sys/kern/vfs_helper.c

/*
 * (The copyright below applies to ufs_access())
 *
 * Copyright (c) 1982, 1986, 1989, 1993, 1995
 *	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.
 *
 * @(#)ufs_vnops.c	8.27 (Berkeley) 5/27/95
 */

#include "opt_quota.h"
#include "opt_suiddir.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/uio.h>
#include <sys/conf.h>
#include <sys/kernel.h>
#include <sys/fcntl.h>
#include <sys/stat.h>
#include <sys/mount.h>
#include <sys/unistd.h>
#include <sys/vnode.h>
#include <sys/file.h>		/* XXX */
#include <sys/proc.h>
#include <sys/caps.h>
#include <sys/jail.h>
#include <sys/sysctl.h>
#include <sys/sfbuf.h>
#include <vm/vm_extern.h>
#include <vm/vm_object.h>
#include <vm/vm_page2.h>

#ifdef LWBUF_IS_OPTIMAL

static int vm_read_shortcut_enable = 1;
SYSCTL_INT(_vm, OID_AUTO, read_shortcut_enable, CTLFLAG_RW,
	  &vm_read_shortcut_enable, 0, "Direct vm_object vop_read shortcut");

#endif

/*
 * vop_helper_access()
 *
 *	Provide standard UNIX semanics for VOP_ACCESS, but without the quota
 *	code.  This procedure was basically pulled out of UFS.
 */
int
vop_helper_access(struct vop_access_args *ap, uid_t ino_uid, gid_t ino_gid,
		  mode_t ino_mode, u_int32_t ino_flags)
{
	struct vnode *vp = ap->a_vp;
	struct ucred *cred = ap->a_cred;
	mode_t mask, mode = ap->a_mode;
	gid_t *gp;
	int i;
	uid_t proc_uid;
	gid_t proc_gid;

	if (ap->a_flags & AT_EACCESS) {
		proc_uid = cred->cr_uid;
		proc_gid = cred->cr_gid;
	} else {
		proc_uid = cred->cr_ruid;
		proc_gid = cred->cr_rgid;
	}

	/*
	 * Disallow write attempts on read-only filesystems;
	 * unless the file is a socket, fifo, or a block or
	 * character device resident on the filesystem.
	 */
	if (mode & VWRITE) {
		switch (vp->v_type) {
		case VDIR:
		case VLNK:
		case VREG:
		case VDATABASE:
			if (vp->v_mount->mnt_flag & MNT_RDONLY)
				return (EROFS);
			break;
		default:
			break;
		}
	}

	/* If immutable bit set, nobody gets to write it. */
	if ((mode & VWRITE) && (ino_flags & IMMUTABLE))
		return (EPERM);

	/* Otherwise, user id 0 always gets access. */
	if (proc_uid == 0)
		return (0);

	mask = 0;

	/* Otherwise, check the owner. */
	if (proc_uid == ino_uid) {
		if (mode & VEXEC)
			mask |= S_IXUSR;
		if (mode & VREAD)
			mask |= S_IRUSR;
		if (mode & VWRITE)
			mask |= S_IWUSR;
		return ((ino_mode & mask) == mask ? 0 : EACCES);
	}

	/*
	 * Otherwise, check the groups.
	 * We must special-case the primary group to, if needed, check against
	 * the real gid and not the effective one.
	 */
	if (proc_gid == ino_gid) {
		if (mode & VEXEC)
			mask |= S_IXGRP;
		if (mode & VREAD)
			mask |= S_IRGRP;
		if (mode & VWRITE)
			mask |= S_IWGRP;
		return ((ino_mode & mask) == mask ? 0 : EACCES);
	}
	for (i = 1, gp = &cred->cr_groups[1]; i < cred->cr_ngroups; i++, gp++)
		if (ino_gid == *gp) {
			if (mode & VEXEC)
				mask |= S_IXGRP;
			if (mode & VREAD)
				mask |= S_IRGRP;
			if (mode & VWRITE)
				mask |= S_IWGRP;
			return ((ino_mode & mask) == mask ? 0 : EACCES);
		}

	/* Otherwise, check everyone else. */
	if (mode & VEXEC)
		mask |= S_IXOTH;
	if (mode & VREAD)
		mask |= S_IROTH;
	if (mode & VWRITE)
		mask |= S_IWOTH;
	return ((ino_mode & mask) == mask ? 0 : EACCES);
}

int
vop_helper_setattr_flags(u_int32_t *ino_flags, u_int32_t vaflags,
			 uid_t uid, struct ucred *cred)
{
	int error;

	/*
	 * If uid doesn't match only a privileged user can change the flags
	 */
	if (cred->cr_uid != uid &&
	    (error = caps_priv_check(cred, SYSCAP_NOVFS_SYSFLAGS)))
	{
		return(error);
	}
	if (cred->cr_uid == 0 &&
	    (!jailed(cred) || PRISON_CAP_ISSET(cred->cr_prison->pr_caps,
		PRISON_CAP_VFS_CHFLAGS))) {
		if ((*ino_flags & (SF_NOUNLINK|SF_IMMUTABLE|SF_APPEND)) &&
		    securelevel > 0)
			return (EPERM);
		*ino_flags = vaflags;
	} else {
		if (*ino_flags & (SF_NOUNLINK|SF_IMMUTABLE|SF_APPEND) ||
		    (vaflags & UF_SETTABLE) != vaflags)
			return (EPERM);
		*ino_flags &= SF_SETTABLE;
		*ino_flags |= vaflags & UF_SETTABLE;
	}
	return(0);
}

/*
 * This helper function may be used by VFSs to implement UNIX initial
 * ownership semantics when creating new objects inside directories.
 */
uid_t
vop_helper_create_uid(struct mount *mp, mode_t dmode, uid_t duid,
		      struct ucred *cred, mode_t *modep)
{
#ifdef SUIDDIR
	if ((mp->mnt_flag & MNT_SUIDDIR) && (dmode & S_ISUID) &&
	    duid != cred->cr_uid && duid) {
		*modep &= ~07111;
		return(duid);
	}
#endif
	return(cred->cr_uid);
}

/*
 * This helper may be used by VFSs to implement unix chmod semantics.
 */
int
vop_helper_chmod(struct vnode *vp, mode_t new_mode, struct ucred *cred,
		 uid_t cur_uid, gid_t cur_gid, mode_t *cur_modep)
{
	int error;

	if (cred->cr_uid != cur_uid) {
		error = caps_priv_check(cred, SYSCAP_NOVFS_CHMOD);
		if (error)
			return (error);
	}
	if (cred->cr_uid) {
		if (vp->v_type != VDIR && (*cur_modep & S_ISTXT))
			return (EFTYPE);
		if (!groupmember(cur_gid, cred) && (*cur_modep & S_ISGID))
			return (EPERM);
	}
	*cur_modep &= ~ALLPERMS;
	*cur_modep |= new_mode & ALLPERMS;
	return(0);
}

/*
 * This helper may be used by VFSs to implement unix chown semantics.
 */
int
vop_helper_chown(struct vnode *vp, uid_t new_uid, gid_t new_gid,
		 struct ucred *cred,
		 uid_t *cur_uidp, gid_t *cur_gidp, mode_t *cur_modep)
{
	gid_t ogid;
	uid_t ouid;
	int error;

	if (new_uid == (uid_t)VNOVAL)
		new_uid = *cur_uidp;
	if (new_gid == (gid_t)VNOVAL)
		new_gid = *cur_gidp;

	/*
	 * If we don't own the file, are trying to change the owner
	 * of the file, or are not a member of the target group,
	 * the caller must be privileged or the call fails.
	 */
	if ((cred->cr_uid != *cur_uidp || new_uid != *cur_uidp ||
	    (new_gid != *cur_gidp && !(cred->cr_gid == new_gid ||
	    groupmember(new_gid, cred)))) &&
	    (error = caps_priv_check(cred, SYSCAP_NOVFS_CHOWN)))
	{
		return (error);
	}
	ogid = *cur_gidp;
	ouid = *cur_uidp;
	/* XXX QUOTA CODE */
	*cur_uidp = new_uid;
	*cur_gidp = new_gid;
	/* XXX QUOTA CODE */

	/*
	 * DragonFly clears both SUID and SGID if either the owner or
	 * group is changed and root isn't doing it.  If root is doing
	 * it we do not clear SUID/SGID.
	 */
	if (cred->cr_uid != 0 && (ouid != new_uid || ogid != new_gid))
		*cur_modep &= ~(S_ISUID | S_ISGID);
	return(0);
}

#ifdef LWBUF_IS_OPTIMAL

/*
 * A VFS can call this function to try to dispose of a read request
 * directly from the VM system, pretty much bypassing almost all VFS
 * overhead except for atime updates.
 *
 * If 0 is returned some or all of the uio was handled.  The caller must
 * check the uio and handle the remainder.
 *
 * The caller must fail on a non-zero error.
 */
int
vop_helper_read_shortcut(struct vop_read_args *ap)
{
	struct vnode *vp;
	struct uio *uio;
	struct lwbuf *lwb;
	struct lwbuf lwb_cache;
	vm_object_t obj;
	vm_page_t m;
	int offset;
	int n;
	int error;

	vp = ap->a_vp;
	uio = ap->a_uio;

	/*
	 * We can't short-cut if there is no VM object or this is a special
	 * UIO_NOCOPY read (typically from VOP_STRATEGY()).  We also can't
	 * do this if we cannot extract the filesize from the vnode.
	 */
	if (vm_read_shortcut_enable == 0)
		return(0);
	if (vp->v_object == NULL || uio->uio_segflg == UIO_NOCOPY)
		return(0);
	if (vp->v_filesize == NOOFFSET)
		return(0);
	if (uio->uio_resid == 0)
		return(0);

	/*
	 * Iterate the uio on a page-by-page basis
	 *
	 * XXX can we leave the object held shared during the uiomove()?
	 */
	obj = vp->v_object;
	vm_object_hold_shared(obj);

	error = 0;
	while (uio->uio_resid && error == 0) {
		offset = (int)uio->uio_offset & PAGE_MASK;
		n = PAGE_SIZE - offset;
		if (n > uio->uio_resid)
			n = uio->uio_resid;
		if (vp->v_filesize < uio->uio_offset)
			break;
		if (uio->uio_offset + n > vp->v_filesize)
			n = vp->v_filesize - uio->uio_offset;
		if (n == 0)
			break;	/* hit EOF */

		m = vm_page_lookup_sbusy_try(obj, OFF_TO_IDX(uio->uio_offset),
					     0, PAGE_SIZE);
		if (error || m == NULL) {
			error = 0;
			break;
		}
		if ((m->valid & VM_PAGE_BITS_ALL) != VM_PAGE_BITS_ALL) {
			vm_page_sbusy_drop(m);
			break;
		}
		lwb = lwbuf_alloc(m, &lwb_cache);

		/*
		 * Use a no-fault uiomove() to avoid deadlocking against
		 * our VM object (which could livelock on the same object
		 * due to shared-vs-exclusive), or deadlocking against
		 * our busied page.  Returns EFAULT on any fault which
		 * winds up diving a vnode.
		 */
		error = uiomove_nofault((char *)lwbuf_kva(lwb) + offset,
					n, uio);

		vm_page_flag_set(m, PG_REFERENCED);
		lwbuf_free(lwb);
		vm_page_sbusy_drop(m);
	}
	vm_object_drop(obj);

	/*
	 * Ignore EFAULT since we used uiomove_nofault(), causes caller
	 * to fall-back to normal code for this case.
	 */
	if (error == EFAULT)
		error = 0;

	return (error);
}

#else

/*
 * If lwbuf's aren't optimal then it's best to just use the buffer
 * cache.
 */
int
vop_helper_read_shortcut(struct vop_read_args *ap)
{
	return(0);
}

#endif