xref: /dflybsd-src/sys/kern/kern_varsym.c (revision 92b817bb6b0d8e22d601698e9d3864697def6575) 
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  * MPALMOSTSAFE
133  */
134 int
135 sys_varsym_set(struct varsym_set_args *uap)
136 {
137     char name[MAXVARSYM_NAME];
138     char *buf;
139     struct proc *p;
140     int error;
141 
142     p = curproc;
143 
144     if ((error = copyinstr(uap->name, name, sizeof(name), NULL)) != 0)
145 	goto done2;
146     buf = kmalloc(MAXVARSYM_DATA, M_TEMP, M_WAITOK);
147     if (uap->data &&
148 	(error = copyinstr(uap->data, buf, MAXVARSYM_DATA, NULL)) != 0)
149     {
150 	goto done1;
151     }
152 
153     get_mplock();
154 
155     switch(uap->level) {
156     case VARSYM_SYS:
157 	if (p != NULL && p->p_ucred->cr_prison != NULL)
158 	    uap->level = VARSYM_PRISON;
159     case VARSYM_PRISON:
160 	if (p != NULL &&
161 	    (error = priv_check_cred(p->p_ucred, PRIV_VARSYM_SYS, 0)) != 0)
162 	    break;
163 	/* fall through */
164     case VARSYM_USER:
165 	/* XXX check jail / implement per-jail user */
166 	/* fall through */
167     case VARSYM_PROC:
168 	if (uap->data) {
169 	    (void)varsymmake(uap->level, name, NULL);
170 	    error = varsymmake(uap->level, name, buf);
171 	} else {
172 	    error = varsymmake(uap->level, name, NULL);
173 	}
174 	break;
175     }
176     rel_mplock();
177 done1:
178     kfree(buf, M_TEMP);
179 done2:
180     return(error);
181 }
182 
183 /*
184  * varsym_get() system call
185  *
186  * (int mask, const char *wild, char *buf, int bufsize)
187  *
188  * MPALMOSTSAFE
189  */
190 int
191 sys_varsym_get(struct varsym_get_args *uap)
192 {
193     char wild[MAXVARSYM_NAME];
194     varsym_t sym;
195     int error;
196     int dlen;
197 
198     get_mplock();
199     if ((error = copyinstr(uap->wild, wild, sizeof(wild), NULL)) != 0)
200 	goto done;
201     sym = varsymfind(uap->mask, wild, strlen(wild));
202     if (sym == NULL) {
203 	error = ENOENT;
204 	goto done;
205     }
206     dlen = strlen(sym->vs_data);
207     if (dlen < uap->bufsize) {
208 	copyout(sym->vs_data, uap->buf, dlen + 1);
209     } else if (uap->bufsize) {
210 	copyout("", uap->buf, 1);
211     }
212     uap->sysmsg_result = dlen + 1;
213     varsymdrop(sym);
214 done:
215     rel_mplock();
216     return(error);
217 }
218 
219 /*
220  * varsym_list() system call
221  *
222  * (int level, char *buf, int maxsize, int *marker)
223  *
224  * MPALMOSTSAFE
225  */
226 int
227 sys_varsym_list(struct varsym_list_args *uap)
228 {
229 	struct varsymset *vss;
230 	struct varsyment *ve;
231 	struct proc *p;
232 	int i;
233 	int error;
234 	int bytes;
235 	int earlyterm;
236 	int marker;
237 
238 	/*
239 	 * Get the marker from userspace.
240 	 */
241 	get_mplock();
242 	if ((error = copyin(uap->marker, &marker, sizeof(marker))) != 0)
243 		goto done;
244 
245 	/*
246 	 * Figure out the varsym set.
247 	 */
248 	p = curproc;
249 	vss = NULL;
250 
251 	switch (uap->level) {
252 	case VARSYM_PROC:
253 		if (p)
254 			vss = &p->p_varsymset;
255 		break;
256 	case VARSYM_USER:
257 		if (p)
258 			vss = &p->p_ucred->cr_uidinfo->ui_varsymset;
259 		break;
260 	case VARSYM_SYS:
261 		vss = &varsymset_sys;
262 		break;
263 	case VARSYM_PRISON:
264 		if (p != NULL && p->p_ucred->cr_prison != NULL)
265 			vss = &p->p_ucred->cr_prison->pr_varsymset;
266 		break;
267 	}
268 	if (vss == NULL) {
269 		error = EINVAL;
270 		goto done;
271 	}
272 
273 	/*
274 	 * Loop through the variables and dump them to uap->buf
275 	 */
276 	i = 0;
277 	bytes = 0;
278 	earlyterm = 0;
279 
280 	lockmgr(&vss->vx_lock, LK_SHARED);
281 	TAILQ_FOREACH(ve, &vss->vx_queue, ve_entry) {
282 		varsym_t sym = ve->ve_sym;
283 		int namelen = strlen(sym->vs_name);
284 		int datalen = strlen(sym->vs_data);
285 		int totlen = namelen + datalen + 2;
286 
287 		/*
288 		 * Skip to our index point
289 		 */
290 		if (i < marker) {
291 			++i;
292 			continue;
293 		}
294 
295 		/*
296 		 * Stop if there is insufficient space in the user buffer.
297 		 * If we haven't stored anything yet return EOVERFLOW.
298 		 * Note that the marker index (i) does not change.
299 		 */
300 		if (bytes + totlen > uap->maxsize) {
301 			if (bytes == 0)
302 				error = EOVERFLOW;
303 			earlyterm = 1;
304 			break;
305 		}
306 
307 		error = copyout(sym->vs_name, uap->buf + bytes, namelen + 1);
308 		if (error == 0) {
309 			bytes += namelen + 1;
310 			error = copyout(sym->vs_data, uap->buf + bytes, datalen + 1);
311 			if (error == 0)
312 				bytes += datalen + 1;
313 			else
314 				bytes -= namelen + 1;	/* revert if error */
315 		}
316 		if (error) {
317 			earlyterm = 1;
318 			break;
319 		}
320 		++i;
321 	}
322 	lockmgr(&vss->vx_lock, LK_RELEASE);
323 
324 	/*
325 	 * Save the marker back.  If no error occured and earlyterm is clear
326 	 * the marker is set to -1 indicating that the variable list has been
327 	 * exhausted.  If no error occured the number of bytes loaded into
328 	 * the buffer will be returned, otherwise the syscall code returns -1.
329 	 */
330 	if (error == 0 && earlyterm == 0)
331 		marker = -1;
332 	else
333 		marker = i;
334 	if (error == 0)
335 		error = copyout(&marker, uap->marker, sizeof(marker));
336 	uap->sysmsg_result = bytes;
337 done:
338 	rel_mplock();
339 	return(error);
340 }
341 
342 /*
343  * Lookup a variant symlink.  XXX use a hash table.
344  */
345 static
346 struct varsyment *
347 varsymlookup(struct varsymset *vss, const char *name, int namelen)
348 {
349     struct varsyment *ve;
350 
351     KKASSERT(lockstatus(&vss->vx_lock, curthread) != 0);
352     TAILQ_FOREACH(ve, &vss->vx_queue, ve_entry) {
353 	varsym_t var = ve->ve_sym;
354 	if (var->vs_namelen == namelen &&
355 	    bcmp(name, var->vs_name, namelen) == 0
356 	) {
357 	    return(ve);
358 	}
359     }
360     return(NULL);
361 }
362 
363 static
364 void
365 vsslock(struct varsymset **vss, struct varsymset *n)
366 {
367 	if (*vss) {
368 		lockmgr(&(*vss)->vx_lock, LK_RELEASE);
369 	}
370 	lockmgr(&n->vx_lock, LK_SHARED);
371 	*vss = n;
372 }
373 
374 varsym_t
375 varsymfind(int mask, const char *name, int namelen)
376 {
377     struct proc *p = curproc;
378     struct varsyment *ve = NULL;
379     struct varsymset *vss = NULL;
380     varsym_t sym;
381 
382     if ((mask & (VARSYM_PROC_MASK|VARSYM_USER_MASK)) && p != NULL) {
383 	if (mask & VARSYM_PROC_MASK) {
384 	    vsslock(&vss, &p->p_varsymset);
385 	    ve = varsymlookup(vss, name, namelen);
386 	}
387 	if (ve == NULL && (mask & VARSYM_USER_MASK)) {
388 	    vsslock(&vss, &p->p_ucred->cr_uidinfo->ui_varsymset);
389 	    ve = varsymlookup(vss, name, namelen);
390 	}
391     }
392     if (ve == NULL && (mask & VARSYM_SYS_MASK)) {
393 	if (p != NULL && p->p_ucred->cr_prison) {
394 	    vsslock(&vss, &p->p_ucred->cr_prison->pr_varsymset);
395 	    ve = varsymlookup(vss, name, namelen);
396 	} else {
397 	    vsslock(&vss, &varsymset_sys);
398 	    ve = varsymlookup(vss, name, namelen);
399 	}
400     }
401     if (ve) {
402 	sym = ve->ve_sym;
403 	atomic_add_int(&sym->vs_refs, 1);
404     } else {
405 	sym = NULL;
406     }
407     lockmgr(&vss->vx_lock, LK_RELEASE);
408     return sym;
409 }
410 
411 int
412 varsymmake(int level, const char *name, const char *data)
413 {
414     struct varsymset *vss = NULL;
415     struct varsyment *ve;
416     struct proc *p = curproc;
417     varsym_t sym;
418     int namelen = strlen(name);
419     int datalen;
420     int error;
421 
422     switch(level) {
423     case VARSYM_PROC:
424 	if (p)
425 	    vss = &p->p_varsymset;
426 	break;
427     case VARSYM_USER:
428 	if (p)
429 	    vss = &p->p_ucred->cr_uidinfo->ui_varsymset;
430 	break;
431     case VARSYM_SYS:
432 	vss = &varsymset_sys;
433 	break;
434     case VARSYM_PRISON:
435 	if (p != NULL && p->p_ucred->cr_prison != NULL)
436 	    vss = &p->p_ucred->cr_prison->pr_varsymset;
437 	break;
438     }
439     if (vss == NULL) {
440 	return EINVAL;
441     }
442     lockmgr(&vss->vx_lock, LK_EXCLUSIVE);
443     if (data && vss->vx_setsize >= MAXVARSYM_SET) {
444 	error = E2BIG;
445     } else if (data) {
446 	datalen = strlen(data);
447 	ve = kmalloc(sizeof(struct varsyment), M_VARSYM, M_WAITOK|M_ZERO);
448 	sym = kmalloc(sizeof(struct varsym) + namelen + datalen + 2, M_VARSYM, M_WAITOK);
449 	ve->ve_sym = sym;
450 	sym->vs_refs = 1;
451 	sym->vs_namelen = namelen;
452 	sym->vs_name = (char *)(sym + 1);
453 	sym->vs_data = sym->vs_name + namelen + 1;
454 	strcpy(sym->vs_name, name);
455 	strcpy(sym->vs_data, data);
456 	TAILQ_INSERT_TAIL(&vss->vx_queue, ve, ve_entry);
457 	vss->vx_setsize += sizeof(struct varsyment) + sizeof(struct varsym) + namelen + datalen + 8;
458 	error = 0;
459     } else {
460 	if ((ve = varsymlookup(vss, name, namelen)) != NULL) {
461 	    TAILQ_REMOVE(&vss->vx_queue, ve, ve_entry);
462 	    vss->vx_setsize -= sizeof(struct varsyment) + sizeof(struct varsym) + namelen + strlen(ve->ve_sym->vs_data) + 8;
463 	    varsymdrop(ve->ve_sym);
464 	    kfree(ve, M_VARSYM);
465 	    error = 0;
466 	} else {
467 	    error = ENOENT;
468 	}
469     }
470     lockmgr(&vss->vx_lock, LK_RELEASE);
471     return(error);
472 }
473 
474 void
475 varsymdrop(varsym_t sym)
476 {
477     KKASSERT(sym->vs_refs > 0);
478     if (atomic_fetchadd_int(&sym->vs_refs, -1) == 1) {
479 	kfree(sym, M_VARSYM);
480     }
481 }
482 
483 /*
484  * Insert a duplicate of ve in vss. Does not do any locking,
485  * so it is the callers responsibility to make sure nobody
486  * else can mess with the TAILQ in vss at the same time.
487  */
488 static void
489 varsymdup(struct varsymset *vss, struct varsyment *ve)
490 {
491     struct varsyment *nve;
492 
493     nve = kmalloc(sizeof(struct varsyment), M_VARSYM, M_WAITOK|M_ZERO);
494     nve->ve_sym = ve->ve_sym;
495     ++nve->ve_sym->vs_refs;	/* can't be reached, no need for atomic add */
496     /*
497      * We're only called through varsymset_init() so vss is not yet reachable,
498      * no need to lock.
499      */
500     TAILQ_INSERT_TAIL(&vss->vx_queue, nve, ve_entry);
501 }
502 
503 void
504 varsymset_init(struct varsymset *vss, struct varsymset *copy)
505 {
506     struct varsyment *ve;
507 
508     TAILQ_INIT(&vss->vx_queue);
509     lockinit(&vss->vx_lock, "vx", 0, 0);
510     if (copy) {
511 	TAILQ_FOREACH(ve, &copy->vx_queue, ve_entry) {
512 	    varsymdup(vss, ve);
513 	}
514 	vss->vx_setsize = copy->vx_setsize;
515     }
516 }
517 
518 void
519 varsymset_clean(struct varsymset *vss)
520 {
521     struct varsyment *ve;
522 
523     lockmgr(&vss->vx_lock, LK_EXCLUSIVE);
524     while ((ve = TAILQ_FIRST(&vss->vx_queue)) != NULL) {
525 	TAILQ_REMOVE(&vss->vx_queue, ve, ve_entry);
526 	varsymdrop(ve->ve_sym);
527 	kfree(ve, M_VARSYM);
528     }
529     vss->vx_setsize = 0;
530     lockmgr(&vss->vx_lock, LK_RELEASE);
531 }
532 
533