summaryrefslogtreecommitdiff
path: root/drivers/misc/lkdtm/perms.c
blob: 53b85c9d16b89247d0fa66d0dce5192d71f9c63e (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
// SPDX-License-Identifier: GPL-2.0
/*
 * This is for all the tests related to validating kernel memory
 * permissions: non-executable regions, non-writable regions, and
 * even non-readable regions.
 */
#include "lkdtm.h"
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/mman.h>
#include <linux/uaccess.h>
#include <asm/cacheflush.h>

/* Whether or not to fill the target memory area with do_nothing(). */
#define CODE_WRITE	true
#define CODE_AS_IS	false

/* How many bytes to copy to be sure we've copied enough of do_nothing(). */
#define EXEC_SIZE 64

/* This is non-const, so it will end up in the .data section. */
static u8 data_area[EXEC_SIZE];

/* This is cost, so it will end up in the .rodata section. */
static const unsigned long rodata = 0xAA55AA55;

/* This is marked __ro_after_init, so it should ultimately be .rodata. */
static unsigned long ro_after_init __ro_after_init = 0x55AA5500;

/*
 * This just returns to the caller. It is designed to be copied into
 * non-executable memory regions.
 */
static void do_nothing(void)
{
	return;
}

/* Must immediately follow do_nothing for size calculuations to work out. */
static void do_overwritten(void)
{
	pr_info("do_overwritten wasn't overwritten!\n");
	return;
}

static noinline void execute_location(void *dst, bool write)
{
	void (*func)(void) = dst;

	pr_info("attempting ok execution at %p\n", do_nothing);
	do_nothing();

	if (write == CODE_WRITE) {
		memcpy(dst, do_nothing, EXEC_SIZE);
		flush_icache_range((unsigned long)dst,
				   (unsigned long)dst + EXEC_SIZE);
	}
	pr_info("attempting bad execution at %p\n", func);
	func();
}

static void execute_user_location(void *dst)
{
	int copied;

	/* Intentionally crossing kernel/user memory boundary. */
	void (*func)(void) = dst;

	pr_info("attempting ok execution at %p\n", do_nothing);
	do_nothing();

	copied = access_process_vm(current, (unsigned long)dst, do_nothing,
				   EXEC_SIZE, FOLL_WRITE);
	if (copied < EXEC_SIZE)
		return;
	pr_info("attempting bad execution at %p\n", func);
	func();
}

void lkdtm_WRITE_RO(void)
{
	/* Explicitly cast away "const" for the test. */
	unsigned long *ptr = (unsigned long *)&rodata;

	pr_info("attempting bad rodata write at %p\n", ptr);
	*ptr ^= 0xabcd1234;
}

void lkdtm_WRITE_RO_AFTER_INIT(void)
{
	unsigned long *ptr = &ro_after_init;

	/*
	 * Verify we were written to during init. Since an Oops
	 * is considered a "success", a failure is to just skip the
	 * real test.
	 */
	if ((*ptr & 0xAA) != 0xAA) {
		pr_info("%p was NOT written during init!?\n", ptr);
		return;
	}

	pr_info("attempting bad ro_after_init write at %p\n", ptr);
	*ptr ^= 0xabcd1234;
}

void lkdtm_WRITE_KERN(void)
{
	size_t size;
	unsigned char *ptr;

	size = (unsigned long)do_overwritten - (unsigned long)do_nothing;
	ptr = (unsigned char *)do_overwritten;

	pr_info("attempting bad %zu byte write at %p\n", size, ptr);
	memcpy(ptr, (unsigned char *)do_nothing, size);
	flush_icache_range((unsigned long)ptr, (unsigned long)(ptr + size));

	do_overwritten();
}

void lkdtm_EXEC_DATA(void)
{
	execute_location(data_area, CODE_WRITE);
}

void lkdtm_EXEC_STACK(void)
{
	u8 stack_area[EXEC_SIZE];
	execute_location(stack_area, CODE_WRITE);
}

void lkdtm_EXEC_KMALLOC(void)
{
	u32 *kmalloc_area = kmalloc(EXEC_SIZE, GFP_KERNEL);
	execute_location(kmalloc_area, CODE_WRITE);
	kfree(kmalloc_area);
}

void lkdtm_EXEC_VMALLOC(void)
{
	u32 *vmalloc_area = vmalloc(EXEC_SIZE);
	execute_location(vmalloc_area, CODE_WRITE);
	vfree(vmalloc_area);
}

void lkdtm_EXEC_RODATA(void)
{
	execute_location(lkdtm_rodata_do_nothing, CODE_AS_IS);
}

void lkdtm_EXEC_USERSPACE(void)
{
	unsigned long user_addr;

	user_addr = vm_mmap(NULL, 0, PAGE_SIZE,
			    PROT_READ | PROT_WRITE | PROT_EXEC,
			    MAP_ANONYMOUS | MAP_PRIVATE, 0);
	if (user_addr >= TASK_SIZE) {
		pr_warn("Failed to allocate user memory\n");
		return;
	}
	execute_user_location((void *)user_addr);
	vm_munmap(user_addr, PAGE_SIZE);
}

void lkdtm_ACCESS_USERSPACE(void)
{
	unsigned long user_addr, tmp = 0;
	unsigned long *ptr;

	user_addr = vm_mmap(NULL, 0, PAGE_SIZE,
			    PROT_READ | PROT_WRITE | PROT_EXEC,
			    MAP_ANONYMOUS | MAP_PRIVATE, 0);
	if (user_addr >= TASK_SIZE) {
		pr_warn("Failed to allocate user memory\n");
		return;
	}

	if (copy_to_user((void __user *)user_addr, &tmp, sizeof(tmp))) {
		pr_warn("copy_to_user failed\n");
		vm_munmap(user_addr, PAGE_SIZE);
		return;
	}

	ptr = (unsigned long *)user_addr;

	pr_info("attempting bad read at %p\n", ptr);
	tmp = *ptr;
	tmp += 0xc0dec0de;

	pr_info("attempting bad write at %p\n", ptr);
	*ptr = tmp;

	vm_munmap(user_addr, PAGE_SIZE);
}

void __init lkdtm_perms_init(void)
{
	/* Make sure we can write to __ro_after_init values during __init */
	ro_after_init |= 0xAA;

}