d5f81602a7
flag is set in the p_pfsflags field. This, essentially, prevents an SUID proram from hanging after being traced. (E.g., "truss /usr/bin/rlogin" would fail, but leave rlogin in a stopevent state.) Yet another case where procctl is (hopefully ;)) no longer needed in the general case. Reviewed by: bde (thanks bruce :))
668 lines
16 KiB
C
668 lines
16 KiB
C
/*
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* Copyright (c) 1993, David Greenman
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* All rights reserved.
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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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* $Id: kern_exec.c,v 1.70 1997/12/16 15:40:29 davidg Exp $
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*/
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/sysproto.h>
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#include <sys/signalvar.h>
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#include <sys/kernel.h>
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#include <sys/mount.h>
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#include <sys/filedesc.h>
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#include <sys/fcntl.h>
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#include <sys/acct.h>
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#include <sys/exec.h>
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#include <sys/imgact.h>
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#include <sys/imgact_elf.h>
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#include <sys/wait.h>
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#include <sys/proc.h>
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#include <sys/pioctl.h>
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#include <sys/malloc.h>
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#include <sys/namei.h>
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#include <sys/sysent.h>
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#include <sys/shm.h>
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#include <sys/sysctl.h>
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#include <sys/vnode.h>
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#include <sys/buf.h>
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#include <vm/vm.h>
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#include <vm/vm_param.h>
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#include <vm/vm_prot.h>
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#include <sys/lock.h>
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#include <vm/pmap.h>
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#include <vm/vm_map.h>
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#include <vm/vm_kern.h>
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#include <vm/vm_extern.h>
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#include <vm/vm_object.h>
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#include <machine/reg.h>
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static int *exec_copyout_strings __P((struct image_params *));
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static int exec_check_permissions(struct image_params *);
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/*
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* XXX trouble here if sizeof(caddr_t) != sizeof(int), other parts
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* of the sysctl code also assumes this, and sizeof(int) == sizeof(long).
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*/
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static struct ps_strings *ps_strings = PS_STRINGS;
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SYSCTL_INT(_kern, KERN_PS_STRINGS, ps_strings, 0, &ps_strings, 0, "");
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static caddr_t usrstack = (caddr_t)USRSTACK;
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SYSCTL_INT(_kern, KERN_USRSTACK, usrstack, 0, &usrstack, 0, "");
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/*
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* execsw_set is constructed for us by the linker. Each of the items
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* is a pointer to a `const struct execsw', hence the double pointer here.
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*/
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static const struct execsw **execsw =
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(const struct execsw **)&execsw_set.ls_items[0];
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#ifndef _SYS_SYSPROTO_H_
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struct execve_args {
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char *fname;
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char **argv;
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char **envv;
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};
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#endif
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/*
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* execve() system call.
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*/
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int
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execve(p, uap)
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struct proc *p;
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register struct execve_args *uap;
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{
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struct nameidata nd, *ndp;
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int *stack_base;
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int error, len, i;
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struct image_params image_params, *imgp;
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struct vattr attr;
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struct buf *bp = NULL;
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imgp = &image_params;
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/*
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* Initialize part of the common data
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*/
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imgp->proc = p;
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imgp->uap = uap;
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imgp->attr = &attr;
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imgp->image_header = NULL;
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imgp->argc = imgp->envc = 0;
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imgp->argv0 = NULL;
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imgp->entry_addr = 0;
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imgp->vmspace_destroyed = 0;
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imgp->interpreted = 0;
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imgp->interpreter_name[0] = '\0';
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imgp->auxargs = NULL;
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/*
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* Allocate temporary demand zeroed space for argument and
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* environment strings
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*/
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imgp->stringbase = (char *)kmem_alloc_wait(exec_map, ARG_MAX);
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if (imgp->stringbase == NULL) {
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error = ENOMEM;
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goto exec_fail;
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}
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imgp->stringp = imgp->stringbase;
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imgp->stringspace = ARG_MAX;
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/*
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* Translate the file name. namei() returns a vnode pointer
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* in ni_vp amoung other things.
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*/
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ndp = &nd;
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NDINIT(ndp, LOOKUP, LOCKLEAF | FOLLOW | SAVENAME,
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UIO_USERSPACE, uap->fname, p);
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interpret:
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error = namei(ndp);
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if (error) {
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kmem_free_wakeup(exec_map, (vm_offset_t)imgp->stringbase, ARG_MAX);
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goto exec_fail;
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}
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imgp->vp = ndp->ni_vp;
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/*
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* Check file permissions (also 'opens' file)
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*/
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error = exec_check_permissions(imgp);
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if (error) {
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VOP_UNLOCK(imgp->vp, 0, p);
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goto exec_fail_dealloc;
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}
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/*
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* Get the image header, which we define here as meaning the first
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* page of the executable.
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*/
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if (imgp->vp->v_object && imgp->vp->v_mount &&
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imgp->vp->v_mount->mnt_stat.f_iosize >= PAGE_SIZE &&
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imgp->vp->v_object->un_pager.vnp.vnp_size >=
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imgp->vp->v_mount->mnt_stat.f_iosize) {
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/*
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* Get a buffer with (at least) the first page.
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*/
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error = bread(imgp->vp, 0, imgp->vp->v_mount->mnt_stat.f_iosize,
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p->p_ucred, &bp);
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imgp->image_header = bp->b_data;
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} else {
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int resid;
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/*
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* The filesystem block size is too small, so do this the hard
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* way. Malloc some space and read PAGE_SIZE worth of the image
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* header into it.
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*/
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imgp->image_header = malloc(PAGE_SIZE, M_TEMP, M_WAITOK);
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error = vn_rdwr(UIO_READ, imgp->vp, (void *)imgp->image_header, PAGE_SIZE, 0,
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UIO_SYSSPACE, IO_NODELOCKED, p->p_ucred, &resid, p);
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/*
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* Clear out any remaining junk.
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*/
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if (!error && resid)
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bzero((char *)imgp->image_header + PAGE_SIZE - resid, resid);
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}
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VOP_UNLOCK(imgp->vp, 0, p);
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if (error)
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goto exec_fail_dealloc;
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/*
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* Loop through list of image activators, calling each one.
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* If there is no match, the activator returns -1. If there
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* is a match, but there was an error during the activation,
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* the error is returned. Otherwise 0 means success. If the
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* image is interpreted, loop back up and try activating
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* the interpreter.
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*/
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for (i = 0; execsw[i]; ++i) {
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if (execsw[i]->ex_imgact)
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error = (*execsw[i]->ex_imgact)(imgp);
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else
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continue;
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if (error == -1)
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continue;
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if (error)
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goto exec_fail_dealloc;
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if (imgp->interpreted) {
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/* free old bp/image_header */
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if (bp != NULL) {
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brelse(bp);
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bp = NULL;
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} else
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free((void *)imgp->image_header, M_TEMP);
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imgp->image_header = NULL;
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/* free old vnode and name buffer */
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vrele(ndp->ni_vp);
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zfree(namei_zone, ndp->ni_cnd.cn_pnbuf);
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/* set new name to that of the interpreter */
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NDINIT(ndp, LOOKUP, LOCKLEAF | FOLLOW | SAVENAME,
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UIO_SYSSPACE, imgp->interpreter_name, p);
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goto interpret;
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}
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break;
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}
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/* If we made it through all the activators and none matched, exit. */
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if (error == -1) {
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error = ENOEXEC;
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goto exec_fail_dealloc;
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}
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/*
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* Copy out strings (args and env) and initialize stack base
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*/
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stack_base = exec_copyout_strings(imgp);
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p->p_vmspace->vm_minsaddr = (char *)stack_base;
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/*
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* If custom stack fixup routine present for this process
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* let it do the stack setup.
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* Else stuff argument count as first item on stack
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*/
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if (p->p_sysent->sv_fixup)
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(*p->p_sysent->sv_fixup)(&stack_base, imgp);
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else
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suword(--stack_base, imgp->argc);
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/*
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* For security and other reasons, the file descriptor table cannot
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* be shared after an exec.
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*/
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if (p->p_fd->fd_refcnt > 1) {
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struct filedesc *tmp;
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tmp = fdcopy(p);
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fdfree(p);
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p->p_fd = tmp;
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}
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/* close files on exec */
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fdcloseexec(p);
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/* reset caught signals */
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execsigs(p);
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/* name this process - nameiexec(p, ndp) */
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len = min(ndp->ni_cnd.cn_namelen,MAXCOMLEN);
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bcopy(ndp->ni_cnd.cn_nameptr, p->p_comm, len);
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p->p_comm[len] = 0;
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/*
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* mark as execed, wakeup the process that vforked (if any) and tell
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* it that it now has it's own resources back
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*/
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p->p_flag |= P_EXEC;
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if (p->p_pptr && (p->p_flag & P_PPWAIT)) {
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p->p_flag &= ~P_PPWAIT;
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wakeup((caddr_t)p->p_pptr);
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}
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/*
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* Implement image setuid/setgid.
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*
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* Don't honor setuid/setgid if the filesystem prohibits it or if
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* the process is being traced.
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*/
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if ((attr.va_mode & VSUID && p->p_ucred->cr_uid != attr.va_uid ||
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attr.va_mode & VSGID && p->p_ucred->cr_gid != attr.va_gid) &&
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(imgp->vp->v_mount->mnt_flag & MNT_NOSUID) == 0 &&
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(p->p_flag & P_TRACED) == 0) {
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/*
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* Turn off syscall tracing for set-id programs, except for
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* root.
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*/
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if (p->p_tracep && suser(p->p_ucred, &p->p_acflag)) {
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p->p_traceflag = 0;
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vrele(p->p_tracep);
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p->p_tracep = NULL;
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}
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/*
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* Set the new credentials.
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*/
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p->p_ucred = crcopy(p->p_ucred);
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if (attr.va_mode & VSUID)
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p->p_ucred->cr_uid = attr.va_uid;
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if (attr.va_mode & VSGID)
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p->p_ucred->cr_gid = attr.va_gid;
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setsugid(p);
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} else {
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if (p->p_ucred->cr_uid == p->p_cred->p_ruid &&
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p->p_ucred->cr_gid == p->p_cred->p_rgid)
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p->p_flag &= ~P_SUGID;
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}
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/*
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* Implement correct POSIX saved-id behavior.
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*/
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p->p_cred->p_svuid = p->p_ucred->cr_uid;
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p->p_cred->p_svgid = p->p_ucred->cr_gid;
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/*
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* Store the vp for use in procfs
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*/
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if (p->p_textvp) /* release old reference */
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vrele(p->p_textvp);
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VREF(ndp->ni_vp);
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p->p_textvp = ndp->ni_vp;
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/*
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* If tracing the process, trap to debugger so breakpoints
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* can be set before the program executes.
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*/
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STOPEVENT(p, S_EXEC, 0);
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if (p->p_flag & P_TRACED)
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psignal(p, SIGTRAP);
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/* clear "fork but no exec" flag, as we _are_ execing */
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p->p_acflag &= ~AFORK;
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/* Set entry address */
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setregs(p, imgp->entry_addr, (u_long)stack_base);
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/*
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* free various allocated resources
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*/
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kmem_free_wakeup(exec_map, (vm_offset_t)imgp->stringbase, ARG_MAX);
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if (bp != NULL)
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brelse(bp);
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else if (imgp->image_header != NULL)
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free((void *)imgp->image_header, M_TEMP);
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vrele(ndp->ni_vp);
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zfree(namei_zone, ndp->ni_cnd.cn_pnbuf);
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return (0);
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exec_fail_dealloc:
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if (imgp->stringbase != NULL)
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kmem_free_wakeup(exec_map, (vm_offset_t)imgp->stringbase, ARG_MAX);
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if (bp != NULL)
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brelse(bp);
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else if (imgp->image_header != NULL)
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free((void *)imgp->image_header, M_TEMP);
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if (ndp->ni_vp) {
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vrele(ndp->ni_vp);
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zfree(namei_zone, ndp->ni_cnd.cn_pnbuf);
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}
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exec_fail:
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if (imgp->vmspace_destroyed) {
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/* sorry, no more process anymore. exit gracefully */
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exit1(p, W_EXITCODE(0, SIGABRT));
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/* NOT REACHED */
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return(0);
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} else {
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return(error);
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}
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}
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/*
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* Destroy old address space, and allocate a new stack
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* The new stack is only SGROWSIZ large because it is grown
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* automatically in trap.c.
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*/
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int
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exec_new_vmspace(imgp)
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struct image_params *imgp;
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{
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int error;
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struct vmspace *vmspace = imgp->proc->p_vmspace;
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caddr_t stack_addr = (caddr_t) (USRSTACK - SGROWSIZ);
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vm_map_t map = &vmspace->vm_map;
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imgp->vmspace_destroyed = 1;
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/*
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* Blow away entire process VM, if address space not shared,
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* otherwise, create a new VM space so that other threads are
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* not disrupted
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*/
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if (vmspace->vm_refcnt == 1) {
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if (vmspace->vm_shm)
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shmexit(imgp->proc);
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pmap_remove_pages(&vmspace->vm_pmap, 0, USRSTACK);
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vm_map_remove(map, 0, USRSTACK);
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} else {
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vmspace_exec(imgp->proc);
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vmspace = imgp->proc->p_vmspace;
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map = &vmspace->vm_map;
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}
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/* Allocate a new stack */
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error = vm_map_find(map, NULL, 0, (vm_offset_t *)&stack_addr,
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SGROWSIZ, FALSE, VM_PROT_ALL, VM_PROT_ALL, 0);
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if (error)
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return(error);
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vmspace->vm_ssize = SGROWSIZ >> PAGE_SHIFT;
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/* Initialize maximum stack address */
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vmspace->vm_maxsaddr = (char *)USRSTACK - MAXSSIZ;
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return(0);
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}
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/*
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* Copy out argument and environment strings from the old process
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* address space into the temporary string buffer.
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*/
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int
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exec_extract_strings(imgp)
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struct image_params *imgp;
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{
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char **argv, **envv;
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char *argp, *envp;
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int error, length;
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/*
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* extract arguments first
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*/
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argv = imgp->uap->argv;
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if (argv) {
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argp = (caddr_t) fuword(argv);
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if (argp == (caddr_t) -1)
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return (EFAULT);
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if (argp)
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argv++;
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if (imgp->argv0)
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argp = imgp->argv0;
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if (argp) {
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do {
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if (argp == (caddr_t) -1)
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return (EFAULT);
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if ((error = copyinstr(argp, imgp->stringp,
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imgp->stringspace, &length))) {
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if (error == ENAMETOOLONG)
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return(E2BIG);
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return (error);
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}
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imgp->stringspace -= length;
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imgp->stringp += length;
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imgp->argc++;
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} while ((argp = (caddr_t) fuword(argv++)));
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}
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}
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/*
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* extract environment strings
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*/
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envv = imgp->uap->envv;
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if (envv) {
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while ((envp = (caddr_t) fuword(envv++))) {
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if (envp == (caddr_t) -1)
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return (EFAULT);
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if ((error = copyinstr(envp, imgp->stringp,
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imgp->stringspace, &length))) {
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if (error == ENAMETOOLONG)
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return(E2BIG);
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return (error);
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}
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imgp->stringspace -= length;
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imgp->stringp += length;
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imgp->envc++;
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}
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}
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return (0);
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}
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/*
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* Copy strings out to the new process address space, constructing
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|
* new arg and env vector tables. Return a pointer to the base
|
|
* so that it can be used as the initial stack pointer.
|
|
*/
|
|
int *
|
|
exec_copyout_strings(imgp)
|
|
struct image_params *imgp;
|
|
{
|
|
int argc, envc;
|
|
char **vectp;
|
|
char *stringp, *destp;
|
|
int *stack_base;
|
|
struct ps_strings *arginfo;
|
|
int szsigcode;
|
|
|
|
/*
|
|
* Calculate string base and vector table pointers.
|
|
* Also deal with signal trampoline code for this exec type.
|
|
*/
|
|
arginfo = PS_STRINGS;
|
|
szsigcode = *(imgp->proc->p_sysent->sv_szsigcode);
|
|
destp = (caddr_t)arginfo - szsigcode - SPARE_USRSPACE -
|
|
roundup((ARG_MAX - imgp->stringspace), sizeof(char *));
|
|
|
|
/*
|
|
* install sigcode
|
|
*/
|
|
if (szsigcode)
|
|
copyout(imgp->proc->p_sysent->sv_sigcode,
|
|
((caddr_t)arginfo - szsigcode), szsigcode);
|
|
|
|
/*
|
|
* If we have a valid auxargs ptr, prepare some room
|
|
* on the stack.
|
|
*/
|
|
if (imgp->auxargs)
|
|
/*
|
|
* The '+ 2' is for the null pointers at the end of each of the
|
|
* arg and env vector sets, and 'AT_COUNT*2' is room for the
|
|
* ELF Auxargs data.
|
|
*/
|
|
vectp = (char **)(destp - (imgp->argc + imgp->envc + 2 +
|
|
AT_COUNT*2) * sizeof(char*));
|
|
else
|
|
/*
|
|
* The '+ 2' is for the null pointers at the end of each of the
|
|
* arg and env vector sets
|
|
*/
|
|
vectp = (char **)
|
|
(destp - (imgp->argc + imgp->envc + 2) * sizeof(char*));
|
|
|
|
/*
|
|
* vectp also becomes our initial stack base
|
|
*/
|
|
stack_base = (int *)vectp;
|
|
|
|
stringp = imgp->stringbase;
|
|
argc = imgp->argc;
|
|
envc = imgp->envc;
|
|
|
|
/*
|
|
* Copy out strings - arguments and environment.
|
|
*/
|
|
copyout(stringp, destp, ARG_MAX - imgp->stringspace);
|
|
|
|
/*
|
|
* Fill in "ps_strings" struct for ps, w, etc.
|
|
*/
|
|
suword(&arginfo->ps_argvstr, (int)vectp);
|
|
suword(&arginfo->ps_nargvstr, argc);
|
|
|
|
/*
|
|
* Fill in argument portion of vector table.
|
|
*/
|
|
for (; argc > 0; --argc) {
|
|
suword(vectp++, (int)destp);
|
|
while (*stringp++ != 0)
|
|
destp++;
|
|
destp++;
|
|
}
|
|
|
|
/* a null vector table pointer seperates the argp's from the envp's */
|
|
suword(vectp++, 0);
|
|
|
|
suword(&arginfo->ps_envstr, (int)vectp);
|
|
suword(&arginfo->ps_nenvstr, envc);
|
|
|
|
/*
|
|
* Fill in environment portion of vector table.
|
|
*/
|
|
for (; envc > 0; --envc) {
|
|
suword(vectp++, (int)destp);
|
|
while (*stringp++ != 0)
|
|
destp++;
|
|
destp++;
|
|
}
|
|
|
|
/* end of vector table is a null pointer */
|
|
suword(vectp, 0);
|
|
|
|
return (stack_base);
|
|
}
|
|
|
|
/*
|
|
* Check permissions of file to execute.
|
|
* Return 0 for success or error code on failure.
|
|
*/
|
|
static int
|
|
exec_check_permissions(imgp)
|
|
struct image_params *imgp;
|
|
{
|
|
struct proc *p = imgp->proc;
|
|
struct vnode *vp = imgp->vp;
|
|
struct vattr *attr = imgp->attr;
|
|
int error;
|
|
|
|
/* Get file attributes */
|
|
error = VOP_GETATTR(vp, attr, p->p_ucred, p);
|
|
if (error)
|
|
return (error);
|
|
|
|
/*
|
|
* 1) Check if file execution is disabled for the filesystem that this
|
|
* file resides on.
|
|
* 2) Insure that at least one execute bit is on - otherwise root
|
|
* will always succeed, and we don't want to happen unless the
|
|
* file really is executable.
|
|
* 3) Insure that the file is a regular file.
|
|
*/
|
|
if ((vp->v_mount->mnt_flag & MNT_NOEXEC) ||
|
|
((attr->va_mode & 0111) == 0) ||
|
|
(attr->va_type != VREG)) {
|
|
return (EACCES);
|
|
}
|
|
|
|
/*
|
|
* Zero length files can't be exec'd
|
|
*/
|
|
if (attr->va_size == 0)
|
|
return (ENOEXEC);
|
|
|
|
/*
|
|
* Check for execute permission to file based on current credentials.
|
|
*/
|
|
error = VOP_ACCESS(vp, VEXEC, p->p_ucred, p);
|
|
if (error)
|
|
return (error);
|
|
|
|
/*
|
|
* Check number of open-for-writes on the file and deny execution
|
|
* if there are any.
|
|
*/
|
|
if (vp->v_writecount)
|
|
return (ETXTBSY);
|
|
|
|
/*
|
|
* Call filesystem specific open routine (which does nothing in the
|
|
* general case).
|
|
*/
|
|
error = VOP_OPEN(vp, FREAD, p->p_ucred, p);
|
|
if (error)
|
|
return (error);
|
|
|
|
return (0);
|
|
}
|