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     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