summaryrefslogtreecommitdiff
path: root/drivers/misc/lkdtm/heap.c
blob: 62516078a619f9408f06077dc7e45107fbdf6f64 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
// SPDX-License-Identifier: GPL-2.0
/*
 * This is for all the tests relating directly to heap memory, including
 * page allocation and slab allocations.
 */
#include "lkdtm.h"
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/sched.h>

static struct kmem_cache *double_free_cache;
static struct kmem_cache *a_cache;
static struct kmem_cache *b_cache;

/*
 * Using volatile here means the compiler cannot ever make assumptions
 * about this value. This means compile-time length checks involving
 * this variable cannot be performed; only run-time checks.
 */
static volatile int __offset = 1;

/*
 * If there aren't guard pages, it's likely that a consecutive allocation will
 * let us overflow into the second allocation without overwriting something real.
 *
 * This should always be caught because there is an unconditional unmapped
 * page after vmap allocations.
 */
static void lkdtm_VMALLOC_LINEAR_OVERFLOW(void)
{
	char *one, *two;

	one = vzalloc(PAGE_SIZE);
	two = vzalloc(PAGE_SIZE);

	pr_info("Attempting vmalloc linear overflow ...\n");
	memset(one, 0xAA, PAGE_SIZE + __offset);

	vfree(two);
	vfree(one);
}

/*
 * This tries to stay within the next largest power-of-2 kmalloc cache
 * to avoid actually overwriting anything important if it's not detected
 * correctly.
 *
 * This should get caught by either memory tagging, KASan, or by using
 * CONFIG_SLUB_DEBUG=y and slub_debug=ZF (or CONFIG_SLUB_DEBUG_ON=y).
 */
static void lkdtm_SLAB_LINEAR_OVERFLOW(void)
{
	size_t len = 1020;
	u32 *data = kmalloc(len, GFP_KERNEL);
	if (!data)
		return;

	pr_info("Attempting slab linear overflow ...\n");
	OPTIMIZER_HIDE_VAR(data);
	data[1024 / sizeof(u32)] = 0x12345678;
	kfree(data);
}

static void lkdtm_WRITE_AFTER_FREE(void)
{
	int *base, *again;
	size_t len = 1024;
	/*
	 * The slub allocator uses the first word to store the free
	 * pointer in some configurations. Use the middle of the
	 * allocation to avoid running into the freelist
	 */
	size_t offset = (len / sizeof(*base)) / 2;

	base = kmalloc(len, GFP_KERNEL);
	if (!base)
		return;
	pr_info("Allocated memory %p-%p\n", base, &base[offset * 2]);
	pr_info("Attempting bad write to freed memory at %p\n",
		&base[offset]);
	kfree(base);
	base[offset] = 0x0abcdef0;
	/* Attempt to notice the overwrite. */
	again = kmalloc(len, GFP_KERNEL);
	kfree(again);
	if (again != base)
		pr_info("Hmm, didn't get the same memory range.\n");
}

static void lkdtm_READ_AFTER_FREE(void)
{
	int *base, *val, saw;
	size_t len = 1024;
	/*
	 * The slub allocator will use the either the first word or
	 * the middle of the allocation to store the free pointer,
	 * depending on configurations. Store in the second word to
	 * avoid running into the freelist.
	 */
	size_t offset = sizeof(*base);

	base = kmalloc(len, GFP_KERNEL);
	if (!base) {
		pr_info("Unable to allocate base memory.\n");
		return;
	}

	val = kmalloc(len, GFP_KERNEL);
	if (!val) {
		pr_info("Unable to allocate val memory.\n");
		kfree(base);
		return;
	}

	*val = 0x12345678;
	base[offset] = *val;
	pr_info("Value in memory before free: %x\n", base[offset]);

	kfree(base);

	pr_info("Attempting bad read from freed memory\n");
	saw = base[offset];
	if (saw != *val) {
		/* Good! Poisoning happened, so declare a win. */
		pr_info("Memory correctly poisoned (%x)\n", saw);
	} else {
		pr_err("FAIL: Memory was not poisoned!\n");
		pr_expected_config_param(CONFIG_INIT_ON_FREE_DEFAULT_ON, "init_on_free");
	}

	kfree(val);
}

static void lkdtm_WRITE_BUDDY_AFTER_FREE(void)
{
	unsigned long p = __get_free_page(GFP_KERNEL);
	if (!p) {
		pr_info("Unable to allocate free page\n");
		return;
	}

	pr_info("Writing to the buddy page before free\n");
	memset((void *)p, 0x3, PAGE_SIZE);
	free_page(p);
	schedule();
	pr_info("Attempting bad write to the buddy page after free\n");
	memset((void *)p, 0x78, PAGE_SIZE);
	/* Attempt to notice the overwrite. */
	p = __get_free_page(GFP_KERNEL);
	free_page(p);
	schedule();
}

static void lkdtm_READ_BUDDY_AFTER_FREE(void)
{
	unsigned long p = __get_free_page(GFP_KERNEL);
	int saw, *val;
	int *base;

	if (!p) {
		pr_info("Unable to allocate free page\n");
		return;
	}

	val = kmalloc(1024, GFP_KERNEL);
	if (!val) {
		pr_info("Unable to allocate val memory.\n");
		free_page(p);
		return;
	}

	base = (int *)p;

	*val = 0x12345678;
	base[0] = *val;
	pr_info("Value in memory before free: %x\n", base[0]);
	free_page(p);
	pr_info("Attempting to read from freed memory\n");
	saw = base[0];
	if (saw != *val) {
		/* Good! Poisoning happened, so declare a win. */
		pr_info("Memory correctly poisoned (%x)\n", saw);
	} else {
		pr_err("FAIL: Buddy page was not poisoned!\n");
		pr_expected_config_param(CONFIG_INIT_ON_FREE_DEFAULT_ON, "init_on_free");
	}

	kfree(val);
}

static void lkdtm_SLAB_INIT_ON_ALLOC(void)
{
	u8 *first;
	u8 *val;

	first = kmalloc(512, GFP_KERNEL);
	if (!first) {
		pr_info("Unable to allocate 512 bytes the first time.\n");
		return;
	}

	memset(first, 0xAB, 512);
	kfree(first);

	val = kmalloc(512, GFP_KERNEL);
	if (!val) {
		pr_info("Unable to allocate 512 bytes the second time.\n");
		return;
	}
	if (val != first) {
		pr_warn("Reallocation missed clobbered memory.\n");
	}

	if (memchr(val, 0xAB, 512) == NULL) {
		pr_info("Memory appears initialized (%x, no earlier values)\n", *val);
	} else {
		pr_err("FAIL: Slab was not initialized\n");
		pr_expected_config_param(CONFIG_INIT_ON_ALLOC_DEFAULT_ON, "init_on_alloc");
	}
	kfree(val);
}

static void lkdtm_BUDDY_INIT_ON_ALLOC(void)
{
	u8 *first;
	u8 *val;

	first = (u8 *)__get_free_page(GFP_KERNEL);
	if (!first) {
		pr_info("Unable to allocate first free page\n");
		return;
	}

	memset(first, 0xAB, PAGE_SIZE);
	free_page((unsigned long)first);

	val = (u8 *)__get_free_page(GFP_KERNEL);
	if (!val) {
		pr_info("Unable to allocate second free page\n");
		return;
	}

	if (val != first) {
		pr_warn("Reallocation missed clobbered memory.\n");
	}

	if (memchr(val, 0xAB, PAGE_SIZE) == NULL) {
		pr_info("Memory appears initialized (%x, no earlier values)\n", *val);
	} else {
		pr_err("FAIL: Slab was not initialized\n");
		pr_expected_config_param(CONFIG_INIT_ON_ALLOC_DEFAULT_ON, "init_on_alloc");
	}
	free_page((unsigned long)val);
}

static void lkdtm_SLAB_FREE_DOUBLE(void)
{
	int *val;

	val = kmem_cache_alloc(double_free_cache, GFP_KERNEL);
	if (!val) {
		pr_info("Unable to allocate double_free_cache memory.\n");
		return;
	}

	/* Just make sure we got real memory. */
	*val = 0x12345678;
	pr_info("Attempting double slab free ...\n");
	kmem_cache_free(double_free_cache, val);
	kmem_cache_free(double_free_cache, val);
}

static void lkdtm_SLAB_FREE_CROSS(void)
{
	int *val;

	val = kmem_cache_alloc(a_cache, GFP_KERNEL);
	if (!val) {
		pr_info("Unable to allocate a_cache memory.\n");
		return;
	}

	/* Just make sure we got real memory. */
	*val = 0x12345679;
	pr_info("Attempting cross-cache slab free ...\n");
	kmem_cache_free(b_cache, val);
}

static void lkdtm_SLAB_FREE_PAGE(void)
{
	unsigned long p = __get_free_page(GFP_KERNEL);

	pr_info("Attempting non-Slab slab free ...\n");
	kmem_cache_free(NULL, (void *)p);
	free_page(p);
}

/*
 * We have constructors to keep the caches distinctly separated without
 * needing to boot with "slab_nomerge".
 */
static void ctor_double_free(void *region)
{ }
static void ctor_a(void *region)
{ }
static void ctor_b(void *region)
{ }

void __init lkdtm_heap_init(void)
{
	double_free_cache = kmem_cache_create("lkdtm-heap-double_free",
					      64, 0, 0, ctor_double_free);
	a_cache = kmem_cache_create("lkdtm-heap-a", 64, 0, 0, ctor_a);
	b_cache = kmem_cache_create("lkdtm-heap-b", 64, 0, 0, ctor_b);
}

void __exit lkdtm_heap_exit(void)
{
	kmem_cache_destroy(double_free_cache);
	kmem_cache_destroy(a_cache);
	kmem_cache_destroy(b_cache);
}

static struct crashtype crashtypes[] = {
	CRASHTYPE(SLAB_LINEAR_OVERFLOW),
	CRASHTYPE(VMALLOC_LINEAR_OVERFLOW),
	CRASHTYPE(WRITE_AFTER_FREE),
	CRASHTYPE(READ_AFTER_FREE),
	CRASHTYPE(WRITE_BUDDY_AFTER_FREE),
	CRASHTYPE(READ_BUDDY_AFTER_FREE),
	CRASHTYPE(SLAB_INIT_ON_ALLOC),
	CRASHTYPE(BUDDY_INIT_ON_ALLOC),
	CRASHTYPE(SLAB_FREE_DOUBLE),
	CRASHTYPE(SLAB_FREE_CROSS),
	CRASHTYPE(SLAB_FREE_PAGE),
};

struct crashtype_category heap_crashtypes = {
	.crashtypes = crashtypes,
	.len	    = ARRAY_SIZE(crashtypes),
};