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 331017 2018-03-15 19:08:33Z kevans $"); 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#include <sys/vmmeter.h> 53 54#include <vm/vm.h> 55#include <vm/uma.h> 56#include <vm/vm_param.h> 57#include <vm/vm_page.h> 58#include <vm/vm_map.h> 59#include <vm/vm_object.h> 60#include <vm/vm_kern.h> 61#include <vm/vm_extern.h> 62#include <vm/uma_int.h> 63#include <vm/memguard.h> 64 65static SYSCTL_NODE(_vm, OID_AUTO, memguard, CTLFLAG_RW, NULL, "MemGuard data"); 66/* 67 * The vm_memguard_divisor variable controls how much of kmem_map should be 68 * reserved for MemGuard. 69 */ 70static u_int vm_memguard_divisor; 71SYSCTL_UINT(_vm_memguard, OID_AUTO, divisor, CTLFLAG_RDTUN | CTLFLAG_NOFETCH, 72 &vm_memguard_divisor, 73 0, "(kmem_size/memguard_divisor) == memguard submap size"); 74 75/* 76 * Short description (ks_shortdesc) of memory type to monitor. 77 */ 78static char vm_memguard_desc[128] = ""; 79static struct malloc_type *vm_memguard_mtype = NULL; 80TUNABLE_STR("vm.memguard.desc", vm_memguard_desc, sizeof(vm_memguard_desc)); 81static int 82memguard_sysctl_desc(SYSCTL_HANDLER_ARGS) 83{ 84 char desc[sizeof(vm_memguard_desc)]; 85 int error; 86 87 strlcpy(desc, vm_memguard_desc, sizeof(desc)); 88 error = sysctl_handle_string(oidp, desc, sizeof(desc), req); 89 if (error != 0 || req->newptr == NULL) 90 return (error); 91 92 mtx_lock(&malloc_mtx); 93 /* If mtp is NULL, it will be initialized in memguard_cmp() */ 94 vm_memguard_mtype = malloc_desc2type(desc); 95 strlcpy(vm_memguard_desc, desc, sizeof(vm_memguard_desc)); 96 mtx_unlock(&malloc_mtx); 97 return (error); 98} 99SYSCTL_PROC(_vm_memguard, OID_AUTO, desc, 100 CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 0, 101 memguard_sysctl_desc, "A", "Short description of memory type to monitor"); 102 103static vm_offset_t memguard_cursor; 104static vm_offset_t memguard_base; 105static vm_size_t memguard_mapsize; 106static vm_size_t memguard_physlimit; 107static u_long memguard_wasted; 108static u_long memguard_wrap; 109static u_long memguard_succ; 110static u_long memguard_fail_kva; 111static u_long memguard_fail_pgs; 112 113SYSCTL_ULONG(_vm_memguard, OID_AUTO, cursor, CTLFLAG_RD, 114 &memguard_cursor, 0, "MemGuard cursor"); 115SYSCTL_ULONG(_vm_memguard, OID_AUTO, mapsize, CTLFLAG_RD, 116 &memguard_mapsize, 0, "MemGuard private arena size"); 117SYSCTL_ULONG(_vm_memguard, OID_AUTO, phys_limit, CTLFLAG_RD, 118 &memguard_physlimit, 0, "Limit on MemGuard memory consumption"); 119SYSCTL_ULONG(_vm_memguard, OID_AUTO, wasted, CTLFLAG_RD, 120 &memguard_wasted, 0, "Excess memory used through page promotion"); 121SYSCTL_ULONG(_vm_memguard, OID_AUTO, wrapcnt, CTLFLAG_RD, 122 &memguard_wrap, 0, "MemGuard cursor wrap count"); 123SYSCTL_ULONG(_vm_memguard, OID_AUTO, numalloc, CTLFLAG_RD, 124 &memguard_succ, 0, "Count of successful MemGuard allocations"); 125SYSCTL_ULONG(_vm_memguard, OID_AUTO, fail_kva, CTLFLAG_RD, 126 &memguard_fail_kva, 0, "MemGuard failures due to lack of KVA"); 127SYSCTL_ULONG(_vm_memguard, OID_AUTO, fail_pgs, CTLFLAG_RD, 128 &memguard_fail_pgs, 0, "MemGuard failures due to lack of pages"); 129 130#define MG_GUARD_AROUND 0x001 131#define MG_GUARD_ALLLARGE 0x002 132#define MG_GUARD_NOFREE 0x004 133static int memguard_options = MG_GUARD_AROUND; 134SYSCTL_INT(_vm_memguard, OID_AUTO, options, CTLFLAG_RWTUN, 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; 150SYSCTL_UINT(_vm_memguard, OID_AUTO, frequency, CTLFLAG_RWTUN, 151 &memguard_frequency, 0, "Times in 100000 that MemGuard will randomly run"); 152SYSCTL_ULONG(_vm_memguard, OID_AUTO, frequency_hits, CTLFLAG_RD, 153 &memguard_frequency_hits, 0, "# times MemGuard randomly chose"); 154 155 156/* 157 * Return a fudged value to be used for vm_kmem_size for allocating 158 * the kmem_map. The memguard memory will be a submap. 159 */ 160unsigned long 161memguard_fudge(unsigned long km_size, const struct vm_map *parent_map) 162{ 163 u_long mem_pgs, parent_size; 164 165 vm_memguard_divisor = 10; 166 /* CTFLAG_RDTUN doesn't work during the early boot process. */ 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 = vm_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(vmem_t *parent) 204{ 205 vm_offset_t base; 206 207 vmem_alloc(parent, memguard_mapsize, M_BESTFIT | M_WAITOK, &base); 208 vmem_init(memguard_arena, "memguard arena", base, memguard_mapsize, 209 PAGE_SIZE, 0, M_WAITOK); 210 memguard_cursor = base; 211 memguard_base = base; 212 213 printf("MEMGUARD DEBUGGING ALLOCATOR INITIALIZED:\n"); 214 printf("\tMEMGUARD map base: 0x%lx\n", (u_long)base); 215 printf("\tMEMGUARD map size: %jd KBytes\n", 216 (uintmax_t)memguard_mapsize >> 10); 217} 218 219/* 220 * Run things that can't be done as early as memguard_init(). 221 */ 222static void 223memguard_sysinit(void) 224{ 225 struct sysctl_oid_list *parent; 226 227 parent = SYSCTL_STATIC_CHILDREN(_vm_memguard); 228 229 SYSCTL_ADD_UAUTO(NULL, parent, OID_AUTO, "mapstart", CTLFLAG_RD, 230 &memguard_base, "MemGuard KVA base"); 231 SYSCTL_ADD_UAUTO(NULL, parent, OID_AUTO, "maplimit", CTLFLAG_RD, 232 &memguard_mapsize, "MemGuard KVA size"); 233#if 0 234 SYSCTL_ADD_ULONG(NULL, parent, OID_AUTO, "mapused", CTLFLAG_RD, 235 &memguard_map->size, "MemGuard KVA used"); 236#endif 237} 238SYSINIT(memguard, SI_SUB_KLD, SI_ORDER_ANY, memguard_sysinit, NULL); 239 240/* 241 * v2sizep() converts a virtual address of the first page allocated for 242 * an item to a pointer to u_long recording the size of the original 243 * allocation request. 244 * 245 * This routine is very similar to those defined by UMA in uma_int.h. 246 * The difference is that this routine stores the originally allocated 247 * size in one of the page's fields that is unused when the page is 248 * wired rather than the object field, which is used. 249 */ 250static u_long * 251v2sizep(vm_offset_t va) 252{ 253 vm_paddr_t pa; 254 struct vm_page *p; 255 256 pa = pmap_kextract(va); 257 if (pa == 0) 258 panic("MemGuard detected double-free of %p", (void *)va); 259 p = PHYS_TO_VM_PAGE(pa); 260 KASSERT(p->wire_count != 0 && p->queue == PQ_NONE, 261 ("MEMGUARD: Expected wired page %p in vtomgfifo!", p)); 262 return (&p->plinks.memguard.p); 263} 264 265static u_long * 266v2sizev(vm_offset_t va) 267{ 268 vm_paddr_t pa; 269 struct vm_page *p; 270 271 pa = pmap_kextract(va); 272 if (pa == 0) 273 panic("MemGuard detected double-free of %p", (void *)va); 274 p = PHYS_TO_VM_PAGE(pa); 275 KASSERT(p->wire_count != 0 && p->queue == PQ_NONE, 276 ("MEMGUARD: Expected wired page %p in vtomgfifo!", p)); 277 return (&p->plinks.memguard.v); 278} 279 280/* 281 * Allocate a single object of specified size with specified flags 282 * (either M_WAITOK or M_NOWAIT). 283 */ 284void * 285memguard_alloc(unsigned long req_size, int flags) 286{ 287 vm_offset_t addr, origaddr; 288 u_long size_p, size_v; 289 int do_guard, rv; 290 291 size_p = round_page(req_size); 292 if (size_p == 0) 293 return (NULL); 294 /* 295 * To ensure there are holes on both sides of the allocation, 296 * request 2 extra pages of KVA. We will only actually add a 297 * vm_map_entry and get pages for the original request. Save 298 * the value of memguard_options so we have a consistent 299 * value. 300 */ 301 size_v = size_p; 302 do_guard = (memguard_options & MG_GUARD_AROUND) != 0; 303 if (do_guard) 304 size_v += 2 * PAGE_SIZE; 305 306 /* 307 * When we pass our memory limit, reject sub-page allocations. 308 * Page-size and larger allocations will use the same amount 309 * of physical memory whether we allocate or hand off to 310 * uma_large_alloc(), so keep those. 311 */ 312 if (vmem_size(memguard_arena, VMEM_ALLOC) >= memguard_physlimit && 313 req_size < PAGE_SIZE) { 314 addr = (vm_offset_t)NULL; 315 memguard_fail_pgs++; 316 goto out; 317 } 318 /* 319 * Keep a moving cursor so we don't recycle KVA as long as 320 * possible. It's not perfect, since we don't know in what 321 * order previous allocations will be free'd, but it's simple 322 * and fast, and requires O(1) additional storage if guard 323 * pages are not used. 324 * 325 * XXX This scheme will lead to greater fragmentation of the 326 * map, unless vm_map_findspace() is tweaked. 327 */ 328 for (;;) { 329 if (vmem_xalloc(memguard_arena, size_v, 0, 0, 0, 330 memguard_cursor, VMEM_ADDR_MAX, 331 M_BESTFIT | M_NOWAIT, &origaddr) == 0) 332 break; 333 /* 334 * The map has no space. This may be due to 335 * fragmentation, or because the cursor is near the 336 * end of the map. 337 */ 338 if (memguard_cursor == memguard_base) { 339 memguard_fail_kva++; 340 addr = (vm_offset_t)NULL; 341 goto out; 342 } 343 memguard_wrap++; 344 memguard_cursor = memguard_base; 345 } 346 addr = origaddr; 347 if (do_guard) 348 addr += PAGE_SIZE; 349 rv = kmem_back(kmem_object, addr, size_p, flags); 350 if (rv != KERN_SUCCESS) { 351 vmem_xfree(memguard_arena, origaddr, size_v); 352 memguard_fail_pgs++; 353 addr = (vm_offset_t)NULL; 354 goto out; 355 } 356 memguard_cursor = addr + size_v; 357 *v2sizep(trunc_page(addr)) = req_size; 358 *v2sizev(trunc_page(addr)) = size_v; 359 memguard_succ++; 360 if (req_size < PAGE_SIZE) { 361 memguard_wasted += (PAGE_SIZE - req_size); 362 if (do_guard) { 363 /* 364 * Align the request to 16 bytes, and return 365 * an address near the end of the page, to 366 * better detect array overrun. 367 */ 368 req_size = roundup2(req_size, 16); 369 addr += (PAGE_SIZE - req_size); 370 } 371 } 372out: 373 return ((void *)addr); 374} 375 376int 377is_memguard_addr(void *addr) 378{ 379 vm_offset_t a = (vm_offset_t)(uintptr_t)addr; 380 381 return (a >= memguard_base && a < memguard_base + memguard_mapsize); 382} 383 384/* 385 * Free specified single object. 386 */ 387void 388memguard_free(void *ptr) 389{ 390 vm_offset_t addr; 391 u_long req_size, size, sizev; 392 char *temp; 393 int i; 394 395 addr = trunc_page((uintptr_t)ptr); 396 req_size = *v2sizep(addr); 397 sizev = *v2sizev(addr); 398 size = round_page(req_size); 399 400 /* 401 * Page should not be guarded right now, so force a write. 402 * The purpose of this is to increase the likelihood of 403 * catching a double-free, but not necessarily a 404 * tamper-after-free (the second thread freeing might not 405 * write before freeing, so this forces it to and, 406 * subsequently, trigger a fault). 407 */ 408 temp = ptr; 409 for (i = 0; i < size; i += PAGE_SIZE) 410 temp[i] = 'M'; 411 412 /* 413 * This requires carnal knowledge of the implementation of 414 * kmem_free(), but since we've already replaced kmem_malloc() 415 * above, it's not really any worse. We want to use the 416 * vm_map lock to serialize updates to memguard_wasted, since 417 * we had the lock at increment. 418 */ 419 kmem_unback(kmem_object, addr, size); 420 if (sizev > size) 421 addr -= PAGE_SIZE; 422 vmem_xfree(memguard_arena, addr, sizev); 423 if (req_size < PAGE_SIZE) 424 memguard_wasted -= (PAGE_SIZE - req_size); 425} 426 427/* 428 * Re-allocate an allocation that was originally guarded. 429 */ 430void * 431memguard_realloc(void *addr, unsigned long size, struct malloc_type *mtp, 432 int flags) 433{ 434 void *newaddr; 435 u_long old_size; 436 437 /* 438 * Allocate the new block. Force the allocation to be guarded 439 * as the original may have been guarded through random 440 * chance, and that should be preserved. 441 */ 442 if ((newaddr = memguard_alloc(size, flags)) == NULL) 443 return (NULL); 444 445 /* Copy over original contents. */ 446 old_size = *v2sizep(trunc_page((uintptr_t)addr)); 447 bcopy(addr, newaddr, min(size, old_size)); 448 memguard_free(addr); 449 return (newaddr); 450} 451 452static int 453memguard_cmp(unsigned long size) 454{ 455 456 if (size < memguard_minsize) { 457 memguard_minsize_reject++; 458 return (0); 459 } 460 if ((memguard_options & MG_GUARD_ALLLARGE) != 0 && size >= PAGE_SIZE) 461 return (1); 462 if (memguard_frequency > 0 && 463 (random() % 100000) < memguard_frequency) { 464 memguard_frequency_hits++; 465 return (1); 466 } 467 468 return (0); 469} 470 471int 472memguard_cmp_mtp(struct malloc_type *mtp, unsigned long size) 473{ 474 475 if (memguard_cmp(size)) 476 return(1); 477 478#if 1 479 /* 480 * The safest way of comparsion is to always compare short description 481 * string of memory type, but it is also the slowest way. 482 */ 483 return (strcmp(mtp->ks_shortdesc, vm_memguard_desc) == 0); 484#else 485 /* 486 * If we compare pointers, there are two possible problems: 487 * 1. Memory type was unloaded and new memory type was allocated at the 488 * same address. 489 * 2. Memory type was unloaded and loaded again, but allocated at a 490 * different address. 491 */ 492 if (vm_memguard_mtype != NULL) 493 return (mtp == vm_memguard_mtype); 494 if (strcmp(mtp->ks_shortdesc, vm_memguard_desc) == 0) { 495 vm_memguard_mtype = mtp; 496 return (1); 497 } 498 return (0); 499#endif 500} 501 502int 503memguard_cmp_zone(uma_zone_t zone) 504{ 505 506 if ((memguard_options & MG_GUARD_NOFREE) == 0 && 507 zone->uz_flags & UMA_ZONE_NOFREE) 508 return (0); 509 510 if (memguard_cmp(zone->uz_size)) 511 return (1); 512 513 /* 514 * The safest way of comparsion is to always compare zone name, 515 * but it is also the slowest way. 516 */ 517 return (strcmp(zone->uz_name, vm_memguard_desc) == 0); 518} 519