTYPE_PROCDESC, ("procdesc_close: !procdesc"));
pd = fp->f_data;
fp->f_ops = &badfileops;
fp->f_data = NULL;
sx_xlock(&proctree_lock);
PROCDESC_LOCK(pd);
pd->pd_flags |= PDF_CLOSED;
PROCDESC_UNLOCK(pd);
p = pd->pd_proc;
if (p == NULL) {
/*
* This is the case where process' exit status was already
* collected and procdesc_reap() was already called.
*/
sx_xunlock(&proctree_lock);
} else {
PROC_LOCK(p);
AUDIT_ARG_PROCESS(p);
if (p->p_state == PRS_ZOMBIE) {
/*
* If the process is already dead and just awaiting
* reaping, do that now. This will release the
* process's reference to the process descriptor when it
* calls back into procdesc_reap().
*/
proc_reap(curthread, p, NULL, 0);
} else {
/*
* If the process is not yet dead, we need to kill it,
* but we can't wait around synchronously for it to go
* away, as that path leads to madness (and deadlocks).
* First, detach the process from its descriptor so that
* its exit status will be reported normally.
*/
pd->pd_proc = NULL;
p->p_procdesc = NULL;
procdesc_free(pd);
/*
* Next, reparent it to its reaper (usually init(8)) so
* that there's someone to pick up the pieces; finally,
* terminate with prejudice.
*/
p->p_sigparent = SIGCHLD;
if ((p->p_flag & P_TRACED) == 0) {
proc_reparent(p, p->p_reaper, true);
} else {
proc_clear_orphan(p);
p->p_oppid = p->p_reaper->p_pid;
proc_add_orphan(p, p->p_reaper);
}
if ((pd->pd_flags & PDF_DAEMON) == 0)
kern_psignal(p, SIGKILL);
PROC_UNLOCK(p);
sx_xunlock(&proctree_lock);
}
}
/*
* Release the file descriptor's reference on the process descriptor.
*/
procdesc_free(pd);
return (0);
}
static int
procdesc_poll(struct file *fp, int events, struct ucred *active_cred,
struct thread *td)
{
struct procdesc *pd;
int revents;
revents = 0;
pd = fp->f_data;
PROCDESC_LOCK(pd);
if (pd->pd_flags & PDF_EXITED)
revents |= POLLHUP;
if (revents == 0) {
selrecord(td, &pd->pd_selinfo);
pd->pd_flags |= PDF_SELECTED;
}
PROCDESC_UNLOCK(pd);
return (revents);
}
static void
procdesc_kqops_detach(struct knote *kn)
{
struct procdesc *pd;
pd = kn->kn_fp->f_data;
knlist_remove(&pd->pd_selinfo.si_note, kn, 0);
}
static int
procdesc_kqops_event(struct knote *kn, long hint)
{
struct procdesc *pd;
u_int event;
pd = kn->kn_fp->f_data;
if (hint == 0) {
/*
* Initial test after registration. Generate a NOTE_EXIT in
* case the process already terminated before registration.
*/
event = pd->pd_flags & PDF_EXITED ? NOTE_EXIT : 0;
} else {
/* Mask off extra data. */
event = (u_int)hint & NOTE_PCTRLMASK;
}
/* If the user is interested in this event, record it. */
if (kn->kn_sfflags & event)
kn->kn_fflags |= event;
/* Process is gone, so flag the event as finished. */
if (event == NOTE_EXIT) {
kn->kn_flags |= EV_EOF | EV_ONESHOT;
if (kn->kn_fflags & NOTE_EXIT)
kn->kn_data = pd->pd_xstat;
if (kn->kn_fflags == 0)
kn->kn_flags |= EV_DROP;
return (1);
}
return (kn->kn_fflags != 0);
}
static struct filterops procdesc_kqops = {
.f_isfd = 1,
.f_detach = procdesc_kqops_detach,
.f_event = procdesc_kqops_event,
};
static int
procdesc_kqfilter(struct file *fp, struct knote *kn)
{
struct procdesc *pd;
pd = fp->f_data;
switch (kn->kn_filter) {
case EVFILT_PROCDESC:
kn->kn_fop = &procdesc_kqops;
kn->kn_flags |= EV_CLEAR;
knlist_add(&pd->pd_selinfo.si_note, kn, 0);
return (0);
default:
return (EINVAL);
}
}
static int
procdesc_stat(struct file *fp, struct stat *sb, struct ucred *active_cred,
struct thread *td)
{
struct procdesc *pd;
struct timeval pstart, boottime;
/*
* XXXRW: Perhaps we should cache some more information from the
* process so that we can return it reliably here even after it has
* died. For example, caching its credential data.
*/
bzero(sb, sizeof(*sb));
pd = fp->f_data;
sx_slock(&proctree_lock);
if (pd->pd_proc != NULL) {
PROC_LOCK(pd->pd_proc);
AUDIT_ARG_PROCESS(pd->pd_proc);
/* Set birth and [acm] times to process start time. */
pstart = pd->pd_proc->p_stats->p_start;
getboottime(&boottime);
timevaladd(&pstart, &boottime);
TIMEVAL_TO_TIMESPEC(&pstart, &sb->st_birthtim);
sb->st_atim = sb->st_birthtim;
sb->st_ctim = sb->st_birthtim;
sb->st_mtim = sb->st_birthtim;
if (pd->pd_proc->p_state != PRS_ZOMBIE)
sb->st_mode = S_IFREG | S_IRWXU;
else
sb->st_mode = S_IFREG;
sb->st_uid = pd->pd_proc->p_ucred->cr_ruid;
sb->st_gid = pd->pd_proc->p_ucred->cr_rgid;
PROC_UNLOCK(pd->pd_proc);
} else
sb->st_mode = S_IFREG;
sx_sunlock(&proctree_lock);
return (0);
}
static int
procdesc_fill_kinfo(struct file *fp, struct kinfo_file *kif,
struct filedesc *fdp)
{
struct procdesc *pdp;
kif->kf_type = KF_TYPE_PROCDESC;
pdp = fp->f_data;
kif->kf_un.kf_proc.kf_pid = pdp->pd_pid;
return (0);
}
