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