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
memguard_sysctl_desc(SYSCTL_HANDLER_ARGS)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
memguard_sysctl_mapused(SYSCTL_HANDLER_ARGS)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
memguard_fudge(unsigned long km_size,const struct vm_map * parent_map)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
memguard_init(vmem_t * parent)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
memguard_sysinit(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 *
v2sizep(vm_offset_t va)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 *
v2sizev(vm_offset_t va)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 *
memguard_alloc(unsigned long req_size,int flags)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
is_memguard_addr(void * addr)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
memguard_free(void * ptr)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 *
memguard_realloc(void * addr,unsigned long size,struct malloc_type * mtp,int flags)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
memguard_cmp(unsigned long size)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
memguard_cmp_mtp(struct malloc_type * mtp,unsigned long size)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
memguard_cmp_zone(uma_zone_t zone)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
memguard_get_req_size(const void * addr)506 memguard_get_req_size(const void *addr)
507 {
508 return (*v2sizep(trunc_page((uintptr_t)addr)));
509 }
510