xref: /dragonfly/sys/kern/kern_varsym.c (revision 201c8c44) 
1 /*
2  * Copyright (c) 2003,2004 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  *
34  * $DragonFly: src/sys/kern/kern_varsym.c,v 1.9 2007/04/30 07:18:54 dillon Exp $
35  */
36 
37 /*
38  * This module implements variable storage and management for variant
39  * symlinks.  These variables may also be used for general purposes.
40  */
41 
42 #include <sys/param.h>
43 #include <sys/systm.h>
44 #include <sys/kernel.h>
45 #include <sys/ucred.h>
46 #include <sys/resourcevar.h>
47 #include <sys/proc.h>
48 #include <sys/priv.h>
49 #include <sys/jail.h>
50 #include <sys/queue.h>
51 #include <sys/sysctl.h>
52 #include <sys/malloc.h>
53 #include <sys/varsym.h>
54 #include <sys/sysproto.h>
55 
56 MALLOC_DEFINE(M_VARSYM, "varsym", "variable sets for variant symlinks");
57 
58 struct varsymset	varsymset_sys;
59 
60 /*
61  * Initialize the variant symlink subsystem
62  */
63 static void
64 varsym_sysinit(void *dummy)
65 {
66     varsymset_init(&varsymset_sys, NULL);
67 }
68 SYSINIT(announce, SI_BOOT2_MACHDEP, SI_ORDER_FIRST, varsym_sysinit, NULL);
69 
70 /*
71  * varsymreplace() - called from namei
72  *
73  *	Do variant symlink variable substitution
74  */
75 int
76 varsymreplace(char *cp, int linklen, int maxlen)
77 {
78     int rlen;
79     int xlen;
80     int nlen;
81     int i;
82     varsym_t var;
83 
84     rlen = linklen;
85     while (linklen > 1) {
86 	if (cp[0] == '$' && cp[1] == '{') {
87 	    for (i = 2; i < linklen; ++i) {
88 		if (cp[i] == '}')
89 		    break;
90 	    }
91 	    if (i < linklen &&
92 		(var = varsymfind(VARSYM_ALL_MASK, cp + 2, i - 2)) != NULL
93 	    ) {
94 		xlen = i + 1;			/* bytes to strike */
95 		nlen = strlen(var->vs_data);	/* bytes to add */
96 		if (linklen + nlen - xlen >= maxlen) {
97 		    varsymdrop(var);
98 		    return(-1);
99 		}
100 		KKASSERT(linklen >= xlen);
101 		if (linklen != xlen)
102 		    bcopy(cp + xlen, cp + nlen, linklen - xlen);
103 		bcopy(var->vs_data, cp, nlen);
104 		linklen += nlen - xlen;	/* new relative length */
105 		rlen += nlen - xlen;	/* returned total length */
106 		cp += nlen;		/* adjust past replacement */
107 		linklen -= nlen;	/* adjust past replacement */
108 		maxlen -= nlen;		/* adjust past replacement */
109 	    } else {
110 		/*
111 		 * It's ok if i points to the '}', it will simply be
112 		 * skipped.  i could also have hit linklen.
113 		 */
114 		cp += i;
115 		linklen -= i;
116 		maxlen -= i;
117 	    }
118 	} else {
119 	    ++cp;
120 	    --linklen;
121 	    --maxlen;
122 	}
123     }
124     return(rlen);
125 }
126 
127 /*
128  * varsym_set() system call
129  *
130  * (int level, const char *name, const char *data)
131  */
132 int
133 sys_varsym_set(struct varsym_set_args *uap)
134 {
135     char name[MAXVARSYM_NAME];
136     char *buf;
137     int error;
138 
139     if ((error = copyinstr(uap->name, name, sizeof(name), NULL)) != 0)
140 	goto done2;
141     buf = kmalloc(MAXVARSYM_DATA, M_TEMP, M_WAITOK);
142     if (uap->data &&
143 	(error = copyinstr(uap->data, buf, MAXVARSYM_DATA, NULL)) != 0)
144     {
145 	goto done1;
146     }
147     switch(uap->level) {
148     case VARSYM_SYS:
149 	if (curthread->td_proc != NULL && curthread->td_proc->p_ucred->cr_prison != NULL)
150 	    uap->level = VARSYM_PRISON;
151     case VARSYM_PRISON:
152 	if (curthread->td_proc != NULL &&
153 	    (error = priv_check_cred(curthread->td_proc->p_ucred, PRIV_ROOT, PRISON_ROOT)) != 0)
154 	    break;
155 	/* fall through */
156     case VARSYM_USER:
157 	/* XXX check jail / implement per-jail user */
158 	/* fall through */
159     case VARSYM_PROC:
160 	if (uap->data) {
161 	    (void)varsymmake(uap->level, name, NULL);
162 	    error = varsymmake(uap->level, name, buf);
163 	} else {
164 	    error = varsymmake(uap->level, name, NULL);
165 	}
166 	break;
167     }
168 done1:
169     kfree(buf, M_TEMP);
170 done2:
171     return(error);
172 }
173 
174 /*
175  * varsym_get() system call
176  *
177  * (int mask, const char *wild, char *buf, int bufsize)
178  */
179 int
180 sys_varsym_get(struct varsym_get_args *uap)
181 {
182     char wild[MAXVARSYM_NAME];
183     varsym_t sym;
184     int error;
185     int dlen;
186 
187     if ((error = copyinstr(uap->wild, wild, sizeof(wild), NULL)) != 0)
188 	goto done;
189     sym = varsymfind(uap->mask, wild, strlen(wild));
190     if (sym == NULL) {
191 	error = ENOENT;
192 	goto done;
193     }
194     dlen = strlen(sym->vs_data);
195     if (dlen < uap->bufsize) {
196 	copyout(sym->vs_data, uap->buf, dlen + 1);
197     } else if (uap->bufsize) {
198 	copyout("", uap->buf, 1);
199     }
200     uap->sysmsg_result = dlen + 1;
201     varsymdrop(sym);
202 done:
203     return(error);
204 }
205 
206 /*
207  * varsym_list() system call
208  *
209  * (int level, char *buf, int maxsize, int *marker)
210  */
211 int
212 sys_varsym_list(struct varsym_list_args *uap)
213 {
214 	struct varsymset *vss;
215 	struct varsyment *ve;
216 	struct proc *p;
217 	int i;
218 	int error;
219 	int bytes;
220 	int earlyterm;
221 	int marker;
222 
223 	/*
224 	 * Get the marker from userspace.
225 	 */
226 	if ((error = copyin(uap->marker, &marker, sizeof(marker))) != 0)
227 		goto done;
228 
229 	/*
230 	 * Figure out the varsym set.
231 	 */
232 	p = curproc;
233 	vss = NULL;
234 
235 	switch (uap->level) {
236 	case VARSYM_PROC:
237 		if (p)
238 			vss = &p->p_varsymset;
239 		break;
240 	case VARSYM_USER:
241 		if (p)
242 			vss = &p->p_ucred->cr_uidinfo->ui_varsymset;
243 		break;
244 	case VARSYM_SYS:
245 		vss = &varsymset_sys;
246 		break;
247 	case VARSYM_PRISON:
248 		if (p != NULL && p->p_ucred->cr_prison != NULL)
249 			vss = &p->p_ucred->cr_prison->pr_varsymset;
250 		break;
251 	}
252 	if (vss == NULL) {
253 		error = EINVAL;
254 		goto done;
255 	}
256 
257 	/*
258 	 * Loop through the variables and dump them to uap->buf
259 	 */
260 	i = 0;
261 	bytes = 0;
262 	earlyterm = 0;
263 
264 	lockmgr(&vss->vx_lock, LK_SHARED);
265 	TAILQ_FOREACH(ve, &vss->vx_queue, ve_entry) {
266 		varsym_t sym = ve->ve_sym;
267 		int namelen = strlen(sym->vs_name);
268 		int datalen = strlen(sym->vs_data);
269 		int totlen = namelen + datalen + 2;
270 
271 		/*
272 		 * Skip to our index point
273 		 */
274 		if (i < marker) {
275 			++i;
276 			continue;
277 		}
278 
279 		/*
280 		 * Stop if there is insufficient space in the user buffer.
281 		 * If we haven't stored anything yet return EOVERFLOW.
282 		 * Note that the marker index (i) does not change.
283 		 */
284 		if (bytes + totlen > uap->maxsize) {
285 			if (bytes == 0)
286 				error = EOVERFLOW;
287 			earlyterm = 1;
288 			break;
289 		}
290 
291 		error = copyout(sym->vs_name, uap->buf + bytes, namelen + 1);
292 		if (error == 0) {
293 			bytes += namelen + 1;
294 			error = copyout(sym->vs_data, uap->buf + bytes, datalen + 1);
295 			if (error == 0)
296 				bytes += datalen + 1;
297 			else
298 				bytes -= namelen + 1;	/* revert if error */
299 		}
300 		if (error) {
301 			earlyterm = 1;
302 			break;
303 		}
304 		++i;
305 	}
306 	lockmgr(&vss->vx_lock, LK_RELEASE);
307 
308 	/*
309 	 * Save the marker back.  If no error occured and earlyterm is clear
310 	 * the marker is set to -1 indicating that the variable list has been
311 	 * exhausted.  If no error occured the number of bytes loaded into
312 	 * the buffer will be returned, otherwise the syscall code returns -1.
313 	 */
314 	if (error == 0 && earlyterm == 0)
315 		marker = -1;
316 	else
317 		marker = i;
318 	if (error == 0)
319 		error = copyout(&marker, uap->marker, sizeof(marker));
320 	uap->sysmsg_result = bytes;
321 done:
322 	return(error);
323 }
324 
325 /*
326  * Lookup a variant symlink.  XXX use a hash table.
327  */
328 static
329 struct varsyment *
330 varsymlookup(struct varsymset *vss, const char *name, int namelen)
331 {
332     struct varsyment *ve;
333 
334     KKASSERT(lockstatus(&vss->vx_lock, curthread) != 0);
335     TAILQ_FOREACH(ve, &vss->vx_queue, ve_entry) {
336 	varsym_t var = ve->ve_sym;
337 	if (var->vs_namelen == namelen &&
338 	    bcmp(name, var->vs_name, namelen) == 0
339 	) {
340 	    return(ve);
341 	}
342     }
343     return(NULL);
344 }
345 
346 static
347 void
348 vsslock(struct varsymset **vss, struct varsymset *n)
349 {
350 	if (*vss) {
351 		lockmgr(&(*vss)->vx_lock, LK_RELEASE);
352 	}
353 	lockmgr(&n->vx_lock, LK_SHARED);
354 	*vss = n;
355 }
356 
357 varsym_t
358 varsymfind(int mask, const char *name, int namelen)
359 {
360     struct proc *p = curproc;
361     struct varsyment *ve = NULL;
362     struct varsymset *vss = NULL;
363     varsym_t sym;
364 
365     if ((mask & (VARSYM_PROC_MASK|VARSYM_USER_MASK)) && p != NULL) {
366 	if (mask & VARSYM_PROC_MASK) {
367 	    vsslock(&vss, &p->p_varsymset);
368 	    ve = varsymlookup(vss, name, namelen);
369 	}
370 	if (ve == NULL && (mask & VARSYM_USER_MASK)) {
371 	    vsslock(&vss, &p->p_ucred->cr_uidinfo->ui_varsymset);
372 	    ve = varsymlookup(vss, name, namelen);
373 	}
374     }
375     if (ve == NULL && (mask & VARSYM_SYS_MASK)) {
376 	if (p != NULL && p->p_ucred->cr_prison) {
377 	    vsslock(&vss, &p->p_ucred->cr_prison->pr_varsymset);
378 	    ve = varsymlookup(vss, name, namelen);
379 	} else {
380 	    vsslock(&vss, &varsymset_sys);
381 	    ve = varsymlookup(vss, name, namelen);
382 	}
383     }
384     if (ve) {
385 	sym = ve->ve_sym;
386 	atomic_add_int(&sym->vs_refs, 1);
387     } else {
388 	sym = NULL;
389     }
390     lockmgr(&vss->vx_lock, LK_RELEASE);
391     return sym;
392 }
393 
394 int
395 varsymmake(int level, const char *name, const char *data)
396 {
397     struct varsymset *vss = NULL;
398     struct varsyment *ve;
399     struct proc *p = curproc;
400     varsym_t sym;
401     int namelen = strlen(name);
402     int datalen;
403     int error;
404 
405     switch(level) {
406     case VARSYM_PROC:
407 	if (p)
408 	    vss = &p->p_varsymset;
409 	break;
410     case VARSYM_USER:
411 	if (p)
412 	    vss = &p->p_ucred->cr_uidinfo->ui_varsymset;
413 	break;
414     case VARSYM_SYS:
415 	vss = &varsymset_sys;
416 	break;
417     case VARSYM_PRISON:
418 	if (p != NULL && p->p_ucred->cr_prison != NULL)
419 	    vss = &p->p_ucred->cr_prison->pr_varsymset;
420 	break;
421     }
422     if (vss == NULL) {
423 	return EINVAL;
424     }
425     lockmgr(&vss->vx_lock, LK_EXCLUSIVE);
426     if (data && vss->vx_setsize >= MAXVARSYM_SET) {
427 	error = E2BIG;
428     } else if (data) {
429 	datalen = strlen(data);
430 	ve = kmalloc(sizeof(struct varsyment), M_VARSYM, M_WAITOK|M_ZERO);
431 	sym = kmalloc(sizeof(struct varsym) + namelen + datalen + 2, M_VARSYM, M_WAITOK);
432 	ve->ve_sym = sym;
433 	sym->vs_refs = 1;
434 	sym->vs_namelen = namelen;
435 	sym->vs_name = (char *)(sym + 1);
436 	sym->vs_data = sym->vs_name + namelen + 1;
437 	strcpy(sym->vs_name, name);
438 	strcpy(sym->vs_data, data);
439 	TAILQ_INSERT_TAIL(&vss->vx_queue, ve, ve_entry);
440 	vss->vx_setsize += sizeof(struct varsyment) + sizeof(struct varsym) + namelen + datalen + 8;
441 	error = 0;
442     } else {
443 	if ((ve = varsymlookup(vss, name, namelen)) != NULL) {
444 	    TAILQ_REMOVE(&vss->vx_queue, ve, ve_entry);
445 	    vss->vx_setsize -= sizeof(struct varsyment) + sizeof(struct varsym) + namelen + strlen(ve->ve_sym->vs_data) + 8;
446 	    varsymdrop(ve->ve_sym);
447 	    kfree(ve, M_VARSYM);
448 	    error = 0;
449 	} else {
450 	    error = ENOENT;
451 	}
452     }
453     lockmgr(&vss->vx_lock, LK_RELEASE);
454     return(error);
455 }
456 
457 void
458 varsymdrop(varsym_t sym)
459 {
460     KKASSERT(sym->vs_refs > 0);
461     if (atomic_fetchadd_int(&sym->vs_refs, -1) == 1) {
462 	kfree(sym, M_VARSYM);
463     }
464 }
465 
466 /*
467  * Insert a duplicate of ve in vss. Does not do any locking,
468  * so it is the callers responsibility to make sure nobody
469  * else can mess with the TAILQ in vss at the same time.
470  */
471 static void
472 varsymdup(struct varsymset *vss, struct varsyment *ve)
473 {
474     struct varsyment *nve;
475 
476     nve = kmalloc(sizeof(struct varsyment), M_VARSYM, M_WAITOK|M_ZERO);
477     nve->ve_sym = ve->ve_sym;
478     ++nve->ve_sym->vs_refs;	/* can't be reached, no need for atomic add */
479     /*
480      * We're only called through varsymset_init() so vss is not yet reachable,
481      * no need to lock.
482      */
483     TAILQ_INSERT_TAIL(&vss->vx_queue, nve, ve_entry);
484 }
485 
486 void
487 varsymset_init(struct varsymset *vss, struct varsymset *copy)
488 {
489     struct varsyment *ve;
490 
491     TAILQ_INIT(&vss->vx_queue);
492     lockinit(&vss->vx_lock, "vx", 0, 0);
493     if (copy) {
494 	TAILQ_FOREACH(ve, &copy->vx_queue, ve_entry) {
495 	    varsymdup(vss, ve);
496 	}
497 	vss->vx_setsize = copy->vx_setsize;
498     }
499 }
500 
501 void
502 varsymset_clean(struct varsymset *vss)
503 {
504     struct varsyment *ve;
505 
506     lockmgr(&vss->vx_lock, LK_EXCLUSIVE);
507     while ((ve = TAILQ_FIRST(&vss->vx_queue)) != NULL) {
508 	TAILQ_REMOVE(&vss->vx_queue, ve, ve_entry);
509 	varsymdrop(ve->ve_sym);
510 	kfree(ve, M_VARSYM);
511     }
512     vss->vx_setsize = 0;
513     lockmgr(&vss->vx_lock, LK_RELEASE);
514 }
515 
516