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7#include "lkdtm.h"
8#include <linux/slab.h>
9#include <linux/vmalloc.h>
10#include <linux/mman.h>
11#include <linux/uaccess.h>
12#include <asm/cacheflush.h>
13
14
15#define CODE_WRITE true
16#define CODE_AS_IS false
17
18
19#define EXEC_SIZE 64
20
21
22static u8 data_area[EXEC_SIZE];
23
24
25static const unsigned long rodata = 0xAA55AA55;
26
27
28static unsigned long ro_after_init __ro_after_init = 0x55AA5500;
29
30
31
32
33
34static void do_nothing(void)
35{
36 return;
37}
38
39
40static void do_overwritten(void)
41{
42 pr_info("do_overwritten wasn't overwritten!\n");
43 return;
44}
45
46static noinline void execute_location(void *dst, bool write)
47{
48 void (*func)(void) = dst;
49
50 pr_info("attempting ok execution at %px\n", do_nothing);
51 do_nothing();
52
53 if (write == CODE_WRITE) {
54 memcpy(dst, do_nothing, EXEC_SIZE);
55 flush_icache_range((unsigned long)dst,
56 (unsigned long)dst + EXEC_SIZE);
57 }
58 pr_info("attempting bad execution at %px\n", func);
59 func();
60 pr_err("FAIL: func returned\n");
61}
62
63static void execute_user_location(void *dst)
64{
65 int copied;
66
67
68 void (*func)(void) = dst;
69
70 pr_info("attempting ok execution at %px\n", do_nothing);
71 do_nothing();
72
73 copied = access_process_vm(current, (unsigned long)dst, do_nothing,
74 EXEC_SIZE, FOLL_WRITE);
75 if (copied < EXEC_SIZE)
76 return;
77 pr_info("attempting bad execution at %px\n", func);
78 func();
79 pr_err("FAIL: func returned\n");
80}
81
82void lkdtm_WRITE_RO(void)
83{
84
85 volatile unsigned long *ptr = (unsigned long *)&rodata;
86
87 pr_info("attempting bad rodata write at %px\n", ptr);
88 *ptr ^= 0xabcd1234;
89 pr_err("FAIL: survived bad write\n");
90}
91
92void lkdtm_WRITE_RO_AFTER_INIT(void)
93{
94 volatile unsigned long *ptr = &ro_after_init;
95
96
97
98
99
100
101 if ((*ptr & 0xAA) != 0xAA) {
102 pr_info("%p was NOT written during init!?\n", ptr);
103 return;
104 }
105
106 pr_info("attempting bad ro_after_init write at %px\n", ptr);
107 *ptr ^= 0xabcd1234;
108 pr_err("FAIL: survived bad write\n");
109}
110
111void lkdtm_WRITE_KERN(void)
112{
113 size_t size;
114 volatile unsigned char *ptr;
115
116 size = (unsigned long)do_overwritten - (unsigned long)do_nothing;
117 ptr = (unsigned char *)do_overwritten;
118
119 pr_info("attempting bad %zu byte write at %px\n", size, ptr);
120 memcpy((void *)ptr, (unsigned char *)do_nothing, size);
121 flush_icache_range((unsigned long)ptr, (unsigned long)(ptr + size));
122 pr_err("FAIL: survived bad write\n");
123
124 do_overwritten();
125}
126
127void lkdtm_EXEC_DATA(void)
128{
129 execute_location(data_area, CODE_WRITE);
130}
131
132void lkdtm_EXEC_STACK(void)
133{
134 u8 stack_area[EXEC_SIZE];
135 execute_location(stack_area, CODE_WRITE);
136}
137
138void lkdtm_EXEC_KMALLOC(void)
139{
140 u32 *kmalloc_area = kmalloc(EXEC_SIZE, GFP_KERNEL);
141 execute_location(kmalloc_area, CODE_WRITE);
142 kfree(kmalloc_area);
143}
144
145void lkdtm_EXEC_VMALLOC(void)
146{
147 u32 *vmalloc_area = vmalloc(EXEC_SIZE);
148 execute_location(vmalloc_area, CODE_WRITE);
149 vfree(vmalloc_area);
150}
151
152void lkdtm_EXEC_RODATA(void)
153{
154 execute_location(lkdtm_rodata_do_nothing, CODE_AS_IS);
155}
156
157void lkdtm_EXEC_USERSPACE(void)
158{
159 unsigned long user_addr;
160
161 user_addr = vm_mmap(NULL, 0, PAGE_SIZE,
162 PROT_READ | PROT_WRITE | PROT_EXEC,
163 MAP_ANONYMOUS | MAP_PRIVATE, 0);
164 if (user_addr >= TASK_SIZE) {
165 pr_warn("Failed to allocate user memory\n");
166 return;
167 }
168 execute_user_location((void *)user_addr);
169 vm_munmap(user_addr, PAGE_SIZE);
170}
171
172void lkdtm_EXEC_NULL(void)
173{
174 execute_location(NULL, CODE_AS_IS);
175}
176
177void lkdtm_ACCESS_USERSPACE(void)
178{
179 unsigned long user_addr, tmp = 0;
180 unsigned long *ptr;
181
182 user_addr = vm_mmap(NULL, 0, PAGE_SIZE,
183 PROT_READ | PROT_WRITE | PROT_EXEC,
184 MAP_ANONYMOUS | MAP_PRIVATE, 0);
185 if (user_addr >= TASK_SIZE) {
186 pr_warn("Failed to allocate user memory\n");
187 return;
188 }
189
190 if (copy_to_user((void __user *)user_addr, &tmp, sizeof(tmp))) {
191 pr_warn("copy_to_user failed\n");
192 vm_munmap(user_addr, PAGE_SIZE);
193 return;
194 }
195
196 ptr = (unsigned long *)user_addr;
197
198 pr_info("attempting bad read at %px\n", ptr);
199 tmp = *ptr;
200 tmp += 0xc0dec0de;
201 pr_err("FAIL: survived bad read\n");
202
203 pr_info("attempting bad write at %px\n", ptr);
204 *ptr = tmp;
205 pr_err("FAIL: survived bad write\n");
206
207 vm_munmap(user_addr, PAGE_SIZE);
208}
209
210void lkdtm_ACCESS_NULL(void)
211{
212 unsigned long tmp;
213 volatile unsigned long *ptr = (unsigned long *)NULL;
214
215 pr_info("attempting bad read at %px\n", ptr);
216 tmp = *ptr;
217 tmp += 0xc0dec0de;
218 pr_err("FAIL: survived bad read\n");
219
220 pr_info("attempting bad write at %px\n", ptr);
221 *ptr = tmp;
222 pr_err("FAIL: survived bad write\n");
223}
224
225void __init lkdtm_perms_init(void)
226{
227
228 ro_after_init |= 0xAA;
229}
230