1 /*
2 * Copyright (c) 2017 FUJITSU LIMITED. All rights reserved.
3 * Author: Guangwen Feng <fenggw-fnst@cn.fujitsu.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 /*
20 * This is a regression test for a crash caused by memcg function
21 * reentrant on buggy kernel. When doing rmdir(), a pending signal can
22 * interrupt the execution and lead to cgroup_clear_css_refs()
23 * being entered repeatedly, this results in a BUG_ON().
24 */
25
26 #include <errno.h>
27 #include <unistd.h>
28 #include <stdlib.h>
29 #include <sys/types.h>
30 #include <sys/mount.h>
31 #include "tst_test.h"
32
33 #define MNTPOINT "memcg"
34 #define SUBDIR "memcg/testdir"
35
36 static int mount_flag;
37 static volatile int sigcounter;
38
sighandler(int sig LTP_ATTRIBUTE_UNUSED)39 static void sighandler(int sig LTP_ATTRIBUTE_UNUSED)
40 {
41 sigcounter++;
42 }
43
do_child(void)44 static void do_child(void)
45 {
46 while (1)
47 SAFE_KILL(getppid(), SIGUSR1);
48
49 exit(0);
50 }
51
do_test(void)52 static void do_test(void)
53 {
54 pid_t cpid;
55
56 SAFE_SIGNAL(SIGUSR1, sighandler);
57
58 cpid = SAFE_FORK();
59 if (cpid == 0)
60 do_child();
61
62 while (sigcounter < 50000) {
63 if (access(SUBDIR, F_OK))
64 SAFE_MKDIR(SUBDIR, 0644);
65 rmdir(SUBDIR);
66 }
67
68 SAFE_KILL(cpid, SIGKILL);
69 SAFE_WAIT(NULL);
70
71 tst_res(TPASS, "Bug not reproduced");
72 }
73
setup(void)74 static void setup(void)
75 {
76 int ret;
77
78 SAFE_MKDIR(MNTPOINT, 0644);
79
80 ret = mount("memcg", MNTPOINT, "cgroup", 0, "memory");
81 if (ret) {
82 if (errno == ENOENT)
83 tst_brk(TCONF | TERRNO, "memcg not supported");
84
85 tst_brk(TCONF | TERRNO, "mounting memcg failed");
86 }
87 mount_flag = 1;
88 }
89
cleanup(void)90 static void cleanup(void)
91 {
92 if (!access(SUBDIR, F_OK))
93 SAFE_RMDIR(SUBDIR);
94
95 if (mount_flag)
96 tst_umount(MNTPOINT);
97 }
98
99 static struct tst_test test = {
100 .needs_root = 1,
101 .needs_tmpdir = 1,
102 .forks_child = 1,
103 .min_kver = "2.6.24",
104 .setup = setup,
105 .cleanup = cleanup,
106 .test_all = do_test,
107 };
108