xref: /openbsd-src/sys/kern/kern_exec.c (revision 8445c53715e7030056b779e8ab40efb7820981f2)

/*	$OpenBSD: kern_exec.c,v 1.57 2001/09/19 20:50:58 mickey Exp $	*/
/*	$NetBSD: kern_exec.c,v 1.75 1996/02/09 18:59:28 christos Exp $	*/

/*-
 * Copyright (C) 1993, 1994 Christopher G. Demetriou
 * Copyright (C) 1992 Wolfgang Solfrank.
 * Copyright (C) 1992 TooLs GmbH.
 * All rights reserved.
 *
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by TooLs GmbH.
 * 4. The name of TooLs GmbH may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY TOOLS GMBH ``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 TOOLS GMBH 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.
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/filedesc.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/mount.h>
#include <sys/malloc.h>
#include <sys/namei.h>
#include <sys/vnode.h>
#include <sys/file.h>
#include <sys/acct.h>
#include <sys/exec.h>
#include <sys/ktrace.h>
#include <sys/resourcevar.h>
#include <sys/wait.h>
#include <sys/mman.h>
#include <sys/signalvar.h>
#include <sys/stat.h>
#include <sys/conf.h>
#ifdef SYSVSHM
#include <sys/shm.h>
#endif

#include <sys/syscallargs.h>

#include <vm/vm.h>
#include <uvm/uvm_extern.h>

#include <machine/cpu.h>
#include <machine/reg.h>

#include <dev/rndvar.h>

/*
 * stackgap_random specifies if the stackgap should have a random size added
 * to it. Must be a n^2. If non-zero, the stack gap will be calculated as:
 * (arc4random() * ALIGNBYTES) & (stackgap_random - 1) + STACKGAPLEN.
 */
int stackgap_random;

/*
 * check exec:
 * given an "executable" described in the exec package's namei info,
 * see what we can do with it.
 *
 * ON ENTRY:
 *	exec package with appropriate namei info
 *	proc pointer of exec'ing proc
 *	NO SELF-LOCKED VNODES
 *
 * ON EXIT:
 *	error:	nothing held, etc.  exec header still allocated.
 *	ok:	filled exec package, one locked vnode.
 *
 * EXEC SWITCH ENTRY:
 * 	Locked vnode to check, exec package, proc.
 *
 * EXEC SWITCH EXIT:
 *	ok:	return 0, filled exec package, one locked vnode.
 *	error:	destructive:
 *			everything deallocated execept exec header.
 *		non-descructive:
 *			error code, locked vnode, exec header unmodified
 */
int
check_exec(p, epp)
	struct proc *p;
	struct exec_package *epp;
{
	int error, i;
	struct vnode *vp;
	struct nameidata *ndp;
	size_t resid;

	ndp = epp->ep_ndp;
	ndp->ni_cnd.cn_nameiop = LOOKUP;
	ndp->ni_cnd.cn_flags = FOLLOW | LOCKLEAF | SAVENAME;
	/* first get the vnode */
	if ((error = namei(ndp)) != 0)
		return (error);
	epp->ep_vp = vp = ndp->ni_vp;

	/* check for regular file */
	if (vp->v_type == VDIR) {
		error = EISDIR;
		goto bad1;
	}
	if (vp->v_type != VREG) {
		error = EACCES;
		goto bad1;
	}

	/* get attributes */
	if ((error = VOP_GETATTR(vp, epp->ep_vap, p->p_ucred, p)) != 0)
		goto bad1;

	/* Check mount point */
	if (vp->v_mount->mnt_flag & MNT_NOEXEC) {
		error = EACCES;
		goto bad1;
	}

	if ((vp->v_mount->mnt_flag & MNT_NOSUID))
		epp->ep_vap->va_mode &= ~(VSUID | VSGID);

	/* check access.  for root we have to see if any exec bit on */
	if ((error = VOP_ACCESS(vp, VEXEC, p->p_ucred, p)) != 0)
		goto bad1;
	if ((epp->ep_vap->va_mode & (S_IXUSR | S_IXGRP | S_IXOTH)) == 0) {
		error = EACCES;
		goto bad1;
	}

	/* try to open it */
	if ((error = VOP_OPEN(vp, FREAD, p->p_ucred, p)) != 0)
		goto bad1;

	/* now we have the file, get the exec header */
	error = vn_rdwr(UIO_READ, vp, epp->ep_hdr, epp->ep_hdrlen, 0,
	    UIO_SYSSPACE, IO_NODELOCKED, p->p_ucred, &resid, p);
	if (error)
		goto bad2;
	epp->ep_hdrvalid = epp->ep_hdrlen - resid;

	/*
	 * set up the vmcmds for creation of the process
	 * address space
	 */
	error = ENOEXEC;
	for (i = 0; i < nexecs && error != 0; i++) {
		int newerror;

		if (execsw[i].es_check == NULL)
			continue;

		newerror = (*execsw[i].es_check)(p, epp);
		/* make sure the first "interesting" error code is saved. */
		if (!newerror || error == ENOEXEC)
			error = newerror;
		if (epp->ep_flags & EXEC_DESTR && error != 0)
			return (error);
	}
	if (!error) {
		/* check that entry point is sane */
		if (epp->ep_entry > VM_MAXUSER_ADDRESS) {
			error = ENOEXEC;
		}

		/* check limits */
		if ((epp->ep_tsize > MAXTSIZ) ||
		    (epp->ep_dsize > p->p_rlimit[RLIMIT_DATA].rlim_cur))
			error = ENOMEM;

		if (!error)
			return (0);
	}

	/*
	 * free any vmspace-creation commands,
	 * and release their references
	 */
	kill_vmcmds(&epp->ep_vmcmds);

bad2:
	/*
	 * unlock and close the vnode, free the
	 * pathname buf, and punt.
	 */
	VOP_UNLOCK(vp, 0, p);
	vn_close(vp, FREAD, p->p_ucred, p);
	FREE(ndp->ni_cnd.cn_pnbuf, M_NAMEI);
	return (error);

bad1:
	/*
	 * free the namei pathname buffer, and put the vnode
	 * (which we don't yet have open).
	 */
	FREE(ndp->ni_cnd.cn_pnbuf, M_NAMEI);
	vput(vp);
	return (error);
}

/*
 * exec system call
 */
/* ARGSUSED */
int
sys_execve(p, v, retval)
	register struct proc *p;
	void *v;
	register_t *retval;
{
	struct sys_execve_args /* {
		syscallarg(char *) path;
		syscallarg(char * *) argp;
		syscallarg(char * *) envp;
	} */ *uap = v;
	int error, i;
	struct exec_package pack;
	struct nameidata nid;
	struct vattr attr;
	struct ucred *cred = p->p_ucred;
	char *argp;
	char * const *cpp, *dp, *sp;
	long argc, envc;
	size_t len, sgap;
#ifdef MACHINE_STACK_GROWS_UP
	size_t slen;
#endif
	char *stack;
	struct ps_strings arginfo;
	struct vmspace *vm = p->p_vmspace;
	char **tmpfap;
	int szsigcode;
	extern struct emul emul_native;

	/*
	 * figure out the maximum size of an exec header, if necessary.
	 * XXX should be able to keep LKM code from modifying exec switch
	 * when we're still using it, but...
	 */
	if (exec_maxhdrsz == 0) {
		for (i = 0; i < nexecs; i++)
			if (execsw[i].es_check != NULL
			    && execsw[i].es_hdrsz > exec_maxhdrsz)
				exec_maxhdrsz = execsw[i].es_hdrsz;
	}

	/* init the namei data to point the file user's program name */
	NDINIT(&nid, LOOKUP, NOFOLLOW, UIO_USERSPACE, SCARG(uap, path), p);

	/*
	 * initialize the fields of the exec package.
	 */
	pack.ep_name = (char *)SCARG(uap, path);
	pack.ep_hdr = malloc(exec_maxhdrsz, M_EXEC, M_WAITOK);
	pack.ep_hdrlen = exec_maxhdrsz;
	pack.ep_hdrvalid = 0;
	pack.ep_ndp = &nid;
	pack.ep_emul_arg = NULL;
	VMCMDSET_INIT(&pack.ep_vmcmds);
	pack.ep_vap = &attr;
	pack.ep_emul = &emul_native;
	pack.ep_flags = 0;

	/* see if we can run it. */
	if ((error = check_exec(p, &pack)) != 0) {
		goto freehdr;
	}

	/* XXX -- THE FOLLOWING SECTION NEEDS MAJOR CLEANUP */

	/* allocate an argument buffer */
	argp = (char *) uvm_km_valloc_wait(exec_map, NCARGS);
#ifdef DIAGNOSTIC
	if (argp == (vaddr_t) 0)
		panic("execve: argp == NULL");
#endif
	dp = argp;
	argc = 0;

	/* copy the fake args list, if there's one, freeing it as we go */
	if (pack.ep_flags & EXEC_HASARGL) {
		tmpfap = pack.ep_fa;
		while (*tmpfap != NULL) {
			char *cp;

			cp = *tmpfap;
			while (*cp)
				*dp++ = *cp++;
			dp++;

			free(*tmpfap, M_EXEC);
			tmpfap++; argc++;
		}
		FREE(pack.ep_fa, M_EXEC);
		pack.ep_flags &= ~EXEC_HASARGL;
	}

	/* Now get argv & environment */
	if (!(cpp = SCARG(uap, argp))) {
		error = EINVAL;
		goto bad;
	}

	if (pack.ep_flags & EXEC_SKIPARG)
		cpp++;

	while (1) {
		len = argp + ARG_MAX - dp;
		if ((error = copyin(cpp, &sp, sizeof(sp))) != 0)
			goto bad;
		if (!sp)
			break;
		if ((error = copyinstr(sp, dp, len, &len)) != 0) {
			if (error == ENAMETOOLONG)
				error = E2BIG;
			goto bad;
		}
		dp += len;
		cpp++;
		argc++;
	}

	envc = 0;
	/* environment need not be there */
	if ((cpp = SCARG(uap, envp)) != NULL ) {
		while (1) {
			len = argp + ARG_MAX - dp;
			if ((error = copyin(cpp, &sp, sizeof(sp))) != 0)
				goto bad;
			if (!sp)
				break;
			if ((error = copyinstr(sp, dp, len, &len)) != 0) {
				if (error == ENAMETOOLONG)
					error = E2BIG;
				goto bad;
			}
			dp += len;
			cpp++;
			envc++;
		}
	}

	dp = (char *)ALIGN(dp);

	szsigcode = pack.ep_emul->e_esigcode - pack.ep_emul->e_sigcode;

	sgap = STACKGAPLEN;
	if (stackgap_random != 0)
		sgap += (arc4random() * ALIGNBYTES) & (stackgap_random - 1);
	/* Now check if args & environ fit into new stack */
	len = ((argc + envc + 2 + pack.ep_emul->e_arglen) * sizeof(char *) +
	    sizeof(long) + dp + sgap + szsigcode +
	    sizeof(struct ps_strings)) - argp;

	len = ALIGN(len);	/* make the stack "safely" aligned */

	if (len > pack.ep_ssize) { /* in effect, compare to initial limit */
		error = ENOMEM;
		goto bad;
	}

	/* adjust "active stack depth" for process VSZ */
	pack.ep_ssize = len;	/* maybe should go elsewhere, but... */

	/*
	 * Prepare vmspace for remapping. Note that uvmspace_exec can replace
	 * p_vmspace!
	 */
	uvmspace_exec(p);

	vm = p->p_vmspace;
	/* Now map address space */
	vm->vm_taddr = (char *)pack.ep_taddr;
	vm->vm_tsize = btoc(pack.ep_tsize);
	vm->vm_daddr = (char *)pack.ep_daddr;
	vm->vm_dsize = btoc(pack.ep_dsize);
	vm->vm_ssize = btoc(pack.ep_ssize);
	vm->vm_maxsaddr = (char *)pack.ep_maxsaddr;

	/* create the new process's VM space by running the vmcmds */
#ifdef DIAGNOSTIC
	if (pack.ep_vmcmds.evs_used == 0)
		panic("execve: no vmcmds");
#endif
	for (i = 0; i < pack.ep_vmcmds.evs_used && !error; i++) {
		struct exec_vmcmd *vcp;

		vcp = &pack.ep_vmcmds.evs_cmds[i];
		error = (*vcp->ev_proc)(p, vcp);
	}

	/* free the vmspace-creation commands, and release their references */
	kill_vmcmds(&pack.ep_vmcmds);

	/* if an error happened, deallocate and punt */
	if (error)
		goto exec_abort;

	/* remember information about the process */
	arginfo.ps_nargvstr = argc;
	arginfo.ps_nenvstr = envc;

#ifdef MACHINE_STACK_GROWS_UP
	stack = (char *)USRSTACK + sizeof(arginfo) + szsigcode;
	slen = len - sizeof(arginfo) - szsigcode;
#else
	stack = (char *)(USRSTACK - len);
#endif
	/* Now copy argc, args & environ to new stack */
	if (!(*pack.ep_emul->e_copyargs)(&pack, &arginfo, stack, argp))
		goto exec_abort;

	/* copy out the process's ps_strings structure */
	if (copyout(&arginfo, (char *)PS_STRINGS, sizeof(arginfo)))
		goto exec_abort;

	/* copy out the process's signal trampoline code */
#ifdef MACHINE_STACK_GROWS_UP
	if (szsigcode && copyout((char *)pack.ep_emul->e_sigcode,
	    ((char *)PS_STRINGS) + sizeof(arginfo), szsigcode))
		goto exec_abort;
#else
	if (szsigcode && copyout((char *)pack.ep_emul->e_sigcode,
	    ((char *)PS_STRINGS) - szsigcode, szsigcode))
		goto exec_abort;
#endif

	stopprofclock(p);	/* stop profiling */
	fdcloseexec(p);		/* handle close on exec */
	execsigs(p);		/* reset catched signals */

	/* set command name & other accounting info */
	len = min(nid.ni_cnd.cn_namelen, MAXCOMLEN);
	bcopy(nid.ni_cnd.cn_nameptr, p->p_comm, len);
	p->p_comm[len] = 0;
	p->p_acflag &= ~AFORK;

	/* record proc's vnode, for use by procfs and others */
	if (p->p_textvp)
		vrele(p->p_textvp);
	VREF(pack.ep_vp);
	p->p_textvp = pack.ep_vp;

	p->p_flag |= P_EXEC;
	if (p->p_flag & P_PPWAIT) {
		p->p_flag &= ~P_PPWAIT;
		wakeup((caddr_t)p->p_pptr);
	}

	/*
	 * If process does execve() while it has euid/uid or egid/gid
	 * which are mismatched, it remains P_SUGIDEXEC.
	 */
	if (p->p_ucred->cr_uid == p->p_cred->p_ruid &&
	    p->p_ucred->cr_gid == p->p_cred->p_rgid)
		p->p_flag &= ~P_SUGIDEXEC;

	/*
	 * deal with set[ug]id.
	 * MNT_NOEXEC has already been used to disable s[ug]id.
	 */
	if ((attr.va_mode & (VSUID | VSGID)) && proc_cansugid(p)) {
		int i;

		p->p_flag |= P_SUGID;
		p->p_flag |= P_SUGIDEXEC;

#ifdef KTRACE
		/*
		 * If process is being ktraced, turn off - unless
		 * root set it.
		 */
		if (p->p_tracep && !(p->p_traceflag & KTRFAC_ROOT)) {
			p->p_traceflag = 0;
			ktrsettracevnode(p, NULL);
		}
#endif
		p->p_ucred = crcopy(cred);
		if (attr.va_mode & VSUID)
			p->p_ucred->cr_uid = attr.va_uid;
		if (attr.va_mode & VSGID)
			p->p_ucred->cr_gid = attr.va_gid;

		/*
		 * For set[ug]id processes, a few caveats apply to
		 * stdin, stdout, and stderr.
		 */
		for (i = 0; i < 3; i++) {
			struct file *fp = NULL;

			if (i < p->p_fd->fd_nfiles)
				fp = p->p_fd->fd_ofiles[i];

#ifdef PROCFS
			/*
			 * Close descriptors that are writing to procfs.
			 */
			if (fp && fp->f_type == DTYPE_VNODE &&
			    ((struct vnode *)(fp->f_data))->v_tag == VT_PROCFS &&
			    (fp->f_flag & FWRITE)) {
				fdrelease(p, i);
				fp = NULL;
			}
#endif

			/*
			 * Ensure that stdin, stdout, and stderr are already
			 * allocated.  We do not want userland to accidentally
			 * allocate descriptors in this range which has implied
			 * meaning to libc.
			 *
			 * XXX - Shouldn't the exec fail if we can't allocate
			 *       resources here?
			 */
			if (fp == NULL) {
				short flags = FREAD | (i == 0 ? 0 : FWRITE);
				struct vnode *vp;
				int indx;

				if ((error = falloc(p, &fp, &indx)) != 0)
					break;
#ifdef DIAGNOSTIC
				if (indx != i)
					panic("sys_execve: falloc indx != i");
#endif
				if ((error = cdevvp(getnulldev(), &vp)) != 0) {
					ffree(fp);
					fdremove(p->p_fd, indx);
					break;
				}
				if ((error = VOP_OPEN(vp, flags, p->p_ucred, p)) != 0) {
					ffree(fp);
					fdremove(p->p_fd, indx);
					vrele(vp);
					break;
				}
				if (flags & FWRITE)
					vp->v_writecount++;
				fp->f_flag = flags;
				fp->f_type = DTYPE_VNODE;
				fp->f_ops = &vnops;
				fp->f_data = (caddr_t)vp;
			}
		}
	} else
		p->p_flag &= ~P_SUGID;
	p->p_cred->p_svuid = p->p_ucred->cr_uid;
	p->p_cred->p_svgid = p->p_ucred->cr_gid;

	if (p->p_flag & P_SUGIDEXEC) {
		int i, s = splclock();

		timeout_del(&p->p_realit_to);
		timerclear(&p->p_realtimer.it_interval);
		timerclear(&p->p_realtimer.it_value);
		for (i = 0; i < sizeof(p->p_stats->p_timer) /
		    sizeof(p->p_stats->p_timer[0]); i++) {
			timerclear(&p->p_stats->p_timer[i].it_interval);
			timerclear(&p->p_stats->p_timer[i].it_value);
		}
		splx(s);
	}

	uvm_km_free_wakeup(exec_map, (vaddr_t) argp, NCARGS);

	FREE(nid.ni_cnd.cn_pnbuf, M_NAMEI);
	VOP_CLOSE(pack.ep_vp, FREAD, cred, p);
	vput(pack.ep_vp);

	/*
	 * notify others that we exec'd
	 */
	KNOTE(&p->p_klist, NOTE_EXEC);

	/* setup new registers and do misc. setup. */
	if (pack.ep_emul->e_fixup != NULL) {
		if ((*pack.ep_emul->e_fixup)(p, &pack) != 0)
			goto free_pack_abort;
	}
#ifdef MACHINE_STACK_GROWS_UP
	(*pack.ep_emul->e_setregs)(p, &pack, (u_long)stack + slen, retval);
#else
	(*pack.ep_emul->e_setregs)(p, &pack, (u_long)stack, retval);
#endif

	if (p->p_flag & P_TRACED)
		psignal(p, SIGTRAP);

	p->p_emul = pack.ep_emul;
	free(pack.ep_hdr, M_EXEC);

#ifdef KTRACE
	if (KTRPOINT(p, KTR_EMUL))
		ktremul(p, p->p_emul->e_name);
#endif
	return (0);

bad:
	/* free the vmspace-creation commands, and release their references */
	kill_vmcmds(&pack.ep_vmcmds);
	/* kill any opened file descriptor, if necessary */
	if (pack.ep_flags & EXEC_HASFD) {
		pack.ep_flags &= ~EXEC_HASFD;
		(void) fdrelease(p, pack.ep_fd);
	}
	/* close and put the exec'd file */
	VOP_CLOSE(pack.ep_vp, FREAD, cred, p);
	vput(pack.ep_vp);
	FREE(nid.ni_cnd.cn_pnbuf, M_NAMEI);
	uvm_km_free_wakeup(exec_map, (vaddr_t) argp, NCARGS);

freehdr:
	free(pack.ep_hdr, M_EXEC);
	return (error);

exec_abort:
	/*
	 * the old process doesn't exist anymore.  exit gracefully.
	 * get rid of the (new) address space we have created, if any, get rid
	 * of our namei data and vnode, and exit noting failure
	 */
	uvm_deallocate(&vm->vm_map, VM_MIN_ADDRESS,
		VM_MAXUSER_ADDRESS - VM_MIN_ADDRESS);
	if (pack.ep_emul_arg)
		FREE(pack.ep_emul_arg, M_TEMP);
	FREE(nid.ni_cnd.cn_pnbuf, M_NAMEI);
	VOP_CLOSE(pack.ep_vp, FREAD, cred, p);
	vput(pack.ep_vp);
	uvm_km_free_wakeup(exec_map, (vaddr_t) argp, NCARGS);

free_pack_abort:
	free(pack.ep_hdr, M_EXEC);
	exit1(p, W_EXITCODE(0, SIGABRT));
	exit1(p, -1);

	/* NOTREACHED */
	return (0);
}


void *
copyargs(pack, arginfo, stack, argp)
	struct exec_package *pack;
	struct ps_strings *arginfo;
	void *stack;
	void *argp;
{
	char **cpp = stack;
	char *dp, *sp;
	size_t len;
	void *nullp = NULL;
	long argc = arginfo->ps_nargvstr;
	int envc = arginfo->ps_nenvstr;

	if (copyout(&argc, cpp++, sizeof(argc)))
		return (NULL);

	dp = (char *) (cpp + argc + envc + 2 + pack->ep_emul->e_arglen);
	sp = argp;

	/* XXX don't copy them out, remap them! */
	arginfo->ps_argvstr = cpp; /* remember location of argv for later */

	for (; --argc >= 0; sp += len, dp += len)
		if (copyout(&dp, cpp++, sizeof(dp)) ||
		    copyoutstr(sp, dp, ARG_MAX, &len))
			return (NULL);

	if (copyout(&nullp, cpp++, sizeof(nullp)))
		return (NULL);

	arginfo->ps_envstr = cpp; /* remember location of envp for later */

	for (; --envc >= 0; sp += len, dp += len)
		if (copyout(&dp, cpp++, sizeof(dp)) ||
		    copyoutstr(sp, dp, ARG_MAX, &len))
			return (NULL);

	if (copyout(&nullp, cpp++, sizeof(nullp)))
		return (NULL);

	return (cpp);
}