1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Copyright (c) 2017 Fujitsu Ltd.
4 * Ported: Guangwen Feng <fenggw-fnst@cn.fujitsu.com>
5 */
6
7 /*
8 * This is a regression test for the race between keyctl_read() and
9 * keyctl_revoke(), if the revoke happens between keyctl_read()
10 * checking the validity of a key and the key's semaphore being taken,
11 * then the key type read method will see a revoked key.
12 *
13 * This causes a problem for the user-defined key type because it
14 * assumes in its read method that there will always be a payload
15 * in a non-revoked key and doesn't check for a NULL pointer.
16 *
17 * This test can crash the buggy kernel, and the bug was fixed in:
18 *
19 * commit b4a1b4f5047e4f54e194681125c74c0aa64d637d
20 * Author: David Howells <dhowells@redhat.com>
21 * Date: Fri Dec 18 01:34:26 2015 +0000
22 *
23 * KEYS: Fix race between read and revoke
24 */
25
26 #include <errno.h>
27 #include <pthread.h>
28 #include <sys/types.h>
29
30 #include "tst_safe_pthread.h"
31 #include "tst_test.h"
32 #include "lapi/keyctl.h"
33
34 #define LOOPS 20000
35 #define MAX_WAIT_FOR_GC_MS 5000
36 #define PATH_KEY_COUNT_QUOTA "/proc/sys/kernel/keys/root_maxkeys"
37
38 static int orig_maxkeys;
39
do_read(void * arg)40 static void *do_read(void *arg)
41 {
42 key_serial_t key = (unsigned long)arg;
43 char buffer[4] = { 0 };
44
45 keyctl(KEYCTL_READ, key, buffer, 4);
46
47 return NULL;
48 }
49
do_revoke(void * arg)50 static void *do_revoke(void *arg)
51 {
52 key_serial_t key = (unsigned long)arg;
53
54 keyctl(KEYCTL_REVOKE, key);
55
56 return NULL;
57 }
58
do_test(void)59 static void do_test(void)
60 {
61 int i, ret;
62 key_serial_t key, key_inv;
63 pthread_t pth[4];
64
65 for (i = 0; i < LOOPS; i++) {
66 key = add_key("user", "ltptestkey", "foo", 3,
67 KEY_SPEC_PROCESS_KEYRING);
68 if (key == -1)
69 tst_brk(TBROK | TERRNO, "Failed to add key");
70
71 SAFE_PTHREAD_CREATE(&pth[0], NULL, do_read,
72 (void *)(unsigned long)key);
73 SAFE_PTHREAD_CREATE(&pth[1], NULL, do_revoke,
74 (void *)(unsigned long)key);
75 SAFE_PTHREAD_CREATE(&pth[2], NULL, do_read,
76 (void *)(unsigned long)key);
77 SAFE_PTHREAD_CREATE(&pth[3], NULL, do_revoke,
78 (void *)(unsigned long)key);
79
80 SAFE_PTHREAD_JOIN(pth[0], NULL);
81 SAFE_PTHREAD_JOIN(pth[1], NULL);
82 SAFE_PTHREAD_JOIN(pth[2], NULL);
83 SAFE_PTHREAD_JOIN(pth[3], NULL);
84
85 if (!tst_remaining_runtime()) {
86 tst_res(TINFO, "Runtime exhausted, exiting after %d loops", i);
87 break;
88 }
89 }
90
91 /*
92 * Kernel should start garbage collect when last reference to key
93 * is removed (see key_put()). Since we are adding keys with identical
94 * description and type, each replacement should schedule a gc run,
95 * see comment at __key_link().
96 *
97 * We create extra key here, to remove reference to last revoked key.
98 */
99 key_inv = add_key("user", "ltptestkey", "foo", 3,
100 KEY_SPEC_PROCESS_KEYRING);
101 if (key_inv == -1)
102 tst_brk(TBROK | TERRNO, "Failed to add key");
103
104 /*
105 * If we have invalidate, we can drop extra key immediately as well,
106 * which also schedules gc.
107 */
108 if (keyctl(KEYCTL_INVALIDATE, key_inv) == -1 && errno != EOPNOTSUPP)
109 tst_brk(TBROK | TERRNO, "Failed to invalidate key");
110
111 /*
112 * At this point we are quite confident that gc has been scheduled,
113 * so we wait and periodically check for last test key to be removed.
114 */
115 for (i = 0; i < MAX_WAIT_FOR_GC_MS; i += 100) {
116 ret = keyctl(KEYCTL_REVOKE, key);
117 if (ret == -1 && errno == ENOKEY)
118 break;
119 usleep(100*1000);
120 }
121
122 if (i)
123 tst_res(TINFO, "waiting for key gc took: %d ms", i);
124 tst_res(TPASS, "Bug not reproduced");
125 }
126
setup(void)127 static void setup(void)
128 {
129 SAFE_FILE_SCANF(PATH_KEY_COUNT_QUOTA, "%d", &orig_maxkeys);
130 SAFE_FILE_PRINTF(PATH_KEY_COUNT_QUOTA, "%d", orig_maxkeys + LOOPS + 1);
131 }
132
cleanup(void)133 static void cleanup(void)
134 {
135 if (orig_maxkeys > 0)
136 SAFE_FILE_PRINTF(PATH_KEY_COUNT_QUOTA, "%d", orig_maxkeys);
137 }
138
139 static struct tst_test test = {
140 .needs_root = 1,
141 .setup = setup,
142 .cleanup = cleanup,
143 .max_runtime = 60,
144 .test_all = do_test,
145 .tags = (const struct tst_tag[]) {
146 {"linux-git", "b4a1b4f5047e"},
147 {"CVE", "2015-7550"},
148 {}
149 }
150 };
151