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
|
#!/bin/sh
#
# SPDX-License-Identifier: BSD-2-Clause-FreeBSD
#
# Copyright (c) 2019 Dell EMC Isilon
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
# 1. Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright
# notice, this list of conditions and the following disclaimer in the
# documentation and/or other materials provided with the distribution.
#
# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
# SUCH DAMAGE.
#
# markj@ wrote:
# I found a kernel bug that caused init to consume 100% CPU if the
# following steps occurred:
# - process A forks and creates process B
# - process C ptrace attaches to process B
# - process A exits
# - process C detaches from process B
# - process B exits
#
# Process B gets reparented to init, and the bug causes wait() to return
# an error each time init attempts to reap process B.
. ../default.cfg
cd /tmp
cat > ptrace11.c <<EOF
#include <sys/types.h>
#include <sys/mman.h>
#include <sys/ptrace.h>
#include <sys/wait.h>
#include <machine/atomic.h>
#include <err.h>
#include <pthread.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
static volatile u_int *share;
#define SYNC 0
int
main(void)
{
pid_t pida, pidb;
size_t len;
int status;
setproctitle("A");
len = PAGE_SIZE;
if ((share = mmap(NULL, len, PROT_READ | PROT_WRITE,
MAP_ANON | MAP_SHARED, -1, 0)) == MAP_FAILED)
err(1, "mmap");
pida = fork();
if (pida < 0)
err(1, "fork");
if (pida == 0) {
setproctitle("B");
while (share[SYNC] != 2)
usleep(10);
_exit(0);
} else {
sleep(1);
pidb = fork();
if (pidb < 0)
err(1, "fork");
if (pidb == 0) {
setproctitle("C");
if (ptrace(PT_ATTACH, pida, NULL, 0) != 0)
err(1, "ptrace(PT_ATTACH)");
wait4(pida, &status, 0, NULL);
share[SYNC] = 1; /* A to exit */
usleep(1000);
if (ptrace(PT_DETACH, pida, NULL, 0) != 0)
err(1, "ptrace(PT_DETACH)");
share[SYNC] = 2; /* B to exit */
_exit(0);
} else {
while (share[SYNC] != 1)
usleep(10);
_exit(0);
}
}
return (0);
}
EOF
mycc -o ptrace11 -Wall -Wextra -O2 -g ptrace11.c || exit 1
rm ptrace11.c
old=`ps auxwwl | grep -v grep | grep "<defunct>" | wc -l`
./ptrace11
new=`ps auxwwl | grep -v grep | grep "<defunct>" | wc -l`
if [ $old -ne $new ]; then
ps auxwwl | sed -n '1p;/<defunct>/p'
echo FAIL
s=1
fi
rm -f ptrace11
exit $s
|
