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 str(s) #s
82 #define SLCAN_FRAME "t00185f5f5f5f5f5f5f5f\r"
83
84 struct ldisc_info {
85 int n;
86 char *name;
87 int mtu;
88 };
89
90 static struct ldisc_info ldiscs[] = {
91 {N_SLIP, "N_SLIP", 8192},
92 {N_SLCAN, "N_SLCAN", CAN_MTU},
93 };
94
95 static int ptmx, pts, sk, mtu, no_check;
96
set_ldisc(int tty,const struct ldisc_info * ldisc)97 static int set_ldisc(int tty, const struct ldisc_info *ldisc)
98 {
99 TEST(ioctl(tty, TIOCSETD, &ldisc->n));
100
101 if (!TST_RET)
102 return 0;
103
104 if (TST_ERR == EINVAL) {
105 tst_res(TCONF | TTERRNO,
106 "You don't appear to have the %s TTY line discipline",
107 ldisc->name);
108 } else {
109 tst_res(TFAIL | TTERRNO,
110 "Failed to set the %s line discipline", ldisc->name);
111 }
112
113 return 1;
114 }
115
open_pty(const struct ldisc_info * ldisc)116 static int open_pty(const struct ldisc_info *ldisc)
117 {
118 char pts_path[PATH_MAX];
119
120 ptmx = SAFE_OPEN("/dev/ptmx", O_RDWR);
121 if (grantpt(ptmx))
122 tst_brk(TBROK | TERRNO, "grantpt(ptmx)");
123 if (unlockpt(ptmx))
124 tst_brk(TBROK | TERRNO, "unlockpt(ptmx)");
125 if (ptsname_r(ptmx, pts_path, sizeof(pts_path)))
126 tst_brk(TBROK | TERRNO, "ptsname_r(ptmx, ...)");
127
128 SAFE_FCNTL(ptmx, F_SETFL, O_NONBLOCK);
129
130 tst_res(TINFO, "PTS path is %s", pts_path);
131 pts = SAFE_OPEN(pts_path, O_RDWR);
132
133 return set_ldisc(pts, ldisc);
134 }
135
try_async_write(int fd,const char * data,ssize_t size,ssize_t * done)136 static ssize_t try_async_write(int fd, const char *data, ssize_t size,
137 ssize_t *done)
138 {
139 ssize_t off = done ? *done : 0;
140 ssize_t ret = write(fd, data + off, size - off);
141
142 if (ret < 0)
143 return -(errno != EAGAIN);
144
145 if (!done)
146 return 1;
147
148 *done += ret;
149 return *done >= size;
150 }
151
try_async_read(int fd,char * data,ssize_t size,ssize_t * done)152 static ssize_t try_async_read(int fd, char *data, ssize_t size,
153 ssize_t *done)
154 {
155 ssize_t off = done ? *done : 0;
156 ssize_t ret = read(fd, data + off, size - off);
157
158 if (ret < 0)
159 return -(errno != EAGAIN);
160
161 if (!done)
162 return 1;
163
164 *done += ret;
165 return *done >= size;
166 }
167
retry_async_write(int fd,const char * data,ssize_t size)168 static ssize_t retry_async_write(int fd, const char *data, ssize_t size)
169 {
170 ssize_t done = 0;
171
172 return TST_RETRY_FUNC(try_async_write(fd, data, size, &done),
173 TST_RETVAL_NOTNULL);
174 }
175
retry_async_read(int fd,char * data,ssize_t size)176 static ssize_t retry_async_read(int fd, char *data, ssize_t size)
177 {
178 ssize_t done = 0;
179
180 return TST_RETRY_FUNC(try_async_read(fd, data, size, &done),
181 TST_RETVAL_NOTNULL);
182 }
183
do_pty(const struct ldisc_info * ldisc)184 static void do_pty(const struct ldisc_info *ldisc)
185 {
186 char *data;
187 ssize_t ret;
188 size_t len = 0;
189
190 switch (ldisc->n) {
191 case N_SLIP:
192 len = mtu;
193 break;
194 case N_SLCAN:
195 len = sizeof(SLCAN_FRAME) - 1;
196 break;
197 }
198
199 data = tst_alloc(len);
200
201 switch (ldisc->n) {
202 case N_SLIP:
203 memset(data, '_', len - 1);
204 data[len - 1] = 0300;
205 break;
206 case N_SLCAN:
207 memcpy(data, SLCAN_FRAME, len);
208 break;
209 }
210
211 ret = retry_async_write(ptmx, data, len);
212 if (ret < 0)
213 tst_brk(TBROK | TERRNO, "Failed 1st write to PTY");
214 tst_res(TPASS, "Wrote PTY %s %d (1)", ldisc->name, ptmx);
215
216 ret = retry_async_write(ptmx, data, len);
217 if (ret < 0)
218 tst_brk(TBROK | TERRNO, "Failed 2nd write to PTY");
219
220 if (tcflush(ptmx, TCIFLUSH))
221 tst_brk(TBROK | TERRNO, "tcflush(ptmx, TCIFLUSH)");
222
223 tst_res(TPASS, "Wrote PTY %s %d (2)", ldisc->name, ptmx);
224
225 ret = retry_async_read(ptmx, data, len);
226 if (ret < 0)
227 tst_brk(TBROK | TERRNO, "Failed read of PTY");
228
229 tst_res(TPASS, "Read PTY %s %d", ldisc->name, ptmx);
230 TST_CHECKPOINT_WAKE(0);
231
232 while (1) {
233 if (retry_async_read(ptmx, data, len) < 0)
234 break;
235
236 if (retry_async_write(ptmx, data, len) < 0)
237 break;
238 }
239
240 tst_res(TPASS, "Transmission on PTY interrupted by hangup");
241
242 tst_free_all();
243 }
244
open_netdev(const struct ldisc_info * ldisc)245 static void open_netdev(const struct ldisc_info *ldisc)
246 {
247 struct ifreq ifreq = { 0 };
248 struct sockaddr_ll lla = { 0 };
249
250 SAFE_IOCTL(pts, SIOCGIFNAME, ifreq.ifr_name);
251 tst_res(TINFO, "Netdev is %s", ifreq.ifr_name);
252
253 sk = SAFE_SOCKET(PF_PACKET, SOCK_RAW, 0);
254
255 ifreq.ifr_mtu = ldisc->mtu;
256 if (ioctl(sk, SIOCSIFMTU, &ifreq))
257 tst_res(TWARN | TERRNO, "Failed to set netdev MTU to maximum");
258 SAFE_IOCTL(sk, SIOCGIFMTU, &ifreq);
259 mtu = ifreq.ifr_mtu;
260 tst_res(TINFO, "Netdev MTU is %d (we set %d)", mtu, ldisc->mtu);
261
262 SAFE_IOCTL(sk, SIOCGIFFLAGS, &ifreq);
263 ifreq.ifr_flags |= IFF_UP | IFF_RUNNING;
264 SAFE_IOCTL(sk, SIOCSIFFLAGS, &ifreq);
265 SAFE_IOCTL(sk, SIOCGIFFLAGS, &ifreq);
266
267 if (!(ifreq.ifr_flags & IFF_UP))
268 tst_brk(TBROK, "Netdev did not come up");
269
270 SAFE_IOCTL(sk, SIOCGIFINDEX, &ifreq);
271
272 lla.sll_family = PF_PACKET;
273 lla.sll_protocol = htons(ETH_P_ALL);
274 lla.sll_ifindex = ifreq.ifr_ifindex;
275 SAFE_BIND(sk, (struct sockaddr *)&lla, sizeof(struct sockaddr_ll));
276
277 tst_res(TINFO, "Bound netdev %d to socket %d", ifreq.ifr_ifindex, sk);
278 }
279
check_data(const struct ldisc_info * ldisc,const char * data,ssize_t len)280 static void check_data(const struct ldisc_info *ldisc,
281 const char *data, ssize_t len)
282 {
283 ssize_t i = 0, j;
284 struct can_frame frm;
285
286 if (no_check)
287 return;
288
289 if (ldisc->n == N_SLCAN) {
290 memcpy(&frm, data, len);
291
292 if (frm.can_id != 1) {
293 tst_res(TFAIL, "can_id = %d != 1",
294 frm.can_id);
295 no_check = 1;
296 }
297
298 if (frm.can_dlc != CAN_MAX_DLEN) {
299 tst_res(TFAIL, "can_dlc = %d != " str(CAN_MAX_DLEN),
300 frm.can_dlc);
301 no_check = 1;
302 }
303
304 i = offsetof(struct can_frame, __pad);
305 if (frm.__pad != frm.__res0 || frm.__res0 != frm.__res1) {
306 tst_res_hexd(TFAIL, data + i,
307 offsetof(struct can_frame, data) - i,
308 "Padding bytes may contain stack data");
309 no_check = 1;
310 }
311
312 i = offsetof(struct can_frame, data);
313 }
314
315 do {
316 if (i >= len)
317 return;
318 } while (data[i++] == '_');
319
320 j = i--;
321
322 while (j < len && j - i < 65 && data[j++] != '_')
323 ;
324 j--;
325
326 tst_res_hexd(TFAIL, data + i, j - i,
327 "Corrupt data (max 64 of %ld bytes shown): data[%ld..%ld] = ",
328 len, i, j);
329 no_check = 1;
330
331 if (no_check)
332 tst_res(TINFO, "Will continue test without data checking");
333 }
334
try_sync_read(int fd,char * data,ssize_t size)335 static ssize_t try_sync_read(int fd, char *data, ssize_t size)
336 {
337 ssize_t ret, n = 0;
338 int retry = mtu;
339
340 while (retry--) {
341 ret = read(fd, data + n, size - n);
342
343 if (ret < 0)
344 return ret;
345
346 if ((n += ret) >= size)
347 return ret;
348 }
349
350 tst_brk(TBROK | TERRNO, "Only read %zd of %zd bytes", n, size);
351
352 return n;
353 }
354
try_sync_write(int fd,const char * data,ssize_t size)355 static ssize_t try_sync_write(int fd, const char *data, ssize_t size)
356 {
357 ssize_t ret, n = 0;
358 int retry = mtu;
359
360 while (retry--) {
361 ret = write(fd, data + n, size - n);
362
363 if (ret < 0)
364 return ret;
365
366 if ((n += ret) >= size)
367 return ret;
368 }
369
370 tst_brk(TBROK | TERRNO, "Only wrote %zd of %zd bytes", n, size);
371
372 return n;
373 }
374
read_netdev(const struct ldisc_info * ldisc)375 static void read_netdev(const struct ldisc_info *ldisc)
376 {
377 int rlen, plen = 0;
378 char *data;
379
380 switch (ldisc->n) {
381 case N_SLIP:
382 plen = mtu - 1;
383 break;
384 case N_SLCAN:
385 plen = CAN_MTU;
386 break;
387 }
388 data = tst_alloc(plen);
389
390 tst_res(TINFO, "Reading from socket %d", sk);
391
392 TEST(try_sync_read(sk, data, plen));
393 if (TST_RET < 0)
394 tst_brk(TBROK | TTERRNO, "Read netdev %s %d (1)", ldisc->name, sk);
395 check_data(ldisc, data, plen);
396 tst_res(TPASS, "Read netdev %s %d (1)", ldisc->name, sk);
397
398 TEST(try_sync_read(sk, data, plen));
399 if (TST_RET < 0)
400 tst_brk(TBROK | TTERRNO, "Read netdev %s %d (2)", ldisc->name, sk);
401 check_data(ldisc, data, plen);
402 tst_res(TPASS, "Read netdev %s %d (2)", ldisc->name, sk);
403
404 TEST(try_sync_write(sk, data, plen));
405 if (TST_RET < 0)
406 tst_brk(TBROK | TTERRNO, "Write netdev %s %d", ldisc->name, sk);
407
408 tst_res(TPASS, "Write netdev %s %d", ldisc->name, sk);
409
410 while (1) {
411 if (try_sync_write(sk, data, plen) < 0)
412 break;
413
414 if ((rlen = try_sync_read(sk, data, plen)) < 0)
415 break;
416 check_data(ldisc, data, rlen);
417 }
418
419 tst_res(TPASS, "Data transmission on netdev interrupted by hangup");
420
421 close(sk);
422 tst_free_all();
423 }
424
do_test(unsigned int n)425 static void do_test(unsigned int n)
426 {
427 struct ldisc_info *ldisc = &ldiscs[n];
428
429 if (open_pty(ldisc))
430 return;
431
432 open_netdev(ldisc);
433
434 if (!SAFE_FORK()) {
435 read_netdev(ldisc);
436 return;
437 }
438
439 if (!SAFE_FORK()) {
440 do_pty(ldisc);
441 return;
442 }
443
444 if (!SAFE_FORK()) {
445 TST_CHECKPOINT_WAIT2(0, 100000);
446 SAFE_IOCTL(pts, TIOCVHANGUP);
447 tst_res(TINFO, "Sent hangup ioctl to PTS");
448 SAFE_IOCTL(ptmx, TIOCVHANGUP);
449 tst_res(TINFO, "Sent hangup ioctl to PTM");
450 return;
451 }
452
453 tst_reap_children();
454 }
455
cleanup(void)456 static void cleanup(void)
457 {
458 ioctl(pts, TIOCVHANGUP);
459 ioctl(ptmx, TIOCVHANGUP);
460 close(sk);
461
462 tst_reap_children();
463 }
464
465 static struct tst_test test = {
466 .test = do_test,
467 .cleanup = cleanup,
468 .tcnt = 2,
469 .forks_child = 1,
470 .needs_checkpoints = 1,
471 .needs_root = 1,
472 .tags = (const struct tst_tag[]){
473 {"linux-git", "b9258a2cece4ec1f020715fe3554bc2e360f6264"},
474 {"CVE", "CVE-2020-11494"},
475 {}
476 }
477 };
478
479 #else
480
481 TST_TEST_TCONF("Need <linux/if_packet.h> and <linux/if_ether.h>");
482
483 #endif
484