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NetBSD/sys/kern/vfs_lookup.c

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/* $NetBSD: vfs_lookup.c,v 1.35 2000/08/03 20:41:23 thorpej 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. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. 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_lookup.c 8.10 (Berkeley) 5/27/95
*/
#include "opt_ktrace.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/syslimits.h>
#include <sys/time.h>
#include <sys/namei.h>
#include <sys/vnode.h>
#include <sys/mount.h>
#include <sys/errno.h>
#include <sys/malloc.h>
#include <sys/filedesc.h>
#include <sys/proc.h>
#ifdef KTRACE
#include <sys/ktrace.h>
#endif
struct pool pnbuf_pool; /* pathname buffer pool */
/*
* Convert a pathname into a pointer to a locked inode.
*
* The FOLLOW flag is set when symbolic links are to be followed
* when they occur at the end of the name translation process.
* Symbolic links are always followed for all other pathname
* components other than the last.
*
* The segflg defines whether the name is to be copied from user
* space or kernel space.
*
* Overall outline of namei:
*
* copy in name
* get starting directory
* while (!done && !error) {
* call lookup to search path.
* if symbolic link, massage name in buffer and continue
* }
*/
int
namei(ndp)
struct nameidata *ndp;
{
struct cwdinfo *cwdi; /* pointer to cwd state */
char *cp; /* pointer into pathname argument */
struct vnode *dp; /* the directory we are searching */
struct iovec aiov; /* uio for reading symbolic links */
struct uio auio;
int error, linklen;
struct componentname *cnp = &ndp->ni_cnd;
ndp->ni_cnd.cn_cred = ndp->ni_cnd.cn_proc->p_ucred;
#ifdef DIAGNOSTIC
if (!cnp->cn_cred || !cnp->cn_proc)
panic ("namei: bad cred/proc");
if (cnp->cn_nameiop & (~OPMASK))
panic ("namei: nameiop contaminated with flags");
if (cnp->cn_flags & OPMASK)
panic ("namei: flags contaminated with nameiops");
#endif
cwdi = cnp->cn_proc->p_cwdi;
/*
* Get a buffer for the name to be translated, and copy the
* name into the buffer.
*/
if ((cnp->cn_flags & HASBUF) == 0)
cnp->cn_pnbuf = PNBUF_GET();
if (ndp->ni_segflg == UIO_SYSSPACE)
error = copystr(ndp->ni_dirp, cnp->cn_pnbuf,
MAXPATHLEN, &ndp->ni_pathlen);
else
error = copyinstr(ndp->ni_dirp, cnp->cn_pnbuf,
MAXPATHLEN, &ndp->ni_pathlen);
/*
* POSIX.1 requirement: "" is not a valid file name.
*/
if (!error && ndp->ni_pathlen == 1)
error = ENOENT;
if (error) {
PNBUF_PUT(cnp->cn_pnbuf);
ndp->ni_vp = NULL;
return (error);
}
ndp->ni_loopcnt = 0;
#ifdef KTRACE
if (KTRPOINT(cnp->cn_proc, KTR_NAMEI))
ktrnamei(cnp->cn_proc, cnp->cn_pnbuf);
#endif
/*
* Get starting point for the translation.
*/
if ((ndp->ni_rootdir = cwdi->cwdi_rdir) == NULL)
ndp->ni_rootdir = rootvnode;
/*
* Check if starting from root directory or current directory.
*/
if (cnp->cn_pnbuf[0] == '/') {
dp = ndp->ni_rootdir;
VREF(dp);
} else {
dp = cwdi->cwdi_cdir;
VREF(dp);
}
for (;;) {
cnp->cn_nameptr = cnp->cn_pnbuf;
ndp->ni_startdir = dp;
if ((error = lookup(ndp)) != 0) {
PNBUF_PUT(cnp->cn_pnbuf);
return (error);
}
/*
* Check for symbolic link
*/
if ((cnp->cn_flags & ISSYMLINK) == 0) {
if ((cnp->cn_flags & (SAVENAME | SAVESTART)) == 0)
PNBUF_PUT(cnp->cn_pnbuf);
else
cnp->cn_flags |= HASBUF;
return (0);
}
if ((cnp->cn_flags & LOCKPARENT) && (cnp->cn_flags & ISLASTCN))
VOP_UNLOCK(ndp->ni_dvp, 0);
if (ndp->ni_loopcnt++ >= MAXSYMLINKS) {
error = ELOOP;
break;
}
if (ndp->ni_vp->v_mount->mnt_flag & MNT_SYMPERM) {
error = VOP_ACCESS(ndp->ni_vp, VEXEC, cnp->cn_cred,
cnp->cn_proc);
if (error != 0)
break;
}
if (ndp->ni_pathlen > 1)
cp = PNBUF_GET();
else
cp = cnp->cn_pnbuf;
aiov.iov_base = cp;
aiov.iov_len = MAXPATHLEN;
auio.uio_iov = &aiov;
auio.uio_iovcnt = 1;
auio.uio_offset = 0;
auio.uio_rw = UIO_READ;
auio.uio_segflg = UIO_SYSSPACE;
auio.uio_procp = (struct proc *)0;
auio.uio_resid = MAXPATHLEN;
error = VOP_READLINK(ndp->ni_vp, &auio, cnp->cn_cred);
if (error) {
badlink:
if (ndp->ni_pathlen > 1)
PNBUF_PUT(cp);
break;
}
linklen = MAXPATHLEN - auio.uio_resid;
if (linklen == 0) {
error = ENOENT;
goto badlink;
}
if (linklen + ndp->ni_pathlen >= MAXPATHLEN) {
error = ENAMETOOLONG;
goto badlink;
}
if (ndp->ni_pathlen > 1) {
memcpy(cp + linklen, ndp->ni_next, ndp->ni_pathlen);
PNBUF_PUT(cnp->cn_pnbuf);
cnp->cn_pnbuf = cp;
} else
cnp->cn_pnbuf[linklen] = '\0';
ndp->ni_pathlen += linklen;
vput(ndp->ni_vp);
dp = ndp->ni_dvp;
/*
* Check if root directory should replace current directory.
*/
if (cnp->cn_pnbuf[0] == '/') {
vrele(dp);
dp = ndp->ni_rootdir;
VREF(dp);
}
}
PNBUF_PUT(cnp->cn_pnbuf);
vrele(ndp->ni_dvp);
vput(ndp->ni_vp);
ndp->ni_vp = NULL;
return (error);
}
/*
* Search a pathname.
* This is a very central and rather complicated routine.
*
* The pathname is pointed to by ni_ptr and is of length ni_pathlen.
* The starting directory is taken from ni_startdir. The pathname is
* descended until done, or a symbolic link is encountered. The variable
* ni_more is clear if the path is completed; it is set to one if a
* symbolic link needing interpretation is encountered.
*
* The flag argument is LOOKUP, CREATE, RENAME, or DELETE depending on
* whether the name is to be looked up, created, renamed, or deleted.
* When CREATE, RENAME, or DELETE is specified, information usable in
* creating, renaming, or deleting a directory entry may be calculated.
* If flag has LOCKPARENT or'ed into it, the parent directory is returned
* locked. If flag has WANTPARENT or'ed into it, the parent directory is
* returned unlocked. Otherwise the parent directory is not returned. If
* the target of the pathname exists and LOCKLEAF is or'ed into the flag
* the target is returned locked, otherwise it is returned unlocked.
* When creating or renaming and LOCKPARENT is specified, the target may not
* be ".". When deleting and LOCKPARENT is specified, the target may be ".".
*
* Overall outline of lookup:
*
* dirloop:
* identify next component of name at ndp->ni_ptr
* handle degenerate case where name is null string
* if .. and crossing mount points and on mounted filesys, find parent
* call VOP_LOOKUP routine for next component name
* directory vnode returned in ni_dvp, unlocked unless LOCKPARENT set
* component vnode returned in ni_vp (if it exists), locked.
* if result vnode is mounted on and crossing mount points,
* find mounted on vnode
* if more components of name, do next level at dirloop
* return the answer in ni_vp, locked if LOCKLEAF set
* if LOCKPARENT set, return locked parent in ni_dvp
* if WANTPARENT set, return unlocked parent in ni_dvp
*/
int
lookup(ndp)
struct nameidata *ndp;
{
const char *cp; /* pointer into pathname argument */
struct vnode *dp = 0; /* the directory we are searching */
struct vnode *tdp; /* saved dp */
struct mount *mp; /* mount table entry */
int docache; /* == 0 do not cache last component */
int wantparent; /* 1 => wantparent or lockparent flag */
int rdonly; /* lookup read-only flag bit */
int error = 0;
int slashes;
int dpunlocked = 0; /* dp has already been unlocked */
struct componentname *cnp = &ndp->ni_cnd;
/*
* Setup: break out flag bits into variables.
*/
wantparent = cnp->cn_flags & (LOCKPARENT | WANTPARENT);
docache = (cnp->cn_flags & NOCACHE) ^ NOCACHE;
if (cnp->cn_nameiop == DELETE ||
(wantparent && cnp->cn_nameiop != CREATE))
docache = 0;
rdonly = cnp->cn_flags & RDONLY;
ndp->ni_dvp = NULL;
cnp->cn_flags &= ~ISSYMLINK;
dp = ndp->ni_startdir;
ndp->ni_startdir = NULLVP;
vn_lock(dp, LK_EXCLUSIVE | LK_RETRY);
/*
* If we have a leading string of slashes, remove them, and just make
* sure the current node is a directory.
*/
cp = cnp->cn_nameptr;
if (*cp == '/') {
do {
cp++;
} while (*cp == '/');
ndp->ni_pathlen -= cp - cnp->cn_nameptr;
cnp->cn_nameptr = cp;
if (dp->v_type != VDIR) {
error = ENOTDIR;
goto bad;
}
/*
* If we've exhausted the path name, then just return the
* current node. If the caller requested the parent node (i.e.
* it's a CREATE, DELETE, or RENAME), and we don't have one
* (because this is the root directory), then we must fail.
*/
if (cnp->cn_nameptr[0] == '\0') {
if (ndp->ni_dvp == NULL && wantparent) {
error = EISDIR;
goto bad;
}
ndp->ni_vp = dp;
cnp->cn_flags |= ISLASTCN;
goto terminal;
}
}
dirloop:
/*
* Search a new directory.
*
* The cn_hash value is for use by vfs_cache.
* The last component of the filename is left accessible via
* cnp->cn_nameptr for callers that need the name. Callers needing
* the name set the SAVENAME flag. When done, they assume
* responsibility for freeing the pathname buffer.
*/
cnp->cn_consume = 0;
cnp->cn_hash = 0;
for (cp = cnp->cn_nameptr; *cp != '\0' && *cp != '/'; cp++)
cnp->cn_hash += (unsigned char)*cp;
cnp->cn_namelen = cp - cnp->cn_nameptr;
if (cnp->cn_namelen > NAME_MAX) {
error = ENAMETOOLONG;
goto bad;
}
#ifdef NAMEI_DIAGNOSTIC
{ char c = *cp;
*cp = '\0';
printf("{%s}: ", cnp->cn_nameptr);
*cp = c; }
#endif
ndp->ni_pathlen -= cnp->cn_namelen;
ndp->ni_next = cp;
/*
* If this component is followed by a slash, then move the pointer to
* the next component forward, and remember that this component must be
* a directory.
*/
if (*cp == '/') {
do {
cp++;
} while (*cp == '/');
slashes = cp - ndp->ni_next;
ndp->ni_pathlen -= slashes;
ndp->ni_next = cp;
cnp->cn_flags |= REQUIREDIR;
} else {
slashes = 0;
cnp->cn_flags &= ~REQUIREDIR;
}
/*
* We do special processing on the last component, whether or not it's
* a directory. Cache all intervening lookups, but not the final one.
*/
if (*cp == '\0') {
if (docache)
cnp->cn_flags |= MAKEENTRY;
else
cnp->cn_flags &= ~MAKEENTRY;
cnp->cn_flags |= ISLASTCN;
} else {
cnp->cn_flags |= MAKEENTRY;
cnp->cn_flags &= ~ISLASTCN;
}
if (cnp->cn_namelen == 2 &&
cnp->cn_nameptr[1] == '.' && cnp->cn_nameptr[0] == '.')
cnp->cn_flags |= ISDOTDOT;
else
cnp->cn_flags &= ~ISDOTDOT;
/*
* Handle "..": two special cases.
* 1. If at root directory (e.g. after chroot)
* or at absolute root directory
* then ignore it so can't get out.
* 2. If this vnode is the root of a mounted
* filesystem, then replace it with the
* vnode which was mounted on so we take the
* .. in the other file system.
*/
if (cnp->cn_flags & ISDOTDOT) {
for (;;) {
if (dp == ndp->ni_rootdir || dp == rootvnode) {
ndp->ni_dvp = dp;
ndp->ni_vp = dp;
VREF(dp);
goto nextname;
}
if ((dp->v_flag & VROOT) == 0 ||
(cnp->cn_flags & NOCROSSMOUNT))
break;
tdp = dp;
dp = dp->v_mount->mnt_vnodecovered;
vput(tdp);
VREF(dp);
vn_lock(dp, LK_EXCLUSIVE | LK_RETRY);
}
}
/*
* We now have a segment name to search for, and a directory to search.
*/
unionlookup:
ndp->ni_dvp = dp;
ndp->ni_vp = NULL;
cnp->cn_flags &= ~PDIRUNLOCK;
if ((error = VOP_LOOKUP(dp, &ndp->ni_vp, cnp)) != 0) {
#ifdef DIAGNOSTIC
if (ndp->ni_vp != NULL)
panic("leaf should be empty");
#endif
#ifdef NAMEI_DIAGNOSTIC
printf("not found\n");
#endif
if ((error == ENOENT) &&
(dp->v_flag & VROOT) &&
(dp->v_mount->mnt_flag & MNT_UNION)) {
tdp = dp;
dp = dp->v_mount->mnt_vnodecovered;
if (cnp->cn_flags & PDIRUNLOCK)
vrele(tdp);
else
vput(tdp);
VREF(dp);
vn_lock(dp, LK_EXCLUSIVE | LK_RETRY);
goto unionlookup;
}
if (error != EJUSTRETURN)
goto bad;
/*
* If this was not the last component, or there were trailing
* slashes, then the name must exist.
*/
if (cnp->cn_flags & REQUIREDIR) {
error = ENOENT;
goto bad;
}
/*
* If creating and at end of pathname, then can consider
* allowing file to be created.
*/
if (rdonly) {
error = EROFS;
goto bad;
}
/*
* We return with ni_vp NULL to indicate that the entry
* doesn't currently exist, leaving a pointer to the
* (possibly locked) directory inode in ndp->ni_dvp.
*/
if (cnp->cn_flags & SAVESTART) {
ndp->ni_startdir = ndp->ni_dvp;
VREF(ndp->ni_startdir);
}
return (0);
}
#ifdef NAMEI_DIAGNOSTIC
printf("found\n");
#endif
/*
* Take into account any additional components consumed by the
* underlying filesystem. This will include any trailing slashes after
* the last component consumed.
*/
if (cnp->cn_consume > 0) {
ndp->ni_pathlen -= cnp->cn_consume - slashes;
ndp->ni_next += cnp->cn_consume - slashes;
cnp->cn_consume = 0;
if (ndp->ni_next[0] == '\0')
cnp->cn_flags |= ISLASTCN;
}
dp = ndp->ni_vp;
/*
* Check to see if the vnode has been mounted on;
* if so find the root of the mounted file system.
*/
while (dp->v_type == VDIR && (mp = dp->v_mountedhere) &&
(cnp->cn_flags & NOCROSSMOUNT) == 0) {
if (vfs_busy(mp, 0, 0))
continue;
VOP_UNLOCK(dp, 0);
error = VFS_ROOT(mp, &tdp);
vfs_unbusy(mp);
if (error) {
dpunlocked = 1;
goto bad2;
}
vrele(dp);
ndp->ni_vp = dp = tdp;
}
/*
* Check for symbolic link. Back up over any slashes that we skipped,
* as we will need them again.
*/
if ((dp->v_type == VLNK) && (cnp->cn_flags & (FOLLOW|REQUIREDIR))) {
ndp->ni_pathlen += slashes;
ndp->ni_next -= slashes;
cnp->cn_flags |= ISSYMLINK;
return (0);
}
/*
* Check for directory, if the component was followed by a series of
* slashes.
*/
if ((dp->v_type != VDIR) && (cnp->cn_flags & REQUIREDIR)) {
error = ENOTDIR;
goto bad2;
}
nextname:
/*
* Not a symbolic link. If this was not the last component, then
* continue at the next component, else return.
*/
if (!(cnp->cn_flags & ISLASTCN)) {
cnp->cn_nameptr = ndp->ni_next;
vrele(ndp->ni_dvp);
goto dirloop;
}
terminal:
/*
* Disallow directory write attempts on read-only file systems.
*/
if (rdonly &&
(cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) {
/*
* Disallow directory write attempts on read-only
* file systems.
*/
error = EROFS;
goto bad2;
}
if (ndp->ni_dvp != NULL) {
if (cnp->cn_flags & SAVESTART) {
ndp->ni_startdir = ndp->ni_dvp;
VREF(ndp->ni_startdir);
}
if (!wantparent)
vrele(ndp->ni_dvp);
}
if ((cnp->cn_flags & LOCKLEAF) == 0)
VOP_UNLOCK(dp, 0);
return (0);
bad2:
if ((cnp->cn_flags & LOCKPARENT) && (cnp->cn_flags & ISLASTCN) &&
((cnp->cn_flags & PDIRUNLOCK) == 0))
VOP_UNLOCK(ndp->ni_dvp, 0);
vrele(ndp->ni_dvp);
bad:
if (dpunlocked)
vrele(dp);
else
vput(dp);
ndp->ni_vp = NULL;
return (error);
}
/*
* Reacquire a path name component.
*/
int
relookup(dvp, vpp, cnp)
struct vnode *dvp, **vpp;
struct componentname *cnp;
{
struct vnode *dp = 0; /* the directory we are searching */
int docache; /* == 0 do not cache last component */
int wantparent; /* 1 => wantparent or lockparent flag */
int rdonly; /* lookup read-only flag bit */
int error = 0;
#ifdef NAMEI_DIAGNOSTIC
int newhash; /* DEBUG: check name hash */
char *cp; /* DEBUG: check name ptr/len */
#endif
/*
* Setup: break out flag bits into variables.
*/
wantparent = cnp->cn_flags & (LOCKPARENT|WANTPARENT);
docache = (cnp->cn_flags & NOCACHE) ^ NOCACHE;
if (cnp->cn_nameiop == DELETE ||
(wantparent && cnp->cn_nameiop != CREATE))
docache = 0;
rdonly = cnp->cn_flags & RDONLY;
cnp->cn_flags &= ~ISSYMLINK;
dp = dvp;
vn_lock(dp, LK_EXCLUSIVE | LK_RETRY);
/* dirloop: */
/*
* Search a new directory.
*
* The cn_hash value is for use by vfs_cache.
* The last component of the filename is left accessible via
* cnp->cn_nameptr for callers that need the name. Callers needing
* the name set the SAVENAME flag. When done, they assume
* responsibility for freeing the pathname buffer.
*/
#ifdef NAMEI_DIAGNOSTIC
for (newhash = 0, cp = cnp->cn_nameptr; *cp != 0 && *cp != '/'; cp++)
newhash += (unsigned char)*cp;
if (newhash != cnp->cn_hash)
panic("relookup: bad hash");
if (cnp->cn_namelen != cp - cnp->cn_nameptr)
panic ("relookup: bad len");
if (*cp != 0)
panic("relookup: not last component");
printf("{%s}: ", cnp->cn_nameptr);
#endif
/*
* Check for degenerate name (e.g. / or "")
* which is a way of talking about a directory,
* e.g. like "/." or ".".
*/
if (cnp->cn_nameptr[0] == '\0')
panic("relookup: null name");
if (cnp->cn_flags & ISDOTDOT)
panic ("relookup: lookup on dot-dot");
/*
* We now have a segment name to search for, and a directory to search.
*/
if ((error = VOP_LOOKUP(dp, vpp, cnp)) != 0) {
#ifdef DIAGNOSTIC
if (*vpp != NULL)
panic("leaf should be empty");
#endif
if (error != EJUSTRETURN)
goto bad;
/*
* If creating and at end of pathname, then can consider
* allowing file to be created.
*/
if (rdonly) {
error = EROFS;
goto bad;
}
/* ASSERT(dvp == ndp->ni_startdir) */
if (cnp->cn_flags & SAVESTART)
VREF(dvp);
/*
* We return with ni_vp NULL to indicate that the entry
* doesn't currently exist, leaving a pointer to the
* (possibly locked) directory inode in ndp->ni_dvp.
*/
return (0);
}
dp = *vpp;
#ifdef DIAGNOSTIC
/*
* Check for symbolic link
*/
if (dp->v_type == VLNK && (cnp->cn_flags & FOLLOW))
panic ("relookup: symlink found.\n");
#endif
/*
* Check for read-only file systems.
*/
if (rdonly &&
(cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) {
error = EROFS;
goto bad2;
}
/* ASSERT(dvp == ndp->ni_startdir) */
if (cnp->cn_flags & SAVESTART)
VREF(dvp);
if (!wantparent)
vrele(dvp);
if ((cnp->cn_flags & LOCKLEAF) == 0)
VOP_UNLOCK(dp, 0);
return (0);
bad2:
if ((cnp->cn_flags & LOCKPARENT) && (cnp->cn_flags & ISLASTCN))
VOP_UNLOCK(dvp, 0);
vrele(dvp);
bad:
vput(dp);
*vpp = NULL;
return (error);
}
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