memguard.c revision 238502
1/*- 2 * Copyright (c) 2005, Bosko Milekic <bmilekic@FreeBSD.org>. 3 * Copyright (c) 2010 Isilon Systems, Inc. (http://www.isilon.com/) 4 * All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice unmodified, this list of conditions, and the following 11 * disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 19 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 26 */ 27 28#include <sys/cdefs.h> 29__FBSDID("$FreeBSD: head/sys/vm/memguard.c 238502 2012-07-15 20:29:48Z mdf $"); 30 31/* 32 * MemGuard is a simple replacement allocator for debugging only 33 * which provides ElectricFence-style memory barrier protection on 34 * objects being allocated, and is used to detect tampering-after-free 35 * scenarios. 36 * 37 * See the memguard(9) man page for more information on using MemGuard. 38 */ 39 40#include "opt_vm.h" 41 42#include <sys/param.h> 43#include <sys/systm.h> 44#include <sys/kernel.h> 45#include <sys/types.h> 46#include <sys/queue.h> 47#include <sys/lock.h> 48#include <sys/mutex.h> 49#include <sys/malloc.h> 50#include <sys/sysctl.h> 51 52#include <vm/vm.h> 53#include <vm/uma.h> 54#include <vm/vm_param.h> 55#include <vm/vm_page.h> 56#include <vm/vm_map.h> 57#include <vm/vm_object.h> 58#include <vm/vm_extern.h> 59#include <vm/uma_int.h> 60#include <vm/memguard.h> 61 62static SYSCTL_NODE(_vm, OID_AUTO, memguard, CTLFLAG_RW, NULL, "MemGuard data"); 63/* 64 * The vm_memguard_divisor variable controls how much of kmem_map should be 65 * reserved for MemGuard. 66 */ 67static u_int vm_memguard_divisor; 68SYSCTL_UINT(_vm_memguard, OID_AUTO, divisor, CTLFLAG_RDTUN, 69 &vm_memguard_divisor, 70 0, "(kmem_size/memguard_divisor) == memguard submap size"); 71 72/* 73 * Short description (ks_shortdesc) of memory type to monitor. 74 */ 75static char vm_memguard_desc[128] = ""; 76static struct malloc_type *vm_memguard_mtype = NULL; 77TUNABLE_STR("vm.memguard.desc", vm_memguard_desc, sizeof(vm_memguard_desc)); 78static int 79memguard_sysctl_desc(SYSCTL_HANDLER_ARGS) 80{ 81 char desc[sizeof(vm_memguard_desc)]; 82 int error; 83 84 strlcpy(desc, vm_memguard_desc, sizeof(desc)); 85 error = sysctl_handle_string(oidp, desc, sizeof(desc), req); 86 if (error != 0 || req->newptr == NULL) 87 return (error); 88 89 mtx_lock(&malloc_mtx); 90 /* 91 * If mtp is NULL, it will be initialized in memguard_cmp(). 92 */ 93 vm_memguard_mtype = malloc_desc2type(desc); 94 strlcpy(vm_memguard_desc, desc, sizeof(vm_memguard_desc)); 95 mtx_unlock(&malloc_mtx); 96 return (error); 97} 98SYSCTL_PROC(_vm_memguard, OID_AUTO, desc, 99 CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 0, 100 memguard_sysctl_desc, "A", "Short description of memory type to monitor"); 101 102static vm_map_t memguard_map = NULL; 103static vm_offset_t memguard_cursor; 104static vm_size_t memguard_mapsize; 105static vm_size_t memguard_physlimit; 106static u_long memguard_wasted; 107static u_long memguard_wrap; 108static u_long memguard_succ; 109static u_long memguard_fail_kva; 110static u_long memguard_fail_pgs; 111 112SYSCTL_ULONG(_vm_memguard, OID_AUTO, cursor, CTLFLAG_RD, 113 &memguard_cursor, 0, "MemGuard cursor"); 114SYSCTL_ULONG(_vm_memguard, OID_AUTO, mapsize, CTLFLAG_RD, 115 &memguard_mapsize, 0, "MemGuard private vm_map size"); 116SYSCTL_ULONG(_vm_memguard, OID_AUTO, phys_limit, CTLFLAG_RD, 117 &memguard_physlimit, 0, "Limit on MemGuard memory consumption"); 118SYSCTL_ULONG(_vm_memguard, OID_AUTO, wasted, CTLFLAG_RD, 119 &memguard_wasted, 0, "Excess memory used through page promotion"); 120SYSCTL_ULONG(_vm_memguard, OID_AUTO, wrapcnt, CTLFLAG_RD, 121 &memguard_wrap, 0, "MemGuard cursor wrap count"); 122SYSCTL_ULONG(_vm_memguard, OID_AUTO, numalloc, CTLFLAG_RD, 123 &memguard_succ, 0, "Count of successful MemGuard allocations"); 124SYSCTL_ULONG(_vm_memguard, OID_AUTO, fail_kva, CTLFLAG_RD, 125 &memguard_fail_kva, 0, "MemGuard failures due to lack of KVA"); 126SYSCTL_ULONG(_vm_memguard, OID_AUTO, fail_pgs, CTLFLAG_RD, 127 &memguard_fail_pgs, 0, "MemGuard failures due to lack of pages"); 128 129#define MG_GUARD_AROUND 0x001 130#define MG_GUARD_ALLLARGE 0x002 131#define MG_GUARD_NOFREE 0x004 132static int memguard_options = MG_GUARD_AROUND; 133TUNABLE_INT("vm.memguard.options", &memguard_options); 134SYSCTL_INT(_vm_memguard, OID_AUTO, options, CTLFLAG_RW, 135 &memguard_options, 0, 136 "MemGuard options:\n" 137 "\t0x001 - add guard pages around each allocation\n" 138 "\t0x002 - always use MemGuard for allocations over a page\n" 139 "\t0x004 - guard uma(9) zones with UMA_ZONE_NOFREE flag"); 140 141static u_int memguard_minsize; 142static u_long memguard_minsize_reject; 143SYSCTL_UINT(_vm_memguard, OID_AUTO, minsize, CTLFLAG_RW, 144 &memguard_minsize, 0, "Minimum size for page promotion"); 145SYSCTL_ULONG(_vm_memguard, OID_AUTO, minsize_reject, CTLFLAG_RD, 146 &memguard_minsize_reject, 0, "# times rejected for size"); 147 148static u_int memguard_frequency; 149static u_long memguard_frequency_hits; 150TUNABLE_INT("vm.memguard.frequency", &memguard_frequency); 151SYSCTL_UINT(_vm_memguard, OID_AUTO, frequency, CTLFLAG_RW, 152 &memguard_frequency, 0, "Times in 100000 that MemGuard will randomly run"); 153SYSCTL_ULONG(_vm_memguard, OID_AUTO, frequency_hits, CTLFLAG_RD, 154 &memguard_frequency_hits, 0, "# times MemGuard randomly chose"); 155 156 157/* 158 * Return a fudged value to be used for vm_kmem_size for allocating 159 * the kmem_map. The memguard memory will be a submap. 160 */ 161unsigned long 162memguard_fudge(unsigned long km_size, const struct vm_map *parent_map) 163{ 164 u_long mem_pgs, parent_size; 165 166 vm_memguard_divisor = 10; 167 TUNABLE_INT_FETCH("vm.memguard.divisor", &vm_memguard_divisor); 168 169 parent_size = vm_map_max(parent_map) - vm_map_min(parent_map) + 170 PAGE_SIZE; 171 /* Pick a conservative value if provided value sucks. */ 172 if ((vm_memguard_divisor <= 0) || 173 ((parent_size / vm_memguard_divisor) == 0)) 174 vm_memguard_divisor = 10; 175 /* 176 * Limit consumption of physical pages to 177 * 1/vm_memguard_divisor of system memory. If the KVA is 178 * smaller than this then the KVA limit comes into play first. 179 * This prevents memguard's page promotions from completely 180 * using up memory, since most malloc(9) calls are sub-page. 181 */ 182 mem_pgs = cnt.v_page_count; 183 memguard_physlimit = (mem_pgs / vm_memguard_divisor) * PAGE_SIZE; 184 /* 185 * We want as much KVA as we can take safely. Use at most our 186 * allotted fraction of the parent map's size. Limit this to 187 * twice the physical memory to avoid using too much memory as 188 * pagetable pages (size must be multiple of PAGE_SIZE). 189 */ 190 memguard_mapsize = round_page(parent_size / vm_memguard_divisor); 191 if (memguard_mapsize / (2 * PAGE_SIZE) > mem_pgs) 192 memguard_mapsize = mem_pgs * 2 * PAGE_SIZE; 193 if (km_size + memguard_mapsize > parent_size) 194 memguard_mapsize = 0; 195 return (km_size + memguard_mapsize); 196} 197 198/* 199 * Initialize the MemGuard mock allocator. All objects from MemGuard come 200 * out of a single VM map (contiguous chunk of address space). 201 */ 202void 203memguard_init(vm_map_t parent_map) 204{ 205 vm_offset_t base, limit; 206 207 memguard_map = kmem_suballoc(parent_map, &base, &limit, 208 memguard_mapsize, FALSE); 209 memguard_map->system_map = 1; 210 KASSERT(memguard_mapsize == limit - base, 211 ("Expected %lu, got %lu", (u_long)memguard_mapsize, 212 (u_long)(limit - base))); 213 memguard_cursor = base; 214 215 printf("MEMGUARD DEBUGGING ALLOCATOR INITIALIZED:\n"); 216 printf("\tMEMGUARD map base: 0x%lx\n", (u_long)base); 217 printf("\tMEMGUARD map limit: 0x%lx\n", (u_long)limit); 218 printf("\tMEMGUARD map size: %jd KBytes\n", 219 (uintmax_t)memguard_mapsize >> 10); 220} 221 222/* 223 * Run things that can't be done as early as memguard_init(). 224 */ 225static void 226memguard_sysinit(void) 227{ 228 struct sysctl_oid_list *parent; 229 230 parent = SYSCTL_STATIC_CHILDREN(_vm_memguard); 231 232 SYSCTL_ADD_ULONG(NULL, parent, OID_AUTO, "mapstart", CTLFLAG_RD, 233 &memguard_map->min_offset, "MemGuard KVA base"); 234 SYSCTL_ADD_ULONG(NULL, parent, OID_AUTO, "maplimit", CTLFLAG_RD, 235 &memguard_map->max_offset, "MemGuard KVA end"); 236 SYSCTL_ADD_ULONG(NULL, parent, OID_AUTO, "mapused", CTLFLAG_RD, 237 &memguard_map->size, "MemGuard KVA used"); 238} 239SYSINIT(memguard, SI_SUB_KLD, SI_ORDER_ANY, memguard_sysinit, NULL); 240 241/* 242 * v2sizep() converts a virtual address of the first page allocated for 243 * an item to a pointer to u_long recording the size of the original 244 * allocation request. 245 * 246 * This routine is very similar to those defined by UMA in uma_int.h. 247 * The difference is that this routine stores the originally allocated 248 * size in one of the page's fields that is unused when the page is 249 * wired rather than the object field, which is used. 250 */ 251static u_long * 252v2sizep(vm_offset_t va) 253{ 254 vm_paddr_t pa; 255 struct vm_page *p; 256 257 pa = pmap_kextract(va); 258 if (pa == 0) 259 panic("MemGuard detected double-free of %p", (void *)va); 260 p = PHYS_TO_VM_PAGE(pa); 261 KASSERT(p->wire_count != 0 && p->queue == PQ_NONE, 262 ("MEMGUARD: Expected wired page %p in vtomgfifo!", p)); 263 return ((u_long *)&p->pageq.tqe_next); 264} 265 266/* 267 * Allocate a single object of specified size with specified flags 268 * (either M_WAITOK or M_NOWAIT). 269 */ 270void * 271memguard_alloc(unsigned long req_size, int flags) 272{ 273 vm_offset_t addr; 274 u_long size_p, size_v; 275 int do_guard, rv; 276 277 size_p = round_page(req_size); 278 if (size_p == 0) 279 return (NULL); 280 /* 281 * To ensure there are holes on both sides of the allocation, 282 * request 2 extra pages of KVA. We will only actually add a 283 * vm_map_entry and get pages for the original request. Save 284 * the value of memguard_options so we have a consistent 285 * value. 286 */ 287 size_v = size_p; 288 do_guard = (memguard_options & MG_GUARD_AROUND) != 0; 289 if (do_guard) 290 size_v += 2 * PAGE_SIZE; 291 292 vm_map_lock(memguard_map); 293 /* 294 * When we pass our memory limit, reject sub-page allocations. 295 * Page-size and larger allocations will use the same amount 296 * of physical memory whether we allocate or hand off to 297 * uma_large_alloc(), so keep those. 298 */ 299 if (memguard_map->size >= memguard_physlimit && 300 req_size < PAGE_SIZE) { 301 addr = (vm_offset_t)NULL; 302 memguard_fail_pgs++; 303 goto out; 304 } 305 /* 306 * Keep a moving cursor so we don't recycle KVA as long as 307 * possible. It's not perfect, since we don't know in what 308 * order previous allocations will be free'd, but it's simple 309 * and fast, and requires O(1) additional storage if guard 310 * pages are not used. 311 * 312 * XXX This scheme will lead to greater fragmentation of the 313 * map, unless vm_map_findspace() is tweaked. 314 */ 315 for (;;) { 316 rv = vm_map_findspace(memguard_map, memguard_cursor, 317 size_v, &addr); 318 if (rv == KERN_SUCCESS) 319 break; 320 /* 321 * The map has no space. This may be due to 322 * fragmentation, or because the cursor is near the 323 * end of the map. 324 */ 325 if (memguard_cursor == vm_map_min(memguard_map)) { 326 memguard_fail_kva++; 327 addr = (vm_offset_t)NULL; 328 goto out; 329 } 330 memguard_wrap++; 331 memguard_cursor = vm_map_min(memguard_map); 332 } 333 if (do_guard) 334 addr += PAGE_SIZE; 335 rv = kmem_back(memguard_map, addr, size_p, flags); 336 if (rv != KERN_SUCCESS) { 337 memguard_fail_pgs++; 338 addr = (vm_offset_t)NULL; 339 goto out; 340 } 341 memguard_cursor = addr + size_p; 342 *v2sizep(trunc_page(addr)) = req_size; 343 memguard_succ++; 344 if (req_size < PAGE_SIZE) { 345 memguard_wasted += (PAGE_SIZE - req_size); 346 if (do_guard) { 347 /* 348 * Align the request to 16 bytes, and return 349 * an address near the end of the page, to 350 * better detect array overrun. 351 */ 352 req_size = roundup2(req_size, 16); 353 addr += (PAGE_SIZE - req_size); 354 } 355 } 356out: 357 vm_map_unlock(memguard_map); 358 return ((void *)addr); 359} 360 361int 362is_memguard_addr(void *addr) 363{ 364 vm_offset_t a = (vm_offset_t)(uintptr_t)addr; 365 366 return (a >= memguard_map->min_offset && a < memguard_map->max_offset); 367} 368 369/* 370 * Free specified single object. 371 */ 372void 373memguard_free(void *ptr) 374{ 375 vm_offset_t addr; 376 u_long req_size, size; 377 char *temp; 378 int i; 379 380 addr = trunc_page((uintptr_t)ptr); 381 req_size = *v2sizep(addr); 382 size = round_page(req_size); 383 384 /* 385 * Page should not be guarded right now, so force a write. 386 * The purpose of this is to increase the likelihood of 387 * catching a double-free, but not necessarily a 388 * tamper-after-free (the second thread freeing might not 389 * write before freeing, so this forces it to and, 390 * subsequently, trigger a fault). 391 */ 392 temp = ptr; 393 for (i = 0; i < size; i += PAGE_SIZE) 394 temp[i] = 'M'; 395 396 /* 397 * This requires carnal knowledge of the implementation of 398 * kmem_free(), but since we've already replaced kmem_malloc() 399 * above, it's not really any worse. We want to use the 400 * vm_map lock to serialize updates to memguard_wasted, since 401 * we had the lock at increment. 402 */ 403 vm_map_lock(memguard_map); 404 if (req_size < PAGE_SIZE) 405 memguard_wasted -= (PAGE_SIZE - req_size); 406 (void)vm_map_delete(memguard_map, addr, addr + size); 407 vm_map_unlock(memguard_map); 408} 409 410/* 411 * Re-allocate an allocation that was originally guarded. 412 */ 413void * 414memguard_realloc(void *addr, unsigned long size, struct malloc_type *mtp, 415 int flags) 416{ 417 void *newaddr; 418 u_long old_size; 419 420 /* 421 * Allocate the new block. Force the allocation to be guarded 422 * as the original may have been guarded through random 423 * chance, and that should be preserved. 424 */ 425 if ((newaddr = memguard_alloc(size, flags)) == NULL) 426 return (NULL); 427 428 /* Copy over original contents. */ 429 old_size = *v2sizep(trunc_page((uintptr_t)addr)); 430 bcopy(addr, newaddr, min(size, old_size)); 431 memguard_free(addr); 432 return (newaddr); 433} 434 435static int 436memguard_cmp(unsigned long size) 437{ 438 439 if (size < memguard_minsize) { 440 memguard_minsize_reject++; 441 return (0); 442 } 443 if ((memguard_options & MG_GUARD_ALLLARGE) != 0 && size >= PAGE_SIZE) 444 return (1); 445 if (memguard_frequency > 0 && 446 (random() % 100000) < memguard_frequency) { 447 memguard_frequency_hits++; 448 return (1); 449 } 450 451 return (0); 452} 453 454int 455memguard_cmp_mtp(struct malloc_type *mtp, unsigned long size) 456{ 457 458 if (memguard_cmp(size)) 459 return(1); 460 461#if 1 462 /* 463 * The safest way of comparsion is to always compare short description 464 * string of memory type, but it is also the slowest way. 465 */ 466 return (strcmp(mtp->ks_shortdesc, vm_memguard_desc) == 0); 467#else 468 /* 469 * If we compare pointers, there are two possible problems: 470 * 1. Memory type was unloaded and new memory type was allocated at the 471 * same address. 472 * 2. Memory type was unloaded and loaded again, but allocated at a 473 * different address. 474 */ 475 if (vm_memguard_mtype != NULL) 476 return (mtp == vm_memguard_mtype); 477 if (strcmp(mtp->ks_shortdesc, vm_memguard_desc) == 0) { 478 vm_memguard_mtype = mtp; 479 return (1); 480 } 481 return (0); 482#endif 483} 484 485int 486memguard_cmp_zone(uma_zone_t zone) 487{ 488 489 if ((memguard_options & MG_GUARD_NOFREE) == 0 && 490 zone->uz_flags & UMA_ZONE_NOFREE) 491 return (0); 492 493 if (memguard_cmp(zone->uz_size)) 494 return (1); 495 496 /* 497 * The safest way of comparsion is to always compare zone name, 498 * but it is also the slowest way. 499 */ 500 return (strcmp(zone->uz_name, vm_memguard_desc) == 0); 501} 502