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
  35 /*
  36  * This module implements variable storage and management for variant
  37  * symlinks.  These variables may also be used for general purposes.
  38  */
  39
  40 #include <sys/param.h>
  41 #include <sys/systm.h>
  42 #include <sys/kernel.h>
  43 #include <sys/ucred.h>
  44 #include <sys/resourcevar.h>
  45 #include <sys/proc.h>
  46 #include <sys/priv.h>
  47 #include <sys/jail.h>
  48 #include <sys/queue.h>
  49 #include <sys/sysctl.h>
  50 #include <sys/malloc.h>
  51 #include <sys/varsym.h>
  52 #include <sys/sysmsg.h>
  53
  54 MALLOC_DEFINE(M_VARSYM, "varsym", "variable sets for variant symlinks");
  55
  56 static struct varsymset varsymset_sys;
  57
  58 /*
  59  * Initialize the variant symlink subsystem
  60  */
  61 static void
  62 varsym_sysinit(void *dummy)
  63 {
  64     varsymset_init(&varsymset_sys, NULL);
  65 }
  66 SYSINIT(announce, SI_BOOT2_MACHDEP, SI_ORDER_FIRST, varsym_sysinit, NULL);
  67
  68 /*
  69  * varsymreplace() - called from namei
  70  *
  71  *      Do variant symlink variable substitution
  72  */
  73 int
  74 varsymreplace(char *cp, int linklen, int maxlen)
  75 {
  76     int rlen;
  77     int xlen;
  78     int nlen;
  79     int i;
  80     varsym_t var;
  81
  82     rlen = linklen;
  83     while (linklen > 1) {
  84         if (cp[0] == '$' && cp[1] == '{') {
  85             for (i = 2; i < linklen; ++i) {
  86                 if (cp[i] == '}')
  87                     break;
  88             }
  89             if (i < linklen &&
  90                 (var = varsymfind(VARSYM_ALL_MASK, cp + 2, i - 2)) != NULL
  91             ) {
  92                 xlen = i + 1;                   /* bytes to strike */
  93                 nlen = strlen(var->vs_data);    /* bytes to add */
  94                 if (linklen + nlen - xlen >= maxlen) {
  95                     varsymdrop(var);
  96                     return(-1);
  97                 }
  98                 KKASSERT(linklen >= xlen);
  99                 if (linklen != xlen)
 100                     bcopy(cp + xlen, cp + nlen, linklen - xlen);
 101                 bcopy(var->vs_data, cp, nlen);
 102                 linklen += nlen - xlen; /* new relative length */
 103                 rlen += nlen - xlen;    /* returned total length */
 104                 cp += nlen;             /* adjust past replacement */
 105                 linklen -= nlen;        /* adjust past replacement */
 106                 maxlen -= nlen;         /* adjust past replacement */
 107             } else {
 108                 /*
 109                  * It's ok if i points to the '}', it will simply be
 110                  * skipped.  i could also have hit linklen.
 111                  */
 112                 cp += i;
 113                 linklen -= i;
 114                 maxlen -= i;
 115             }
 116         } else {
 117             ++cp;
 118             --linklen;
 119             --maxlen;
 120         }
 121     }
 122     return(rlen);
 123 }
 124
 125 /*
 126  * varsym_set() system call
 127  *
 128  * (int level, const char *name, const char *data)
 129  */
 130 int
 131 sys_varsym_set(struct sysmsg *sysmsg, const struct varsym_set_args *uap)
 132 {
 133     char name[MAXVARSYM_NAME];
 134     char *buf;
 135     struct thread *td;
 136     struct lwp *lp;
 137     int error;
 138     int level = uap->level;
 139
 140     td = curthread;
 141     lp = td->td_lwp;
 142
 143     if ((error = copyinstr(uap->name, name, sizeof(name), NULL)) != 0)
 144         goto done2;
 145     buf = kmalloc(MAXVARSYM_DATA, M_TEMP, M_WAITOK);
 146     if (uap->data &&
 147         (error = copyinstr(uap->data, buf, MAXVARSYM_DATA, NULL)) != 0)
 148     {
 149         goto done1;
 150     }
 151
 152     switch(level) {
 153     case VARSYM_SYS:
 154         if (lp != NULL && td->td_ucred->cr_prison != NULL)
 155             level = VARSYM_PRISON;
 156         /* fall through */
 157     case VARSYM_PRISON:
 158         if (lp != NULL &&
 159             (error = priv_check_cred(td->td_ucred, PRIV_VARSYM_SYS, 0)) != 0)
 160             break;
 161         /* fall through */
 162     case VARSYM_USER:
 163         /* XXX check jail / implement per-jail user */
 164         /* fall through */
 165     case VARSYM_PROC:
 166         if (uap->data) {
 167             (void)varsymmake(level, name, NULL);
 168             error = varsymmake(level, name, buf);
 169         } else {
 170             error = varsymmake(level, name, NULL);
 171         }
 172         break;
 173     }
 174 done1:
 175     kfree(buf, M_TEMP);
 176 done2:
 177     return(error);
 178 }
 179
 180 /*
 181  * varsym_get() system call
 182  *
 183  * (int mask, const char *wild, char *buf, int bufsize)
 184  *
 185  * MPALMOSTSAFE
 186  */
 187 int
 188 sys_varsym_get(struct sysmsg *sysmsg, const struct varsym_get_args *uap)
 189 {
 190     char wild[MAXVARSYM_NAME];
 191     varsym_t sym;
 192     int error;
 193     int dlen;
 194
 195     if ((error = copyinstr(uap->wild, wild, sizeof(wild), NULL)) != 0)
 196         goto done;
 197     sym = varsymfind(uap->mask, wild, strlen(wild));
 198     if (sym == NULL) {
 199         error = ENOENT;
 200         goto done;
 201     }
 202     dlen = strlen(sym->vs_data);
 203     if (dlen < uap->bufsize) {
 204         error = copyout(sym->vs_data, uap->buf, dlen + 1);
 205     } else if (uap->bufsize) {
 206         copyout("", uap->buf, 1);
 207         error = EOVERFLOW;
 208     }
 209     sysmsg->sysmsg_result = 0;
 210     varsymdrop(sym);
 211 done:
 212
 213     return(error);
 214 }
 215
 216 /*
 217  * varsym_list() system call
 218  *
 219  * (int level, char *buf, int maxsize, int *marker)
 220  *
 221  * MPALMOSTSAFE
 222  */
 223 int
 224 sys_varsym_list(struct sysmsg *sysmsg, const struct varsym_list_args *uap)
 225 {
 226         struct varsymset *vss;
 227         struct varsyment *ve;
 228         struct thread *td;
 229         struct proc *p;
 230         struct lwp *lp;
 231         int i;
 232         int error;
 233         int bytes;
 234         int earlyterm;
 235         int marker;
 236
 237         /*
 238          * Get the marker from userspace.
 239          */
 240         if ((error = copyin(uap->marker, &marker, sizeof(marker))) != 0)
 241                 goto done;
 242
 243         /*
 244          * Figure out the varsym set.
 245          */
 246         td = curthread;
 247         lp = td->td_lwp;
 248         p = lp ? lp->lwp_proc : NULL;
 249
 250         vss = NULL;
 251
 252         switch (uap->level) {
 253         case VARSYM_PROC:
 254                 if (p)
 255                         vss = &p->p_varsymset;
 256                 break;
 257         case VARSYM_USER:
 258                 if (lp)
 259                         vss = &td->td_ucred->cr_uidinfo->ui_varsymset;
 260                 break;
 261         case VARSYM_SYS:
 262                 vss = &varsymset_sys;
 263                 break;
 264         case VARSYM_PRISON:
 265                 if (lp && td->td_ucred->cr_prison)
 266                         vss = &td->td_ucred->cr_prison->pr_varsymset;
 267                 break;
 268         }
 269         if (vss == NULL) {
 270                 error = EINVAL;
 271                 goto done;
 272         }
 273
 274         /*
 275          * Loop through the variables and dump them to uap->buf
 276          */
 277         i = 0;
 278         bytes = 0;
 279         earlyterm = 0;
 280
 281         lockmgr(&vss->vx_lock, LK_SHARED);
 282         TAILQ_FOREACH(ve, &vss->vx_queue, ve_entry) {
 283                 varsym_t sym = ve->ve_sym;
 284                 int namelen = strlen(sym->vs_name);
 285                 int datalen = strlen(sym->vs_data);
 286                 int totlen = namelen + datalen + 2;
 287
 288                 /*
 289                  * Skip to our index point
 290                  */
 291                 if (i < marker) {
 292                         ++i;
 293                         continue;
 294                 }
 295
 296                 /*
 297                  * Stop if there is insufficient space in the user buffer.
 298                  * If we haven't stored anything yet return EOVERFLOW.
 299                  * Note that the marker index (i) does not change.
 300                  */
 301                 if (bytes + totlen > uap->maxsize) {
 302                         if (bytes == 0)
 303                                 error = EOVERFLOW;
 304                         earlyterm = 1;
 305                         break;
 306                 }
 307
 308                 error = copyout(sym->vs_name, uap->buf + bytes, namelen + 1);
 309                 if (error == 0) {
 310                         bytes += namelen + 1;
 311                         error = copyout(sym->vs_data, uap->buf + bytes, datalen + 1);
 312                         if (error == 0)
 313                                 bytes += datalen + 1;
 314                         else
 315                                 bytes -= namelen + 1;   /* revert if error */
 316                 }
 317                 if (error) {
 318                         earlyterm = 1;
 319                         break;
 320                 }
 321                 ++i;
 322         }
 323         lockmgr(&vss->vx_lock, LK_RELEASE);
 324
 325         /*
 326          * Save the marker back.  If no error occured and earlyterm is clear
 327          * the marker is set to -1 indicating that the variable list has been
 328          * exhausted.  If no error occured the number of bytes loaded into
 329          * the buffer will be returned, otherwise the syscall code returns -1.
 330          */
 331         if (error == 0 && earlyterm == 0)
 332                 marker = -1;
 333         else
 334                 marker = i;
 335         if (error == 0)
 336                 error = copyout(&marker, uap->marker, sizeof(marker));
 337         sysmsg->sysmsg_result = bytes;
 338 done:
 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 varsyment *ve = NULL;
 378     struct varsymset *vss = NULL;
 379     struct thread *td;
 380     struct lwp *lp;
 381     struct proc *p;
 382     varsym_t sym;
 383
 384     td = curthread;
 385     lp = td->td_lwp;
 386     p = lp ? lp->lwp_proc : NULL;
 387
 388     if ((mask & (VARSYM_PROC_MASK|VARSYM_USER_MASK)) && lp != NULL) {
 389         if (mask & VARSYM_PROC_MASK) {
 390             vsslock(&vss, &p->p_varsymset);
 391             ve = varsymlookup(vss, name, namelen);
 392         }
 393         if (ve == NULL && (mask & VARSYM_USER_MASK)) {
 394             vsslock(&vss, &td->td_ucred->cr_uidinfo->ui_varsymset);
 395             ve = varsymlookup(vss, name, namelen);
 396         }
 397     }
 398     if (ve == NULL && (mask & VARSYM_SYS_MASK)) {
 399         if (lp != NULL && td->td_ucred->cr_prison) {
 400             vsslock(&vss, &td->td_ucred->cr_prison->pr_varsymset);
 401             ve = varsymlookup(vss, name, namelen);
 402         } else {
 403             vsslock(&vss, &varsymset_sys);
 404             ve = varsymlookup(vss, name, namelen);
 405         }
 406     }
 407     if (ve) {
 408         sym = ve->ve_sym;
 409         atomic_add_int(&sym->vs_refs, 1);
 410     } else {
 411         sym = NULL;
 412     }
 413     if (vss)
 414         lockmgr(&vss->vx_lock, LK_RELEASE);
 415     return sym;
 416 }
 417
 418 int
 419 varsymmake(int level, const char *name, const char *data)
 420 {
 421     struct varsymset *vss = NULL;
 422     struct varsyment *ve;
 423     struct thread *td;
 424     struct proc *p;
 425     struct lwp *lp;
 426     varsym_t sym;
 427     int namelen = strlen(name);
 428     int datalen;
 429     int error;
 430
 431     td = curthread;
 432     lp = td->td_lwp;
 433     p = lp ? lp->lwp_proc : NULL;
 434
 435     switch(level) {
 436     case VARSYM_PROC:
 437         if (p)
 438             vss = &p->p_varsymset;
 439         break;
 440     case VARSYM_USER:
 441         if (lp)
 442             vss = &td->td_ucred->cr_uidinfo->ui_varsymset;
 443         break;
 444     case VARSYM_SYS:
 445         vss = &varsymset_sys;
 446         break;
 447     case VARSYM_PRISON:
 448         if (lp && td->td_ucred->cr_prison)
 449             vss = &td->td_ucred->cr_prison->pr_varsymset;
 450         break;
 451     }
 452     if (vss == NULL) {
 453         return EINVAL;
 454     }
 455     lockmgr(&vss->vx_lock, LK_EXCLUSIVE);
 456     if (data && vss->vx_setsize >= MAXVARSYM_SET) {
 457         error = E2BIG;
 458     } else if (data) {
 459         datalen = strlen(data);
 460         ve = kmalloc(sizeof(struct varsyment), M_VARSYM, M_WAITOK|M_ZERO);
 461         sym = kmalloc(sizeof(struct varsym) + namelen + datalen + 2, M_VARSYM, M_WAITOK);
 462         ve->ve_sym = sym;
 463         sym->vs_refs = 1;
 464         sym->vs_namelen = namelen;
 465         sym->vs_name = (char *)(sym + 1);
 466         sym->vs_data = sym->vs_name + namelen + 1;
 467         strcpy(sym->vs_name, name);
 468         strcpy(sym->vs_data, data);
 469         TAILQ_INSERT_TAIL(&vss->vx_queue, ve, ve_entry);
 470         vss->vx_setsize += sizeof(struct varsyment) + sizeof(struct varsym) + namelen + datalen + 8;
 471         error = 0;
 472     } else {
 473         if ((ve = varsymlookup(vss, name, namelen)) != NULL) {
 474             TAILQ_REMOVE(&vss->vx_queue, ve, ve_entry);
 475             vss->vx_setsize -= sizeof(struct varsyment) + sizeof(struct varsym) + namelen + strlen(ve->ve_sym->vs_data) + 8;
 476             varsymdrop(ve->ve_sym);
 477             kfree(ve, M_VARSYM);
 478             error = 0;
 479         } else {
 480             error = ENOENT;
 481         }
 482     }
 483     lockmgr(&vss->vx_lock, LK_RELEASE);
 484     return(error);
 485 }
 486
 487 void
 488 varsymdrop(varsym_t sym)
 489 {
 490     KKASSERT(sym->vs_refs > 0);
 491     if (atomic_fetchadd_int(&sym->vs_refs, -1) == 1) {
 492         kfree(sym, M_VARSYM);
 493     }
 494 }
 495
 496 /*
 497  * Insert a duplicate of ve in vss. Does not do any locking,
 498  * so it is the callers responsibility to make sure nobody
 499  * else can mess with the TAILQ in vss at the same time.
 500  */
 501 static void
 502 varsymdup(struct varsymset *vss, struct varsyment *ve)
 503 {
 504     struct varsyment *nve;
 505
 506     nve = kmalloc(sizeof(struct varsyment), M_VARSYM, M_WAITOK|M_ZERO);
 507     nve->ve_sym = ve->ve_sym;
 508     ++nve->ve_sym->vs_refs;     /* can't be reached, no need for atomic add */
 509     /*
 510      * We're only called through varsymset_init() so vss is not yet reachable,
 511      * no need to lock.
 512      */
 513     TAILQ_INSERT_TAIL(&vss->vx_queue, nve, ve_entry);
 514 }
 515
 516 void
 517 varsymset_init(struct varsymset *vss, struct varsymset *copy)
 518 {
 519     struct varsyment *ve;
 520
 521     TAILQ_INIT(&vss->vx_queue);
 522     lockinit(&vss->vx_lock, "vx", 0, 0);
 523     if (copy) {
 524         TAILQ_FOREACH(ve, &copy->vx_queue, ve_entry) {
 525             varsymdup(vss, ve);
 526         }
 527         vss->vx_setsize = copy->vx_setsize;
 528     }
 529 }
 530
 531 void
 532 varsymset_clean(struct varsymset *vss)
 533 {
 534     struct varsyment *ve;
 535
 536     lockmgr(&vss->vx_lock, LK_EXCLUSIVE);
 537     while ((ve = TAILQ_FIRST(&vss->vx_queue)) != NULL) {
 538         TAILQ_REMOVE(&vss->vx_queue, ve, ve_entry);
 539         varsymdrop(ve->ve_sym);
 540         kfree(ve, M_VARSYM);
 541     }
 542     vss->vx_setsize = 0;
 543     lockmgr(&vss->vx_lock, LK_RELEASE);
 544 }
 545