/* $OpenBSD: vfs_lookup.c,v 1.39 2009/03/09 16:56:55 blambert Exp $ */ /* $NetBSD: vfs_lookup.c,v 1.17 1996/02/09 19:00:59 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_lookup.c 8.6 (Berkeley) 11/21/94 */ #include #include #include #include #include #include #include #include #include #include #include #include #include #ifdef KTRACE #include #endif #include #include "systrace.h" /* * Convert a pathname into a pointer to a vnode. * * 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. * * If the LOCKLEAF flag is set, a locked vnode is returned. * * 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(struct nameidata *ndp) { struct filedesc *fdp; /* pointer to file descriptor 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; struct proc *p = cnp->cn_proc; 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 fdp = cnp->cn_proc->p_fd; /* * 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 = pool_get(&namei_pool, PR_WAITOK); 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); /* * Fail on null pathnames */ if (error == 0 && ndp->ni_pathlen == 1) error = ENOENT; if (error) { pool_put(&namei_pool, cnp->cn_pnbuf); ndp->ni_vp = NULL; return (error); } #ifdef KTRACE if (KTRPOINT(cnp->cn_proc, KTR_NAMEI)) ktrnamei(cnp->cn_proc, cnp->cn_pnbuf); #endif #if NSYSTRACE > 0 if (ISSET(cnp->cn_proc->p_flag, P_SYSTRACE)) systrace_namei(ndp); #endif /* * Strip trailing slashes, as requested */ if (cnp->cn_flags & STRIPSLASHES) { char *end = cnp->cn_pnbuf + ndp->ni_pathlen - 2; cp = end; while (cp >= cnp->cn_pnbuf && (*cp == '/')) cp--; /* Still some remaining characters in the buffer */ if (cp >= cnp->cn_pnbuf) { ndp->ni_pathlen -= (end - cp); *(cp + 1) = '\0'; } } ndp->ni_loopcnt = 0; /* * Get starting point for the translation. */ if ((ndp->ni_rootdir = fdp->fd_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 = fdp->fd_cdir; VREF(dp); } for (;;) { if (!dp->v_mount) { /* Give up if the directory is no longer mounted */ pool_put(&namei_pool, cnp->cn_pnbuf); return (ENOENT); } cnp->cn_nameptr = cnp->cn_pnbuf; ndp->ni_startdir = dp; if ((error = lookup(ndp)) != 0) { pool_put(&namei_pool, cnp->cn_pnbuf); return (error); } /* * If not a symbolic link, return search result. */ if ((cnp->cn_flags & ISSYMLINK) == 0) { if ((cnp->cn_flags & (SAVENAME | SAVESTART)) == 0) pool_put(&namei_pool, 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, p); if (ndp->ni_loopcnt++ >= MAXSYMLINKS) { error = ELOOP; break; } if (ndp->ni_pathlen > 1) cp = pool_get(&namei_pool, PR_WAITOK); 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 = cnp->cn_proc; auio.uio_resid = MAXPATHLEN; error = VOP_READLINK(ndp->ni_vp, &auio, cnp->cn_cred); if (error) { badlink: if (ndp->ni_pathlen > 1) pool_put(&namei_pool, 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) { bcopy(ndp->ni_next, cp + linklen, ndp->ni_pathlen); pool_put(&namei_pool, 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); } } pool_put(&namei_pool, 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_cnd.cn_nameptr 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. * If the path is completed the flag ISLASTCN is set in ni_cnd.cn_flags. * If a symbolic link need interpretation is encountered, the flag ISSYMLINK * is set in ni_cnd.cn_flags. * * 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(struct nameidata *ndp) { 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 dpunlocked = 0; /* dp has already been unlocked */ int slashes; struct componentname *cnp = &ndp->ni_cnd; struct proc *p = cnp->cn_proc; /* * 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, p); /* * 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. */ cp = NULL; cnp->cn_consume = 0; cnp->cn_hash = hash32_stre(cnp->cn_nameptr, '/', &cp, HASHINIT); 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, p); } } /* * We now have a segment name to search for, and a directory to search. */ 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 != 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 || (ndp->ni_dvp->v_mount->mnt_flag & MNT_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) { if (cnp->cn_consume >= slashes) { cnp->cn_flags &= ~REQUIREDIR; } 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, VB_READ|VB_WAIT)) continue; VOP_UNLOCK(dp, 0, p); 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: /* * Check for read-only file systems. */ if (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME) { /* * Disallow directory write attempts on read-only * file systems. */ if (rdonly || (dp->v_mount->mnt_flag & MNT_RDONLY) || (wantparent && (ndp->ni_dvp->v_mount->mnt_flag & MNT_RDONLY))) { 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, p); return (0); bad2: if ((cnp->cn_flags & LOCKPARENT) && (cnp->cn_flags & ISLASTCN) && ((cnp->cn_flags & PDIRUNLOCK) == 0)) VOP_UNLOCK(ndp->ni_dvp, 0, p); 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(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp) { struct proc *p = cnp->cn_proc; struct vnode *dp = 0; /* the directory we are searching */ int wantparent; /* 1 => wantparent or lockparent flag */ int rdonly; /* lookup read-only flag bit */ int error = 0; #ifdef NAMEI_DIAGNOSTIC u_int32_t 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); rdonly = cnp->cn_flags & RDONLY; cnp->cn_flags &= ~ISSYMLINK; dp = dvp; vn_lock(dp, LK_EXCLUSIVE | LK_RETRY, p); /* 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 cp = NULL; newhash = hash32_stre(cnp->cn_nameptr, '/', &cp, HASHINIT); 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 || (dvp->v_mount->mnt_flag & MNT_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."); #endif /* * Check for read-only file systems. */ if (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME) { /* * Disallow directory write attempts on read-only * file systems. */ if (rdonly || (dp->v_mount->mnt_flag & MNT_RDONLY) || (wantparent && (dvp->v_mount->mnt_flag & MNT_RDONLY))) { 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, p); return (0); bad2: if ((cnp->cn_flags & LOCKPARENT) && (cnp->cn_flags & ISLASTCN)) VOP_UNLOCK(dvp, 0, p); vrele(dvp); bad: vput(dp); *vpp = NULL; return (error); }