Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
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linux
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * This is for all the tests related to validating kernel memory
4 * permissions: non-executable regions, non-writable regions, and
5 * even non-readable regions.
6 */
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 <linux/objtool.h>
13#include <asm/cacheflush.h>
14#include <asm/sections.h>
15
16/* Whether or not to fill the target memory area with do_nothing(). */
17#define CODE_WRITE true
18#define CODE_AS_IS false
19
20/* How many bytes to copy to be sure we've copied enough of do_nothing(). */
21#define EXEC_SIZE 64
22
23/* This is non-const, so it will end up in the .data section. */
24static u8 data_area[EXEC_SIZE];
25
26/* This is const, so it will end up in the .rodata section. */
27static const unsigned long rodata = 0xAA55AA55;
28
29/* This is marked __ro_after_init, so it should ultimately be .rodata. */
30static unsigned long ro_after_init __ro_after_init = 0x55AA5500;
31
32/*
33 * This is a pointer to do_nothing() which is initialized at runtime rather
34 * than build time to avoid objtool IBT validation warnings caused by an
35 * inlined unrolled memcpy() in execute_location().
36 */
37static void __ro_after_init *do_nothing_ptr;
38
39/*
40 * This just returns to the caller. It is designed to be copied into
41 * non-executable memory regions.
42 */
43static noinline void do_nothing(void)
44{
45 return;
46}
47
48/* Must immediately follow do_nothing for size calculuations to work out. */
49static noinline void do_overwritten(void)
50{
51 pr_info("do_overwritten wasn't overwritten!\n");
52 return;
53}
54
55static noinline void do_almost_nothing(void)
56{
57 pr_info("do_nothing was hijacked!\n");
58}
59
60static void *setup_function_descriptor(func_desc_t *fdesc, void *dst)
61{
62 if (!have_function_descriptors())
63 return dst;
64
65 memcpy(fdesc, do_nothing, sizeof(*fdesc));
66 fdesc->addr = (unsigned long)dst;
67 barrier();
68
69 return fdesc;
70}
71
72static noinline __nocfi void execute_location(void *dst, bool write)
73{
74 void (*func)(void);
75 func_desc_t fdesc;
76
77 pr_info("attempting ok execution at %px\n", do_nothing_ptr);
78 do_nothing();
79
80 if (write == CODE_WRITE) {
81 memcpy(dst, do_nothing_ptr, EXEC_SIZE);
82 flush_icache_range((unsigned long)dst,
83 (unsigned long)dst + EXEC_SIZE);
84 }
85 pr_info("attempting bad execution at %px\n", dst);
86 func = setup_function_descriptor(&fdesc, dst);
87 func();
88 pr_err("FAIL: func returned\n");
89}
90/*
91 * Explicitly doing the wrong thing for testing.
92 */
93ANNOTATE_NOCFI_SYM(execute_location);
94
95static void execute_user_location(void *dst)
96{
97 int copied;
98
99 /* Intentionally crossing kernel/user memory boundary. */
100 void (*func)(void);
101 func_desc_t fdesc;
102 void *do_nothing_text = dereference_function_descriptor(do_nothing);
103
104 pr_info("attempting ok execution at %px\n", do_nothing_text);
105 do_nothing();
106
107 copied = access_process_vm(current, (unsigned long)dst, do_nothing_text,
108 EXEC_SIZE, FOLL_WRITE);
109 if (copied < EXEC_SIZE)
110 return;
111 pr_info("attempting bad execution at %px\n", dst);
112 func = setup_function_descriptor(&fdesc, dst);
113 func();
114 pr_err("FAIL: func returned\n");
115}
116
117static void lkdtm_WRITE_RO(void)
118{
119 /* Explicitly cast away "const" for the test and make volatile. */
120 volatile unsigned long *ptr = (unsigned long *)&rodata;
121
122 pr_info("attempting bad rodata write at %px\n", ptr);
123 *ptr ^= 0xabcd1234;
124 pr_err("FAIL: survived bad write\n");
125}
126
127static void lkdtm_WRITE_RO_AFTER_INIT(void)
128{
129 volatile unsigned long *ptr = &ro_after_init;
130
131 /*
132 * Verify we were written to during init. Since an Oops
133 * is considered a "success", a failure is to just skip the
134 * real test.
135 */
136 if ((*ptr & 0xAA) != 0xAA) {
137 pr_info("%p was NOT written during init!?\n", ptr);
138 return;
139 }
140
141 pr_info("attempting bad ro_after_init write at %px\n", ptr);
142 *ptr ^= 0xabcd1234;
143 pr_err("FAIL: survived bad write\n");
144}
145
146static void lkdtm_WRITE_KERN(void)
147{
148 size_t size;
149 volatile unsigned char *ptr;
150
151 size = (unsigned long)dereference_function_descriptor(do_overwritten) -
152 (unsigned long)dereference_function_descriptor(do_nothing);
153 ptr = dereference_function_descriptor(do_overwritten);
154
155 pr_info("attempting bad %zu byte write at %px\n", size, ptr);
156 memcpy((void *)ptr, (unsigned char *)do_nothing, size);
157 flush_icache_range((unsigned long)ptr, (unsigned long)(ptr + size));
158 pr_err("FAIL: survived bad write\n");
159
160 do_overwritten();
161}
162
163static void lkdtm_WRITE_OPD(void)
164{
165 size_t size = sizeof(func_desc_t);
166 void (*func)(void) = do_nothing;
167
168 if (!have_function_descriptors()) {
169 pr_info("XFAIL: Platform doesn't use function descriptors.\n");
170 return;
171 }
172 pr_info("attempting bad %zu bytes write at %px\n", size, do_nothing);
173 memcpy(do_nothing, do_almost_nothing, size);
174 pr_err("FAIL: survived bad write\n");
175
176 asm("" : "=m"(func));
177 func();
178}
179
180static void lkdtm_EXEC_DATA(void)
181{
182 execute_location(data_area, CODE_WRITE);
183}
184
185static void lkdtm_EXEC_STACK(void)
186{
187 u8 stack_area[EXEC_SIZE];
188 execute_location(stack_area, CODE_WRITE);
189}
190
191static void lkdtm_EXEC_KMALLOC(void)
192{
193 u32 *kmalloc_area = kmalloc(EXEC_SIZE, GFP_KERNEL);
194 execute_location(kmalloc_area, CODE_WRITE);
195 kfree(kmalloc_area);
196}
197
198static void lkdtm_EXEC_VMALLOC(void)
199{
200 u32 *vmalloc_area = vmalloc(EXEC_SIZE);
201 execute_location(vmalloc_area, CODE_WRITE);
202 vfree(vmalloc_area);
203}
204
205static void lkdtm_EXEC_RODATA(void)
206{
207 execute_location(dereference_function_descriptor(lkdtm_rodata_do_nothing),
208 CODE_AS_IS);
209}
210
211static void lkdtm_EXEC_USERSPACE(void)
212{
213 unsigned long user_addr;
214
215 user_addr = vm_mmap(NULL, 0, PAGE_SIZE,
216 PROT_READ | PROT_WRITE | PROT_EXEC,
217 MAP_ANONYMOUS | MAP_PRIVATE, 0);
218 if (user_addr >= TASK_SIZE) {
219 pr_warn("Failed to allocate user memory\n");
220 return;
221 }
222 execute_user_location((void *)user_addr);
223 vm_munmap(user_addr, PAGE_SIZE);
224}
225
226static void lkdtm_EXEC_NULL(void)
227{
228 execute_location(NULL, CODE_AS_IS);
229}
230
231static void lkdtm_ACCESS_USERSPACE(void)
232{
233 unsigned long user_addr, tmp = 0;
234 unsigned long *ptr;
235
236 user_addr = vm_mmap(NULL, 0, PAGE_SIZE,
237 PROT_READ | PROT_WRITE | PROT_EXEC,
238 MAP_ANONYMOUS | MAP_PRIVATE, 0);
239 if (user_addr >= TASK_SIZE) {
240 pr_warn("Failed to allocate user memory\n");
241 return;
242 }
243
244 if (copy_to_user((void __user *)user_addr, &tmp, sizeof(tmp))) {
245 pr_warn("copy_to_user failed\n");
246 vm_munmap(user_addr, PAGE_SIZE);
247 return;
248 }
249
250 ptr = (unsigned long *)user_addr;
251
252 pr_info("attempting bad read at %px\n", ptr);
253 tmp = *ptr;
254 tmp += 0xc0dec0de;
255 pr_err("FAIL: survived bad read\n");
256
257 pr_info("attempting bad write at %px\n", ptr);
258 *ptr = tmp;
259 pr_err("FAIL: survived bad write\n");
260
261 vm_munmap(user_addr, PAGE_SIZE);
262}
263
264static void lkdtm_ACCESS_NULL(void)
265{
266 unsigned long tmp;
267 volatile unsigned long *ptr = (unsigned long *)NULL;
268
269 pr_info("attempting bad read at %px\n", ptr);
270 tmp = *ptr;
271 tmp += 0xc0dec0de;
272 pr_err("FAIL: survived bad read\n");
273
274 pr_info("attempting bad write at %px\n", ptr);
275 *ptr = tmp;
276 pr_err("FAIL: survived bad write\n");
277}
278
279void __init lkdtm_perms_init(void)
280{
281 do_nothing_ptr = dereference_function_descriptor(do_nothing);
282
283 /* Make sure we can write to __ro_after_init values during __init */
284 ro_after_init |= 0xAA;
285}
286
287static struct crashtype crashtypes[] = {
288 CRASHTYPE(WRITE_RO),
289 CRASHTYPE(WRITE_RO_AFTER_INIT),
290 CRASHTYPE(WRITE_KERN),
291 CRASHTYPE(WRITE_OPD),
292 CRASHTYPE(EXEC_DATA),
293 CRASHTYPE(EXEC_STACK),
294 CRASHTYPE(EXEC_KMALLOC),
295 CRASHTYPE(EXEC_VMALLOC),
296 CRASHTYPE(EXEC_RODATA),
297 CRASHTYPE(EXEC_USERSPACE),
298 CRASHTYPE(EXEC_NULL),
299 CRASHTYPE(ACCESS_USERSPACE),
300 CRASHTYPE(ACCESS_NULL),
301};
302
303struct crashtype_category perms_crashtypes = {
304 .crashtypes = crashtypes,
305 .len = ARRAY_SIZE(crashtypes),
306};