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/sysproto.h>
  53
  54 MALLOC_DEFINE(M_VARSYM, "varsym", "variable sets for variant symlinks");
  55
  56 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 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
 139     td = curthread;
 140     lp = td->td_lwp;
 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
 151     switch(uap->level) {
 152     case VARSYM_SYS:
 153         if (lp != NULL && td->td_ucred->cr_prison != NULL)
 154             uap->level = VARSYM_PRISON;
 155         /* fall through */
 156     case VARSYM_PRISON:
 157         if (lp != NULL &&
 158             (error = priv_check_cred(td->td_ucred, PRIV_VARSYM_SYS, 0)) != 0)
 159             break;
 160         /* fall through */
 161     case VARSYM_USER:
 162         /* XXX check jail / implement per-jail user */
 163         /* fall through */
 164     case VARSYM_PROC:
 165         if (uap->data) {
 166             (void)varsymmake(uap->level, name, NULL);
 167             error = varsymmake(uap->level, name, buf);
 168         } else {
 169             error = varsymmake(uap->level, name, NULL);
 170         }
 171         break;
 172     }
 173 done1:
 174     kfree(buf, M_TEMP);
 175 done2:
 176     return(error);
 177 }
 178
 179 /*
 180  * varsym_get() system call
 181  *
 182  * (int mask, const char *wild, char *buf, int bufsize)
 183  *
 184  * MPALMOSTSAFE
 185  */
 186 int
 187 sys_varsym_get(struct varsym_get_args *uap)
 188 {
 189     char wild[MAXVARSYM_NAME];
 190     varsym_t sym;
 191     int error;
 192     int dlen;
 193
 194     if ((error = copyinstr(uap->wild, wild, sizeof(wild), NULL)) != 0)
 195         goto done;
 196     sym = varsymfind(uap->mask, wild, strlen(wild));
 197     if (sym == NULL) {
 198         error = ENOENT;
 199         goto done;
 200     }
 201     dlen = strlen(sym->vs_data);
 202     if (dlen < uap->bufsize) {
 203         copyout(sym->vs_data, uap->buf, dlen + 1);
 204     } else if (uap->bufsize) {
 205         copyout("", uap->buf, 1);
 206     }
 207     uap->sysmsg_result = dlen + 1;
 208     varsymdrop(sym);
 209 done:
 210
 211     return(error);
 212 }
 213
 214 /*
 215  * varsym_list() system call
 216  *
 217  * (int level, char *buf, int maxsize, int *marker)
 218  *
 219  * MPALMOSTSAFE
 220  */
 221 int
 222 sys_varsym_list(struct varsym_list_args *uap)
 223 {
 224         struct varsymset *vss;
 225         struct varsyment *ve;
 226         struct thread *td;
 227         struct proc *p;
 228         struct lwp *lp;
 229         int i;
 230         int error;
 231         int bytes;
 232         int earlyterm;
 233         int marker;
 234
 235         /*
 236          * Get the marker from userspace.
 237          */
 238         if ((error = copyin(uap->marker, &marker, sizeof(marker))) != 0)
 239                 goto done;
 240
 241         /*
 242          * Figure out the varsym set.
 243          */
 244         td = curthread;
 245         lp = td->td_lwp;
 246         p = lp ? lp->lwp_proc : NULL;
 247
 248         vss = NULL;
 249
 250         switch (uap->level) {
 251         case VARSYM_PROC:
 252                 if (p)
 253                         vss = &p->p_varsymset;
 254                 break;
 255         case VARSYM_USER:
 256                 if (lp)
 257                         vss = &td->td_ucred->cr_uidinfo->ui_varsymset;
 258                 break;
 259         case VARSYM_SYS:
 260                 vss = &varsymset_sys;
 261                 break;
 262         case VARSYM_PRISON:
 263                 if (lp && td->td_ucred->cr_prison)
 264                         vss = &td->td_ucred->cr_prison->pr_varsymset;
 265                 break;
 266         }
 267         if (vss == NULL) {
 268                 error = EINVAL;
 269                 goto done;
 270         }
 271
 272         /*
 273          * Loop through the variables and dump them to uap->buf
 274          */
 275         i = 0;
 276         bytes = 0;
 277         earlyterm = 0;
 278
 279         lockmgr(&vss->vx_lock, LK_SHARED);
 280         TAILQ_FOREACH(ve, &vss->vx_queue, ve_entry) {
 281                 varsym_t sym = ve->ve_sym;
 282                 int namelen = strlen(sym->vs_name);
 283                 int datalen = strlen(sym->vs_data);
 284                 int totlen = namelen + datalen + 2;
 285
 286                 /*
 287                  * Skip to our index point
 288                  */
 289                 if (i < marker) {
 290                         ++i;
 291                         continue;
 292                 }
 293
 294                 /*
 295                  * Stop if there is insufficient space in the user buffer.
 296                  * If we haven't stored anything yet return EOVERFLOW.
 297                  * Note that the marker index (i) does not change.
 298                  */
 299                 if (bytes + totlen > uap->maxsize) {
 300                         if (bytes == 0)
 301                                 error = EOVERFLOW;
 302                         earlyterm = 1;
 303                         break;
 304                 }
 305
 306                 error = copyout(sym->vs_name, uap->buf + bytes, namelen + 1);
 307                 if (error == 0) {
 308                         bytes += namelen + 1;
 309                         error = copyout(sym->vs_data, uap->buf + bytes, datalen + 1);
 310                         if (error == 0)
 311                                 bytes += datalen + 1;
 312                         else
 313                                 bytes -= namelen + 1;   /* revert if error */
 314                 }
 315                 if (error) {
 316                         earlyterm = 1;
 317                         break;
 318                 }
 319                 ++i;
 320         }
 321         lockmgr(&vss->vx_lock, LK_RELEASE);
 322
 323         /*
 324          * Save the marker back.  If no error occured and earlyterm is clear
 325          * the marker is set to -1 indicating that the variable list has been
 326          * exhausted.  If no error occured the number of bytes loaded into
 327          * the buffer will be returned, otherwise the syscall code returns -1.
 328          */
 329         if (error == 0 && earlyterm == 0)
 330                 marker = -1;
 331         else
 332                 marker = i;
 333         if (error == 0)
 334                 error = copyout(&marker, uap->marker, sizeof(marker));
 335         uap->sysmsg_result = bytes;
 336 done:
 337         return(error);
 338 }
 339
 340 /*
 341  * Lookup a variant symlink.  XXX use a hash table.
 342  */
 343 static
 344 struct varsyment *
 345 varsymlookup(struct varsymset *vss, const char *name, int namelen)
 346 {
 347     struct varsyment *ve;
 348
 349     KKASSERT(lockstatus(&vss->vx_lock, curthread) != 0);
 350     TAILQ_FOREACH(ve, &vss->vx_queue, ve_entry) {
 351         varsym_t var = ve->ve_sym;
 352         if (var->vs_namelen == namelen &&
 353             bcmp(name, var->vs_name, namelen) == 0
 354         ) {
 355             return(ve);
 356         }
 357     }
 358     return(NULL);
 359 }
 360
 361 static
 362 void
 363 vsslock(struct varsymset **vss, struct varsymset *n)
 364 {
 365         if (*vss) {
 366                 lockmgr(&(*vss)->vx_lock, LK_RELEASE);
 367         }
 368         lockmgr(&n->vx_lock, LK_SHARED);
 369         *vss = n;
 370 }
 371
 372 varsym_t
 373 varsymfind(int mask, const char *name, int namelen)
 374 {
 375     struct varsyment *ve = NULL;
 376     struct varsymset *vss = NULL;
 377     struct thread *td;
 378     struct lwp *lp;
 379     struct proc *p;
 380     varsym_t sym;
 381
 382     td = curthread;
 383     lp = td->td_lwp;
 384     p = lp ? lp->lwp_proc : NULL;
 385
 386     if ((mask & (VARSYM_PROC_MASK|VARSYM_USER_MASK)) && lp != NULL) {
 387         if (mask & VARSYM_PROC_MASK) {
 388             vsslock(&vss, &p->p_varsymset);
 389             ve = varsymlookup(vss, name, namelen);
 390         }
 391         if (ve == NULL && (mask & VARSYM_USER_MASK)) {
 392             vsslock(&vss, &td->td_ucred->cr_uidinfo->ui_varsymset);
 393             ve = varsymlookup(vss, name, namelen);
 394         }
 395     }
 396     if (ve == NULL && (mask & VARSYM_SYS_MASK)) {
 397         if (lp != NULL && td->td_ucred->cr_prison) {
 398             vsslock(&vss, &td->td_ucred->cr_prison->pr_varsymset);
 399             ve = varsymlookup(vss, name, namelen);
 400         } else {
 401             vsslock(&vss, &varsymset_sys);
 402             ve = varsymlookup(vss, name, namelen);
 403         }
 404     }
 405     if (ve) {
 406         sym = ve->ve_sym;
 407         atomic_add_int(&sym->vs_refs, 1);
 408     } else {
 409         sym = NULL;
 410     }
 411     if (vss)
 412         lockmgr(&vss->vx_lock, LK_RELEASE);
 413     return sym;
 414 }
 415
 416 int
 417 varsymmake(int level, const char *name, const char *data)
 418 {
 419     struct varsymset *vss = NULL;
 420     struct varsyment *ve;
 421     struct thread *td;
 422     struct proc *p;
 423     struct lwp *lp;
 424     varsym_t sym;
 425     int namelen = strlen(name);
 426     int datalen;
 427     int error;
 428
 429     td = curthread;
 430     lp = td->td_lwp;
 431     p = lp ? lp->lwp_proc : NULL;
 432
 433     switch(level) {
 434     case VARSYM_PROC:
 435         if (p)
 436             vss = &p->p_varsymset;
 437         break;
 438     case VARSYM_USER:
 439         if (lp)
 440             vss = &td->td_ucred->cr_uidinfo->ui_varsymset;
 441         break;
 442     case VARSYM_SYS:
 443         vss = &varsymset_sys;
 444         break;
 445     case VARSYM_PRISON:
 446         if (lp && td->td_ucred->cr_prison)
 447             vss = &td->td_ucred->cr_prison->pr_varsymset;
 448         break;
 449     }
 450     if (vss == NULL) {
 451         return EINVAL;
 452     }
 453     lockmgr(&vss->vx_lock, LK_EXCLUSIVE);
 454     if (data && vss->vx_setsize >= MAXVARSYM_SET) {
 455         error = E2BIG;
 456     } else if (data) {
 457         datalen = strlen(data);
 458         ve = kmalloc(sizeof(struct varsyment), M_VARSYM, M_WAITOK|M_ZERO);
 459         sym = kmalloc(sizeof(struct varsym) + namelen + datalen + 2, M_VARSYM, M_WAITOK);
 460         ve->ve_sym = sym;
 461         sym->vs_refs = 1;
 462         sym->vs_namelen = namelen;
 463         sym->vs_name = (char *)(sym + 1);
 464         sym->vs_data = sym->vs_name + namelen + 1;
 465         strcpy(sym->vs_name, name);
 466         strcpy(sym->vs_data, data);
 467         TAILQ_INSERT_TAIL(&vss->vx_queue, ve, ve_entry);
 468         vss->vx_setsize += sizeof(struct varsyment) + sizeof(struct varsym) + namelen + datalen + 8;
 469         error = 0;
 470     } else {
 471         if ((ve = varsymlookup(vss, name, namelen)) != NULL) {
 472             TAILQ_REMOVE(&vss->vx_queue, ve, ve_entry);
 473             vss->vx_setsize -= sizeof(struct varsyment) + sizeof(struct varsym) + namelen + strlen(ve->ve_sym->vs_data) + 8;
 474             varsymdrop(ve->ve_sym);
 475             kfree(ve, M_VARSYM);
 476             error = 0;
 477         } else {
 478             error = ENOENT;
 479         }
 480     }
 481     lockmgr(&vss->vx_lock, LK_RELEASE);
 482     return(error);
 483 }
 484
 485 void
 486 varsymdrop(varsym_t sym)
 487 {
 488     KKASSERT(sym->vs_refs > 0);
 489     if (atomic_fetchadd_int(&sym->vs_refs, -1) == 1) {
 490         kfree(sym, M_VARSYM);
 491     }
 492 }
 493
 494 /*
 495  * Insert a duplicate of ve in vss. Does not do any locking,
 496  * so it is the callers responsibility to make sure nobody
 497  * else can mess with the TAILQ in vss at the same time.
 498  */
 499 static void
 500 varsymdup(struct varsymset *vss, struct varsyment *ve)
 501 {
 502     struct varsyment *nve;
 503
 504     nve = kmalloc(sizeof(struct varsyment), M_VARSYM, M_WAITOK|M_ZERO);
 505     nve->ve_sym = ve->ve_sym;
 506     ++nve->ve_sym->vs_refs;     /* can't be reached, no need for atomic add */
 507     /*
 508      * We're only called through varsymset_init() so vss is not yet reachable,
 509      * no need to lock.
 510      */
 511     TAILQ_INSERT_TAIL(&vss->vx_queue, nve, ve_entry);
 512 }
 513
 514 void
 515 varsymset_init(struct varsymset *vss, struct varsymset *copy)
 516 {
 517     struct varsyment *ve;
 518
 519     TAILQ_INIT(&vss->vx_queue);
 520     lockinit(&vss->vx_lock, "vx", 0, 0);
 521     if (copy) {
 522         TAILQ_FOREACH(ve, &copy->vx_queue, ve_entry) {
 523             varsymdup(vss, ve);
 524         }
 525         vss->vx_setsize = copy->vx_setsize;
 526     }
 527 }
 528
 529 void
 530 varsymset_clean(struct varsymset *vss)
 531 {
 532     struct varsyment *ve;
 533
 534     lockmgr(&vss->vx_lock, LK_EXCLUSIVE);
 535     while ((ve = TAILQ_FIRST(&vss->vx_queue)) != NULL) {
 536         TAILQ_REMOVE(&vss->vx_queue, ve, ve_entry);
 537         varsymdrop(ve->ve_sym);
 538         kfree(ve, M_VARSYM);
 539     }
 540     vss->vx_setsize = 0;
 541     lockmgr(&vss->vx_lock, LK_RELEASE);
 542 }
 543