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Allow unveiled programs to dump core (in the default, classic, into . way)
by passing BYPASSUNVEIL just for this vnode.  The coredump() code is quite
careful, so this will be fine.
ok kn kettenis semarie

/*	$OpenBSD: vfs_vnops.c,v 1.122 2023/07/10 22:54:40 deraadt Exp $	*/
/*	$NetBSD: vfs_vnops.c,v 1.20 1996/02/04 02:18:41 christos Exp $	*/

/*
 * Copyright (c) 1982, 1986, 1989, 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.
 *
 *	@(#)vfs_vnops.c	8.5 (Berkeley) 12/8/94
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/malloc.h>
#include <sys/fcntl.h>
#include <sys/file.h>
#include <sys/stat.h>
#include <sys/proc.h>
#include <sys/resourcevar.h>
#include <sys/signalvar.h>
#include <sys/mount.h>
#include <sys/namei.h>
#include <sys/lock.h>
#include <sys/vnode.h>
#include <sys/ioctl.h>
#include <sys/tty.h>
#include <sys/specdev.h>
#include <sys/unistd.h>

int vn_read(struct file *, struct uio *, int);
int vn_write(struct file *, struct uio *, int);
int vn_kqfilter(struct file *, struct knote *);
int vn_closefile(struct file *, struct proc *);
int vn_seek(struct file *, off_t *, int, struct proc *);

const struct fileops vnops = {
	.fo_read	= vn_read,
	.fo_write	= vn_write,
	.fo_ioctl	= vn_ioctl,
	.fo_kqfilter	= vn_kqfilter,
	.fo_stat	= vn_statfile,
	.fo_close	= vn_closefile,
	.fo_seek	= vn_seek,
};

/*
 * Common code for vnode open operations.
 * Check permissions, and call the VOP_OPEN or VOP_CREATE routine.
 */
int
vn_open(struct nameidata *ndp, int fmode, int cmode)
{
	struct vnode *vp;
	struct proc *p = ndp->ni_cnd.cn_proc;
	struct ucred *cred = p->p_ucred;
	struct vattr va;
	struct cloneinfo *cip;
	int error;

	/*
	 * The only valid flags to pass in here from NDINIT are
	 * KERNELPATH or BYPASSUNVEIL. This function will override the
	 * nameiop based on the fmode and cmode flags, so validate that
	 * our caller has not set other flags or operations in the nameidata
	 * structure.
	 */
	KASSERT((ndp->ni_cnd.cn_flags & ~(KERNELPATH|BYPASSUNVEIL)) == 0);
	KASSERT(ndp->ni_cnd.cn_nameiop == 0);

        if ((fmode & (FREAD|FWRITE)) == 0)
		return (EINVAL);
	if ((fmode & (O_TRUNC | FWRITE)) == O_TRUNC)
		return (EINVAL);
	if (fmode & O_CREAT) {
		ndp->ni_cnd.cn_nameiop = CREATE;
		ndp->ni_cnd.cn_flags |= LOCKPARENT | LOCKLEAF;
		if ((fmode & O_EXCL) == 0 && (fmode & O_NOFOLLOW) == 0)
			ndp->ni_cnd.cn_flags |= FOLLOW;
		if ((error = namei(ndp)) != 0)
			return (error);

		if (ndp->ni_vp == NULL) {
			VATTR_NULL(&va);
			va.va_type = VREG;
			va.va_mode = cmode;
			if (fmode & O_EXCL)
				va.va_vaflags |= VA_EXCLUSIVE;
			error = VOP_CREATE(ndp->ni_dvp, &ndp->ni_vp,
					   &ndp->ni_cnd, &va);
			vput(ndp->ni_dvp);
			if (error)
				return (error);
			fmode &= ~O_TRUNC;
			vp = ndp->ni_vp;
		} else {
			VOP_ABORTOP(ndp->ni_dvp, &ndp->ni_cnd);
			if (ndp->ni_dvp == ndp->ni_vp)
				vrele(ndp->ni_dvp);
			else
				vput(ndp->ni_dvp);
			ndp->ni_dvp = NULL;
			vp = ndp->ni_vp;
			if (fmode & O_EXCL) {
				error = EEXIST;
				goto bad;
			}
			fmode &= ~O_CREAT;
		}
	} else {
		ndp->ni_cnd.cn_nameiop = LOOKUP;
		ndp->ni_cnd.cn_flags |= ((fmode & O_NOFOLLOW) ? NOFOLLOW : FOLLOW) | LOCKLEAF;
		if ((error = namei(ndp)) != 0)
			return (error);
		vp = ndp->ni_vp;
	}
	if (vp->v_type == VSOCK) {
		error = EOPNOTSUPP;
		goto bad;
	}
	if (vp->v_type == VLNK) {
		error = ELOOP;
		goto bad;
	}
	if ((fmode & O_DIRECTORY) && vp->v_type != VDIR) {
		error = ENOTDIR;
		goto bad;
	}
	if ((fmode & O_CREAT) == 0) {
		if (fmode & FREAD) {
			if ((error = VOP_ACCESS(vp, VREAD, cred, p)) != 0)
				goto bad;
		}
		if (fmode & FWRITE) {
			if (vp->v_type == VDIR) {
				error = EISDIR;
				goto bad;
			}
			if ((error = vn_writechk(vp)) != 0 ||
			    (error = VOP_ACCESS(vp, VWRITE, cred, p)) != 0)
				goto bad;
		}
	}
	if ((fmode & O_TRUNC) && vp->v_type == VREG) {
		VATTR_NULL(&va);
		va.va_size = 0;
		if ((error = VOP_SETATTR(vp, &va, cred, p)) != 0)
			goto bad;
	}
	if ((error = VOP_OPEN(vp, fmode, cred, p)) != 0)
		goto bad;

	if (vp->v_flag & VCLONED) {
		cip = (struct cloneinfo *)vp->v_data;

		vp->v_flag &= ~VCLONED;

		ndp->ni_vp = cip->ci_vp;	/* return cloned vnode */
		vp->v_data = cip->ci_data;	/* restore v_data */
		VOP_UNLOCK(vp);			/* keep a reference */
		vp = ndp->ni_vp;		/* for the increment below */

		free(cip, M_TEMP, sizeof(*cip));
	}

	if (fmode & FWRITE)
		vp->v_writecount++;
	return (0);
bad:
	vput(vp);
	return (error);
}

/*
 * Check for write permissions on the specified vnode.
 * Prototype text segments cannot be written.
 */
int
vn_writechk(struct vnode *vp)
{
	/*
	 * Disallow write attempts on read-only file systems;
	 * unless the file is a socket or a block or character
	 * device resident on the file system.
	 */
	if (vp->v_mount && (vp->v_mount->mnt_flag & MNT_RDONLY)) {
		switch (vp->v_type) {
		case VREG:
		case VDIR:
		case VLNK:
			return (EROFS);
		case VNON:
		case VCHR:
		case VSOCK:
		case VFIFO:
		case VBAD:
		case VBLK:
			break;
		}
	}
	/*
	 * If there's shared text associated with
	 * the vnode, try to free it up once.  If
	 * we fail, we can't allow writing.
	 */
	if ((vp->v_flag & VTEXT) && !uvm_vnp_uncache(vp))
		return (ETXTBSY);

	return (0);
}

/*
 * Check whether a write operation would exceed the file size rlimit
 * for the process, if one should be applied for this operation.
 * If a partial write should take place, the uio is adjusted and the
 * amount by which the request would have exceeded the limit is returned
 * via the 'overrun' argument.
 */
int
vn_fsizechk(struct vnode *vp, struct uio *uio, int ioflag, ssize_t *overrun)
{
	struct proc *p = uio->uio_procp;

	*overrun = 0;
	if (vp->v_type == VREG && p != NULL && !(ioflag & IO_NOLIMIT)) {
		rlim_t limit = lim_cur_proc(p, RLIMIT_FSIZE);

		/* if already at or over the limit, send the signal and fail */
		if (uio->uio_offset >= limit) {
			psignal(p, SIGXFSZ);
			return (EFBIG);
		}

		/* otherwise, clamp the write to stay under the limit */
		if (uio->uio_resid > limit - uio->uio_offset) {
			*overrun = uio->uio_resid - (limit - uio->uio_offset);
			uio->uio_resid = limit - uio->uio_offset;
		}
	}

	return (0);
}


/*
 * Mark a vnode as being the text image of a running process.
 */
void
vn_marktext(struct vnode *vp)
{
	vp->v_flag |= VTEXT;
}

/*
 * Vnode close call
 */
int
vn_close(struct vnode *vp, int flags, struct ucred *cred, struct proc *p)
{
	int error;

	if (flags & FWRITE)
		vp->v_writecount--;
	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
	error = VOP_CLOSE(vp, flags, cred, p);
	vput(vp);
	return (error);
}

/*
 * Package up an I/O request on a vnode into a uio and do it.
 */
int
vn_rdwr(enum uio_rw rw, struct vnode *vp, caddr_t base, int len, off_t offset,
    enum uio_seg segflg, int ioflg, struct ucred *cred, size_t *aresid,
    struct proc *p)
{
	struct uio auio;
	struct iovec aiov;
	int error;

	auio.uio_iov = &aiov;
	auio.uio_iovcnt = 1;
	aiov.iov_base = base;
	aiov.iov_len = len;
	auio.uio_resid = len;
	auio.uio_offset = offset;
	auio.uio_segflg = segflg;
	auio.uio_rw = rw;
	auio.uio_procp = p;

	if ((ioflg & IO_NODELOCKED) == 0)
		vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
	if (rw == UIO_READ) {
		error = VOP_READ(vp, &auio, ioflg, cred);
	} else {
		error = VOP_WRITE(vp, &auio, ioflg, cred);
	}
	if ((ioflg & IO_NODELOCKED) == 0)
		VOP_UNLOCK(vp);

	if (aresid)
		*aresid = auio.uio_resid;
	else
		if (auio.uio_resid && error == 0)
			error = EIO;
	return (error);
}

/*
 * File table vnode read routine.
 */
int
vn_read(struct file *fp, struct uio *uio, int fflags)
{
	struct vnode *vp = fp->f_data;
	struct ucred *cred = fp->f_cred;
	size_t count = uio->uio_resid;
	off_t offset;
	int error;

	KERNEL_LOCK();

	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);

	if ((fflags & FO_POSITION) == 0)
		offset = uio->uio_offset = fp->f_offset;
	else
		offset = uio->uio_offset;

	/* no wrap around of offsets except on character devices */
	if (vp->v_type != VCHR && count > LLONG_MAX - offset) {
		error = EINVAL;
		goto done;
	}

	if (vp->v_type == VDIR) {
		error = EISDIR;
		goto done;
	}

	error = VOP_READ(vp, uio, (fp->f_flag & FNONBLOCK) ? IO_NDELAY : 0,
	    cred);
	if ((fflags & FO_POSITION) == 0) {
		mtx_enter(&fp->f_mtx);
		fp->f_offset += count - uio->uio_resid;
		mtx_leave(&fp->f_mtx);
	}
done:
	VOP_UNLOCK(vp);
	KERNEL_UNLOCK();
	return (error);
}

/*
 * File table vnode write routine.
 */
int
vn_write(struct file *fp, struct uio *uio, int fflags)
{
	struct vnode *vp = fp->f_data;
	struct ucred *cred = fp->f_cred;
	int error, ioflag = IO_UNIT;
	size_t count;

	KERNEL_LOCK();

	/* note: pwrite/pwritev are unaffected by O_APPEND */
	if (vp->v_type == VREG && (fp->f_flag & O_APPEND) &&
	    (fflags & FO_POSITION) == 0)
		ioflag |= IO_APPEND;
	if (fp->f_flag & FNONBLOCK)
		ioflag |= IO_NDELAY;
	if ((fp->f_flag & FFSYNC) ||
	    (vp->v_mount && (vp->v_mount->mnt_flag & MNT_SYNCHRONOUS)))
		ioflag |= IO_SYNC;
	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
	if ((fflags & FO_POSITION) == 0)
		uio->uio_offset = fp->f_offset;
	count = uio->uio_resid;
	error = VOP_WRITE(vp, uio, ioflag, cred);
	if ((fflags & FO_POSITION) == 0) {
		mtx_enter(&fp->f_mtx);
		if (ioflag & IO_APPEND)
			fp->f_offset = uio->uio_offset;
		else
			fp->f_offset += count - uio->uio_resid;
		mtx_leave(&fp->f_mtx);
	}
	VOP_UNLOCK(vp);

	KERNEL_UNLOCK();
	return (error);
}

/*
 * File table wrapper for vn_stat
 */
int
vn_statfile(struct file *fp, struct stat *sb, struct proc *p)
{
	struct vnode *vp = fp->f_data;
	return vn_stat(vp, sb, p);
}

/*
 * vnode stat routine.
 */
int
vn_stat(struct vnode *vp, struct stat *sb, struct proc *p)
{
	struct vattr va;
	int error;
	mode_t mode;

	error = VOP_GETATTR(vp, &va, p->p_ucred, p);
	if (error)
		return (error);
	/*
	 * Copy from vattr table
	 */
	memset(sb, 0, sizeof(*sb));
	sb->st_dev = va.va_fsid;
	sb->st_ino = va.va_fileid;
	mode = va.va_mode;
	switch (vp->v_type) {
	case VREG:
		mode |= S_IFREG;
		break;
	case VDIR:
		mode |= S_IFDIR;
		break;
	case VBLK:
		mode |= S_IFBLK;
		break;
	case VCHR:
		mode |= S_IFCHR;
		break;
	case VLNK:
		mode |= S_IFLNK;
		break;
	case VSOCK:
		mode |= S_IFSOCK;
		break;
	case VFIFO:
		mode |= S_IFIFO;
		break;
	default:
		return (EBADF);
	}
	sb->st_mode = mode;
	sb->st_nlink = va.va_nlink;
	sb->st_uid = va.va_uid;
	sb->st_gid = va.va_gid;
	sb->st_rdev = va.va_rdev;
	sb->st_size = va.va_size;
	sb->st_atim.tv_sec  = va.va_atime.tv_sec;
	sb->st_atim.tv_nsec = va.va_atime.tv_nsec;
	sb->st_mtim.tv_sec  = va.va_mtime.tv_sec;
	sb->st_mtim.tv_nsec = va.va_mtime.tv_nsec;
	sb->st_ctim.tv_sec  = va.va_ctime.tv_sec;
	sb->st_ctim.tv_nsec = va.va_ctime.tv_nsec;
	sb->st_blksize = va.va_blocksize;
	sb->st_flags = va.va_flags;
	sb->st_gen = va.va_gen;
	sb->st_blocks = va.va_bytes / S_BLKSIZE;
	return (0);
}

/*
 * File table vnode ioctl routine.
 */
int
vn_ioctl(struct file *fp, u_long com, caddr_t data, struct proc *p)
{
	struct vnode *vp = fp->f_data;
	struct vattr vattr;
	int error = ENOTTY;

	KERNEL_LOCK();
	switch (vp->v_type) {

	case VREG:
	case VDIR:
		if (com == FIONREAD) {
			error = VOP_GETATTR(vp, &vattr, p->p_ucred, p);
			if (error)
				break;
			*(int *)data = vattr.va_size - foffset(fp);

		} else if (com == FIONBIO || com == FIOASYNC)	/* XXX */
			error = 0;				/* XXX */
		break;

	case VFIFO:
	case VCHR:
	case VBLK:
		error = VOP_IOCTL(vp, com, data, fp->f_flag, p->p_ucred, p);
		if (error == 0 && com == TIOCSCTTY) {
			struct session *s = p->p_p->ps_session;
			struct vnode *ovp = s->s_ttyvp;
			s->s_ttyvp = vp;
			vref(vp);
			if (ovp)
				vrele(ovp);
		}
		break;

	default:
		break;
	}
	KERNEL_UNLOCK();

	return (error);
}

/*
 * Check that the vnode is still valid, and if so
 * acquire requested lock.
 */
int
vn_lock(struct vnode *vp, int flags)
{
	int error, xlocked, do_wakeup;

	do {
		mtx_enter(&vnode_mtx);
		if (vp->v_lflag & VXLOCK) {
			vp->v_lflag |= VXWANT;
			msleep_nsec(vp, &vnode_mtx, PINOD, "vn_lock", INFSLP);
			mtx_leave(&vnode_mtx);
			error = ENOENT;
		} else {
			vp->v_lockcount++;
			mtx_leave(&vnode_mtx);

			error = VOP_LOCK(vp, flags);

			mtx_enter(&vnode_mtx);
			vp->v_lockcount--;
			do_wakeup = (vp->v_lockcount == 0);
			xlocked = vp->v_lflag & VXLOCK;
			mtx_leave(&vnode_mtx);

			if (error == 0) {
				if (!xlocked)
					return (0);

				/*
				 * The vnode was exclusively locked while
				 * acquiring the requested lock. Release it and
				 * try again.
				 */
				error = ENOENT;
				VOP_UNLOCK(vp);
				if (do_wakeup)
					wakeup_one(&vp->v_lockcount);
			}
		}
	} while (flags & LK_RETRY);
	return (error);
}

/*
 * File table vnode close routine.
 */
int
vn_closefile(struct file *fp, struct proc *p)
{
	struct vnode *vp = fp->f_data;
	struct flock lf;
	int error;

	KERNEL_LOCK();
	if ((fp->f_iflags & FIF_HASLOCK)) {
		lf.l_whence = SEEK_SET;
		lf.l_start = 0;
		lf.l_len = 0;
		lf.l_type = F_UNLCK;
		(void) VOP_ADVLOCK(vp, (caddr_t)fp, F_UNLCK, &lf, F_FLOCK);
	}
	error = vn_close(vp, fp->f_flag, fp->f_cred, p);
	KERNEL_UNLOCK();
	return (error);
}

int
vn_kqfilter(struct file *fp, struct knote *kn)
{
	int error;

	KERNEL_LOCK();
	error = VOP_KQFILTER(fp->f_data, fp->f_flag, kn);
	KERNEL_UNLOCK();
	return (error);
}

int
vn_seek(struct file *fp, off_t *offset, int whence, struct proc *p)
{
	struct ucred *cred = p->p_ucred;
	struct vnode *vp = fp->f_data;
	struct vattr vattr;
	off_t newoff;
	int error = 0;
	int special;

	if (vp->v_type == VFIFO)
		return (ESPIPE);

	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);

	if (vp->v_type == VCHR)
		special = 1;
	else
		special = 0;

	switch (whence) {
	case SEEK_CUR:
		newoff = fp->f_offset + *offset;
		break;
	case SEEK_END:
		KERNEL_LOCK();
		error = VOP_GETATTR(vp, &vattr, cred, p);
		KERNEL_UNLOCK();
		if (error)
			goto out;
		newoff = *offset + (off_t)vattr.va_size;
		break;
	case SEEK_SET:
		newoff = *offset;
		break;
	default:
		error = EINVAL;
		goto out;
	}
	if (!special && newoff < 0) {
		error = EINVAL;
		goto out;
	}
	mtx_enter(&fp->f_mtx);
	fp->f_offset = newoff;
	mtx_leave(&fp->f_mtx);
	*offset = newoff;

out:
	VOP_UNLOCK(vp);
	return (error);
}

/*
 * Common code for vnode access operations.
 */

/* Check if a directory can be found inside another in the hierarchy */
int
vn_isunder(struct vnode *lvp, struct vnode *rvp, struct proc *p)
{
	int error;

	error = vfs_getcwd_common(lvp, rvp, NULL, NULL, MAXPATHLEN/2, 0, p);

	if (!error)
		return (1);

	return (0);
}