Disallow writes to filesystems mounted read-only via NULLFS. In this case
[dragonfly.git] / sys / kern / vfs_nlookup.c
CommitLineData
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1/*
2 * Copyright (c) 2004 The DragonFly Project. All rights reserved.
3 *
4 * This code is derived from software contributed to The DragonFly Project
5 * by Matthew Dillon <dillon@backplane.com>
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 *
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in
15 * the documentation and/or other materials provided with the
16 * distribution.
17 * 3. Neither the name of The DragonFly Project nor the names of its
18 * contributors may be used to endorse or promote products derived
19 * from this software without specific, prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
22 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
23 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
24 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
25 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
26 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
27 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
28 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
29 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
30 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
31 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 *
a11aaa81 34 * $DragonFly: src/sys/kern/vfs_nlookup.c,v 1.18 2006/08/12 00:26:20 dillon Exp $
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35 */
36/*
37 * nlookup() is the 'new' namei interface. Rather then return directory and
38 * leaf vnodes (in various lock states) the new interface instead deals in
39 * namecache records. Namecache records may represent both a positive or
40 * a negative hit. The namespace is locked via the namecache record instead
41 * of via the vnode, and only the leaf namecache record (representing the
42 * filename) needs to be locked.
43 *
44 * This greatly improves filesystem parallelism and is a huge simplification
45 * of the API verses the old vnode locking / namei scheme.
46 *
47 * Filesystems must actively control the caching aspects of the namecache,
48 * and since namecache pointers are used as handles they are non-optional
49 * even for filesystems which do not generally wish to cache things. It is
50 * intended that a separate cache coherency API will be constructed to handle
51 * these issues.
52 */
53
54#include "opt_ktrace.h"
55
56#include <sys/param.h>
57#include <sys/systm.h>
58#include <sys/kernel.h>
59#include <sys/vnode.h>
60#include <sys/mount.h>
61#include <sys/filedesc.h>
62#include <sys/proc.h>
63#include <sys/namei.h>
64#include <sys/nlookup.h>
65#include <sys/malloc.h>
21739618 66#include <sys/stat.h>
70aac194 67#include <sys/objcache.h>
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68
69#ifdef KTRACE
70#include <sys/ktrace.h>
71#endif
72
73/*
74 * Initialize a nlookup() structure, early error return for copyin faults
75 * or a degenerate empty string (which is not allowed).
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76 *
77 * The first process proc0's credentials are used if the calling thread
78 * is not associated with a process context.
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79 */
80int
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81nlookup_init(struct nlookupdata *nd,
82 const char *path, enum uio_seg seg, int flags)
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83{
84 size_t pathlen;
85 struct proc *p;
86 thread_t td;
87 int error;
88
89 td = curthread;
90 p = td->td_proc;
91
92 /*
93 * note: the pathlen set by copy*str() includes the terminating \0.
94 */
95 bzero(nd, sizeof(struct nlookupdata));
70aac194 96 nd->nl_path = objcache_get(namei_oc, M_WAITOK);
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97 nd->nl_flags |= NLC_HASBUF;
98 if (seg == UIO_SYSSPACE)
99 error = copystr(path, nd->nl_path, MAXPATHLEN, &pathlen);
100 else
101 error = copyinstr(path, nd->nl_path, MAXPATHLEN, &pathlen);
102
103 /*
104 * Don't allow empty pathnames.
105 * POSIX.1 requirement: "" is not a vaild file name.
106 */
107 if (error == 0 && pathlen <= 1)
108 error = ENOENT;
109
110 if (error == 0) {
21739618 111 if (p && p->p_fd) {
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112 nd->nl_ncp = cache_hold(p->p_fd->fd_ncdir);
113 nd->nl_rootncp = cache_hold(p->p_fd->fd_nrdir);
114 if (p->p_fd->fd_njdir)
115 nd->nl_jailncp = cache_hold(p->p_fd->fd_njdir);
21739618 116 nd->nl_cred = crhold(p->p_ucred);
690a3127 117 } else {
21739618 118 nd->nl_ncp = cache_hold(rootncp);
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119 nd->nl_rootncp = cache_hold(nd->nl_ncp);
120 nd->nl_jailncp = cache_hold(nd->nl_ncp);
21739618 121 nd->nl_cred = crhold(proc0.p_ucred);
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122 }
123 nd->nl_td = td;
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124 nd->nl_flags |= flags;
125 } else {
126 nlookup_done(nd);
127 }
128 return(error);
129}
130
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131/*
132 * This works similarly to nlookup_init() but does not assume a process
133 * context. rootncp is always chosen for the root directory and the cred
134 * and starting directory are supplied in arguments.
135 */
136int
137nlookup_init_raw(struct nlookupdata *nd,
138 const char *path, enum uio_seg seg, int flags,
139 struct ucred *cred, struct namecache *ncstart)
140{
141 size_t pathlen;
142 thread_t td;
143 int error;
144
145 td = curthread;
146
147 bzero(nd, sizeof(struct nlookupdata));
70aac194 148 nd->nl_path = objcache_get(namei_oc, M_WAITOK);
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149 nd->nl_flags |= NLC_HASBUF;
150 if (seg == UIO_SYSSPACE)
151 error = copystr(path, nd->nl_path, MAXPATHLEN, &pathlen);
152 else
153 error = copyinstr(path, nd->nl_path, MAXPATHLEN, &pathlen);
154
155 /*
156 * Don't allow empty pathnames.
157 * POSIX.1 requirement: "" is not a vaild file name.
158 */
159 if (error == 0 && pathlen <= 1)
160 error = ENOENT;
161
162 if (error == 0) {
163 nd->nl_ncp = cache_hold(ncstart);
164 nd->nl_rootncp = cache_hold(rootncp);
165 nd->nl_jailncp = cache_hold(rootncp);
166 nd->nl_cred = crhold(cred);
167 nd->nl_td = td;
168 nd->nl_flags |= flags;
169 } else {
170 nlookup_done(nd);
171 }
172 return(error);
173}
174
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175/*
176 * Set a different credential; this credential will be used by future
177 * operations performed on nd.nl_open_vp and nlookupdata structure.
178 */
179void
180nlookup_set_cred(struct nlookupdata *nd, struct ucred *cred)
181{
182 KKASSERT(nd->nl_cred != NULL);
183
184 if (nd->nl_cred != cred) {
185 cred = crhold(cred);
186 crfree(nd->nl_cred);
187 nd->nl_cred = cred;
188 }
189}
190
690a3127 191/*
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192 * Cleanup a nlookupdata structure after we are through with it. This may
193 * be called on any nlookupdata structure initialized with nlookup_init().
194 * Calling nlookup_done() is mandatory in all cases except where nlookup_init()
195 * returns an error, even if as a consumer you believe you have taken all
196 * dynamic elements out of the nlookupdata structure.
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197 */
198void
199nlookup_done(struct nlookupdata *nd)
200{
201 if (nd->nl_ncp) {
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202 if (nd->nl_flags & NLC_NCPISLOCKED) {
203 nd->nl_flags &= ~NLC_NCPISLOCKED;
204 cache_unlock(nd->nl_ncp);
205 }
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206 cache_drop(nd->nl_ncp);
207 nd->nl_ncp = NULL;
208 }
209 if (nd->nl_rootncp) {
210 cache_drop(nd->nl_rootncp);
211 nd->nl_rootncp = NULL;
212 }
213 if (nd->nl_jailncp) {
214 cache_drop(nd->nl_jailncp);
215 nd->nl_jailncp = NULL;
216 }
217 if ((nd->nl_flags & NLC_HASBUF) && nd->nl_path) {
70aac194 218 objcache_put(namei_oc, nd->nl_path);
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219 nd->nl_path = NULL;
220 }
221 if (nd->nl_cred) {
222 crfree(nd->nl_cred);
223 nd->nl_cred = NULL;
224 }
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225 if (nd->nl_open_vp) {
226 if (nd->nl_flags & NLC_LOCKVP) {
a11aaa81 227 vn_unlock(nd->nl_open_vp);
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228 nd->nl_flags &= ~NLC_LOCKVP;
229 }
87de5057 230 vn_close(nd->nl_open_vp, nd->nl_vp_fmode);
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231 nd->nl_open_vp = NULL;
232 }
233 nd->nl_flags = 0; /* clear remaining flags (just clear everything) */
234}
235
236void
237nlookup_zero(struct nlookupdata *nd)
238{
239 bzero(nd, sizeof(struct nlookupdata));
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240}
241
242/*
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243 * Simple all-in-one nlookup. Returns a locked namecache structure or NULL
244 * if an error occured.
245 *
246 * Note that the returned ncp is not checked for permissions, though VEXEC
247 * is checked on the directory path leading up to the result. The caller
248 * must call naccess() to check the permissions of the returned leaf.
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249 */
250struct namecache *
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251nlookup_simple(const char *str, enum uio_seg seg,
252 int niflags, int *error)
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253{
254 struct nlookupdata nd;
255 struct namecache *ncp;
256
257 *error = nlookup_init(&nd, str, seg, niflags);
258 if (*error == 0) {
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259 if ((*error = nlookup(&nd)) == 0) {
260 ncp = nd.nl_ncp; /* keep hold ref from structure */
261 nd.nl_ncp = NULL; /* and NULL out */
262 } else {
263 ncp = NULL;
264 }
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265 nlookup_done(&nd);
266 } else {
267 ncp = NULL;
268 }
269 return(ncp);
270}
271
272/*
273 * Do a generic nlookup. Note that the passed nd is not nlookup_done()'d
274 * on return, even if an error occurs. If no error occurs the returned
275 * nl_ncp is always referenced and locked, otherwise it may or may not be.
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276 *
277 * Intermediate directory elements, including the current directory, require
278 * execute (search) permission. nlookup does not examine the access
279 * permissions on the returned element.
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280 *
281 * If NLC_CREATE or NLC_DELETE is set the last directory must allow node
282 * creation (VCREATE/VDELETE), and an error code of 0 will be returned for
283 * a non-existant target. Otherwise a non-existant target will cause
284 * ENOENT to be returned.
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285 */
286int
287nlookup(struct nlookupdata *nd)
288{
289 struct nlcomponent nlc;
290 struct namecache *ncp;
f4d4e93a 291 int wasdotordotdot;
690a3127 292 char *ptr;
fad57d0e 293 char *xptr;
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294 int error;
295 int len;
296
297#ifdef KTRACE
298 if (KTRPOINT(nd->nl_td, KTR_NAMEI))
a9b80e23 299 ktrnamei(nd->nl_td->td_proc, nd->nl_path);
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300#endif
301 bzero(&nlc, sizeof(nlc));
302
303 /*
304 * Setup for the loop. The current working namecache element must
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305 * be in a refd + unlocked state. This typically the case on entry except
306 * when stringing nlookup()'s along in a chain, since nlookup() always
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307 * returns nl_ncp in a locked state.
308 */
309 nd->nl_loopcnt = 0;
310 if (nd->nl_flags & NLC_NCPISLOCKED) {
311 nd->nl_flags &= ~NLC_NCPISLOCKED;
312 cache_unlock(nd->nl_ncp);
313 }
314 ptr = nd->nl_path;
315
316 /*
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317 * Loop on the path components. At the top of the loop nd->nl_ncp
318 * is ref'd and unlocked and represents our current position.
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319 */
320 for (;;) {
321 /*
322 * Check if the root directory should replace the current
323 * directory. This is done at the start of a translation
324 * or after a symbolic link has been found. In other cases
325 * ptr will never be pointing at a '/'.
326 */
327 if (*ptr == '/') {
328 do {
329 ++ptr;
330 } while (*ptr == '/');
524c845c 331 ncp = cache_hold(nd->nl_rootncp);
690a3127 332 cache_drop(nd->nl_ncp);
524c845c 333 nd->nl_ncp = ncp;
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334 if (*ptr == 0) {
335 cache_lock(nd->nl_ncp);
336 nd->nl_flags |= NLC_NCPISLOCKED;
337 error = 0;
338 break;
339 }
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340 continue;
341 }
342
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343 /*
344 * Check directory search permissions
345 */
346 if ((error = naccess(nd->nl_ncp, VEXEC, nd->nl_cred)) != 0)
347 break;
348
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349 /*
350 * Extract the path component
351 */
352 nlc.nlc_nameptr = ptr;
353 while (*ptr && *ptr != '/')
354 ++ptr;
355 nlc.nlc_namelen = ptr - nlc.nlc_nameptr;
356
357 /*
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358 * Lookup the path component in the cache, creating an unresolved
359 * entry if necessary. We have to handle "." and ".." as special
360 * cases.
361 *
362 * When handling ".." we have to detect a traversal back through a
363 * mount point and skip the mount-under node. If we are at the root
364 * ".." just returns the root.
524c845c 365 *
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366 * This subsection returns a locked, refd 'ncp' unless it errors out.
367 * The namecache topology is not allowed to be disconnected, so
368 * encountering a NULL parent will generate EINVAL. This typically
369 * occurs when a directory is removed out from under a process.
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370 *
371 * If NLC_DELETE is set neither '.' or '..' can be the last component
372 * of a path.
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373 */
374 if (nlc.nlc_namelen == 1 && nlc.nlc_nameptr[0] == '.') {
375 ncp = cache_get(nd->nl_ncp);
f4d4e93a 376 wasdotordotdot = 1;
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377 } else if (nlc.nlc_namelen == 2 &&
378 nlc.nlc_nameptr[0] == '.' && nlc.nlc_nameptr[1] == '.') {
379 ncp = nd->nl_ncp;
380 if (ncp == nd->nl_rootncp) {
381 ncp = cache_get(ncp);
382 } else {
524c845c 383 while ((ncp->nc_flag & NCF_MOUNTPT) && ncp != nd->nl_rootncp) {
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384 if (ncp->nc_parent->nc_flag & NCF_DESTROYED)
385 break;
524c845c 386 ncp = ncp->nc_parent; /* get to underlying node */
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387 KKASSERT(ncp != NULL && 1);
388 }
fad57d0e 389 if (ncp != nd->nl_rootncp) {
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390 if (ncp->nc_parent->nc_flag & NCF_DESTROYED) {
391 error = EINVAL;
392 break;
393 }
524c845c 394 ncp = ncp->nc_parent;
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395 if (ncp == NULL) {
396 error = EINVAL;
397 break;
398 }
399 }
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400 ncp = cache_get(ncp);
401 }
f4d4e93a 402 wasdotordotdot = 1;
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403 } else {
404 ncp = cache_nlookup(nd->nl_ncp, &nlc);
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405 while ((error = cache_resolve(ncp, nd->nl_cred)) == EAGAIN) {
406 printf("[diagnostic] nlookup: relookup %*.*s\n",
407 ncp->nc_nlen, ncp->nc_nlen, ncp->nc_name);
408 cache_put(ncp);
409 ncp = cache_nlookup(nd->nl_ncp, &nlc);
8e005a45 410 }
f4d4e93a 411 wasdotordotdot = 0;
21739618 412 }
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413 /*
414 * [end of subsection] ncp is locked and ref'd. nd->nl_ncp is ref'd
415 */
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416
417 /*
418 * Resolve the namespace if necessary. The ncp returned by
419 * cache_nlookup() is referenced and locked.
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420 *
421 * XXX neither '.' nor '..' should return EAGAIN since they were
422 * previously resolved and thus cannot be newly created ncp's.
690a3127 423 */
690a3127 424 if (ncp->nc_flag & NCF_UNRESOLVED) {
21739618 425 error = cache_resolve(ncp, nd->nl_cred);
8e005a45 426 KKASSERT(error != EAGAIN);
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427 } else {
428 error = ncp->nc_error;
429 }
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430
431 /*
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432 * Early completion. ENOENT is not an error if this is the last
433 * component and NLC_CREATE was requested. Note that ncp->nc_error
434 * is left as ENOENT in that case, which we check later on.
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435 *
436 * Also handle invalid '.' or '..' components terminating a path
437 * during removal. The standard requires this and pax pretty
438 *stupidly depends on it.
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439 */
440 for (xptr = ptr; *xptr == '/'; ++xptr)
441 ;
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442 if (*xptr == 0) {
443 if (error == ENOENT && (nd->nl_flags & NLC_CREATE))
444 error = naccess(ncp, VCREATE, nd->nl_cred);
445 if (error == 0 && wasdotordotdot && (nd->nl_flags & NLC_DELETE))
446 error = EINVAL;
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447 }
448
449 /*
450 * Early completion on error.
21739618 451 */
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452 if (error) {
453 cache_put(ncp);
454 break;
455 }
456
457 /*
458 * If the element is a symlink and it is either not the last
459 * element or it is the last element and we are allowed to
460 * follow symlinks, resolve the symlink.
461 */
462 if ((ncp->nc_flag & NCF_ISSYMLINK) &&
463 (*ptr || (nd->nl_flags & NLC_FOLLOW))
464 ) {
465 if (nd->nl_loopcnt++ >= MAXSYMLINKS) {
21739618 466 error = ELOOP;
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467 cache_put(ncp);
468 break;
469 }
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470 error = nreadsymlink(nd, ncp, &nlc);
471 cache_put(ncp);
472 if (error)
473 break;
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474
475 /*
476 * Concatenate trailing path elements onto the returned symlink.
477 * Note that if the path component (ptr) is not exhausted, it
478 * will being with a '/', so we do not have to add another one.
479 *
480 * The symlink may not be empty.
481 */
482 len = strlen(ptr);
483 if (nlc.nlc_namelen == 0 || nlc.nlc_namelen + len >= MAXPATHLEN) {
484 error = nlc.nlc_namelen ? ENAMETOOLONG : ENOENT;
70aac194 485 objcache_put(namei_oc, nlc.nlc_nameptr);
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486 break;
487 }
488 bcopy(ptr, nlc.nlc_nameptr + nlc.nlc_namelen, len + 1);
489 if (nd->nl_flags & NLC_HASBUF)
70aac194 490 objcache_put(namei_oc, nd->nl_path);
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491 nd->nl_path = nlc.nlc_nameptr;
492 nd->nl_flags |= NLC_HASBUF;
493 ptr = nd->nl_path;
494
495 /*
496 * Go back up to the top to resolve any initial '/'s in the
497 * symlink.
498 */
499 continue;
500 }
501
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502 /*
503 * If the element is a directory and we are crossing a mount point,
504 * retrieve the root of the mounted filesystem from mnt_ncp and
505 * resolve it if necessary.
506 *
507 * XXX mnt_ncp should really be resolved in the mount code.
508 * NOTE! the normal nresolve() code cannot resolve mount point ncp's!
509 *
510 * XXX NOCROSSMOUNT
511 */
512 while ((ncp->nc_flag & NCF_ISDIR) && ncp->nc_vp->v_mountedhere &&
513 (nd->nl_flags & NLC_NOCROSSMOUNT) == 0
514 ) {
515 struct mount *mp;
516 struct vnode *tdp;
517
518 mp = ncp->nc_vp->v_mountedhere;
519 cache_put(ncp);
524c845c 520 ncp = cache_get(mp->mnt_ncp);
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521
522 if (ncp->nc_flag & NCF_UNRESOLVED) {
f9642f56 523 while (vfs_busy(mp, 0))
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524 ;
525 error = VFS_ROOT(mp, &tdp);
f9642f56 526 vfs_unbusy(mp);
524c845c 527 if (error)
21739618 528 break;
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529 cache_setvp(ncp, tdp);
530 vput(tdp);
531 }
532 }
533 if (error) {
534 cache_put(ncp);
535 break;
536 }
537
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538 /*
539 * Skip any slashes to get to the next element. If there
540 * are any slashes at all the current element must be a
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541 * directory or, in the create case, intended to become a directory.
542 * If it isn't we break without incrementing ptr and fall through
543 * to the failure case below.
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544 */
545 while (*ptr == '/') {
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546 if ((ncp->nc_flag & NCF_ISDIR) == 0 &&
547 !(nd->nl_flags & NLC_WILLBEDIR)
548 ) {
690a3127 549 break;
fad57d0e 550 }
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551 ++ptr;
552 }
553
554 /*
555 * Continuation case: additional elements and the current
556 * element is a directory.
557 */
558 if (*ptr && (ncp->nc_flag & NCF_ISDIR)) {
559 cache_drop(nd->nl_ncp);
560 cache_unlock(ncp);
561 nd->nl_ncp = ncp;
562 continue;
563 }
564
565 /*
566 * Failure case: additional elements and the current element
567 * is not a directory
568 */
569 if (*ptr) {
570 cache_put(ncp);
571 error = ENOTDIR;
572 break;
573 }
574
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575 /*
576 * Successful lookup of last element.
577 *
578 * Check directory permissions if a deletion is specified.
579 */
580 if (*ptr == 0 && (nd->nl_flags & NLC_DELETE)) {
581 if ((error = naccess(ncp, VDELETE, nd->nl_cred)) != 0) {
582 cache_put(ncp);
583 break;
584 }
585 }
586
690a3127 587 /*
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588 * Termination: no more elements. If NLC_CREATE was set the
589 * ncp may represent a negative hit (ncp->nc_error will be ENOENT),
590 * but we still return an error code of 0.
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591 */
592 cache_drop(nd->nl_ncp);
593 nd->nl_ncp = ncp;
594 nd->nl_flags |= NLC_NCPISLOCKED;
595 error = 0;
596 break;
597 }
598 return(error);
599}
600
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601/*
602 * Resolve a mount point's glue ncp. This ncp connects creates the illusion
603 * of continuity in the namecache tree by connecting the ncp related to the
604 * vnode under the mount to the ncp related to the mount's root vnode.
605 *
606 * If no error occured a locked, ref'd ncp is stored in *ncpp.
607 */
608int
609nlookup_mp(struct mount *mp, struct namecache **ncpp)
610{
611 struct namecache *ncp;
612 struct vnode *vp;
613 int error;
614
615 error = 0;
616 ncp = mp->mnt_ncp;
617 cache_get(ncp);
618 if (ncp->nc_flag & NCF_UNRESOLVED) {
f9642f56 619 while (vfs_busy(mp, 0))
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620 ;
621 error = VFS_ROOT(mp, &vp);
f9642f56 622 vfs_unbusy(mp);
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623 if (error) {
624 cache_put(ncp);
625 ncp = NULL;
626 } else {
627 cache_setvp(ncp, vp);
628 vput(vp);
629 }
630 }
631 *ncpp = ncp;
632 return(error);
633}
634
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635/*
636 * Read the contents of a symlink, allocate a path buffer out of the
70aac194 637 * namei_oc and initialize the supplied nlcomponent with the result.
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638 *
639 * If an error occurs no buffer will be allocated or returned in the nlc.
640 */
641int
642nreadsymlink(struct nlookupdata *nd, struct namecache *ncp,
643 struct nlcomponent *nlc)
644{
21739618 645 struct vnode *vp;
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646 struct iovec aiov;
647 struct uio auio;
648 int linklen;
649 int error;
650 char *cp;
651
652 nlc->nlc_nameptr = NULL;
653 nlc->nlc_namelen = 0;
654 if (ncp->nc_vp == NULL)
655 return(ENOENT);
21739618 656 if ((error = cache_vget(ncp, nd->nl_cred, LK_SHARED, &vp)) != 0)
690a3127 657 return(error);
70aac194 658 cp = objcache_get(namei_oc, M_WAITOK);
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659 aiov.iov_base = cp;
660 aiov.iov_len = MAXPATHLEN;
661 auio.uio_iov = &aiov;
662 auio.uio_iovcnt = 1;
663 auio.uio_offset = 0;
664 auio.uio_rw = UIO_READ;
665 auio.uio_segflg = UIO_SYSSPACE;
666 auio.uio_td = nd->nl_td;
667 auio.uio_resid = MAXPATHLEN - 1;
21739618 668 error = VOP_READLINK(vp, &auio, nd->nl_cred);
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669 if (error)
670 goto fail;
21739618 671 linklen = MAXPATHLEN - 1 - auio.uio_resid;
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672 if (varsym_enable) {
673 linklen = varsymreplace(cp, linklen, MAXPATHLEN - 1);
674 if (linklen < 0) {
675 error = ENAMETOOLONG;
676 goto fail;
677 }
678 }
679 cp[linklen] = 0;
680 nlc->nlc_nameptr = cp;
681 nlc->nlc_namelen = linklen;
21739618 682 vput(vp);
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683 return(0);
684fail:
70aac194 685 objcache_put(namei_oc, cp);
21739618 686 vput(vp);
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687 return(error);
688}
689
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690/*
691 * Check access [XXX cache vattr!] [XXX quota]
692 *
693 * Generally check the V* access bits from sys/vnode.h. All specified bits
694 * must pass for this function to return 0.
695 *
696 * If VCREATE is specified and the target ncp represents a non-existant
697 * file or dir, or if VDELETE is specified and the target exists, the parent
698 * directory is checked for VWRITE. If VEXCL is specified and the target
699 * ncp represents a positive hit, an error is returned.
700 *
701 * If VCREATE is not specified and the target does not exist (negative hit),
702 * ENOENT is returned. Note that nlookup() does not (and should not) return
703 * ENOENT for non-existant leafs.
704 *
705 * The passed ncp may or may not be locked. The caller should use a
706 * locked ncp on leaf lookups, especially for VCREATE, VDELETE, and VEXCL
707 * checks.
708 */
709int
710naccess(struct namecache *ncp, int vmode, struct ucred *cred)
711{
ff793caa 712 struct namecache *par;
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713 struct vnode *vp;
714 struct vattr va;
715 int error;
716
717 if (ncp->nc_flag & NCF_UNRESOLVED) {
718 cache_lock(ncp);
719 cache_resolve(ncp, cred);
720 cache_unlock(ncp);
721 }
722 error = ncp->nc_error;
723 if (vmode & (VDELETE|VCREATE|VEXCL)) {
724 if (((vmode & VCREATE) && ncp->nc_vp == NULL) ||
725 ((vmode & VDELETE) && ncp->nc_vp != NULL)
726 ) {
ff793caa 727 if ((par = ncp->nc_parent) == NULL) {
8e005a45 728 if (error != EAGAIN)
fad57d0e 729 error = EINVAL;
8e005a45 730 } else {
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731 cache_hold(par);
732 error = naccess(par, VWRITE, cred);
733 cache_drop(par);
8e005a45 734 }
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735 }
736 if ((vmode & VEXCL) && ncp->nc_vp != NULL)
737 error = EEXIST;
738 }
739 if (error == 0) {
740 error = cache_vget(ncp, cred, LK_SHARED, &vp);
741 if (error == ENOENT) {
742 if (vmode & VCREATE)
743 error = 0;
744 } else if (error == 0) {
745 /* XXX cache the va in the namecache or in the vnode */
87de5057 746 if ((error = VOP_GETATTR(vp, &va)) == 0) {
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747 if ((vmode & VWRITE) && vp->v_mount) {
748 if (vp->v_mount->mnt_flag & MNT_RDONLY)
749 error = EROFS;
750 }
751 }
752 vput(vp);
753 if (error == 0)
754 error = naccess_va(&va, vmode, cred);
755 }
756 }
757 return(error);
758}
759
760/*
761 * Check the requested access against the given vattr using cred.
762 */
763int
764naccess_va(struct vattr *va, int vmode, struct ucred *cred)
765{
766 int i;
767
768 /*
769 * Test the immutable bit for files, directories, and softlinks.
770 */
771 if (vmode & (VWRITE|VDELETE)) {
772 if (va->va_type == VDIR || va->va_type == VLNK || va->va_type == VREG) {
773 if (va->va_flags & IMMUTABLE)
774 return (EPERM);
775 }
776 }
777
778 /*
779 * root gets universal access
780 */
781 if (cred->cr_uid == 0)
782 return(0);
783
784 /*
785 * Check owner perms, group perms, and world perms
786 */
787 vmode &= S_IRWXU;
788 if (cred->cr_uid == va->va_uid) {
789 if ((vmode & va->va_mode) != vmode)
790 return(EACCES);
791 return(0);
792 }
793
794 vmode >>= 3;
795 for (i = 0; i < cred->cr_ngroups; ++i) {
796 if (va->va_gid == cred->cr_groups[i]) {
797 if ((vmode & va->va_mode) != vmode)
798 return(EACCES);
799 return(0);
800 }
801 }
802
803 vmode >>= 3;
804 if ((vmode & va->va_mode) != vmode)
805 return(EACCES);
806 return(0);
807}
808