memguard.c revision 325036
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: stable/11/sys/vm/memguard.c 325036 2017-10-27 14:22:56Z markj $"); 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#include <sys/vmem.h> 52 53#include <vm/vm.h> 54#include <vm/uma.h> 55#include <vm/vm_param.h> 56#include <vm/vm_page.h> 57#include <vm/vm_map.h> 58#include <vm/vm_object.h> 59#include <vm/vm_kern.h> 60#include <vm/vm_extern.h> 61#include <vm/uma_int.h> 62#include <vm/memguard.h> 63 64static SYSCTL_NODE(_vm, OID_AUTO, memguard, CTLFLAG_RW, NULL, "MemGuard data"); 65/* 66 * The vm_memguard_divisor variable controls how much of kmem_map should be 67 * reserved for MemGuard. 68 */ 69static u_int vm_memguard_divisor; 70SYSCTL_UINT(_vm_memguard, OID_AUTO, divisor, CTLFLAG_RDTUN | CTLFLAG_NOFETCH, 71 &vm_memguard_divisor, 72 0, "(kmem_size/memguard_divisor) == memguard submap size"); 73 74/* 75 * Short description (ks_shortdesc) of memory type to monitor. 76 */ 77static char vm_memguard_desc[128] = ""; 78static struct malloc_type *vm_memguard_mtype = NULL; 79TUNABLE_STR("vm.memguard.desc", vm_memguard_desc, sizeof(vm_memguard_desc)); 80static int 81memguard_sysctl_desc(SYSCTL_HANDLER_ARGS) 82{ 83 char desc[sizeof(vm_memguard_desc)]; 84 int error; 85 86 strlcpy(desc, vm_memguard_desc, sizeof(desc)); 87 error = sysctl_handle_string(oidp, desc, sizeof(desc), req); 88 if (error != 0 || req->newptr == NULL) 89 return (error); 90 91 mtx_lock(&malloc_mtx); 92 /* If mtp is NULL, it will be initialized in memguard_cmp() */ 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_offset_t memguard_cursor; 103static vm_offset_t memguard_base; 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 arena 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; 133SYSCTL_INT(_vm_memguard, OID_AUTO, options, CTLFLAG_RWTUN, 134 &memguard_options, 0, 135 "MemGuard options:\n" 136 "\t0x001 - add guard pages around each allocation\n" 137 "\t0x002 - always use MemGuard for allocations over a page\n" 138 "\t0x004 - guard uma(9) zones with UMA_ZONE_NOFREE flag"); 139 140static u_int memguard_minsize; 141static u_long memguard_minsize_reject; 142SYSCTL_UINT(_vm_memguard, OID_AUTO, minsize, CTLFLAG_RW, 143 &memguard_minsize, 0, "Minimum size for page promotion"); 144SYSCTL_ULONG(_vm_memguard, OID_AUTO, minsize_reject, CTLFLAG_RD, 145 &memguard_minsize_reject, 0, "# times rejected for size"); 146 147static u_int memguard_frequency; 148static u_long memguard_frequency_hits; 149SYSCTL_UINT(_vm_memguard, OID_AUTO, frequency, CTLFLAG_RWTUN, 150 &memguard_frequency, 0, "Times in 100000 that MemGuard will randomly run"); 151SYSCTL_ULONG(_vm_memguard, OID_AUTO, frequency_hits, CTLFLAG_RD, 152 &memguard_frequency_hits, 0, "# times MemGuard randomly chose"); 153 154 155/* 156 * Return a fudged value to be used for vm_kmem_size for allocating 157 * the kmem_map. The memguard memory will be a submap. 158 */ 159unsigned long 160memguard_fudge(unsigned long km_size, const struct vm_map *parent_map) 161{ 162 u_long mem_pgs, parent_size; 163 164 vm_memguard_divisor = 10; 165 /* CTFLAG_RDTUN doesn't work during the early boot process. */ 166 TUNABLE_INT_FETCH("vm.memguard.divisor", &vm_memguard_divisor); 167 168 parent_size = vm_map_max(parent_map) - vm_map_min(parent_map) + 169 PAGE_SIZE; 170 /* Pick a conservative value if provided value sucks. */ 171 if ((vm_memguard_divisor <= 0) || 172 ((parent_size / vm_memguard_divisor) == 0)) 173 vm_memguard_divisor = 10; 174 /* 175 * Limit consumption of physical pages to 176 * 1/vm_memguard_divisor of system memory. If the KVA is 177 * smaller than this then the KVA limit comes into play first. 178 * This prevents memguard's page promotions from completely 179 * using up memory, since most malloc(9) calls are sub-page. 180 */ 181 mem_pgs = vm_cnt.v_page_count; 182 memguard_physlimit = (mem_pgs / vm_memguard_divisor) * PAGE_SIZE; 183 /* 184 * We want as much KVA as we can take safely. Use at most our 185 * allotted fraction of the parent map's size. Limit this to 186 * twice the physical memory to avoid using too much memory as 187 * pagetable pages (size must be multiple of PAGE_SIZE). 188 */ 189 memguard_mapsize = round_page(parent_size / vm_memguard_divisor); 190 if (memguard_mapsize / (2 * PAGE_SIZE) > mem_pgs) 191 memguard_mapsize = mem_pgs * 2 * PAGE_SIZE; 192 if (km_size + memguard_mapsize > parent_size) 193 memguard_mapsize = 0; 194 return (km_size + memguard_mapsize); 195} 196 197/* 198 * Initialize the MemGuard mock allocator. All objects from MemGuard come 199 * out of a single VM map (contiguous chunk of address space). 200 */ 201void 202memguard_init(vmem_t *parent) 203{ 204 vm_offset_t base; 205 206 vmem_alloc(parent, memguard_mapsize, M_BESTFIT | M_WAITOK, &base); 207 vmem_init(memguard_arena, "memguard arena", base, memguard_mapsize, 208 PAGE_SIZE, 0, M_WAITOK); 209 memguard_cursor = base; 210 memguard_base = base; 211 212 printf("MEMGUARD DEBUGGING ALLOCATOR INITIALIZED:\n"); 213 printf("\tMEMGUARD map base: 0x%lx\n", (u_long)base); 214 printf("\tMEMGUARD map size: %jd KBytes\n", 215 (uintmax_t)memguard_mapsize >> 10); 216} 217 218/* 219 * Run things that can't be done as early as memguard_init(). 220 */ 221static void 222memguard_sysinit(void) 223{ 224 struct sysctl_oid_list *parent; 225 226 parent = SYSCTL_STATIC_CHILDREN(_vm_memguard); 227 228 SYSCTL_ADD_UAUTO(NULL, parent, OID_AUTO, "mapstart", CTLFLAG_RD, 229 &memguard_base, "MemGuard KVA base"); 230 SYSCTL_ADD_UAUTO(NULL, parent, OID_AUTO, "maplimit", CTLFLAG_RD, 231 &memguard_mapsize, "MemGuard KVA size"); 232#if 0 233 SYSCTL_ADD_ULONG(NULL, parent, OID_AUTO, "mapused", CTLFLAG_RD, 234 &memguard_map->size, "MemGuard KVA used"); 235#endif 236} 237SYSINIT(memguard, SI_SUB_KLD, SI_ORDER_ANY, memguard_sysinit, NULL); 238 239/* 240 * v2sizep() converts a virtual address of the first page allocated for 241 * an item to a pointer to u_long recording the size of the original 242 * allocation request. 243 * 244 * This routine is very similar to those defined by UMA in uma_int.h. 245 * The difference is that this routine stores the originally allocated 246 * size in one of the page's fields that is unused when the page is 247 * wired rather than the object field, which is used. 248 */ 249static u_long * 250v2sizep(vm_offset_t va) 251{ 252 vm_paddr_t pa; 253 struct vm_page *p; 254 255 pa = pmap_kextract(va); 256 if (pa == 0) 257 panic("MemGuard detected double-free of %p", (void *)va); 258 p = PHYS_TO_VM_PAGE(pa); 259 KASSERT(p->wire_count != 0 && p->queue == PQ_NONE, 260 ("MEMGUARD: Expected wired page %p in vtomgfifo!", p)); 261 return (&p->plinks.memguard.p); 262} 263 264static u_long * 265v2sizev(vm_offset_t va) 266{ 267 vm_paddr_t pa; 268 struct vm_page *p; 269 270 pa = pmap_kextract(va); 271 if (pa == 0) 272 panic("MemGuard detected double-free of %p", (void *)va); 273 p = PHYS_TO_VM_PAGE(pa); 274 KASSERT(p->wire_count != 0 && p->queue == PQ_NONE, 275 ("MEMGUARD: Expected wired page %p in vtomgfifo!", p)); 276 return (&p->plinks.memguard.v); 277} 278 279/* 280 * Allocate a single object of specified size with specified flags 281 * (either M_WAITOK or M_NOWAIT). 282 */ 283void * 284memguard_alloc(unsigned long req_size, int flags) 285{ 286 vm_offset_t addr, origaddr; 287 u_long size_p, size_v; 288 int do_guard, rv; 289 290 size_p = round_page(req_size); 291 if (size_p == 0) 292 return (NULL); 293 /* 294 * To ensure there are holes on both sides of the allocation, 295 * request 2 extra pages of KVA. We will only actually add a 296 * vm_map_entry and get pages for the original request. Save 297 * the value of memguard_options so we have a consistent 298 * value. 299 */ 300 size_v = size_p; 301 do_guard = (memguard_options & MG_GUARD_AROUND) != 0; 302 if (do_guard) 303 size_v += 2 * PAGE_SIZE; 304 305 /* 306 * When we pass our memory limit, reject sub-page allocations. 307 * Page-size and larger allocations will use the same amount 308 * of physical memory whether we allocate or hand off to 309 * uma_large_alloc(), so keep those. 310 */ 311 if (vmem_size(memguard_arena, VMEM_ALLOC) >= memguard_physlimit && 312 req_size < PAGE_SIZE) { 313 addr = (vm_offset_t)NULL; 314 memguard_fail_pgs++; 315 goto out; 316 } 317 /* 318 * Keep a moving cursor so we don't recycle KVA as long as 319 * possible. It's not perfect, since we don't know in what 320 * order previous allocations will be free'd, but it's simple 321 * and fast, and requires O(1) additional storage if guard 322 * pages are not used. 323 * 324 * XXX This scheme will lead to greater fragmentation of the 325 * map, unless vm_map_findspace() is tweaked. 326 */ 327 for (;;) { 328 if (vmem_xalloc(memguard_arena, size_v, 0, 0, 0, 329 memguard_cursor, VMEM_ADDR_MAX, 330 M_BESTFIT | M_NOWAIT, &origaddr) == 0) 331 break; 332 /* 333 * The map has no space. This may be due to 334 * fragmentation, or because the cursor is near the 335 * end of the map. 336 */ 337 if (memguard_cursor == memguard_base) { 338 memguard_fail_kva++; 339 addr = (vm_offset_t)NULL; 340 goto out; 341 } 342 memguard_wrap++; 343 memguard_cursor = memguard_base; 344 } 345 addr = origaddr; 346 if (do_guard) 347 addr += PAGE_SIZE; 348 rv = kmem_back(kmem_object, addr, size_p, flags); 349 if (rv != KERN_SUCCESS) { 350 vmem_xfree(memguard_arena, origaddr, size_v); 351 memguard_fail_pgs++; 352 addr = (vm_offset_t)NULL; 353 goto out; 354 } 355 memguard_cursor = addr + size_v; 356 *v2sizep(trunc_page(addr)) = req_size; 357 *v2sizev(trunc_page(addr)) = size_v; 358 memguard_succ++; 359 if (req_size < PAGE_SIZE) { 360 memguard_wasted += (PAGE_SIZE - req_size); 361 if (do_guard) { 362 /* 363 * Align the request to 16 bytes, and return 364 * an address near the end of the page, to 365 * better detect array overrun. 366 */ 367 req_size = roundup2(req_size, 16); 368 addr += (PAGE_SIZE - req_size); 369 } 370 } 371out: 372 return ((void *)addr); 373} 374 375int 376is_memguard_addr(void *addr) 377{ 378 vm_offset_t a = (vm_offset_t)(uintptr_t)addr; 379 380 return (a >= memguard_base && a < memguard_base + memguard_mapsize); 381} 382 383/* 384 * Free specified single object. 385 */ 386void 387memguard_free(void *ptr) 388{ 389 vm_offset_t addr; 390 u_long req_size, size, sizev; 391 char *temp; 392 int i; 393 394 addr = trunc_page((uintptr_t)ptr); 395 req_size = *v2sizep(addr); 396 sizev = *v2sizev(addr); 397 size = round_page(req_size); 398 399 /* 400 * Page should not be guarded right now, so force a write. 401 * The purpose of this is to increase the likelihood of 402 * catching a double-free, but not necessarily a 403 * tamper-after-free (the second thread freeing might not 404 * write before freeing, so this forces it to and, 405 * subsequently, trigger a fault). 406 */ 407 temp = ptr; 408 for (i = 0; i < size; i += PAGE_SIZE) 409 temp[i] = 'M'; 410 411 /* 412 * This requires carnal knowledge of the implementation of 413 * kmem_free(), but since we've already replaced kmem_malloc() 414 * above, it's not really any worse. We want to use the 415 * vm_map lock to serialize updates to memguard_wasted, since 416 * we had the lock at increment. 417 */ 418 kmem_unback(kmem_object, addr, size); 419 if (sizev > size) 420 addr -= PAGE_SIZE; 421 vmem_xfree(memguard_arena, addr, sizev); 422 if (req_size < PAGE_SIZE) 423 memguard_wasted -= (PAGE_SIZE - req_size); 424} 425 426/* 427 * Re-allocate an allocation that was originally guarded. 428 */ 429void * 430memguard_realloc(void *addr, unsigned long size, struct malloc_type *mtp, 431 int flags) 432{ 433 void *newaddr; 434 u_long old_size; 435 436 /* 437 * Allocate the new block. Force the allocation to be guarded 438 * as the original may have been guarded through random 439 * chance, and that should be preserved. 440 */ 441 if ((newaddr = memguard_alloc(size, flags)) == NULL) 442 return (NULL); 443 444 /* Copy over original contents. */ 445 old_size = *v2sizep(trunc_page((uintptr_t)addr)); 446 bcopy(addr, newaddr, min(size, old_size)); 447 memguard_free(addr); 448 return (newaddr); 449} 450 451static int 452memguard_cmp(unsigned long size) 453{ 454 455 if (size < memguard_minsize) { 456 memguard_minsize_reject++; 457 return (0); 458 } 459 if ((memguard_options & MG_GUARD_ALLLARGE) != 0 && size >= PAGE_SIZE) 460 return (1); 461 if (memguard_frequency > 0 && 462 (random() % 100000) < memguard_frequency) { 463 memguard_frequency_hits++; 464 return (1); 465 } 466 467 return (0); 468} 469 470int 471memguard_cmp_mtp(struct malloc_type *mtp, unsigned long size) 472{ 473 474 if (memguard_cmp(size)) 475 return(1); 476 477#if 1 478 /* 479 * The safest way of comparsion is to always compare short description 480 * string of memory type, but it is also the slowest way. 481 */ 482 return (strcmp(mtp->ks_shortdesc, vm_memguard_desc) == 0); 483#else 484 /* 485 * If we compare pointers, there are two possible problems: 486 * 1. Memory type was unloaded and new memory type was allocated at the 487 * same address. 488 * 2. Memory type was unloaded and loaded again, but allocated at a 489 * different address. 490 */ 491 if (vm_memguard_mtype != NULL) 492 return (mtp == vm_memguard_mtype); 493 if (strcmp(mtp->ks_shortdesc, vm_memguard_desc) == 0) { 494 vm_memguard_mtype = mtp; 495 return (1); 496 } 497 return (0); 498#endif 499} 500 501int 502memguard_cmp_zone(uma_zone_t zone) 503{ 504 505 if ((memguard_options & MG_GUARD_NOFREE) == 0 && 506 zone->uz_flags & UMA_ZONE_NOFREE) 507 return (0); 508 509 if (memguard_cmp(zone->uz_size)) 510 return (1); 511 512 /* 513 * The safest way of comparsion is to always compare zone name, 514 * but it is also the slowest way. 515 */ 516 return (strcmp(zone->uz_name, vm_memguard_desc) == 0); 517} 518