1 /* 2 * Copyright (c) 1982, 1986, 1989 Regents of the University of California. 3 * All rights reserved. 4 * 5 * %sccs.include.redist.c% 6 * 7 * @(#)vfs_lookup.c 7.27 (Berkeley) 03/17/91 8 */ 9 10 #include "param.h" 11 #include "time.h" 12 #include "namei.h" 13 #include "vnode.h" 14 #include "mount.h" 15 #include "errno.h" 16 #include "malloc.h" 17 #include "filedesc.h" 18 #include "user.h" 19 #include "proc.h" 20 21 #ifdef KTRACE 22 #include "ktrace.h" 23 #endif 24 25 /* 26 * Convert a pathname into a pointer to a locked inode. 27 * This is a very central and rather complicated routine. 28 * 29 * The flag argument is LOOKUP, CREATE, RENAME, or DELETE depending on 30 * whether the name is to be looked up, created, renamed, or deleted. 31 * When CREATE, RENAME, or DELETE is specified, information usable in 32 * creating, renaming, or deleting a directory entry may be calculated. 33 * If flag has LOCKPARENT or'ed into it and the target of the pathname 34 * exists, namei returns both the target and its parent directory locked. 35 * When creating or renaming and LOCKPARENT is specified, the target may not 36 * be ".". When deleting and LOCKPARENT is specified, the target may be ".". 37 * 38 * The FOLLOW flag is set when symbolic links are to be followed 39 * when they occur at the end of the name translation process. 40 * Symbolic links are always followed for all other pathname 41 * components other than the last. 42 * 43 * The segflg defines whether the name is to be copied from user 44 * space or kernel space. 45 * 46 * Overall outline of namei: 47 * 48 * copy in name 49 * get starting directory 50 * dirloop: 51 * copy next component of name to ndp->ni_dent 52 * handle degenerate case where name is null string 53 * if .. and on mounted filesys, find parent 54 * call lookup routine for next component name 55 * directory vnode returned in ni_dvp, unlocked unless LOCKPARENT set 56 * component vnode returned in ni_vp (if it exists), locked. 57 * if symbolic link, massage name in buffer and continue at dirloop 58 * if result inode is mounted on, find mounted on vnode 59 * if more components of name, do next level at dirloop 60 * return the answer in ni_vp as locked vnode; 61 * if LOCKPARENT set, return locked parent in ni_dvp 62 * 63 * NOTE: (LOOKUP | LOCKPARENT) currently returns the parent vnode unlocked. 64 */ 65 namei(ndp, p) 66 register struct nameidata *ndp; 67 struct proc *p; 68 { 69 register struct filedesc *fdp; /* pointer to file descriptor state */ 70 register char *cp; /* pointer into pathname argument */ 71 register struct vnode *dp = 0; /* the directory we are searching */ 72 register int i; /* Temp counter */ 73 struct vnode *tdp; /* saved dp */ 74 struct mount *mp; /* mount table entry */ 75 int docache; /* == 0 do not cache last component */ 76 int flag; /* LOOKUP, CREATE, RENAME or DELETE */ 77 int wantparent; /* 1 => wantparent or lockparent flag */ 78 int lockparent; /* 1 => lockparent flag */ 79 int getbuf; /* 1 => Malloc a pathname buffer */ 80 int rdonly; /* mounted read-only flag bit(s) */ 81 int error = 0; 82 83 /* 84 * Setup: break out flag bits into variables. 85 */ 86 ndp->ni_cred = p->p_ucred; 87 fdp = p->p_fd; 88 ndp->ni_dvp = NULL; 89 flag = ndp->ni_nameiop & OPMASK; 90 wantparent = ndp->ni_nameiop & (LOCKPARENT|WANTPARENT); 91 lockparent = ndp->ni_nameiop & LOCKPARENT; 92 docache = (ndp->ni_nameiop & NOCACHE) ^ NOCACHE; 93 getbuf = (ndp->ni_nameiop & HASBUF) ^ HASBUF; 94 if (flag == DELETE || (wantparent && flag != CREATE)) 95 docache = 0; 96 rdonly = MNT_RDONLY; 97 if (ndp->ni_nameiop & REMOTE) 98 rdonly |= MNT_EXRDONLY; 99 /* 100 * Get a buffer for the name to be translated, and copy the 101 * name into the buffer. 102 */ 103 if (getbuf) { 104 MALLOC(ndp->ni_pnbuf, caddr_t, MAXPATHLEN, M_NAMEI, M_WAITOK); 105 if (ndp->ni_segflg == UIO_SYSSPACE) 106 error = copystr(ndp->ni_dirp, ndp->ni_pnbuf, 107 MAXPATHLEN, &ndp->ni_pathlen); 108 else 109 error = copyinstr(ndp->ni_dirp, ndp->ni_pnbuf, 110 MAXPATHLEN, &ndp->ni_pathlen); 111 if (error) { 112 free(ndp->ni_pnbuf, M_NAMEI); 113 ndp->ni_vp = NULL; 114 return (error); 115 } 116 } 117 ndp->ni_ptr = ndp->ni_pnbuf; 118 ndp->ni_loopcnt = 0; 119 #ifdef KTRACE 120 if (KTRPOINT(p, KTR_NAMEI)) 121 ktrnamei(p->p_tracep, ndp->ni_pnbuf); 122 #endif 123 124 /* 125 * Get starting point for the translation. 126 */ 127 if (ndp->ni_nameiop & STARTDIR) 128 dp = ndp->ni_startdir; 129 else 130 dp = fdp->fd_cdir; 131 VREF(dp); 132 start: 133 /* 134 * Get starting directory. 135 * Done at start of translation and after symbolic link. 136 */ 137 if (*ndp->ni_ptr == '/') { 138 if (ndp->ni_nameiop & STARTDIR) 139 panic("namei: illegal path"); 140 vrele(dp); 141 while (*ndp->ni_ptr == '/') { 142 ndp->ni_ptr++; 143 ndp->ni_pathlen--; 144 } 145 if ((dp = fdp->fd_rdir) == NULL) 146 dp = rootdir; 147 VREF(dp); 148 } 149 VOP_LOCK(dp); 150 ndp->ni_endoff = 0; 151 152 /* 153 * We come to dirloop to search a new directory. 154 */ 155 dirloop: 156 /* 157 * Copy next component of name to ndp->ni_dent. 158 * XXX kern_exec looks at d_name 159 * ??? The ni_hash value may be useful for vfs_cache 160 * XXX There must be the last component of the filename left 161 * somewhere accessible via. ndp for NFS (and any other stateless file 162 * systems) in case they are doing a CREATE. The "Towards a..." noted 163 * that ni_ptr would be left pointing to the last component, but since 164 * the ni_pnbuf gets free'd, that is not a good idea. 165 */ 166 if (getbuf) { 167 ndp->ni_hash = 0; 168 for (cp = ndp->ni_ptr, i = 0; *cp != 0 && *cp != '/'; cp++) { 169 if (i >= MAXNAMLEN) { 170 error = ENAMETOOLONG; 171 goto bad; 172 } 173 if (*cp & 0200) 174 if ((*cp&0377) == ('/'|0200) || 175 flag != DELETE) { 176 error = EINVAL; 177 goto bad; 178 } 179 ndp->ni_dent.d_name[i++] = *cp; 180 ndp->ni_hash += (unsigned char)*cp * i; 181 } 182 ndp->ni_namelen = i; 183 ndp->ni_dent.d_namlen = i; 184 ndp->ni_dent.d_name[i] = '\0'; 185 ndp->ni_pathlen -= i; 186 ndp->ni_next = cp; 187 #ifdef NAMEI_DIAGNOSTIC 188 printf("{%s}: ", ndp->ni_dent.d_name); 189 #endif 190 } 191 cp = ndp->ni_next; 192 ndp->ni_makeentry = 1; 193 if (*cp == '\0' && docache == 0) 194 ndp->ni_makeentry = 0; 195 ndp->ni_isdotdot = (ndp->ni_namelen == 2 && 196 ndp->ni_dent.d_name[1] == '.' && ndp->ni_dent.d_name[0] == '.'); 197 198 /* 199 * Check for degenerate name (e.g. / or "") 200 * which is a way of talking about a directory, 201 * e.g. like "/." or ".". 202 */ 203 if (ndp->ni_ptr[0] == '\0') { 204 if (flag != LOOKUP || wantparent) { 205 error = EISDIR; 206 goto bad; 207 } 208 if (getbuf) 209 free(ndp->ni_pnbuf, M_NAMEI); 210 if (!(ndp->ni_nameiop & LOCKLEAF)) 211 VOP_UNLOCK(dp); 212 ndp->ni_vp = dp; 213 return (0); 214 } 215 216 /* 217 * Handle "..": two special cases. 218 * 1. If at root directory (e.g. after chroot) 219 * then ignore it so can't get out. 220 * 2. If this vnode is the root of a mounted 221 * file system, then replace it with the 222 * vnode which was mounted on so we take the 223 * .. in the other file system. 224 */ 225 if (ndp->ni_isdotdot) { 226 for (;;) { 227 if (dp == fdp->fd_rdir || dp == rootdir) { 228 ndp->ni_dvp = dp; 229 ndp->ni_vp = dp; 230 VREF(dp); 231 goto nextname; 232 } 233 if ((dp->v_flag & VROOT) == 0 || 234 (ndp->ni_nameiop & NOCROSSMOUNT)) 235 break; 236 tdp = dp; 237 dp = dp->v_mount->mnt_vnodecovered; 238 vput(tdp); 239 VREF(dp); 240 VOP_LOCK(dp); 241 } 242 } 243 244 /* 245 * We now have a segment name to search for, and a directory to search. 246 */ 247 if (error = VOP_LOOKUP(dp, ndp)) { 248 if (ndp->ni_vp != NULL) 249 panic("leaf should be empty"); 250 #ifdef NAMEI_DIAGNOSTIC 251 printf("not found\n"); 252 #endif 253 if (flag == LOOKUP || flag == DELETE || 254 error != ENOENT || *cp != 0) 255 goto bad; 256 /* 257 * If creating and at end of pathname, then can consider 258 * allowing file to be created. 259 */ 260 if (ndp->ni_dvp->v_mount->mnt_flag & rdonly) { 261 error = EROFS; 262 goto bad; 263 } 264 /* 265 * We return with ni_vp NULL to indicate that the entry 266 * doesn't currently exist, leaving a pointer to the 267 * (possibly locked) directory inode in ndp->ni_dvp. 268 */ 269 if (getbuf) 270 FREE(ndp->ni_pnbuf, M_NAMEI); 271 return (0); /* should this be ENOENT? */ 272 } 273 #ifdef NAMEI_DIAGNOSTIC 274 printf("found\n"); 275 #endif 276 277 /* 278 * Check for symbolic link 279 */ 280 dp = ndp->ni_vp; 281 if ((dp->v_type == VLNK) && 282 ((ndp->ni_nameiop & FOLLOW) || *ndp->ni_next == '/')) { 283 struct iovec aiov; 284 struct uio auio; 285 int linklen; 286 287 if (!getbuf) 288 panic("namei: unexpected symlink"); 289 if (++ndp->ni_loopcnt > MAXSYMLINKS) { 290 error = ELOOP; 291 goto bad2; 292 } 293 if (ndp->ni_pathlen > 1) 294 MALLOC(cp, char *, MAXPATHLEN, M_NAMEI, M_WAITOK); 295 else 296 cp = ndp->ni_pnbuf; 297 aiov.iov_base = cp; 298 aiov.iov_len = MAXPATHLEN; 299 auio.uio_iov = &aiov; 300 auio.uio_iovcnt = 1; 301 auio.uio_offset = 0; 302 auio.uio_rw = UIO_READ; 303 auio.uio_segflg = UIO_SYSSPACE; 304 auio.uio_resid = MAXPATHLEN; 305 if (error = VOP_READLINK(dp, &auio, p->p_ucred)) { 306 if (ndp->ni_pathlen > 1) 307 free(cp, M_NAMEI); 308 goto bad2; 309 } 310 linklen = MAXPATHLEN - auio.uio_resid; 311 if (linklen + ndp->ni_pathlen >= MAXPATHLEN) { 312 if (ndp->ni_pathlen > 1) 313 free(cp, M_NAMEI); 314 error = ENAMETOOLONG; 315 goto bad2; 316 } 317 if (ndp->ni_pathlen > 1) { 318 bcopy(ndp->ni_next, cp + linklen, ndp->ni_pathlen); 319 FREE(ndp->ni_pnbuf, M_NAMEI); 320 ndp->ni_pnbuf = cp; 321 } else 322 ndp->ni_pnbuf[linklen] = '\0'; 323 ndp->ni_ptr = cp; 324 vput(dp); 325 dp = ndp->ni_dvp; 326 if (lockparent && ndp->ni_pathlen == 1) 327 VOP_UNLOCK(dp); 328 ndp->ni_pathlen += linklen; 329 goto start; 330 } 331 332 /* 333 * Check to see if the vnode has been mounted on; 334 * if so find the root of the mounted file system. 335 */ 336 mntloop: 337 while (dp->v_type == VDIR && (mp = dp->v_mountedhere) && 338 (ndp->ni_nameiop & NOCROSSMOUNT) == 0) { 339 while(mp->mnt_flag & MNT_MLOCK) { 340 mp->mnt_flag |= MNT_MWAIT; 341 sleep((caddr_t)mp, PVFS); 342 goto mntloop; 343 } 344 error = VFS_ROOT(dp->v_mountedhere, &tdp); 345 if (error) 346 goto bad2; 347 vput(dp); 348 ndp->ni_vp = dp = tdp; 349 } 350 351 nextname: 352 /* 353 * Not a symbolic link. If more pathname, 354 * continue at next component, else return. 355 */ 356 ndp->ni_ptr = ndp->ni_next; 357 if (*ndp->ni_ptr == '/') { 358 while (*ndp->ni_ptr == '/') { 359 ndp->ni_ptr++; 360 ndp->ni_pathlen--; 361 } 362 vrele(ndp->ni_dvp); 363 goto dirloop; 364 } 365 /* 366 * Check for read-only file systems. 367 */ 368 if (flag == DELETE || flag == RENAME) { 369 /* 370 * Disallow directory write attempts on read-only 371 * file systems. 372 */ 373 if ((dp->v_mount->mnt_flag & rdonly) || 374 (wantparent && (ndp->ni_dvp->v_mount->mnt_flag & rdonly))) { 375 error = EROFS; 376 goto bad2; 377 } 378 } 379 if (!wantparent) 380 vrele(ndp->ni_dvp); 381 if ((ndp->ni_nameiop & LOCKLEAF) == 0) 382 VOP_UNLOCK(dp); 383 if (getbuf) 384 FREE(ndp->ni_pnbuf, M_NAMEI); 385 return (0); 386 387 bad2: 388 if (lockparent && *ndp->ni_next == '\0') 389 VOP_UNLOCK(ndp->ni_dvp); 390 vrele(ndp->ni_dvp); 391 bad: 392 vput(dp); 393 ndp->ni_vp = NULL; 394 if (getbuf) 395 FREE(ndp->ni_pnbuf, M_NAMEI); 396 return (error); 397 } 398