File: [local] / src / sys / kern / kern_fork.c (download)
Revision 1.63, Tue Sep 23 20:26:18 2003 UTC (20 years, 8 months ago) by millert
Branch: MAIN
CVS Tags: OPENBSD_3_5_BASE, OPENBSD_3_5 Changes since 1.62: +8 -2 lines
Limit "proc: table is full" messages to once every 10 seconds which helps when there is a fork bomb going on. From NetBSD (jdolecek)
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/* $OpenBSD: kern_fork.c,v 1.63 2003/09/23 20:26:18 millert Exp $ */
/* $NetBSD: kern_fork.c,v 1.29 1996/02/09 18:59:34 christos Exp $ */
/*
* Copyright (c) 1982, 1986, 1989, 1991, 1993
* The Regents of the University of California. All rights reserved.
* (c) UNIX System Laboratories, Inc.
* All or some portions of this file are derived from material licensed
* to the University of California by American Telephone and Telegraph
* Co. or Unix System Laboratories, Inc. and are reproduced herein with
* the permission of UNIX System Laboratories, Inc.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* @(#)kern_fork.c 8.6 (Berkeley) 4/8/94
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/filedesc.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/mount.h>
#include <sys/proc.h>
#include <sys/resourcevar.h>
#include <sys/signalvar.h>
#include <sys/vnode.h>
#include <sys/file.h>
#include <sys/acct.h>
#include <sys/ktrace.h>
#include <sys/sched.h>
#include <dev/rndvar.h>
#include <sys/pool.h>
#include <sys/mman.h>
#include <sys/syscallargs.h>
#include "systrace.h"
#include <dev/systrace.h>
#include <uvm/uvm_extern.h>
#include <uvm/uvm_map.h>
int nprocs = 1; /* process 0 */
int randompid; /* when set to 1, pid's go random */
pid_t lastpid;
struct forkstat forkstat;
int pidtaken(pid_t);
/*ARGSUSED*/
int
sys_fork(struct proc *p, void *v, register_t *retval)
{
return (fork1(p, SIGCHLD, FORK_FORK, NULL, 0, NULL, NULL, retval));
}
/*ARGSUSED*/
int
sys_vfork(struct proc *p, void *v, register_t *retval)
{
return (fork1(p, SIGCHLD, FORK_VFORK|FORK_PPWAIT, NULL, 0, NULL,
NULL, retval));
}
int
sys_rfork(struct proc *p, void *v, register_t *retval)
{
struct sys_rfork_args /* {
syscallarg(int) flags;
} */ *uap = v;
int rforkflags;
int flags;
flags = FORK_RFORK;
rforkflags = SCARG(uap, flags);
if ((rforkflags & RFPROC) == 0)
return (EINVAL);
switch(rforkflags & (RFFDG|RFCFDG)) {
case (RFFDG|RFCFDG):
return EINVAL;
case RFCFDG:
flags |= FORK_CLEANFILES;
break;
case RFFDG:
break;
default:
flags |= FORK_SHAREFILES;
break;
}
if (rforkflags & RFNOWAIT)
flags |= FORK_NOZOMBIE;
if (rforkflags & RFMEM)
flags |= FORK_VMNOSTACK;
return (fork1(p, SIGCHLD, flags, NULL, 0, NULL, NULL, retval));
}
/* print the 'table full' message once per 10 seconds */
struct timeval fork_tfmrate = { 10, 0 };
int
fork1(struct proc *p1, int exitsig, int flags, void *stack, size_t stacksize,
void (*func)(void *), void *arg, register_t *retval)
{
struct proc *p2;
uid_t uid;
struct vmspace *vm;
int count;
vaddr_t uaddr;
int s;
extern void endtsleep(void *);
extern void realitexpire(void *);
/*
* Although process entries are dynamically created, we still keep
* a global limit on the maximum number we will create. We reserve
* the last 5 processes to root. The variable nprocs is the current
* number of processes, maxproc is the limit.
*/
uid = p1->p_cred->p_ruid;
if ((nprocs >= maxproc - 5 && uid != 0) || nprocs >= maxproc) {
static struct timeval lasttfm;
if (ratecheck(&lasttfm, &fork_tfmrate))
tablefull("proc");
return (EAGAIN);
}
nprocs++;
/*
* Increment the count of procs running with this uid. Don't allow
* a nonprivileged user to exceed their current limit.
*/
count = chgproccnt(uid, 1);
if (uid != 0 && count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur) {
(void)chgproccnt(uid, -1);
nprocs--;
return (EAGAIN);
}
/*
* Allocate a pcb and kernel stack for the process
*/
uaddr = uvm_km_valloc(kernel_map, USPACE);
if (uaddr == 0) {
chgproccnt(uid, -1);
nprocs--;
return (ENOMEM);
}
/*
* From now on, we're committed to the fork and cannot fail.
*/
/* Allocate new proc. */
p2 = pool_get(&proc_pool, PR_WAITOK);
p2->p_stat = SIDL; /* protect against others */
p2->p_exitsig = exitsig;
p2->p_forw = p2->p_back = NULL;
/*
* Make a proc table entry for the new process.
* Start by zeroing the section of proc that is zero-initialized,
* then copy the section that is copied directly from the parent.
*/
bzero(&p2->p_startzero,
(unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero));
bcopy(&p1->p_startcopy, &p2->p_startcopy,
(unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy));
/*
* Initialize the timeouts.
*/
timeout_set(&p2->p_sleep_to, endtsleep, p2);
timeout_set(&p2->p_realit_to, realitexpire, p2);
/*
* Duplicate sub-structures as needed.
* Increase reference counts on shared objects.
* The p_stats and p_sigacts substructs are set in vm_fork.
*/
p2->p_flag = P_INMEM;
p2->p_emul = p1->p_emul;
if (p1->p_flag & P_PROFIL)
startprofclock(p2);
p2->p_flag |= (p1->p_flag & (P_SUGID | P_SUGIDEXEC));
p2->p_cred = pool_get(&pcred_pool, PR_WAITOK);
bcopy(p1->p_cred, p2->p_cred, sizeof(*p2->p_cred));
p2->p_cred->p_refcnt = 1;
crhold(p1->p_ucred);
/* bump references to the text vnode (for procfs) */
p2->p_textvp = p1->p_textvp;
if (p2->p_textvp)
VREF(p2->p_textvp);
if (flags & FORK_CLEANFILES)
p2->p_fd = fdinit(p1);
else if (flags & FORK_SHAREFILES)
p2->p_fd = fdshare(p1);
else
p2->p_fd = fdcopy(p1);
/*
* If p_limit is still copy-on-write, bump refcnt,
* otherwise get a copy that won't be modified.
* (If PL_SHAREMOD is clear, the structure is shared
* copy-on-write.)
*/
if (p1->p_limit->p_lflags & PL_SHAREMOD)
p2->p_limit = limcopy(p1->p_limit);
else {
p2->p_limit = p1->p_limit;
p2->p_limit->p_refcnt++;
}
if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT)
p2->p_flag |= P_CONTROLT;
if (flags & FORK_PPWAIT)
p2->p_flag |= P_PPWAIT;
LIST_INSERT_AFTER(p1, p2, p_pglist);
p2->p_pptr = p1;
if (flags & FORK_NOZOMBIE)
p2->p_flag |= P_NOZOMBIE;
LIST_INSERT_HEAD(&p1->p_children, p2, p_sibling);
LIST_INIT(&p2->p_children);
#ifdef KTRACE
/*
* Copy traceflag and tracefile if enabled.
* If not inherited, these were zeroed above.
*/
if (p1->p_traceflag & KTRFAC_INHERIT) {
p2->p_traceflag = p1->p_traceflag;
if ((p2->p_tracep = p1->p_tracep) != NULL)
VREF(p2->p_tracep);
}
#endif
/*
* set priority of child to be that of parent
* XXX should move p_estcpu into the region of struct proc which gets
* copied.
*/
scheduler_fork_hook(p1, p2);
/*
* Create signal actions for the child process.
*/
if (flags & FORK_SIGHAND)
sigactsshare(p1, p2);
else
p2->p_sigacts = sigactsinit(p1);
/*
* If emulation has process fork hook, call it now.
*/
if (p2->p_emul->e_proc_fork)
(*p2->p_emul->e_proc_fork)(p2, p1);
/*
* This begins the section where we must prevent the parent
* from being swapped.
*/
PHOLD(p1);
if (flags & FORK_VMNOSTACK) {
/* share everything, but ... */
uvm_map_inherit(&p1->p_vmspace->vm_map,
VM_MIN_ADDRESS, VM_MAXUSER_ADDRESS,
MAP_INHERIT_SHARE);
/* ... don't share stack */
#ifdef MACHINE_STACK_GROWS_UP
uvm_map_inherit(&p1->p_vmspace->vm_map,
USRSTACK, USRSTACK + MAXSSIZ,
MAP_INHERIT_COPY);
#else
uvm_map_inherit(&p1->p_vmspace->vm_map,
USRSTACK - MAXSSIZ, USRSTACK,
MAP_INHERIT_COPY);
#endif
}
p2->p_addr = (struct user *)uaddr;
/*
* Finish creating the child process. It will return through a
* different path later.
*/
uvm_fork(p1, p2, ((flags & FORK_SHAREVM) ? TRUE : FALSE), stack,
stacksize, func ? func : child_return, arg ? arg : p2);
vm = p2->p_vmspace;
if (flags & FORK_FORK) {
forkstat.cntfork++;
forkstat.sizfork += vm->vm_dsize + vm->vm_ssize;
} else if (flags & FORK_VFORK) {
forkstat.cntvfork++;
forkstat.sizvfork += vm->vm_dsize + vm->vm_ssize;
} else if (flags & FORK_RFORK) {
forkstat.cntrfork++;
forkstat.sizrfork += vm->vm_dsize + vm->vm_ssize;
} else {
forkstat.cntkthread++;
forkstat.sizkthread += vm->vm_dsize + vm->vm_ssize;
}
/* Find an unused pid satisfying 1 <= lastpid <= PID_MAX */
do {
lastpid = 1 + (randompid ? arc4random() : lastpid) % PID_MAX;
} while (pidtaken(lastpid));
p2->p_pid = lastpid;
LIST_INSERT_HEAD(&allproc, p2, p_list);
LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash);
#if NSYSTRACE > 0
if (ISSET(p1->p_flag, P_SYSTRACE))
systrace_fork(p1, p2);
#endif
/*
* Make child runnable, set start time, and add to run queue.
*/
s = splstatclock();
p2->p_stats->p_start = time;
p2->p_acflag = AFORK;
p2->p_stat = SRUN;
setrunqueue(p2);
splx(s);
/*
* Now can be swapped.
*/
PRELE(p1);
uvmexp.forks++;
if (flags & FORK_PPWAIT)
uvmexp.forks_ppwait++;
if (flags & FORK_SHAREVM)
uvmexp.forks_sharevm++;
/*
* tell any interested parties about the new process
*/
KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid);
/*
* Preserve synchronization semantics of vfork. If waiting for
* child to exec or exit, set P_PPWAIT on child, and sleep on our
* proc (in case of exit).
*/
if (flags & FORK_PPWAIT)
while (p2->p_flag & P_PPWAIT)
tsleep(p1, PWAIT, "ppwait", 0);
/*
* Return child pid to parent process,
* marking us as parent via retval[1].
*/
retval[0] = p2->p_pid;
retval[1] = 0;
return (0);
}
/*
* Checks for current use of a pid, either as a pid or pgid.
*/
int
pidtaken(pid_t pid)
{
struct proc *p;
if (pfind(pid) != NULL)
return (1);
if (pgfind(pid) != NULL)
return (1);
LIST_FOREACH(p, &zombproc, p_list)
if (p->p_pid == pid || p->p_pgid == pid)
return (1);
return (0);
}