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#include <sys/mman.h>
#include <unistd.h>
#include <sys/types.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
int backdoor = 0;
struct node {
int prio;
struct node* next;
struct node* prev;
};
struct prio_list {
struct node* first;
};
struct prio_list zlist;
void add_to_tail(struct node* new_node, struct node* node_after) {
struct node* node_before = node_after->prev;
new_node->next = node_after;
new_node->prev = node_before;
node_before->next = new_node;
node_after->prev = new_node;
}
void add_node(struct node* new_node) {
struct node* cur = zlist.first;
struct node* node_before = zlist.first->prev; //last
bool new_node_the_largest = 1;
do {
if(cur->prio > new_node->prio) {
node_before = cur->prev;
new_node_the_largest = 0;
break;
}
cur = cur->next;
}
while(cur != zlist.first);
add_to_tail(new_node, cur);
if(cur == zlist.first && new_node_the_largest == 0) { // new node needs to be inserted in the front
zlist.first = new_node;
}
}
struct node* alloc(int prio)
{
struct node* new_node = malloc(sizeof(struct node));
new_node->prio = prio;
return new_node;
}
void main(int argc, char** argv) {
struct node* a_node = malloc(sizeof(struct node));
a_node->prio = 0;
a_node->prev = a_node;
a_node->next = a_node;
zlist.first = a_node;
int opt;
printf("Option menu:\n[1] add a node;\n[2] changing the prev pointer of the last node;\n[3] debugging feature (disabled);\n[4] exit;\n");
while(1){
printf("Input option: ");
scanf("%d", &opt);
char prev_str[20];
int prev;
switch(opt){
case 1:
printf("Input priority of the new node: ");
int prio;
scanf("%d", &prio);
struct node* new_node = alloc(prio);
add_node(new_node);
printf("Address: %p\n", new_node);
break;
case 2:
printf("Input the new prev pointer of the last node: ");
scanf("%10s", prev_str);
prev = (int)strtol(prev_str, NULL, 0);
printf("prev pointer: %x\n", prev);
zlist.first->prev->prev = (struct node*)prev;
break;
case 3:
printf("backdoor: %d\n", backdoor);
if(backdoor) {
printf("debugging feature is enabled, will give a root shell\n");
execve("/bin/sh", NULL, NULL);
}
else {
printf("I'm sorry this feature is disabled\n");
}
break;
case 4:
return;
default:
break;
}
}
}
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