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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * This is for all the tests relating directly to heap memory, including
4 * page allocation and slab allocations.
5 */
6#include "lkdtm.h"
7#include <linux/slab.h>
8#include <linux/vmalloc.h>
9#include <linux/sched.h>
10
11static struct kmem_cache *double_free_cache;
12static struct kmem_cache *a_cache;
13static struct kmem_cache *b_cache;
14
15/*
16 * Using volatile here means the compiler cannot ever make assumptions
17 * about this value. This means compile-time length checks involving
18 * this variable cannot be performed; only run-time checks.
19 */
20static volatile int __offset = 1;
21
22/*
23 * If there aren't guard pages, it's likely that a consecutive allocation will
24 * let us overflow into the second allocation without overwriting something real.
25 *
26 * This should always be caught because there is an unconditional unmapped
27 * page after vmap allocations.
28 */
29static void lkdtm_VMALLOC_LINEAR_OVERFLOW(void)
30{
31 char *one, *two;
32
33 one = vzalloc(PAGE_SIZE);
34 two = vzalloc(PAGE_SIZE);
35
36 pr_info("Attempting vmalloc linear overflow ...\n");
37 memset(one, 0xAA, PAGE_SIZE + __offset);
38
39 vfree(two);
40 vfree(one);
41}
42
43/*
44 * This tries to stay within the next largest power-of-2 kmalloc cache
45 * to avoid actually overwriting anything important if it's not detected
46 * correctly.
47 *
48 * This should get caught by either memory tagging, KASan, or by using
49 * CONFIG_SLUB_DEBUG=y and slub_debug=ZF (or CONFIG_SLUB_DEBUG_ON=y).
50 */
51static void lkdtm_SLAB_LINEAR_OVERFLOW(void)
52{
53 size_t len = 1020;
54 u32 *data = kmalloc(len, GFP_KERNEL);
55 if (!data)
56 return;
57
58 pr_info("Attempting slab linear overflow ...\n");
59 OPTIMIZER_HIDE_VAR(data);
60 data[1024 / sizeof(u32)] = 0x12345678;
61 kfree(data);
62}
63
64static void lkdtm_WRITE_AFTER_FREE(void)
65{
66 int *base, *again;
67 size_t len = 1024;
68 /*
69 * The slub allocator uses the first word to store the free
70 * pointer in some configurations. Use the middle of the
71 * allocation to avoid running into the freelist
72 */
73 size_t offset = (len / sizeof(*base)) / 2;
74
75 base = kmalloc(len, GFP_KERNEL);
76 if (!base)
77 return;
78 pr_info("Allocated memory %p-%p\n", base, &base[offset * 2]);
79 pr_info("Attempting bad write to freed memory at %p\n",
80 &base[offset]);
81 kfree(base);
82 base[offset] = 0x0abcdef0;
83 /* Attempt to notice the overwrite. */
84 again = kmalloc(len, GFP_KERNEL);
85 kfree(again);
86 if (again != base)
87 pr_info("Hmm, didn't get the same memory range.\n");
88}
89
90static void lkdtm_READ_AFTER_FREE(void)
91{
92 int *base, *val, saw;
93 size_t len = 1024;
94 /*
95 * The slub allocator will use the either the first word or
96 * the middle of the allocation to store the free pointer,
97 * depending on configurations. Store in the second word to
98 * avoid running into the freelist.
99 */
100 size_t offset = sizeof(*base);
101
102 base = kmalloc(len, GFP_KERNEL);
103 if (!base) {
104 pr_info("Unable to allocate base memory.\n");
105 return;
106 }
107
108 val = kmalloc(len, GFP_KERNEL);
109 if (!val) {
110 pr_info("Unable to allocate val memory.\n");
111 kfree(base);
112 return;
113 }
114
115 *val = 0x12345678;
116 base[offset] = *val;
117 pr_info("Value in memory before free: %x\n", base[offset]);
118
119 kfree(base);
120
121 pr_info("Attempting bad read from freed memory\n");
122 saw = base[offset];
123 if (saw != *val) {
124 /* Good! Poisoning happened, so declare a win. */
125 pr_info("Memory correctly poisoned (%x)\n", saw);
126 } else {
127 pr_err("FAIL: Memory was not poisoned!\n");
128 pr_expected_config_param(CONFIG_INIT_ON_FREE_DEFAULT_ON, "init_on_free");
129 }
130
131 kfree(val);
132}
133
134static void lkdtm_WRITE_BUDDY_AFTER_FREE(void)
135{
136 unsigned long p = __get_free_page(GFP_KERNEL);
137 if (!p) {
138 pr_info("Unable to allocate free page\n");
139 return;
140 }
141
142 pr_info("Writing to the buddy page before free\n");
143 memset((void *)p, 0x3, PAGE_SIZE);
144 free_page(p);
145 schedule();
146 pr_info("Attempting bad write to the buddy page after free\n");
147 memset((void *)p, 0x78, PAGE_SIZE);
148 /* Attempt to notice the overwrite. */
149 p = __get_free_page(GFP_KERNEL);
150 free_page(p);
151 schedule();
152}
153
154static void lkdtm_READ_BUDDY_AFTER_FREE(void)
155{
156 unsigned long p = __get_free_page(GFP_KERNEL);
157 int saw, *val;
158 int *base;
159
160 if (!p) {
161 pr_info("Unable to allocate free page\n");
162 return;
163 }
164
165 val = kmalloc(1024, GFP_KERNEL);
166 if (!val) {
167 pr_info("Unable to allocate val memory.\n");
168 free_page(p);
169 return;
170 }
171
172 base = (int *)p;
173
174 *val = 0x12345678;
175 base[0] = *val;
176 pr_info("Value in memory before free: %x\n", base[0]);
177 free_page(p);
178 pr_info("Attempting to read from freed memory\n");
179 saw = base[0];
180 if (saw != *val) {
181 /* Good! Poisoning happened, so declare a win. */
182 pr_info("Memory correctly poisoned (%x)\n", saw);
183 } else {
184 pr_err("FAIL: Buddy page was not poisoned!\n");
185 pr_expected_config_param(CONFIG_INIT_ON_FREE_DEFAULT_ON, "init_on_free");
186 }
187
188 kfree(val);
189}
190
191static void lkdtm_SLAB_INIT_ON_ALLOC(void)
192{
193 u8 *first;
194 u8 *val;
195
196 first = kmalloc(512, GFP_KERNEL);
197 if (!first) {
198 pr_info("Unable to allocate 512 bytes the first time.\n");
199 return;
200 }
201
202 memset(first, 0xAB, 512);
203 kfree(first);
204
205 val = kmalloc(512, GFP_KERNEL);
206 if (!val) {
207 pr_info("Unable to allocate 512 bytes the second time.\n");
208 return;
209 }
210 if (val != first) {
211 pr_warn("Reallocation missed clobbered memory.\n");
212 }
213
214 if (memchr(val, 0xAB, 512) == NULL) {
215 pr_info("Memory appears initialized (%x, no earlier values)\n", *val);
216 } else {
217 pr_err("FAIL: Slab was not initialized\n");
218 pr_expected_config_param(CONFIG_INIT_ON_ALLOC_DEFAULT_ON, "init_on_alloc");
219 }
220 kfree(val);
221}
222
223static void lkdtm_BUDDY_INIT_ON_ALLOC(void)
224{
225 u8 *first;
226 u8 *val;
227
228 first = (u8 *)__get_free_page(GFP_KERNEL);
229 if (!first) {
230 pr_info("Unable to allocate first free page\n");
231 return;
232 }
233
234 memset(first, 0xAB, PAGE_SIZE);
235 free_page((unsigned long)first);
236
237 val = (u8 *)__get_free_page(GFP_KERNEL);
238 if (!val) {
239 pr_info("Unable to allocate second free page\n");
240 return;
241 }
242
243 if (val != first) {
244 pr_warn("Reallocation missed clobbered memory.\n");
245 }
246
247 if (memchr(val, 0xAB, PAGE_SIZE) == NULL) {
248 pr_info("Memory appears initialized (%x, no earlier values)\n", *val);
249 } else {
250 pr_err("FAIL: Slab was not initialized\n");
251 pr_expected_config_param(CONFIG_INIT_ON_ALLOC_DEFAULT_ON, "init_on_alloc");
252 }
253 free_page((unsigned long)val);
254}
255
256static void lkdtm_SLAB_FREE_DOUBLE(void)
257{
258 int *val;
259
260 val = kmem_cache_alloc(double_free_cache, GFP_KERNEL);
261 if (!val) {
262 pr_info("Unable to allocate double_free_cache memory.\n");
263 return;
264 }
265
266 /* Just make sure we got real memory. */
267 *val = 0x12345678;
268 pr_info("Attempting double slab free ...\n");
269 kmem_cache_free(double_free_cache, val);
270 kmem_cache_free(double_free_cache, val);
271}
272
273static void lkdtm_SLAB_FREE_CROSS(void)
274{
275 int *val;
276
277 val = kmem_cache_alloc(a_cache, GFP_KERNEL);
278 if (!val) {
279 pr_info("Unable to allocate a_cache memory.\n");
280 return;
281 }
282
283 /* Just make sure we got real memory. */
284 *val = 0x12345679;
285 pr_info("Attempting cross-cache slab free ...\n");
286 kmem_cache_free(b_cache, val);
287}
288
289static void lkdtm_SLAB_FREE_PAGE(void)
290{
291 unsigned long p = __get_free_page(GFP_KERNEL);
292
293 pr_info("Attempting non-Slab slab free ...\n");
294 kmem_cache_free(NULL, (void *)p);
295 free_page(p);
296}
297
298/*
299 * We have constructors to keep the caches distinctly separated without
300 * needing to boot with "slab_nomerge".
301 */
302static void ctor_double_free(void *region)
303{ }
304static void ctor_a(void *region)
305{ }
306static void ctor_b(void *region)
307{ }
308
309void __init lkdtm_heap_init(void)
310{
311 double_free_cache = kmem_cache_create("lkdtm-heap-double_free",
312 64, 0, 0, ctor_double_free);
313 a_cache = kmem_cache_create("lkdtm-heap-a", 64, 0, 0, ctor_a);
314 b_cache = kmem_cache_create("lkdtm-heap-b", 64, 0, 0, ctor_b);
315}
316
317void __exit lkdtm_heap_exit(void)
318{
319 kmem_cache_destroy(double_free_cache);
320 kmem_cache_destroy(a_cache);
321 kmem_cache_destroy(b_cache);
322}
323
324static struct crashtype crashtypes[] = {
325 CRASHTYPE(SLAB_LINEAR_OVERFLOW),
326 CRASHTYPE(VMALLOC_LINEAR_OVERFLOW),
327 CRASHTYPE(WRITE_AFTER_FREE),
328 CRASHTYPE(READ_AFTER_FREE),
329 CRASHTYPE(WRITE_BUDDY_AFTER_FREE),
330 CRASHTYPE(READ_BUDDY_AFTER_FREE),
331 CRASHTYPE(SLAB_INIT_ON_ALLOC),
332 CRASHTYPE(BUDDY_INIT_ON_ALLOC),
333 CRASHTYPE(SLAB_FREE_DOUBLE),
334 CRASHTYPE(SLAB_FREE_CROSS),
335 CRASHTYPE(SLAB_FREE_PAGE),
336};
337
338struct crashtype_category heap_crashtypes = {
339 .crashtypes = crashtypes,
340 .len = ARRAY_SIZE(crashtypes),
341};
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * This is for all the tests relating directly to heap memory, including
4 * page allocation and slab allocations.
5 */
6#include "lkdtm.h"
7#include <linux/slab.h>
8#include <linux/sched.h>
9
10/*
11 * This tries to stay within the next largest power-of-2 kmalloc cache
12 * to avoid actually overwriting anything important if it's not detected
13 * correctly.
14 */
15void lkdtm_OVERWRITE_ALLOCATION(void)
16{
17 size_t len = 1020;
18 u32 *data = kmalloc(len, GFP_KERNEL);
19 if (!data)
20 return;
21
22 data[1024 / sizeof(u32)] = 0x12345678;
23 kfree(data);
24}
25
26void lkdtm_WRITE_AFTER_FREE(void)
27{
28 int *base, *again;
29 size_t len = 1024;
30 /*
31 * The slub allocator uses the first word to store the free
32 * pointer in some configurations. Use the middle of the
33 * allocation to avoid running into the freelist
34 */
35 size_t offset = (len / sizeof(*base)) / 2;
36
37 base = kmalloc(len, GFP_KERNEL);
38 if (!base)
39 return;
40 pr_info("Allocated memory %p-%p\n", base, &base[offset * 2]);
41 pr_info("Attempting bad write to freed memory at %p\n",
42 &base[offset]);
43 kfree(base);
44 base[offset] = 0x0abcdef0;
45 /* Attempt to notice the overwrite. */
46 again = kmalloc(len, GFP_KERNEL);
47 kfree(again);
48 if (again != base)
49 pr_info("Hmm, didn't get the same memory range.\n");
50}
51
52void lkdtm_READ_AFTER_FREE(void)
53{
54 int *base, *val, saw;
55 size_t len = 1024;
56 /*
57 * The slub allocator uses the first word to store the free
58 * pointer in some configurations. Use the middle of the
59 * allocation to avoid running into the freelist
60 */
61 size_t offset = (len / sizeof(*base)) / 2;
62
63 base = kmalloc(len, GFP_KERNEL);
64 if (!base) {
65 pr_info("Unable to allocate base memory.\n");
66 return;
67 }
68
69 val = kmalloc(len, GFP_KERNEL);
70 if (!val) {
71 pr_info("Unable to allocate val memory.\n");
72 kfree(base);
73 return;
74 }
75
76 *val = 0x12345678;
77 base[offset] = *val;
78 pr_info("Value in memory before free: %x\n", base[offset]);
79
80 kfree(base);
81
82 pr_info("Attempting bad read from freed memory\n");
83 saw = base[offset];
84 if (saw != *val) {
85 /* Good! Poisoning happened, so declare a win. */
86 pr_info("Memory correctly poisoned (%x)\n", saw);
87 BUG();
88 }
89 pr_info("Memory was not poisoned\n");
90
91 kfree(val);
92}
93
94void lkdtm_WRITE_BUDDY_AFTER_FREE(void)
95{
96 unsigned long p = __get_free_page(GFP_KERNEL);
97 if (!p) {
98 pr_info("Unable to allocate free page\n");
99 return;
100 }
101
102 pr_info("Writing to the buddy page before free\n");
103 memset((void *)p, 0x3, PAGE_SIZE);
104 free_page(p);
105 schedule();
106 pr_info("Attempting bad write to the buddy page after free\n");
107 memset((void *)p, 0x78, PAGE_SIZE);
108 /* Attempt to notice the overwrite. */
109 p = __get_free_page(GFP_KERNEL);
110 free_page(p);
111 schedule();
112}
113
114void lkdtm_READ_BUDDY_AFTER_FREE(void)
115{
116 unsigned long p = __get_free_page(GFP_KERNEL);
117 int saw, *val;
118 int *base;
119
120 if (!p) {
121 pr_info("Unable to allocate free page\n");
122 return;
123 }
124
125 val = kmalloc(1024, GFP_KERNEL);
126 if (!val) {
127 pr_info("Unable to allocate val memory.\n");
128 free_page(p);
129 return;
130 }
131
132 base = (int *)p;
133
134 *val = 0x12345678;
135 base[0] = *val;
136 pr_info("Value in memory before free: %x\n", base[0]);
137 free_page(p);
138 pr_info("Attempting to read from freed memory\n");
139 saw = base[0];
140 if (saw != *val) {
141 /* Good! Poisoning happened, so declare a win. */
142 pr_info("Memory correctly poisoned (%x)\n", saw);
143 BUG();
144 }
145 pr_info("Buddy page was not poisoned\n");
146
147 kfree(val);
148}