sys/kern/kern_varsym.c

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