Net2/usr/src/sys/kern/vfs_lookup.c
/*
* Copyright (c) 1982, 1986, 1989 Regents of the University of California.
* 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 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 7.32 (Berkeley) 5/21/91
*/
#include "param.h"
#include "syslimits.h"
#include "time.h"
#include "namei.h"
#include "vnode.h"
#include "mount.h"
#include "errno.h"
#include "malloc.h"
#include "filedesc.h"
#include "proc.h"
#ifdef KTRACE
#include "ktrace.h"
#endif
/*
* 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
* }
*/
namei(ndp, p)
register struct nameidata *ndp;
struct proc *p;
{
register struct filedesc *fdp; /* pointer to file descriptor state */
register char *cp; /* pointer into pathname argument */
register struct vnode *dp; /* the directory we are searching */
struct iovec aiov; /* uio for reading symbolic links */
struct uio auio;
int error, linklen;
ndp->ni_cred = p->p_ucred;
fdp = p->p_fd;
/*
* Get a buffer for the name to be translated, and copy the
* name into the buffer.
*/
if ((ndp->ni_nameiop & HASBUF) == 0)
MALLOC(ndp->ni_pnbuf, caddr_t, MAXPATHLEN, M_NAMEI, M_WAITOK);
if (ndp->ni_segflg == UIO_SYSSPACE)
error = copystr(ndp->ni_dirp, ndp->ni_pnbuf,
MAXPATHLEN, &ndp->ni_pathlen);
else
error = copyinstr(ndp->ni_dirp, ndp->ni_pnbuf,
MAXPATHLEN, &ndp->ni_pathlen);
if (error) {
free(ndp->ni_pnbuf, M_NAMEI);
ndp->ni_vp = NULL;
return (error);
}
ndp->ni_loopcnt = 0;
#ifdef KTRACE
if (KTRPOINT(p, KTR_NAMEI))
ktrnamei(p->p_tracep, ndp->ni_pnbuf);
#endif
/*
* Get starting point for the translation.
*/
if ((ndp->ni_rootdir = fdp->fd_rdir) == NULL)
ndp->ni_rootdir = rootdir;
dp = fdp->fd_cdir;
VREF(dp);
for (;;) {
/*
* Check if root directory should replace current directory.
* Done at start of translation and after symbolic link.
*/
ndp->ni_ptr = ndp->ni_pnbuf;
if (*ndp->ni_ptr == '/') {
vrele(dp);
while (*ndp->ni_ptr == '/') {
ndp->ni_ptr++;
ndp->ni_pathlen--;
}
dp = ndp->ni_rootdir;
VREF(dp);
}
ndp->ni_startdir = dp;
if (error = lookup(ndp, p)) {
FREE(ndp->ni_pnbuf, M_NAMEI);
return (error);
}
/*
* Check for symbolic link
*/
if (ndp->ni_more == 0) {
if ((ndp->ni_nameiop & (SAVENAME | SAVESTART)) == 0)
FREE(ndp->ni_pnbuf, M_NAMEI);
else
ndp->ni_nameiop |= HASBUF;
return (0);
}
if ((ndp->ni_nameiop & LOCKPARENT) && ndp->ni_pathlen == 1)
VOP_UNLOCK(ndp->ni_dvp);
if (ndp->ni_loopcnt++ >= MAXSYMLINKS) {
error = ELOOP;
break;
}
if (ndp->ni_pathlen > 1)
MALLOC(cp, char *, MAXPATHLEN, M_NAMEI, M_WAITOK);
else
cp = ndp->ni_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;
if (error = VOP_READLINK(ndp->ni_vp, &auio, p->p_ucred)) {
if (ndp->ni_pathlen > 1)
free(cp, M_NAMEI);
break;
}
linklen = MAXPATHLEN - auio.uio_resid;
if (linklen + ndp->ni_pathlen >= MAXPATHLEN) {
if (ndp->ni_pathlen > 1)
free(cp, M_NAMEI);
error = ENAMETOOLONG;
break;
}
if (ndp->ni_pathlen > 1) {
bcopy(ndp->ni_next, cp + linklen, ndp->ni_pathlen);
FREE(ndp->ni_pnbuf, M_NAMEI);
ndp->ni_pnbuf = cp;
} else
ndp->ni_pnbuf[linklen] = '\0';
ndp->ni_pathlen += linklen;
vput(ndp->ni_vp);
dp = ndp->ni_dvp;
}
FREE(ndp->ni_pnbuf, M_NAMEI);
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 ".".
* NOTE: (LOOKUP | LOCKPARENT) currently returns the parent vnode unlocked.
*
* 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
*/
lookup(ndp, p)
register struct nameidata *ndp;
struct proc *p;
{
register char *cp; /* pointer into pathname argument */
register 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 flag; /* LOOKUP, CREATE, RENAME or DELETE */
int wantparent; /* 1 => wantparent or lockparent flag */
int rdonly; /* mounted read-only flag bit(s) */
int error = 0;
/*
* Setup: break out flag bits into variables.
*/
flag = ndp->ni_nameiop & OPMASK;
wantparent = ndp->ni_nameiop & (LOCKPARENT|WANTPARENT);
docache = (ndp->ni_nameiop & NOCACHE) ^ NOCACHE;
if (flag == DELETE || (wantparent && flag != CREATE))
docache = 0;
rdonly = MNT_RDONLY;
if (ndp->ni_nameiop & REMOTE)
rdonly |= MNT_EXRDONLY;
ndp->ni_dvp = NULL;
ndp->ni_more = 0;
dp = ndp->ni_startdir;
ndp->ni_startdir = NULLVP;
VOP_LOCK(dp);
dirloop:
/*
* Search a new directory.
*
* The ni_hash value is for use by vfs_cache.
* The last component of the filename is left accessible via
* ndp->ptr for callers that need the name. Callers needing
* the name set the SAVENAME flag. When done, they assume
* responsibility for freeing the pathname buffer.
*/
ndp->ni_hash = 0;
for (cp = ndp->ni_ptr; *cp != 0 && *cp != '/'; cp++)
ndp->ni_hash += (unsigned char)*cp;
ndp->ni_namelen = cp - ndp->ni_ptr;
if (ndp->ni_namelen >= NAME_MAX) {
error = ENAMETOOLONG;
goto bad;
}
#ifdef NAMEI_DIAGNOSTIC
{ char c = *cp;
*cp = '\0';
printf("{%s}: ", ndp->ni_ptr);
*cp = c; }
#endif
ndp->ni_pathlen -= ndp->ni_namelen;
ndp->ni_next = cp;
ndp->ni_makeentry = 1;
if (*cp == '\0' && docache == 0)
ndp->ni_makeentry = 0;
ndp->ni_isdotdot = (ndp->ni_namelen == 2 &&
ndp->ni_ptr[1] == '.' && ndp->ni_ptr[0] == '.');
/*
* Check for degenerate name (e.g. / or "")
* which is a way of talking about a directory,
* e.g. like "/." or ".".
*/
if (ndp->ni_ptr[0] == '\0') {
if (flag != LOOKUP || wantparent) {
error = EISDIR;
goto bad;
}
if (dp->v_type != VDIR) {
error = ENOTDIR;
goto bad;
}
if (!(ndp->ni_nameiop & LOCKLEAF))
VOP_UNLOCK(dp);
ndp->ni_vp = dp;
if (ndp->ni_nameiop & SAVESTART)
panic("lookup: SAVESTART");
return (0);
}
/*
* Handle "..": two special cases.
* 1. If at root directory (e.g. after chroot)
* 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 (ndp->ni_isdotdot) {
for (;;) {
if (dp == ndp->ni_rootdir) {
ndp->ni_dvp = dp;
ndp->ni_vp = dp;
VREF(dp);
goto nextname;
}
if ((dp->v_flag & VROOT) == 0 ||
(ndp->ni_nameiop & NOCROSSMOUNT))
break;
tdp = dp;
dp = dp->v_mount->mnt_vnodecovered;
vput(tdp);
VREF(dp);
VOP_LOCK(dp);
}
}
/*
* We now have a segment name to search for, and a directory to search.
*/
if (error = VOP_LOOKUP(dp, ndp, p)) {
#ifdef DIAGNOSTIC
if (ndp->ni_vp != NULL)
panic("leaf should be empty");
#endif
#ifdef NAMEI_DIAGNOSTIC
printf("not found\n");
#endif
if (flag == LOOKUP || flag == DELETE ||
error != ENOENT || *cp != 0)
goto bad;
/*
* If creating and at end of pathname, then can consider
* allowing file to be created.
*/
if (ndp->ni_dvp->v_mount->mnt_flag & 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 (ndp->ni_nameiop & SAVESTART) {
ndp->ni_startdir = ndp->ni_dvp;
VREF(ndp->ni_startdir);
}
return (0);
}
#ifdef NAMEI_DIAGNOSTIC
printf("found\n");
#endif
dp = ndp->ni_vp;
/*
* Check for symbolic link
*/
if ((dp->v_type == VLNK) &&
((ndp->ni_nameiop & FOLLOW) || *ndp->ni_next == '/')) {
ndp->ni_more = 1;
return (0);
}
/*
* Check to see if the vnode has been mounted on;
* if so find the root of the mounted file system.
*/
mntloop:
while (dp->v_type == VDIR && (mp = dp->v_mountedhere) &&
(ndp->ni_nameiop & NOCROSSMOUNT) == 0) {
while(mp->mnt_flag & MNT_MLOCK) {
mp->mnt_flag |= MNT_MWAIT;
sleep((caddr_t)mp, PVFS);
goto mntloop;
}
if (error = VFS_ROOT(dp->v_mountedhere, &tdp))
goto bad2;
vput(dp);
ndp->ni_vp = dp = tdp;
}
nextname:
/*
* Not a symbolic link. If more pathname,
* continue at next component, else return.
*/
if (*ndp->ni_next == '/') {
ndp->ni_ptr = ndp->ni_next;
while (*ndp->ni_ptr == '/') {
ndp->ni_ptr++;
ndp->ni_pathlen--;
}
vrele(ndp->ni_dvp);
goto dirloop;
}
/*
* Check for read-only file systems.
*/
if (flag == DELETE || flag == RENAME) {
/*
* Disallow directory write attempts on read-only
* file systems.
*/
if ((dp->v_mount->mnt_flag & rdonly) ||
(wantparent && (ndp->ni_dvp->v_mount->mnt_flag & rdonly))) {
error = EROFS;
goto bad2;
}
}
if (ndp->ni_nameiop & SAVESTART) {
ndp->ni_startdir = ndp->ni_dvp;
VREF(ndp->ni_startdir);
}
if (!wantparent)
vrele(ndp->ni_dvp);
if ((ndp->ni_nameiop & LOCKLEAF) == 0)
VOP_UNLOCK(dp);
return (0);
bad2:
if ((ndp->ni_nameiop & LOCKPARENT) && *ndp->ni_next == '\0')
VOP_UNLOCK(ndp->ni_dvp);
vrele(ndp->ni_dvp);
bad:
vput(dp);
ndp->ni_vp = NULL;
return (error);
}