1 /*
2 * Copyright (c) 2019 Alexey Dobriyan <adobriyan@gmail.com>
3 *
4 * Permission to use, copy, modify, and distribute this software for any
5 * purpose with or without fee is hereby granted, provided that the above
6 * copyright notice and this permission notice appear in all copies.
7 *
8 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
9 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
11 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
14 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
15 */
16 /*
17 * Fork and exec tiny 1 page executable which precisely controls its VM.
18 * Test /proc/$PID/maps
19 * Test /proc/$PID/smaps
20 * Test /proc/$PID/smaps_rollup
21 * Test /proc/$PID/statm
22 *
23 * FIXME require CONFIG_TMPFS which can be disabled
24 * FIXME test other values from "smaps"
25 * FIXME support other archs
26 */
27 #undef NDEBUG
28 #include <assert.h>
29 #include <errno.h>
30 #include <sched.h>
31 #include <signal.h>
32 #include <stdbool.h>
33 #include <stdint.h>
34 #include <stdio.h>
35 #include <string.h>
36 #include <stdlib.h>
37 #include <sys/mount.h>
38 #include <sys/types.h>
39 #include <sys/stat.h>
40 #include <sys/wait.h>
41 #include <fcntl.h>
42 #include <unistd.h>
43 #include <sys/syscall.h>
44 #include <sys/uio.h>
45 #include <linux/kdev_t.h>
46 #include <sys/time.h>
47 #include <sys/resource.h>
48
sys_execveat(int dirfd,const char * pathname,char ** argv,char ** envp,int flags)49 static inline long sys_execveat(int dirfd, const char *pathname, char **argv, char **envp, int flags)
50 {
51 return syscall(SYS_execveat, dirfd, pathname, argv, envp, flags);
52 }
53
make_private_tmp(void)54 static void make_private_tmp(void)
55 {
56 if (unshare(CLONE_NEWNS) == -1) {
57 if (errno == ENOSYS || errno == EPERM) {
58 exit(4);
59 }
60 exit(1);
61 }
62 if (mount(NULL, "/", NULL, MS_PRIVATE|MS_REC, NULL) == -1) {
63 exit(1);
64 }
65 if (mount(NULL, "/tmp", "tmpfs", 0, NULL) == -1) {
66 exit(1);
67 }
68 }
69
70 static pid_t pid = -1;
ate(void)71 static void ate(void)
72 {
73 if (pid > 0) {
74 kill(pid, SIGTERM);
75 }
76 }
77
78 struct elf64_hdr {
79 uint8_t e_ident[16];
80 uint16_t e_type;
81 uint16_t e_machine;
82 uint32_t e_version;
83 uint64_t e_entry;
84 uint64_t e_phoff;
85 uint64_t e_shoff;
86 uint32_t e_flags;
87 uint16_t e_ehsize;
88 uint16_t e_phentsize;
89 uint16_t e_phnum;
90 uint16_t e_shentsize;
91 uint16_t e_shnum;
92 uint16_t e_shstrndx;
93 };
94
95 struct elf64_phdr {
96 uint32_t p_type;
97 uint32_t p_flags;
98 uint64_t p_offset;
99 uint64_t p_vaddr;
100 uint64_t p_paddr;
101 uint64_t p_filesz;
102 uint64_t p_memsz;
103 uint64_t p_align;
104 };
105
106 #ifdef __x86_64__
107 #define PAGE_SIZE 4096
108 #define VADDR (1UL << 32)
109 #define MAPS_OFFSET 73
110
111 #define syscall 0x0f, 0x05
112 #define mov_rdi(x) \
113 0x48, 0xbf, \
114 (x)&0xff, ((x)>>8)&0xff, ((x)>>16)&0xff, ((x)>>24)&0xff, \
115 ((x)>>32)&0xff, ((x)>>40)&0xff, ((x)>>48)&0xff, ((x)>>56)&0xff
116
117 #define mov_rsi(x) \
118 0x48, 0xbe, \
119 (x)&0xff, ((x)>>8)&0xff, ((x)>>16)&0xff, ((x)>>24)&0xff, \
120 ((x)>>32)&0xff, ((x)>>40)&0xff, ((x)>>48)&0xff, ((x)>>56)&0xff
121
122 #define mov_eax(x) \
123 0xb8, (x)&0xff, ((x)>>8)&0xff, ((x)>>16)&0xff, ((x)>>24)&0xff
124
125 static const uint8_t payload[] = {
126 /* Casually unmap stack, vDSO and everything else. */
127 /* munmap */
128 mov_rdi(VADDR + 4096),
129 mov_rsi((1ULL << 47) - 4096 - VADDR - 4096),
130 mov_eax(11),
131 syscall,
132
133 /* Ping parent. */
134 /* write(0, &c, 1); */
135 0x31, 0xff, /* xor edi, edi */
136 0x48, 0x8d, 0x35, 0x00, 0x00, 0x00, 0x00, /* lea rsi, [rip] */
137 0xba, 0x01, 0x00, 0x00, 0x00, /* mov edx, 1 */
138 mov_eax(1),
139 syscall,
140
141 /* 1: pause(); */
142 mov_eax(34),
143 syscall,
144
145 0xeb, 0xf7, /* jmp 1b */
146 };
147
make_exe(const uint8_t * payload,size_t len)148 static int make_exe(const uint8_t *payload, size_t len)
149 {
150 struct elf64_hdr h;
151 struct elf64_phdr ph;
152
153 struct iovec iov[3] = {
154 {&h, sizeof(struct elf64_hdr)},
155 {&ph, sizeof(struct elf64_phdr)},
156 {(void *)payload, len},
157 };
158 int fd, fd1;
159 char buf[64];
160
161 memset(&h, 0, sizeof(h));
162 h.e_ident[0] = 0x7f;
163 h.e_ident[1] = 'E';
164 h.e_ident[2] = 'L';
165 h.e_ident[3] = 'F';
166 h.e_ident[4] = 2;
167 h.e_ident[5] = 1;
168 h.e_ident[6] = 1;
169 h.e_ident[7] = 0;
170 h.e_type = 2;
171 h.e_machine = 0x3e;
172 h.e_version = 1;
173 h.e_entry = VADDR + sizeof(struct elf64_hdr) + sizeof(struct elf64_phdr);
174 h.e_phoff = sizeof(struct elf64_hdr);
175 h.e_shoff = 0;
176 h.e_flags = 0;
177 h.e_ehsize = sizeof(struct elf64_hdr);
178 h.e_phentsize = sizeof(struct elf64_phdr);
179 h.e_phnum = 1;
180 h.e_shentsize = 0;
181 h.e_shnum = 0;
182 h.e_shstrndx = 0;
183
184 memset(&ph, 0, sizeof(ph));
185 ph.p_type = 1;
186 ph.p_flags = (1<<2)|1;
187 ph.p_offset = 0;
188 ph.p_vaddr = VADDR;
189 ph.p_paddr = 0;
190 ph.p_filesz = sizeof(struct elf64_hdr) + sizeof(struct elf64_phdr) + len;
191 ph.p_memsz = sizeof(struct elf64_hdr) + sizeof(struct elf64_phdr) + len;
192 ph.p_align = 4096;
193
194 fd = openat(AT_FDCWD, "/tmp", O_WRONLY|O_EXCL|O_TMPFILE, 0700);
195 if (fd == -1) {
196 exit(1);
197 }
198
199 if (writev(fd, iov, 3) != sizeof(struct elf64_hdr) + sizeof(struct elf64_phdr) + len) {
200 exit(1);
201 }
202
203 /* Avoid ETXTBSY on exec. */
204 snprintf(buf, sizeof(buf), "/proc/self/fd/%u", fd);
205 fd1 = open(buf, O_RDONLY|O_CLOEXEC);
206 close(fd);
207
208 return fd1;
209 }
210 #endif
211
212 static bool g_vsyscall = false;
213
214 static const char str_vsyscall[] =
215 "ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0 [vsyscall]\n";
216
217 #ifdef __x86_64__
sigaction_SIGSEGV(int _,siginfo_t * __,void * ___)218 static void sigaction_SIGSEGV(int _, siginfo_t *__, void *___)
219 {
220 _exit(1);
221 }
222
223 /*
224 * vsyscall page can't be unmapped, probe it with memory load.
225 */
vsyscall(void)226 static void vsyscall(void)
227 {
228 pid_t pid;
229 int wstatus;
230
231 pid = fork();
232 if (pid < 0) {
233 fprintf(stderr, "fork, errno %d\n", errno);
234 exit(1);
235 }
236 if (pid == 0) {
237 struct rlimit rlim = {0, 0};
238 (void)setrlimit(RLIMIT_CORE, &rlim);
239
240 /* Hide "segfault at ffffffffff600000" messages. */
241 struct sigaction act;
242 memset(&act, 0, sizeof(struct sigaction));
243 act.sa_flags = SA_SIGINFO;
244 act.sa_sigaction = sigaction_SIGSEGV;
245 (void)sigaction(SIGSEGV, &act, NULL);
246
247 *(volatile int *)0xffffffffff600000UL;
248 exit(0);
249 }
250 waitpid(pid, &wstatus, 0);
251 if (WIFEXITED(wstatus) && WEXITSTATUS(wstatus) == 0) {
252 g_vsyscall = true;
253 }
254 }
255
main(void)256 int main(void)
257 {
258 int pipefd[2];
259 int exec_fd;
260
261 vsyscall();
262
263 atexit(ate);
264
265 make_private_tmp();
266
267 /* Reserve fd 0 for 1-byte pipe ping from child. */
268 close(0);
269 if (open("/", O_RDONLY|O_DIRECTORY|O_PATH) != 0) {
270 return 1;
271 }
272
273 exec_fd = make_exe(payload, sizeof(payload));
274
275 if (pipe(pipefd) == -1) {
276 return 1;
277 }
278 if (dup2(pipefd[1], 0) != 0) {
279 return 1;
280 }
281
282 pid = fork();
283 if (pid == -1) {
284 return 1;
285 }
286 if (pid == 0) {
287 sys_execveat(exec_fd, "", NULL, NULL, AT_EMPTY_PATH);
288 return 1;
289 }
290
291 char _;
292 if (read(pipefd[0], &_, 1) != 1) {
293 return 1;
294 }
295
296 struct stat st;
297 if (fstat(exec_fd, &st) == -1) {
298 return 1;
299 }
300
301 /* Generate "head -n1 /proc/$PID/maps" */
302 char buf0[256];
303 memset(buf0, ' ', sizeof(buf0));
304 int len = snprintf(buf0, sizeof(buf0),
305 "%08lx-%08lx r-xp 00000000 %02lx:%02lx %llu",
306 VADDR, VADDR + PAGE_SIZE,
307 MAJOR(st.st_dev), MINOR(st.st_dev),
308 (unsigned long long)st.st_ino);
309 buf0[len] = ' ';
310 snprintf(buf0 + MAPS_OFFSET, sizeof(buf0) - MAPS_OFFSET,
311 "/tmp/#%llu (deleted)\n", (unsigned long long)st.st_ino);
312
313 /* Test /proc/$PID/maps */
314 {
315 const size_t len = strlen(buf0) + (g_vsyscall ? strlen(str_vsyscall) : 0);
316 char buf[256];
317 ssize_t rv;
318 int fd;
319
320 snprintf(buf, sizeof(buf), "/proc/%u/maps", pid);
321 fd = open(buf, O_RDONLY);
322 if (fd == -1) {
323 return 1;
324 }
325 rv = read(fd, buf, sizeof(buf));
326 assert(rv == len);
327 assert(memcmp(buf, buf0, strlen(buf0)) == 0);
328 if (g_vsyscall) {
329 assert(memcmp(buf + strlen(buf0), str_vsyscall, strlen(str_vsyscall)) == 0);
330 }
331 }
332
333 /* Test /proc/$PID/smaps */
334 {
335 char buf[4096];
336 ssize_t rv;
337 int fd;
338
339 snprintf(buf, sizeof(buf), "/proc/%u/smaps", pid);
340 fd = open(buf, O_RDONLY);
341 if (fd == -1) {
342 return 1;
343 }
344 rv = read(fd, buf, sizeof(buf));
345 assert(0 <= rv && rv <= sizeof(buf));
346
347 assert(rv >= strlen(buf0));
348 assert(memcmp(buf, buf0, strlen(buf0)) == 0);
349
350 #define RSS1 "Rss: 4 kB\n"
351 #define RSS2 "Rss: 0 kB\n"
352 #define PSS1 "Pss: 4 kB\n"
353 #define PSS2 "Pss: 0 kB\n"
354 assert(memmem(buf, rv, RSS1, strlen(RSS1)) ||
355 memmem(buf, rv, RSS2, strlen(RSS2)));
356 assert(memmem(buf, rv, PSS1, strlen(PSS1)) ||
357 memmem(buf, rv, PSS2, strlen(PSS2)));
358
359 static const char *S[] = {
360 "Size: 4 kB\n",
361 "KernelPageSize: 4 kB\n",
362 "MMUPageSize: 4 kB\n",
363 "Anonymous: 0 kB\n",
364 "AnonHugePages: 0 kB\n",
365 "Shared_Hugetlb: 0 kB\n",
366 "Private_Hugetlb: 0 kB\n",
367 "Locked: 0 kB\n",
368 };
369 int i;
370
371 for (i = 0; i < sizeof(S)/sizeof(S[0]); i++) {
372 assert(memmem(buf, rv, S[i], strlen(S[i])));
373 }
374
375 if (g_vsyscall) {
376 assert(memmem(buf, rv, str_vsyscall, strlen(str_vsyscall)));
377 }
378 }
379
380 /* Test /proc/$PID/smaps_rollup */
381 {
382 char bufr[256];
383 memset(bufr, ' ', sizeof(bufr));
384 len = snprintf(bufr, sizeof(bufr),
385 "%08lx-%08lx ---p 00000000 00:00 0",
386 VADDR, VADDR + PAGE_SIZE);
387 bufr[len] = ' ';
388 snprintf(bufr + MAPS_OFFSET, sizeof(bufr) - MAPS_OFFSET,
389 "[rollup]\n");
390
391 char buf[1024];
392 ssize_t rv;
393 int fd;
394
395 snprintf(buf, sizeof(buf), "/proc/%u/smaps_rollup", pid);
396 fd = open(buf, O_RDONLY);
397 if (fd == -1) {
398 return 1;
399 }
400 rv = read(fd, buf, sizeof(buf));
401 assert(0 <= rv && rv <= sizeof(buf));
402
403 assert(rv >= strlen(bufr));
404 assert(memcmp(buf, bufr, strlen(bufr)) == 0);
405
406 assert(memmem(buf, rv, RSS1, strlen(RSS1)) ||
407 memmem(buf, rv, RSS2, strlen(RSS2)));
408 assert(memmem(buf, rv, PSS1, strlen(PSS1)) ||
409 memmem(buf, rv, PSS2, strlen(PSS2)));
410
411 static const char *S[] = {
412 "Anonymous: 0 kB\n",
413 "AnonHugePages: 0 kB\n",
414 "Shared_Hugetlb: 0 kB\n",
415 "Private_Hugetlb: 0 kB\n",
416 "Locked: 0 kB\n",
417 };
418 int i;
419
420 for (i = 0; i < sizeof(S)/sizeof(S[0]); i++) {
421 assert(memmem(buf, rv, S[i], strlen(S[i])));
422 }
423 }
424
425 /* Test /proc/$PID/statm */
426 {
427 char buf[64];
428 ssize_t rv;
429 int fd;
430
431 snprintf(buf, sizeof(buf), "/proc/%u/statm", pid);
432 fd = open(buf, O_RDONLY);
433 if (fd == -1) {
434 return 1;
435 }
436 rv = read(fd, buf, sizeof(buf));
437 assert(rv == 7 * 2);
438
439 assert(buf[0] == '1'); /* ->total_vm */
440 assert(buf[1] == ' ');
441 assert(buf[2] == '0' || buf[2] == '1'); /* rss */
442 assert(buf[3] == ' ');
443 assert(buf[4] == '0' || buf[2] == '1'); /* file rss */
444 assert(buf[5] == ' ');
445 assert(buf[6] == '1'); /* ELF executable segments */
446 assert(buf[7] == ' ');
447 assert(buf[8] == '0');
448 assert(buf[9] == ' ');
449 assert(buf[10] == '0'); /* ->data_vm + ->stack_vm */
450 assert(buf[11] == ' ');
451 assert(buf[12] == '0');
452 assert(buf[13] == '\n');
453 }
454
455 return 0;
456 }
457 #else
main(void)458 int main(void)
459 {
460 return 4;
461 }
462 #endif
463