1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Copyright IBM Corporation, 2021
4  *
5  * Author: Mike Rapoport <rppt@linux.ibm.com>
6  */
7 
8 #define _GNU_SOURCE
9 #include <sys/uio.h>
10 #include <sys/mman.h>
11 #include <sys/wait.h>
12 #include <sys/types.h>
13 #include <sys/ptrace.h>
14 #include <sys/syscall.h>
15 #include <sys/resource.h>
16 #include <sys/capability.h>
17 
18 #include <stdlib.h>
19 #include <string.h>
20 #include <unistd.h>
21 #include <errno.h>
22 #include <stdio.h>
23 
24 #include "../kselftest.h"
25 
26 #define fail(fmt, ...) ksft_test_result_fail(fmt, ##__VA_ARGS__)
27 #define pass(fmt, ...) ksft_test_result_pass(fmt, ##__VA_ARGS__)
28 #define skip(fmt, ...) ksft_test_result_skip(fmt, ##__VA_ARGS__)
29 
30 #ifdef __NR_memfd_secret
31 
32 #define PATTERN	0x55
33 
34 static const int prot = PROT_READ | PROT_WRITE;
35 static const int mode = MAP_SHARED;
36 
37 static unsigned long page_size;
38 static unsigned long mlock_limit_cur;
39 static unsigned long mlock_limit_max;
40 
41 static int memfd_secret(unsigned int flags)
42 {
43 	return syscall(__NR_memfd_secret, flags);
44 }
45 
46 static void test_file_apis(int fd)
47 {
48 	char buf[64];
49 
50 	if ((read(fd, buf, sizeof(buf)) >= 0) ||
51 	    (write(fd, buf, sizeof(buf)) >= 0) ||
52 	    (pread(fd, buf, sizeof(buf), 0) >= 0) ||
53 	    (pwrite(fd, buf, sizeof(buf), 0) >= 0))
54 		fail("unexpected file IO\n");
55 	else
56 		pass("file IO is blocked as expected\n");
57 }
58 
59 static void test_mlock_limit(int fd)
60 {
61 	size_t len;
62 	char *mem;
63 
64 	len = mlock_limit_cur;
65 	mem = mmap(NULL, len, prot, mode, fd, 0);
66 	if (mem == MAP_FAILED) {
67 		fail("unable to mmap secret memory\n");
68 		return;
69 	}
70 	munmap(mem, len);
71 
72 	len = mlock_limit_max * 2;
73 	mem = mmap(NULL, len, prot, mode, fd, 0);
74 	if (mem != MAP_FAILED) {
75 		fail("unexpected mlock limit violation\n");
76 		munmap(mem, len);
77 		return;
78 	}
79 
80 	pass("mlock limit is respected\n");
81 }
82 
83 static void try_process_vm_read(int fd, int pipefd[2])
84 {
85 	struct iovec liov, riov;
86 	char buf[64];
87 	char *mem;
88 
89 	if (read(pipefd[0], &mem, sizeof(mem)) < 0) {
90 		fail("pipe write: %s\n", strerror(errno));
91 		exit(KSFT_FAIL);
92 	}
93 
94 	liov.iov_len = riov.iov_len = sizeof(buf);
95 	liov.iov_base = buf;
96 	riov.iov_base = mem;
97 
98 	if (process_vm_readv(getppid(), &liov, 1, &riov, 1, 0) < 0) {
99 		if (errno == ENOSYS)
100 			exit(KSFT_SKIP);
101 		exit(KSFT_PASS);
102 	}
103 
104 	exit(KSFT_FAIL);
105 }
106 
107 static void try_ptrace(int fd, int pipefd[2])
108 {
109 	pid_t ppid = getppid();
110 	int status;
111 	char *mem;
112 	long ret;
113 
114 	if (read(pipefd[0], &mem, sizeof(mem)) < 0) {
115 		perror("pipe write");
116 		exit(KSFT_FAIL);
117 	}
118 
119 	ret = ptrace(PTRACE_ATTACH, ppid, 0, 0);
120 	if (ret) {
121 		perror("ptrace_attach");
122 		exit(KSFT_FAIL);
123 	}
124 
125 	ret = waitpid(ppid, &status, WUNTRACED);
126 	if ((ret != ppid) || !(WIFSTOPPED(status))) {
127 		fprintf(stderr, "weird waitppid result %ld stat %x\n",
128 			ret, status);
129 		exit(KSFT_FAIL);
130 	}
131 
132 	if (ptrace(PTRACE_PEEKDATA, ppid, mem, 0))
133 		exit(KSFT_PASS);
134 
135 	exit(KSFT_FAIL);
136 }
137 
138 static void check_child_status(pid_t pid, const char *name)
139 {
140 	int status;
141 
142 	waitpid(pid, &status, 0);
143 
144 	if (WIFEXITED(status) && WEXITSTATUS(status) == KSFT_SKIP) {
145 		skip("%s is not supported\n", name);
146 		return;
147 	}
148 
149 	if ((WIFEXITED(status) && WEXITSTATUS(status) == KSFT_PASS) ||
150 	    WIFSIGNALED(status)) {
151 		pass("%s is blocked as expected\n", name);
152 		return;
153 	}
154 
155 	fail("%s: unexpected memory access\n", name);
156 }
157 
158 static void test_remote_access(int fd, const char *name,
159 			       void (*func)(int fd, int pipefd[2]))
160 {
161 	int pipefd[2];
162 	pid_t pid;
163 	char *mem;
164 
165 	if (pipe(pipefd)) {
166 		fail("pipe failed: %s\n", strerror(errno));
167 		return;
168 	}
169 
170 	pid = fork();
171 	if (pid < 0) {
172 		fail("fork failed: %s\n", strerror(errno));
173 		return;
174 	}
175 
176 	if (pid == 0) {
177 		func(fd, pipefd);
178 		return;
179 	}
180 
181 	mem = mmap(NULL, page_size, prot, mode, fd, 0);
182 	if (mem == MAP_FAILED) {
183 		fail("Unable to mmap secret memory\n");
184 		return;
185 	}
186 
187 	ftruncate(fd, page_size);
188 	memset(mem, PATTERN, page_size);
189 
190 	if (write(pipefd[1], &mem, sizeof(mem)) < 0) {
191 		fail("pipe write: %s\n", strerror(errno));
192 		return;
193 	}
194 
195 	check_child_status(pid, name);
196 }
197 
198 static void test_process_vm_read(int fd)
199 {
200 	test_remote_access(fd, "process_vm_read", try_process_vm_read);
201 }
202 
203 static void test_ptrace(int fd)
204 {
205 	test_remote_access(fd, "ptrace", try_ptrace);
206 }
207 
208 static int set_cap_limits(rlim_t max)
209 {
210 	struct rlimit new;
211 	cap_t cap = cap_init();
212 
213 	new.rlim_cur = max;
214 	new.rlim_max = max;
215 	if (setrlimit(RLIMIT_MEMLOCK, &new)) {
216 		perror("setrlimit() returns error");
217 		return -1;
218 	}
219 
220 	/* drop capabilities including CAP_IPC_LOCK */
221 	if (cap_set_proc(cap)) {
222 		perror("cap_set_proc() returns error");
223 		return -2;
224 	}
225 
226 	return 0;
227 }
228 
229 static void prepare(void)
230 {
231 	struct rlimit rlim;
232 
233 	page_size = sysconf(_SC_PAGE_SIZE);
234 	if (!page_size)
235 		ksft_exit_fail_msg("Failed to get page size %s\n",
236 				   strerror(errno));
237 
238 	if (getrlimit(RLIMIT_MEMLOCK, &rlim))
239 		ksft_exit_fail_msg("Unable to detect mlock limit: %s\n",
240 				   strerror(errno));
241 
242 	mlock_limit_cur = rlim.rlim_cur;
243 	mlock_limit_max = rlim.rlim_max;
244 
245 	printf("page_size: %ld, mlock.soft: %ld, mlock.hard: %ld\n",
246 	       page_size, mlock_limit_cur, mlock_limit_max);
247 
248 	if (page_size > mlock_limit_cur)
249 		mlock_limit_cur = page_size;
250 	if (page_size > mlock_limit_max)
251 		mlock_limit_max = page_size;
252 
253 	if (set_cap_limits(mlock_limit_max))
254 		ksft_exit_fail_msg("Unable to set mlock limit: %s\n",
255 				   strerror(errno));
256 }
257 
258 #define NUM_TESTS 4
259 
260 int main(int argc, char *argv[])
261 {
262 	int fd;
263 
264 	prepare();
265 
266 	ksft_print_header();
267 	ksft_set_plan(NUM_TESTS);
268 
269 	fd = memfd_secret(0);
270 	if (fd < 0) {
271 		if (errno == ENOSYS)
272 			ksft_exit_skip("memfd_secret is not supported\n");
273 		else
274 			ksft_exit_fail_msg("memfd_secret failed: %s\n",
275 					   strerror(errno));
276 	}
277 
278 	test_mlock_limit(fd);
279 	test_file_apis(fd);
280 	test_process_vm_read(fd);
281 	test_ptrace(fd);
282 
283 	close(fd);
284 
285 	ksft_finished();
286 }
287 
288 #else /* __NR_memfd_secret */
289 
290 int main(int argc, char *argv[])
291 {
292 	printf("skip: skipping memfd_secret test (missing __NR_memfd_secret)\n");
293 	return KSFT_SKIP;
294 }
295 
296 #endif /* __NR_memfd_secret */
297