1 | /* Test case for async-signal-safe fork (with respect to malloc). |
2 | Copyright (C) 2016-2022 Free Software Foundation, Inc. |
3 | This file is part of the GNU C Library. |
4 | |
5 | The GNU C Library is free software; you can redistribute it and/or |
6 | modify it under the terms of the GNU Lesser General Public License as |
7 | published by the Free Software Foundation; either version 2.1 of the |
8 | License, or (at your option) any later version. |
9 | |
10 | The GNU C Library 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 GNU |
13 | Lesser General Public License for more details. |
14 | |
15 | You should have received a copy of the GNU Lesser General Public |
16 | License along with the GNU C Library; see the file COPYING.LIB. If |
17 | not, see <https://www.gnu.org/licenses/>. */ |
18 | |
19 | /* This test will fail if the process is multi-threaded because we |
20 | only have an async-signal-safe fork in the single-threaded case |
21 | (where we skip acquiring the malloc heap locks). |
22 | |
23 | This test only checks async-signal-safety with regards to malloc; |
24 | other, more rarely-used glibc subsystems could have locks which |
25 | still make fork unsafe, even in single-threaded processes. */ |
26 | |
27 | #include <errno.h> |
28 | #include <sched.h> |
29 | #include <signal.h> |
30 | #include <stdbool.h> |
31 | #include <stdio.h> |
32 | #include <stdlib.h> |
33 | #include <string.h> |
34 | #include <sys/wait.h> |
35 | #include <time.h> |
36 | #include <unistd.h> |
37 | #include <array_length.h> |
38 | #include <support/check.h> |
39 | #include <support/support.h> |
40 | #include <support/xthread.h> |
41 | #include <support/xunistd.h> |
42 | |
43 | /* How many malloc objects to keep arond. */ |
44 | enum { malloc_objects = 1009 }; |
45 | |
46 | /* The maximum size of an object. */ |
47 | enum { malloc_maximum_size = 70000 }; |
48 | |
49 | /* How many iterations the test performs before exiting. */ |
50 | enum { iterations = 10000 }; |
51 | |
52 | /* Barrier for synchronization with the processes sending SIGUSR1 |
53 | signals, to make it more likely that the signals arrive during a |
54 | fork/free/malloc call. */ |
55 | static struct { pthread_barrier_t barrier; } *shared; |
56 | |
57 | /* Set to 1 if SIGUSR1 is received. Used to detect a signal during |
58 | fork/free/malloc. */ |
59 | static volatile sig_atomic_t sigusr1_received; |
60 | |
61 | /* Periodically set to 1, to indicate that the process is making |
62 | progress. Checked by liveness_signal_handler. */ |
63 | static volatile sig_atomic_t progress_indicator = 1; |
64 | |
65 | /* Set to 1 if an error occurs in the signal handler. */ |
66 | static volatile sig_atomic_t error_indicator = 0; |
67 | |
68 | static void |
69 | sigusr1_handler (int signo) |
70 | { |
71 | sigusr1_received = 1; |
72 | |
73 | /* Perform a fork with a trivial subprocess. */ |
74 | pid_t pid = fork (); |
75 | if (pid == -1) |
76 | { |
77 | write_message (message: "error: fork\n" ); |
78 | error_indicator = 1; |
79 | return; |
80 | } |
81 | if (pid == 0) |
82 | _exit (0); |
83 | int status; |
84 | int ret = TEMP_FAILURE_RETRY (waitpid (pid, &status, 0)); |
85 | if (ret < 0) |
86 | { |
87 | write_message (message: "error: waitpid\n" ); |
88 | error_indicator = 1; |
89 | return; |
90 | } |
91 | if (status != 0) |
92 | { |
93 | write_message (message: "error: unexpected exit status from subprocess\n" ); |
94 | error_indicator = 1; |
95 | return; |
96 | } |
97 | } |
98 | |
99 | static void |
100 | liveness_signal_handler (int signo) |
101 | { |
102 | if (progress_indicator) |
103 | progress_indicator = 0; |
104 | else |
105 | write_message (message: "warning: process seems to be stuck\n" ); |
106 | } |
107 | |
108 | /* Send SIGNO to the parent process. If SLEEP, wait a second between |
109 | signals, otherwise use barriers to delay sending signals. */ |
110 | static void |
111 | __attribute__ ((noreturn)) |
112 | signal_sender (int signo, bool sleep) |
113 | { |
114 | pid_t target = getppid (); |
115 | while (true) |
116 | { |
117 | if (!sleep) |
118 | xpthread_barrier_wait (barrier: &shared->barrier); |
119 | if (kill (pid: target, sig: signo) != 0) |
120 | { |
121 | dprintf (STDOUT_FILENO, "error: kill: %m\n" ); |
122 | abort (); |
123 | } |
124 | if (sleep) |
125 | usleep (useconds: 1 * 1000 * 1000); |
126 | else |
127 | xpthread_barrier_wait (barrier: &shared->barrier); |
128 | } |
129 | } |
130 | |
131 | /* Children processes. */ |
132 | static pid_t sigusr1_sender_pids[5] = { 0 }; |
133 | static pid_t sigusr2_sender_pid = 0; |
134 | |
135 | static void |
136 | kill_children (void) |
137 | { |
138 | for (size_t i = 0; i < array_length (sigusr1_sender_pids); ++i) |
139 | if (sigusr1_sender_pids[i] > 0) |
140 | kill (pid: sigusr1_sender_pids[i], SIGKILL); |
141 | if (sigusr2_sender_pid > 0) |
142 | kill (pid: sigusr2_sender_pid, SIGKILL); |
143 | } |
144 | |
145 | static int |
146 | do_test (void) |
147 | { |
148 | atexit (func: kill_children); |
149 | |
150 | /* shared->barrier is intialized along with sigusr1_sender_pids |
151 | below. */ |
152 | shared = support_shared_allocate (size: sizeof (*shared)); |
153 | |
154 | struct sigaction action = |
155 | { |
156 | .sa_handler = sigusr1_handler, |
157 | }; |
158 | sigemptyset (&action.sa_mask); |
159 | |
160 | if (sigaction (SIGUSR1, act: &action, NULL) != 0) |
161 | { |
162 | printf (format: "error: sigaction: %m" ); |
163 | return 1; |
164 | } |
165 | |
166 | action.sa_handler = liveness_signal_handler; |
167 | if (sigaction (SIGUSR2, act: &action, NULL) != 0) |
168 | { |
169 | printf (format: "error: sigaction: %m" ); |
170 | return 1; |
171 | } |
172 | |
173 | sigusr2_sender_pid = xfork (); |
174 | if (sigusr2_sender_pid == 0) |
175 | signal_sender (SIGUSR2, true); |
176 | |
177 | /* Send SIGUSR1 signals from several processes. Hopefully, one |
178 | signal will hit one of the ciritical functions. Use a barrier to |
179 | avoid sending signals while not running fork/free/malloc. */ |
180 | { |
181 | pthread_barrierattr_t attr; |
182 | xpthread_barrierattr_init (&attr); |
183 | xpthread_barrierattr_setpshared (&attr, PTHREAD_PROCESS_SHARED); |
184 | xpthread_barrier_init (barrier: &shared->barrier, attr: &attr, |
185 | array_length (sigusr1_sender_pids) + 1); |
186 | xpthread_barrierattr_destroy (&attr); |
187 | } |
188 | for (size_t i = 0; i < array_length (sigusr1_sender_pids); ++i) |
189 | { |
190 | sigusr1_sender_pids[i] = xfork (); |
191 | if (sigusr1_sender_pids[i] == 0) |
192 | signal_sender (SIGUSR1, false); |
193 | } |
194 | |
195 | void *objects[malloc_objects] = {}; |
196 | unsigned int fork_signals = 0; |
197 | unsigned int free_signals = 0; |
198 | unsigned int malloc_signals = 0; |
199 | unsigned seed = 1; |
200 | for (int i = 0; i < iterations; ++i) |
201 | { |
202 | progress_indicator = 1; |
203 | int slot = rand_r (seed: &seed) % malloc_objects; |
204 | size_t size = rand_r (seed: &seed) % malloc_maximum_size; |
205 | |
206 | /* Occasionally do a fork first, to catch deadlocks there as |
207 | well (see bug 24161). */ |
208 | bool do_fork = (rand_r (seed: &seed) % 7) == 0; |
209 | |
210 | xpthread_barrier_wait (barrier: &shared->barrier); |
211 | if (do_fork) |
212 | { |
213 | sigusr1_received = 0; |
214 | pid_t pid = xfork (); |
215 | if (sigusr1_received) |
216 | ++fork_signals; |
217 | if (pid == 0) |
218 | _exit (0); |
219 | int status; |
220 | int ret = TEMP_FAILURE_RETRY (waitpid (pid, &status, 0)); |
221 | if (ret < 0) |
222 | FAIL_EXIT1 ("waitpid: %m" ); |
223 | TEST_COMPARE (status, 0); |
224 | } |
225 | sigusr1_received = 0; |
226 | free (ptr: objects[slot]); |
227 | if (sigusr1_received) |
228 | ++free_signals; |
229 | sigusr1_received = 0; |
230 | objects[slot] = malloc (size: size); |
231 | if (sigusr1_received) |
232 | ++malloc_signals; |
233 | xpthread_barrier_wait (barrier: &shared->barrier); |
234 | |
235 | if (objects[slot] == NULL || error_indicator != 0) |
236 | { |
237 | printf (format: "error: malloc: %m\n" ); |
238 | for (size_t i = 0; i < array_length (sigusr1_sender_pids); ++i) |
239 | kill (pid: sigusr1_sender_pids[i], SIGKILL); |
240 | kill (pid: sigusr2_sender_pid, SIGKILL); |
241 | return 1; |
242 | } |
243 | } |
244 | |
245 | /* Clean up allocations. */ |
246 | for (int slot = 0; slot < malloc_objects; ++slot) |
247 | free (ptr: objects[slot]); |
248 | |
249 | printf (format: "info: signals received during fork: %u\n" , fork_signals); |
250 | printf (format: "info: signals received during free: %u\n" , free_signals); |
251 | printf (format: "info: signals received during malloc: %u\n" , malloc_signals); |
252 | |
253 | /* Do not destroy the barrier because of the SIGKILL above, which |
254 | may have left the barrier in an inconsistent state. */ |
255 | support_shared_free (shared); |
256 | |
257 | return 0; |
258 | } |
259 | |
260 | #define TIMEOUT 100 |
261 | #include <support/test-driver.c> |
262 | |