1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Copyright (c) 2020 SUSE
4 *
5 * Test transmitting data over a PTY/TTY line discipline and reading from the
6 * virtual netdev created by the line discipline. Also hangup the PTY while
7 * data is in flight to try to cause a race between the netdev being deleted
8 * and the discipline receive function writing to the netdev.
9 *
10 * For SLCAN we check stack data is not leaked in the frame padding
11 * (CVE-2020-11494).
12 *
13 * Test flow:
14 * 1. Create PTY with ldisc X which creates netdev Y
15 * 2. Open raw packet socket and bind to netdev Y
16 * 3. Send data on ptmx and read packets from socket
17 * 4. Hangup while transmission in progress
18 *
19 * Note that not all line disciplines call unthrottle when they are ready to
20 * read more bytes. So it is possible to fill all the write buffers causing
21 * write to block forever (because once write sleeps it needs unthrottle to
22 * wake it). So we write with O_NONBLOCK.
23 *
24 * Also the max buffer size for PTYs is 8192, so even if the protocol MTU is
25 * greater everything may still be processed in 8129 byte chunks. At least
26 * until we are in the netdev code which can have a bigger buffer. Of course
27 * the MTU still decides exactly where the packet delimiter goes, this just
28 * concerns choosing the best packet size to cause a race.
29 *
30 * Note on line discipline encapsulation formats:
31 * - For SLIP frames we just write the data followed by a delimiter char
32 * - SLCAN we write some ASCII described in drivers/net/can/slcan.c which is
33 * converted to the actual frame by the kernel
34 */
35
36 #define _GNU_SOURCE
37 #include "config.h"
38 #include "tst_test.h"
39 #include "tst_buffers.h"
40 #include "lapi/tty.h"
41
42 #if defined(HAVE_LINUX_IF_PACKET_H) && defined(HAVE_LINUX_IF_ETHER_H)
43
44 #include <linux/if_packet.h>
45 #include <linux/if_ether.h>
46 #include <linux/tty.h>
47
48 /*
49 * define instead of including <linux/can.h> to support kernel headers
50 * before change from v4.2-rc1
51 * a2f11835994e ("can.h: make padding given by gcc explicit").
52 */
53
54 #define CAN_MTU (sizeof(struct can_frame))
55 #define CAN_MAX_DLEN 8
56
57 typedef uint32_t canid_t;
58
59 struct can_frame {
60 canid_t can_id;
61 uint8_t can_dlc;
62 uint8_t __pad;
63 uint8_t __res0;
64 uint8_t __res1;
65 uint8_t data[CAN_MAX_DLEN] __attribute__((aligned(8)));
66 };
67
68 #include <stddef.h>
69 #include <stdlib.h>
70 #include <stdio.h>
71 #include <errno.h>
72 #include <unistd.h>
73 #include <termios.h>
74 #include <sys/types.h>
75 #include <sys/socket.h>
76 #include <net/if.h>
77 #include "lapi/ioctl.h"
78
79 #include "tst_safe_stdio.h"
80
81 #define SLCAN_FRAME "t00185f5f5f5f5f5f5f5f\r"
82
83 struct ldisc_info {
84 int n;
85 char *name;
86 int mtu;
87 };
88
89 static struct ldisc_info ldiscs[] = {
90 {N_SLIP, "N_SLIP", 8192},
91 {N_SLCAN, "N_SLCAN", CAN_MTU},
92 };
93
94 static int ptmx = -1, pts = -1, sk = -1, mtu, no_check;
95
set_ldisc(int tty,const struct ldisc_info * ldisc)96 static int set_ldisc(int tty, const struct ldisc_info *ldisc)
97 {
98 TEST(ioctl(tty, TIOCSETD, &ldisc->n));
99
100 if (!TST_RET)
101 return 0;
102
103 if (TST_ERR == EINVAL) {
104 tst_res(TCONF | TTERRNO,
105 "You don't appear to have the %s TTY line discipline",
106 ldisc->name);
107 } else {
108 tst_res(TFAIL | TTERRNO,
109 "Failed to set the %s line discipline", ldisc->name);
110 }
111
112 return 1;
113 }
114
open_pty(const struct ldisc_info * ldisc)115 static int open_pty(const struct ldisc_info *ldisc)
116 {
117 char pts_path[PATH_MAX];
118
119 ptmx = SAFE_OPEN("/dev/ptmx", O_RDWR);
120 if (grantpt(ptmx))
121 tst_brk(TBROK | TERRNO, "grantpt(ptmx)");
122 if (unlockpt(ptmx))
123 tst_brk(TBROK | TERRNO, "unlockpt(ptmx)");
124 if (ptsname_r(ptmx, pts_path, sizeof(pts_path)))
125 tst_brk(TBROK | TERRNO, "ptsname_r(ptmx, ...)");
126
127 SAFE_FCNTL(ptmx, F_SETFL, O_NONBLOCK);
128
129 tst_res(TINFO, "PTS path is %s", pts_path);
130 pts = SAFE_OPEN(pts_path, O_RDWR);
131
132 return set_ldisc(pts, ldisc);
133 }
134
try_async_write(int fd,const char * data,ssize_t size,ssize_t * done)135 static ssize_t try_async_write(int fd, const char *data, ssize_t size,
136 ssize_t *done)
137 {
138 ssize_t off = done ? *done : 0;
139 ssize_t ret = write(fd, data + off, size - off);
140
141 if (ret < 0)
142 return -(errno != EAGAIN);
143
144 if (!done)
145 return 1;
146
147 *done += ret;
148 return *done >= size;
149 }
150
try_async_read(int fd,char * data,ssize_t size,ssize_t * done)151 static ssize_t try_async_read(int fd, char *data, ssize_t size,
152 ssize_t *done)
153 {
154 ssize_t off = done ? *done : 0;
155 ssize_t ret = read(fd, data + off, size - off);
156
157 if (ret < 0)
158 return -(errno != EAGAIN);
159
160 if (!done)
161 return 1;
162
163 *done += ret;
164 return *done >= size;
165 }
166
retry_async_write(int fd,const char * data,ssize_t size)167 static ssize_t retry_async_write(int fd, const char *data, ssize_t size)
168 {
169 ssize_t done = 0;
170
171 return TST_RETRY_FUNC(try_async_write(fd, data, size, &done),
172 TST_RETVAL_NOTNULL);
173 }
174
retry_async_read(int fd,char * data,ssize_t size)175 static ssize_t retry_async_read(int fd, char *data, ssize_t size)
176 {
177 ssize_t done = 0;
178
179 return TST_RETRY_FUNC(try_async_read(fd, data, size, &done),
180 TST_RETVAL_NOTNULL);
181 }
182
do_pty(const struct ldisc_info * ldisc)183 static void do_pty(const struct ldisc_info *ldisc)
184 {
185 char *data;
186 ssize_t ret;
187 size_t len = 0;
188
189 switch (ldisc->n) {
190 case N_SLIP:
191 len = mtu;
192 break;
193 case N_SLCAN:
194 len = sizeof(SLCAN_FRAME) - 1;
195 break;
196 }
197
198 data = tst_alloc(len);
199
200 switch (ldisc->n) {
201 case N_SLIP:
202 memset(data, '_', len - 1);
203 data[len - 1] = 0300;
204 break;
205 case N_SLCAN:
206 memcpy(data, SLCAN_FRAME, len);
207 break;
208 }
209
210 ret = retry_async_write(ptmx, data, len);
211 if (ret < 0)
212 tst_brk(TBROK | TERRNO, "Failed 1st write to PTY");
213 tst_res(TPASS, "Wrote PTY %s %d (1)", ldisc->name, ptmx);
214
215 ret = retry_async_write(ptmx, data, len);
216 if (ret < 0)
217 tst_brk(TBROK | TERRNO, "Failed 2nd write to PTY");
218
219 if (tcflush(ptmx, TCIFLUSH))
220 tst_brk(TBROK | TERRNO, "tcflush(ptmx, TCIFLUSH)");
221
222 tst_res(TPASS, "Wrote PTY %s %d (2)", ldisc->name, ptmx);
223
224 ret = retry_async_read(ptmx, data, len);
225 if (ret < 0)
226 tst_brk(TBROK | TERRNO, "Failed read of PTY");
227
228 tst_res(TPASS, "Read PTY %s %d", ldisc->name, ptmx);
229 TST_CHECKPOINT_WAKE(0);
230
231 while (1) {
232 if (retry_async_read(ptmx, data, len) < 0)
233 break;
234
235 if (retry_async_write(ptmx, data, len) < 0)
236 break;
237 }
238
239 tst_res(TPASS, "Transmission on PTY interrupted by hangup");
240
241 tst_free_all();
242 }
243
open_netdev(const struct ldisc_info * ldisc)244 static void open_netdev(const struct ldisc_info *ldisc)
245 {
246 struct ifreq ifreq = { 0 };
247 struct sockaddr_ll lla = { 0 };
248
249 SAFE_IOCTL(pts, SIOCGIFNAME, ifreq.ifr_name);
250 tst_res(TINFO, "Netdev is %s", ifreq.ifr_name);
251
252 sk = SAFE_SOCKET(PF_PACKET, SOCK_RAW, 0);
253
254 ifreq.ifr_mtu = ldisc->mtu;
255 if (ioctl(sk, SIOCSIFMTU, &ifreq))
256 tst_res(TWARN | TERRNO, "Failed to set netdev MTU to maximum");
257 SAFE_IOCTL(sk, SIOCGIFMTU, &ifreq);
258 mtu = ifreq.ifr_mtu;
259 tst_res(TINFO, "Netdev MTU is %d (we set %d)", mtu, ldisc->mtu);
260
261 SAFE_IOCTL(sk, SIOCGIFFLAGS, &ifreq);
262 ifreq.ifr_flags |= IFF_UP | IFF_RUNNING;
263 SAFE_IOCTL(sk, SIOCSIFFLAGS, &ifreq);
264 SAFE_IOCTL(sk, SIOCGIFFLAGS, &ifreq);
265
266 if (!(ifreq.ifr_flags & IFF_UP))
267 tst_brk(TBROK, "Netdev did not come up");
268
269 SAFE_IOCTL(sk, SIOCGIFINDEX, &ifreq);
270
271 lla.sll_family = PF_PACKET;
272 lla.sll_protocol = htons(ETH_P_ALL);
273 lla.sll_ifindex = ifreq.ifr_ifindex;
274 SAFE_BIND(sk, (struct sockaddr *)&lla, sizeof(struct sockaddr_ll));
275
276 tst_res(TINFO, "Bound netdev %d to socket %d", ifreq.ifr_ifindex, sk);
277 }
278
check_data(const struct ldisc_info * ldisc,const char * data,ssize_t len)279 static void check_data(const struct ldisc_info *ldisc,
280 const char *data, ssize_t len)
281 {
282 ssize_t i = 0, j;
283 struct can_frame frm;
284
285 if (no_check)
286 return;
287
288 if (ldisc->n == N_SLCAN) {
289 memcpy(&frm, data, len);
290
291 if (frm.can_id != 1) {
292 tst_res(TFAIL, "can_id = %d != 1",
293 frm.can_id);
294 no_check = 1;
295 }
296
297 if (frm.can_dlc != CAN_MAX_DLEN) {
298 tst_res(TFAIL, "can_dlc = %d != " TST_TO_STR_(CAN_MAX_DLEN),
299 frm.can_dlc);
300 no_check = 1;
301 }
302
303 i = offsetof(struct can_frame, __pad);
304 if (frm.__pad != frm.__res0 || frm.__res0 != frm.__res1) {
305 tst_res_hexd(TFAIL, data + i,
306 offsetof(struct can_frame, data) - i,
307 "Padding bytes may contain stack data");
308 no_check = 1;
309 }
310
311 i = offsetof(struct can_frame, data);
312 }
313
314 do {
315 if (i >= len)
316 return;
317 } while (data[i++] == '_');
318
319 j = i--;
320
321 while (j < len && j - i < 65 && data[j++] != '_')
322 ;
323 j--;
324
325 tst_res_hexd(TFAIL, data + i, j - i,
326 "Corrupt data (max 64 of %ld bytes shown): data[%ld..%ld] = ",
327 len, i, j);
328 no_check = 1;
329
330 if (no_check)
331 tst_res(TINFO, "Will continue test without data checking");
332 }
333
try_sync_read(int fd,char * data,ssize_t size)334 static ssize_t try_sync_read(int fd, char *data, ssize_t size)
335 {
336 ssize_t ret, n = 0;
337 int retry = mtu;
338
339 while (retry--) {
340 ret = read(fd, data + n, size - n);
341
342 if (ret < 0)
343 return ret;
344
345 if ((n += ret) >= size)
346 return ret;
347 }
348
349 tst_brk(TBROK | TERRNO, "Only read %zd of %zd bytes", n, size);
350
351 return n;
352 }
353
try_sync_write(int fd,const char * data,ssize_t size)354 static ssize_t try_sync_write(int fd, const char *data, ssize_t size)
355 {
356 ssize_t ret, n = 0;
357 int retry = mtu;
358
359 while (retry--) {
360 ret = write(fd, data + n, size - n);
361
362 if (ret < 0)
363 return ret;
364
365 if ((n += ret) >= size)
366 return ret;
367 }
368
369 tst_brk(TBROK | TERRNO, "Only wrote %zd of %zd bytes", n, size);
370
371 return n;
372 }
373
read_netdev(const struct ldisc_info * ldisc)374 static void read_netdev(const struct ldisc_info *ldisc)
375 {
376 int rlen, plen = 0;
377 char *data;
378
379 switch (ldisc->n) {
380 case N_SLIP:
381 plen = mtu - 1;
382 break;
383 case N_SLCAN:
384 plen = CAN_MTU;
385 break;
386 }
387 data = tst_alloc(plen);
388
389 tst_res(TINFO, "Reading from socket %d", sk);
390
391 TEST(try_sync_read(sk, data, plen));
392 if (TST_RET < 0)
393 tst_brk(TBROK | TTERRNO, "Read netdev %s %d (1)", ldisc->name, sk);
394 check_data(ldisc, data, plen);
395 tst_res(TPASS, "Read netdev %s %d (1)", ldisc->name, sk);
396
397 TEST(try_sync_read(sk, data, plen));
398 if (TST_RET < 0)
399 tst_brk(TBROK | TTERRNO, "Read netdev %s %d (2)", ldisc->name, sk);
400 check_data(ldisc, data, plen);
401 tst_res(TPASS, "Read netdev %s %d (2)", ldisc->name, sk);
402
403 TEST(try_sync_write(sk, data, plen));
404 if (TST_RET < 0)
405 tst_brk(TBROK | TTERRNO, "Write netdev %s %d", ldisc->name, sk);
406
407 tst_res(TPASS, "Write netdev %s %d", ldisc->name, sk);
408
409 while (1) {
410 if (try_sync_write(sk, data, plen) < 0)
411 break;
412
413 if ((rlen = try_sync_read(sk, data, plen)) < 0)
414 break;
415 check_data(ldisc, data, rlen);
416 }
417
418 tst_res(TPASS, "Data transmission on netdev interrupted by hangup");
419
420 close(sk);
421 tst_free_all();
422 }
423
do_test(unsigned int n)424 static void do_test(unsigned int n)
425 {
426 struct ldisc_info *ldisc = &ldiscs[n];
427
428 if (open_pty(ldisc))
429 return;
430
431 open_netdev(ldisc);
432
433 if (!SAFE_FORK()) {
434 read_netdev(ldisc);
435 return;
436 }
437
438 if (!SAFE_FORK()) {
439 do_pty(ldisc);
440 return;
441 }
442
443 if (!SAFE_FORK()) {
444 TST_CHECKPOINT_WAIT2(0, 100000);
445 SAFE_IOCTL(pts, TIOCVHANGUP);
446 tst_res(TINFO, "Sent hangup ioctl to PTS");
447 SAFE_IOCTL(ptmx, TIOCVHANGUP);
448 tst_res(TINFO, "Sent hangup ioctl to PTM");
449 return;
450 }
451
452 tst_reap_children();
453 }
454
cleanup(void)455 static void cleanup(void)
456 {
457 if (pts >= 0)
458 ioctl(pts, TIOCVHANGUP);
459
460 if (ptmx >= 0)
461 ioctl(ptmx, TIOCVHANGUP);
462
463 if (sk >= 0)
464 close(sk);
465
466 tst_reap_children();
467 }
468
469 static struct tst_test test = {
470 .test = do_test,
471 .cleanup = cleanup,
472 .tcnt = 2,
473 .forks_child = 1,
474 .needs_checkpoints = 1,
475 .needs_root = 1,
476 .tags = (const struct tst_tag[]){
477 {"linux-git", "b9258a2cece4ec1f020715fe3554bc2e360f6264"},
478 {"CVE", "CVE-2020-11494"},
479 {}
480 }
481 };
482
483 #else
484
485 TST_TEST_TCONF("Need <linux/if_packet.h> and <linux/if_ether.h>");
486
487 #endif
488