1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause 3 * 4 * Copyright (c) 2005, Bosko Milekic <bmilekic@FreeBSD.org>. 5 * Copyright (c) 2010 Isilon Systems, Inc. (http://www.isilon.com/) 6 * All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice unmodified, this list of conditions, and the following 13 * disclaimer. 14 * 2. Redistributions in binary form must reproduce the above copyright 15 * notice, this list of conditions and the following disclaimer in the 16 * documentation and/or other materials provided with the distribution. 17 * 18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 19 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 20 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 21 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 22 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 23 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 24 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 25 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 26 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 27 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 28 */ 29 30 #include <sys/cdefs.h> 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 65 static SYSCTL_NODE(_vm, OID_AUTO, memguard, CTLFLAG_RW | CTLFLAG_MPSAFE, NULL, 66 "MemGuard data"); 67 /* 68 * The vm_memguard_divisor variable controls how much of kernel_arena should be 69 * reserved for MemGuard. 70 */ 71 static u_int vm_memguard_divisor; 72 SYSCTL_UINT(_vm_memguard, OID_AUTO, divisor, CTLFLAG_RDTUN | CTLFLAG_NOFETCH, 73 &vm_memguard_divisor, 74 0, "(kmem_size/memguard_divisor) == memguard submap size"); 75 76 /* 77 * Short description (ks_shortdesc) of memory type to monitor. 78 */ 79 static char vm_memguard_desc[128] = ""; 80 static struct malloc_type *vm_memguard_mtype = NULL; 81 TUNABLE_STR("vm.memguard.desc", vm_memguard_desc, sizeof(vm_memguard_desc)); 82 static int 83 memguard_sysctl_desc(SYSCTL_HANDLER_ARGS) 84 { 85 char desc[sizeof(vm_memguard_desc)]; 86 int error; 87 88 strlcpy(desc, vm_memguard_desc, sizeof(desc)); 89 error = sysctl_handle_string(oidp, desc, sizeof(desc), req); 90 if (error != 0 || req->newptr == NULL) 91 return (error); 92 93 mtx_lock(&malloc_mtx); 94 /* If mtp is NULL, it will be initialized in memguard_cmp() */ 95 vm_memguard_mtype = malloc_desc2type(desc); 96 strlcpy(vm_memguard_desc, desc, sizeof(vm_memguard_desc)); 97 mtx_unlock(&malloc_mtx); 98 return (error); 99 } 100 SYSCTL_PROC(_vm_memguard, OID_AUTO, desc, 101 CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 0, 102 memguard_sysctl_desc, "A", "Short description of memory type to monitor"); 103 104 static int 105 memguard_sysctl_mapused(SYSCTL_HANDLER_ARGS) 106 { 107 vmem_size_t size; 108 109 size = vmem_size(memguard_arena, VMEM_ALLOC); 110 return (sysctl_handle_long(oidp, &size, sizeof(size), req)); 111 } 112 113 static vm_offset_t memguard_base; 114 static vm_size_t memguard_mapsize; 115 static vm_size_t memguard_physlimit; 116 static u_long memguard_wasted; 117 static u_long memguard_succ; 118 static u_long memguard_fail_kva; 119 static u_long memguard_fail_pgs; 120 121 SYSCTL_ULONG(_vm_memguard, OID_AUTO, mapsize, CTLFLAG_RD, 122 &memguard_mapsize, 0, "MemGuard private arena size"); 123 SYSCTL_ULONG(_vm_memguard, OID_AUTO, phys_limit, CTLFLAG_RD, 124 &memguard_physlimit, 0, "Limit on MemGuard memory consumption"); 125 SYSCTL_ULONG(_vm_memguard, OID_AUTO, wasted, CTLFLAG_RD, 126 &memguard_wasted, 0, "Excess memory used through page promotion"); 127 SYSCTL_ULONG(_vm_memguard, OID_AUTO, numalloc, CTLFLAG_RD, 128 &memguard_succ, 0, "Count of successful MemGuard allocations"); 129 SYSCTL_ULONG(_vm_memguard, OID_AUTO, fail_kva, CTLFLAG_RD, 130 &memguard_fail_kva, 0, "MemGuard failures due to lack of KVA"); 131 SYSCTL_ULONG(_vm_memguard, OID_AUTO, fail_pgs, CTLFLAG_RD, 132 &memguard_fail_pgs, 0, "MemGuard failures due to lack of pages"); 133 134 #define MG_GUARD_AROUND 0x001 135 #define MG_GUARD_ALLLARGE 0x002 136 #define MG_GUARD_NOFREE 0x004 137 static int memguard_options = MG_GUARD_AROUND; 138 SYSCTL_INT(_vm_memguard, OID_AUTO, options, CTLFLAG_RWTUN, 139 &memguard_options, 0, 140 "MemGuard options:\n" 141 "\t0x001 - add guard pages around each allocation\n" 142 "\t0x002 - always use MemGuard for allocations over a page\n" 143 "\t0x004 - guard uma(9) zones with UMA_ZONE_NOFREE flag"); 144 145 static u_int memguard_minsize; 146 static u_long memguard_minsize_reject; 147 SYSCTL_UINT(_vm_memguard, OID_AUTO, minsize, CTLFLAG_RW, 148 &memguard_minsize, 0, "Minimum size for page promotion"); 149 SYSCTL_ULONG(_vm_memguard, OID_AUTO, minsize_reject, CTLFLAG_RD, 150 &memguard_minsize_reject, 0, "# times rejected for size"); 151 152 static u_int memguard_frequency; 153 static u_long memguard_frequency_hits; 154 SYSCTL_UINT(_vm_memguard, OID_AUTO, frequency, CTLFLAG_RWTUN, 155 &memguard_frequency, 0, "Times in 100000 that MemGuard will randomly run"); 156 SYSCTL_ULONG(_vm_memguard, OID_AUTO, frequency_hits, CTLFLAG_RD, 157 &memguard_frequency_hits, 0, "# times MemGuard randomly chose"); 158 159 /* 160 * Return a fudged value to be used for vm_kmem_size for allocating 161 * the kernel_arena. 162 */ 163 unsigned long 164 memguard_fudge(unsigned long km_size, const struct vm_map *parent_map) 165 { 166 u_long mem_pgs, parent_size; 167 168 vm_memguard_divisor = 10; 169 /* CTFLAG_RDTUN doesn't work during the early boot process. */ 170 TUNABLE_INT_FETCH("vm.memguard.divisor", &vm_memguard_divisor); 171 172 parent_size = vm_map_max(parent_map) - vm_map_min(parent_map) + 173 PAGE_SIZE; 174 /* Pick a conservative value if provided value sucks. */ 175 if ((vm_memguard_divisor <= 0) || 176 ((parent_size / vm_memguard_divisor) == 0)) 177 vm_memguard_divisor = 10; 178 /* 179 * Limit consumption of physical pages to 180 * 1/vm_memguard_divisor of system memory. If the KVA is 181 * smaller than this then the KVA limit comes into play first. 182 * This prevents memguard's page promotions from completely 183 * using up memory, since most malloc(9) calls are sub-page. 184 */ 185 mem_pgs = vm_cnt.v_page_count; 186 memguard_physlimit = (mem_pgs / vm_memguard_divisor) * PAGE_SIZE; 187 /* 188 * We want as much KVA as we can take safely. Use at most our 189 * allotted fraction of the parent map's size. Limit this to 190 * twice the physical memory to avoid using too much memory as 191 * pagetable pages (size must be multiple of PAGE_SIZE). 192 */ 193 memguard_mapsize = round_page(parent_size / vm_memguard_divisor); 194 if (memguard_mapsize / (2 * PAGE_SIZE) > mem_pgs) 195 memguard_mapsize = mem_pgs * 2 * PAGE_SIZE; 196 if (km_size + memguard_mapsize > parent_size) 197 memguard_mapsize = 0; 198 return (km_size + memguard_mapsize); 199 } 200 201 /* 202 * Initialize the MemGuard mock allocator. All objects from MemGuard come 203 * out of a single contiguous chunk of kernel address space that is managed 204 * by a vmem arena. 205 */ 206 void 207 memguard_init(vmem_t *parent) 208 { 209 vm_offset_t base; 210 211 vmem_alloc(parent, memguard_mapsize, M_BESTFIT | M_WAITOK, &base); 212 vmem_init(memguard_arena, "memguard arena", base, memguard_mapsize, 213 PAGE_SIZE, 0, M_WAITOK); 214 memguard_base = base; 215 216 printf("MEMGUARD DEBUGGING ALLOCATOR INITIALIZED:\n"); 217 printf("\tMEMGUARD map base: 0x%lx\n", (u_long)base); 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 */ 225 static void 226 memguard_sysinit(void) 227 { 228 struct sysctl_oid_list *parent; 229 230 parent = SYSCTL_STATIC_CHILDREN(_vm_memguard); 231 SYSCTL_ADD_UAUTO(NULL, parent, OID_AUTO, "mapstart", 232 CTLFLAG_RD, &memguard_base, 233 "MemGuard KVA base"); 234 SYSCTL_ADD_UAUTO(NULL, parent, OID_AUTO, "maplimit", 235 CTLFLAG_RD, &memguard_mapsize, 236 "MemGuard KVA size"); 237 SYSCTL_ADD_PROC(NULL, parent, OID_AUTO, "mapused", 238 CTLFLAG_RD | CTLFLAG_MPSAFE | CTLTYPE_ULONG, NULL, 0, memguard_sysctl_mapused, "LU", 239 "MemGuard KVA used"); 240 } 241 SYSINIT(memguard, SI_SUB_KLD, SI_ORDER_ANY, memguard_sysinit, NULL); 242 243 /* 244 * v2sizep() converts a virtual address of the first page allocated for 245 * an item to a pointer to u_long recording the size of the original 246 * allocation request. 247 * 248 * This routine is very similar to those defined by UMA in uma_int.h. 249 * The difference is that this routine stores the originally allocated 250 * size in one of the page's fields that is unused when the page is 251 * wired rather than the object field, which is used. 252 */ 253 static u_long * 254 v2sizep(vm_offset_t va) 255 { 256 vm_paddr_t pa; 257 struct vm_page *p; 258 259 pa = pmap_kextract(va); 260 if (pa == 0) 261 panic("MemGuard detected double-free of %p", (void *)va); 262 p = PHYS_TO_VM_PAGE(pa); 263 KASSERT(vm_page_wired(p) && p->a.queue == PQ_NONE, 264 ("MEMGUARD: Expected wired page %p in vtomgfifo!", p)); 265 return (&p->plinks.memguard.p); 266 } 267 268 static u_long * 269 v2sizev(vm_offset_t va) 270 { 271 vm_paddr_t pa; 272 struct vm_page *p; 273 274 pa = pmap_kextract(va); 275 if (pa == 0) 276 panic("MemGuard detected double-free of %p", (void *)va); 277 p = PHYS_TO_VM_PAGE(pa); 278 KASSERT(vm_page_wired(p) && p->a.queue == PQ_NONE, 279 ("MEMGUARD: Expected wired page %p in vtomgfifo!", p)); 280 return (&p->plinks.memguard.v); 281 } 282 283 /* 284 * Allocate a single object of specified size with specified flags 285 * (either M_WAITOK or M_NOWAIT). 286 */ 287 void * 288 memguard_alloc(unsigned long req_size, int flags) 289 { 290 vm_offset_t addr, origaddr; 291 u_long size_p, size_v; 292 int do_guard, error, rv; 293 294 size_p = round_page(req_size); 295 if (size_p == 0) 296 return (NULL); 297 298 /* 299 * To ensure there are holes on both sides of the allocation, 300 * request 2 extra pages of KVA. Save the value of memguard_options 301 * so that we use a consistent value throughout this function. 302 */ 303 size_v = size_p; 304 do_guard = (memguard_options & MG_GUARD_AROUND) != 0; 305 if (do_guard) 306 size_v += 2 * PAGE_SIZE; 307 308 /* 309 * When we pass our memory limit, reject sub-page allocations. 310 * Page-size and larger allocations will use the same amount 311 * of physical memory whether we allocate or hand off to 312 * malloc_large(), so keep those. 313 */ 314 if (vmem_size(memguard_arena, VMEM_ALLOC) >= memguard_physlimit && 315 req_size < PAGE_SIZE) { 316 addr = (vm_offset_t)NULL; 317 memguard_fail_pgs++; 318 goto out; 319 } 320 321 /* 322 * Attempt to avoid address reuse for as long as possible, to increase 323 * the likelihood of catching a use-after-free. 324 */ 325 error = vmem_alloc(memguard_arena, size_v, M_NEXTFIT | M_NOWAIT, 326 &origaddr); 327 if (error != 0) { 328 memguard_fail_kva++; 329 addr = (vm_offset_t)NULL; 330 goto out; 331 } 332 addr = origaddr; 333 if (do_guard) 334 addr += PAGE_SIZE; 335 rv = kmem_back(kernel_object, addr, size_p, flags); 336 if (rv != KERN_SUCCESS) { 337 vmem_xfree(memguard_arena, origaddr, size_v); 338 memguard_fail_pgs++; 339 addr = (vm_offset_t)NULL; 340 goto out; 341 } 342 *v2sizep(trunc_page(addr)) = req_size; 343 *v2sizev(trunc_page(addr)) = size_v; 344 memguard_succ++; 345 if (req_size < PAGE_SIZE) { 346 memguard_wasted += (PAGE_SIZE - req_size); 347 if (do_guard) { 348 /* 349 * Align the request to 16 bytes, and return 350 * an address near the end of the page, to 351 * better detect array overrun. 352 */ 353 req_size = roundup2(req_size, 16); 354 addr += (PAGE_SIZE - req_size); 355 } 356 } 357 out: 358 return ((void *)addr); 359 } 360 361 int 362 is_memguard_addr(void *addr) 363 { 364 vm_offset_t a = (vm_offset_t)(uintptr_t)addr; 365 366 return (a >= memguard_base && a < memguard_base + memguard_mapsize); 367 } 368 369 /* 370 * Free specified single object. 371 */ 372 void 373 memguard_free(void *ptr) 374 { 375 vm_offset_t addr; 376 u_long req_size, size, sizev; 377 char *temp; 378 int i; 379 380 addr = trunc_page((uintptr_t)ptr); 381 req_size = *v2sizep(addr); 382 sizev = *v2sizev(addr); 383 size = round_page(req_size); 384 385 /* 386 * Page should not be guarded right now, so force a write. 387 * The purpose of this is to increase the likelihood of 388 * catching a double-free, but not necessarily a 389 * tamper-after-free (the second thread freeing might not 390 * write before freeing, so this forces it to and, 391 * subsequently, trigger a fault). 392 */ 393 temp = ptr; 394 for (i = 0; i < size; i += PAGE_SIZE) 395 temp[i] = 'M'; 396 397 /* 398 * This requires carnal knowledge of the implementation of 399 * kmem_free(), but since we've already replaced kmem_malloc() 400 * above, it's not really any worse. We want to use the 401 * vm_map lock to serialize updates to memguard_wasted, since 402 * we had the lock at increment. 403 */ 404 kmem_unback(kernel_object, addr, size); 405 if (sizev > size) 406 addr -= PAGE_SIZE; 407 vmem_xfree(memguard_arena, addr, sizev); 408 if (req_size < PAGE_SIZE) 409 memguard_wasted -= (PAGE_SIZE - req_size); 410 } 411 412 /* 413 * Re-allocate an allocation that was originally guarded. 414 */ 415 void * 416 memguard_realloc(void *addr, unsigned long size, struct malloc_type *mtp, 417 int flags) 418 { 419 void *newaddr; 420 u_long old_size; 421 422 /* 423 * Allocate the new block. Force the allocation to be guarded 424 * as the original may have been guarded through random 425 * chance, and that should be preserved. 426 */ 427 if ((newaddr = memguard_alloc(size, flags)) == NULL) 428 return (NULL); 429 430 /* Copy over original contents. */ 431 old_size = *v2sizep(trunc_page((uintptr_t)addr)); 432 bcopy(addr, newaddr, min(size, old_size)); 433 memguard_free(addr); 434 return (newaddr); 435 } 436 437 static int 438 memguard_cmp(unsigned long size) 439 { 440 441 if (size < memguard_minsize) { 442 memguard_minsize_reject++; 443 return (0); 444 } 445 if ((memguard_options & MG_GUARD_ALLLARGE) != 0 && size >= PAGE_SIZE) 446 return (1); 447 if (memguard_frequency > 0 && 448 (random() % 100000) < memguard_frequency) { 449 memguard_frequency_hits++; 450 return (1); 451 } 452 453 return (0); 454 } 455 456 int 457 memguard_cmp_mtp(struct malloc_type *mtp, unsigned long size) 458 { 459 460 if (memguard_cmp(size)) 461 return(1); 462 463 #if 1 464 /* 465 * The safest way of comparison is to always compare short description 466 * string of memory type, but it is also the slowest way. 467 */ 468 return (strcmp(mtp->ks_shortdesc, vm_memguard_desc) == 0); 469 #else 470 /* 471 * If we compare pointers, there are two possible problems: 472 * 1. Memory type was unloaded and new memory type was allocated at the 473 * same address. 474 * 2. Memory type was unloaded and loaded again, but allocated at a 475 * different address. 476 */ 477 if (vm_memguard_mtype != NULL) 478 return (mtp == vm_memguard_mtype); 479 if (strcmp(mtp->ks_shortdesc, vm_memguard_desc) == 0) { 480 vm_memguard_mtype = mtp; 481 return (1); 482 } 483 return (0); 484 #endif 485 } 486 487 int 488 memguard_cmp_zone(uma_zone_t zone) 489 { 490 491 if ((memguard_options & MG_GUARD_NOFREE) == 0 && 492 zone->uz_flags & UMA_ZONE_NOFREE) 493 return (0); 494 495 if (memguard_cmp(zone->uz_size)) 496 return (1); 497 498 /* 499 * The safest way of comparison is to always compare zone name, 500 * but it is also the slowest way. 501 */ 502 return (strcmp(zone->uz_name, vm_memguard_desc) == 0); 503 } 504 505 unsigned long 506 memguard_get_req_size(const void *addr) 507 { 508 return (*v2sizep(trunc_page((uintptr_t)addr))); 509 } 510