The process is reparented to the debugger while it is attached. B B / ----> | A A D Every time when the process is reparented, it is added to the orphan list of the previous parent: A->orphan = B D->orphan = NULL When the A process will close the process descriptor to the B process, the B process will be reparented to the init process. B B - init | ----> A D A D A->orphan = B D->orphan = B In this scenario, the B process is in the orphan list of A and D. When the last process descriptor is closed instead of reparenting it to the reaper let it stay with the debugger process and set our previews parent to the reaper. Add test case for this situation. Notice that without this patch the kernel will crash with this test case: panic: orphan 0xfffff8000e990530 of 0xfffff8000e990000 has unexpected oppid 1 Reviewed by: markj, kib MFC after: 1 month Differential Revision: https://reviews.freebsd.org/D20361
578 lines
15 KiB
C
578 lines
15 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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* - How to handle ptrace(2)?
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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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static uma_zone_t procdesc_zone;
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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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* Initialize with VFS so that process descriptors are available along with
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* other file descriptor types. As long as it runs before init(8) starts,
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* there shouldn't be a problem.
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*/
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static void
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procdesc_init(void *dummy __unused)
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{
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procdesc_zone = uma_zcreate("procdesc", sizeof(struct procdesc),
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NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
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if (procdesc_zone == NULL)
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panic("procdesc_init: procdesc_zone not initialized");
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}
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SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_ANY, procdesc_init, NULL);
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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 = uma_zalloc(procdesc_zone, 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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uma_zfree(procdesc_zone, pd);
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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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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)
|
|
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);
|
|
}
|