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
|
// 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/sched.h>
static struct kmem_cache *double_free_cache;
static struct kmem_cache *a_cache;
static struct kmem_cache *b_cache;
/*
* 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.
*/
void lkdtm_OVERWRITE_ALLOCATION(void)
{
size_t len = 1020;
u32 *data = kmalloc(len, GFP_KERNEL);
if (!data)
return;
data[1024 / sizeof(u32)] = 0x12345678;
kfree(data);
}
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");
}
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);
BUG();
}
pr_info("Memory was not poisoned\n");
kfree(val);
}
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();
}
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);
BUG();
}
pr_info("Buddy page was not poisoned\n");
kfree(val);
}
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);
}
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);
}
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);
}
|
