1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
|
// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (c) 2020 Collabora Ltd.
*
* Test code for syscall user dispatch
*/
#define _GNU_SOURCE
#include <sys/prctl.h>
#include <sys/sysinfo.h>
#include <sys/syscall.h>
#include <signal.h>
#include <asm/unistd.h>
#include "../kselftest_harness.h"
#ifndef PR_SET_SYSCALL_USER_DISPATCH
# define PR_SET_SYSCALL_USER_DISPATCH 59
# define PR_SYS_DISPATCH_OFF 0
# define PR_SYS_DISPATCH_ON 1
# define SYSCALL_DISPATCH_FILTER_ALLOW 0
# define SYSCALL_DISPATCH_FILTER_BLOCK 1
#endif
#ifndef SYS_USER_DISPATCH
# define SYS_USER_DISPATCH 2
#endif
#ifdef __NR_syscalls
# define MAGIC_SYSCALL_1 (__NR_syscalls + 1) /* Bad Linux syscall number */
#else
# define MAGIC_SYSCALL_1 (0xff00) /* Bad Linux syscall number */
#endif
#define SYSCALL_DISPATCH_ON(x) ((x) = SYSCALL_DISPATCH_FILTER_BLOCK)
#define SYSCALL_DISPATCH_OFF(x) ((x) = SYSCALL_DISPATCH_FILTER_ALLOW)
/* Test Summary:
*
* - dispatch_trigger_sigsys: Verify if PR_SET_SYSCALL_USER_DISPATCH is
* able to trigger SIGSYS on a syscall.
*
* - bad_selector: Test that a bad selector value triggers SIGSYS with
* si_errno EINVAL.
*
* - bad_prctl_param: Test that the API correctly rejects invalid
* parameters on prctl
*
* - dispatch_and_return: Test that a syscall is selectively dispatched
* to userspace depending on the value of selector.
*
* - disable_dispatch: Test that the PR_SYS_DISPATCH_OFF correctly
* disables the dispatcher
*
* - direct_dispatch_range: Test that a syscall within the allowed range
* can bypass the dispatcher.
*/
TEST_SIGNAL(dispatch_trigger_sigsys, SIGSYS)
{
char sel = SYSCALL_DISPATCH_FILTER_ALLOW;
struct sysinfo info;
int ret;
ret = sysinfo(&info);
ASSERT_EQ(0, ret);
ret = prctl(PR_SET_SYSCALL_USER_DISPATCH, PR_SYS_DISPATCH_ON, 0, 0, &sel);
ASSERT_EQ(0, ret) {
TH_LOG("Kernel does not support CONFIG_SYSCALL_USER_DISPATCH");
}
SYSCALL_DISPATCH_ON(sel);
sysinfo(&info);
EXPECT_FALSE(true) {
TH_LOG("Unreachable!");
}
}
TEST(bad_prctl_param)
{
char sel = SYSCALL_DISPATCH_FILTER_ALLOW;
int op;
/* Invalid op */
op = -1;
prctl(PR_SET_SYSCALL_USER_DISPATCH, op, 0, 0, &sel);
ASSERT_EQ(EINVAL, errno);
/* PR_SYS_DISPATCH_OFF */
op = PR_SYS_DISPATCH_OFF;
/* offset != 0 */
prctl(PR_SET_SYSCALL_USER_DISPATCH, op, 0x1, 0x0, 0);
EXPECT_EQ(EINVAL, errno);
/* len != 0 */
prctl(PR_SET_SYSCALL_USER_DISPATCH, op, 0x0, 0xff, 0);
EXPECT_EQ(EINVAL, errno);
/* sel != NULL */
prctl(PR_SET_SYSCALL_USER_DISPATCH, op, 0x0, 0x0, &sel);
EXPECT_EQ(EINVAL, errno);
/* Valid parameter */
errno = 0;
prctl(PR_SET_SYSCALL_USER_DISPATCH, op, 0x0, 0x0, 0x0);
EXPECT_EQ(0, errno);
/* PR_SYS_DISPATCH_ON */
op = PR_SYS_DISPATCH_ON;
/* Dispatcher region is bad (offset > 0 && len == 0) */
prctl(PR_SET_SYSCALL_USER_DISPATCH, op, 0x1, 0x0, &sel);
EXPECT_EQ(EINVAL, errno);
prctl(PR_SET_SYSCALL_USER_DISPATCH, op, -1L, 0x0, &sel);
EXPECT_EQ(EINVAL, errno);
/* Invalid selector */
prctl(PR_SET_SYSCALL_USER_DISPATCH, op, 0x0, 0x1, (void *) -1);
ASSERT_EQ(EFAULT, errno);
/*
* Dispatcher range overflows unsigned long
*/
prctl(PR_SET_SYSCALL_USER_DISPATCH, PR_SYS_DISPATCH_ON, 1, -1L, &sel);
ASSERT_EQ(EINVAL, errno) {
TH_LOG("Should reject bad syscall range");
}
/*
* Allowed range overflows usigned long
*/
prctl(PR_SET_SYSCALL_USER_DISPATCH, PR_SYS_DISPATCH_ON, -1L, 0x1, &sel);
ASSERT_EQ(EINVAL, errno) {
TH_LOG("Should reject bad syscall range");
}
}
/*
* Use global selector for handle_sigsys tests, to avoid passing
* selector to signal handler
*/
char glob_sel;
int nr_syscalls_emulated;
int si_code;
int si_errno;
static void handle_sigsys(int sig, siginfo_t *info, void *ucontext)
{
si_code = info->si_code;
si_errno = info->si_errno;
if (info->si_syscall == MAGIC_SYSCALL_1)
nr_syscalls_emulated++;
/* In preparation for sigreturn. */
SYSCALL_DISPATCH_OFF(glob_sel);
}
TEST(dispatch_and_return)
{
long ret;
struct sigaction act;
sigset_t mask;
glob_sel = 0;
nr_syscalls_emulated = 0;
si_code = 0;
si_errno = 0;
memset(&act, 0, sizeof(act));
sigemptyset(&mask);
act.sa_sigaction = handle_sigsys;
act.sa_flags = SA_SIGINFO;
act.sa_mask = mask;
ret = sigaction(SIGSYS, &act, NULL);
ASSERT_EQ(0, ret);
/* Make sure selector is good prior to prctl. */
SYSCALL_DISPATCH_OFF(glob_sel);
ret = prctl(PR_SET_SYSCALL_USER_DISPATCH, PR_SYS_DISPATCH_ON, 0, 0, &glob_sel);
ASSERT_EQ(0, ret) {
TH_LOG("Kernel does not support CONFIG_SYSCALL_USER_DISPATCH");
}
/* MAGIC_SYSCALL_1 doesn't exist. */
SYSCALL_DISPATCH_OFF(glob_sel);
ret = syscall(MAGIC_SYSCALL_1);
EXPECT_EQ(-1, ret) {
TH_LOG("Dispatch triggered unexpectedly");
}
/* MAGIC_SYSCALL_1 should be emulated. */
nr_syscalls_emulated = 0;
SYSCALL_DISPATCH_ON(glob_sel);
ret = syscall(MAGIC_SYSCALL_1);
EXPECT_EQ(MAGIC_SYSCALL_1, ret) {
TH_LOG("Failed to intercept syscall");
}
EXPECT_EQ(1, nr_syscalls_emulated) {
TH_LOG("Failed to emulate syscall");
}
ASSERT_EQ(SYS_USER_DISPATCH, si_code) {
TH_LOG("Bad si_code in SIGSYS");
}
ASSERT_EQ(0, si_errno) {
TH_LOG("Bad si_errno in SIGSYS");
}
}
TEST_SIGNAL(bad_selector, SIGSYS)
{
long ret;
struct sigaction act;
sigset_t mask;
struct sysinfo info;
glob_sel = SYSCALL_DISPATCH_FILTER_ALLOW;
nr_syscalls_emulated = 0;
si_code = 0;
si_errno = 0;
memset(&act, 0, sizeof(act));
sigemptyset(&mask);
act.sa_sigaction = handle_sigsys;
act.sa_flags = SA_SIGINFO;
act.sa_mask = mask;
ret = sigaction(SIGSYS, &act, NULL);
ASSERT_EQ(0, ret);
/* Make sure selector is good prior to prctl. */
SYSCALL_DISPATCH_OFF(glob_sel);
ret = prctl(PR_SET_SYSCALL_USER_DISPATCH, PR_SYS_DISPATCH_ON, 0, 0, &glob_sel);
ASSERT_EQ(0, ret) {
TH_LOG("Kernel does not support CONFIG_SYSCALL_USER_DISPATCH");
}
glob_sel = -1;
sysinfo(&info);
/* Even though it is ready to catch SIGSYS, the signal is
* supposed to be uncatchable.
*/
EXPECT_FALSE(true) {
TH_LOG("Unreachable!");
}
}
TEST(disable_dispatch)
{
int ret;
struct sysinfo info;
char sel = 0;
ret = prctl(PR_SET_SYSCALL_USER_DISPATCH, PR_SYS_DISPATCH_ON, 0, 0, &sel);
ASSERT_EQ(0, ret) {
TH_LOG("Kernel does not support CONFIG_SYSCALL_USER_DISPATCH");
}
/* MAGIC_SYSCALL_1 doesn't exist. */
SYSCALL_DISPATCH_OFF(glob_sel);
ret = prctl(PR_SET_SYSCALL_USER_DISPATCH, PR_SYS_DISPATCH_OFF, 0, 0, 0);
EXPECT_EQ(0, ret) {
TH_LOG("Failed to unset syscall user dispatch");
}
/* Shouldn't have any effect... */
SYSCALL_DISPATCH_ON(glob_sel);
ret = syscall(__NR_sysinfo, &info);
EXPECT_EQ(0, ret) {
TH_LOG("Dispatch triggered unexpectedly");
}
}
TEST(direct_dispatch_range)
{
int ret = 0;
struct sysinfo info;
char sel = SYSCALL_DISPATCH_FILTER_ALLOW;
/*
* Instead of calculating libc addresses; allow the entire
* memory map and lock the selector.
*/
ret = prctl(PR_SET_SYSCALL_USER_DISPATCH, PR_SYS_DISPATCH_ON, 0, -1L, &sel);
ASSERT_EQ(0, ret) {
TH_LOG("Kernel does not support CONFIG_SYSCALL_USER_DISPATCH");
}
SYSCALL_DISPATCH_ON(sel);
ret = sysinfo(&info);
ASSERT_EQ(0, ret) {
TH_LOG("Dispatch triggered unexpectedly");
}
}
TEST_HARNESS_MAIN
|
