According to <sys/proc.h>, this field needs to be locked with either the p_mtx or the p_slock. In this case the damage was quite small. Instead of being reaped, the process would just be reparented to init, so it could be reaped from there.
523 lines
13 KiB
C
523 lines
13 KiB
C
/*-
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* Copyright (c) 2009 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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* 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 pfork(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 <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_rdwr_t procdesc_read;
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static fo_rdwr_t procdesc_write;
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static fo_truncate_t procdesc_truncate;
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static fo_ioctl_t procdesc_ioctl;
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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_chmod_t procdesc_chmod;
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static fo_chown_t procdesc_chown;
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static struct fileops procdesc_ops = {
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.fo_read = procdesc_read,
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.fo_write = procdesc_write,
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.fo_truncate = procdesc_truncate,
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.fo_ioctl = procdesc_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 = procdesc_chmod,
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.fo_chown = procdesc_chown,
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.fo_sendfile = invfo_sendfile,
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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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cap_rights_t rights;
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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,
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cap_rights_init(&rights, CAP_PDGETPID), &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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/*
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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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* 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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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 == initproc,
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("procdesc_exit: closed && parent not init"));
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pd->pd_flags |= PDF_EXITED;
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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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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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* init(8) clean up the mess; if not, we have to clean up the zombie 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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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_SLOCK(p);
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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 init(8) so that there's someone
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* to pick up the pieces; finally, terminate with
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* prejudice.
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*/
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p->p_sigparent = SIGCHLD;
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proc_reparent(p, initproc);
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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_read(struct file *fp, struct uio *uio, struct ucred *active_cred,
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int flags, struct thread *td)
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{
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return (EOPNOTSUPP);
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}
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static int
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procdesc_write(struct file *fp, struct uio *uio, struct ucred *active_cred,
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int flags, struct thread *td)
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{
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return (EOPNOTSUPP);
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}
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static int
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procdesc_truncate(struct file *fp, off_t length, struct ucred *active_cred,
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struct thread *td)
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{
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return (EOPNOTSUPP);
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}
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static int
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procdesc_ioctl(struct file *fp, u_long com, void *data,
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struct ucred *active_cred, struct thread *td)
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{
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return (EOPNOTSUPP);
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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 int
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procdesc_kqfilter(struct file *fp, struct knote *kn)
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{
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return (EOPNOTSUPP);
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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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struct thread *td)
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{
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struct procdesc *pd;
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struct timeval pstart;
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/*
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* XXXRW: Perhaps we should cache some more information from the
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* process so that we can return it reliably here even after it has
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* died. For example, caching its credential data.
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*/
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bzero(sb, sizeof(*sb));
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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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PROC_LOCK(pd->pd_proc);
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/* Set birth and [acm] times to process start time. */
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pstart = pd->pd_proc->p_stats->p_start;
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timevaladd(&pstart, &boottime);
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TIMEVAL_TO_TIMESPEC(&pstart, &sb->st_birthtim);
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sb->st_atim = sb->st_birthtim;
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sb->st_ctim = sb->st_birthtim;
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sb->st_mtim = sb->st_birthtim;
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if (pd->pd_proc->p_state != PRS_ZOMBIE)
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sb->st_mode = S_IFREG | S_IRWXU;
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else
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sb->st_mode = S_IFREG;
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sb->st_uid = pd->pd_proc->p_ucred->cr_ruid;
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sb->st_gid = pd->pd_proc->p_ucred->cr_rgid;
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PROC_UNLOCK(pd->pd_proc);
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} else
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sb->st_mode = S_IFREG;
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sx_sunlock(&proctree_lock);
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return (0);
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}
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static int
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procdesc_chmod(struct file *fp, mode_t mode, struct ucred *active_cred,
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struct thread *td)
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{
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return (EOPNOTSUPP);
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}
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static int
|
|
procdesc_chown(struct file *fp, uid_t uid, gid_t gid, struct ucred *active_cred,
|
|
struct thread *td)
|
|
{
|
|
|
|
return (EOPNOTSUPP);
|
|
}
|