double free
时间: 2023-11-17 10:59:18 浏览: 44
Double Free是指同一个指针被释放两次,这种情况可能会导致程序崩溃或者被攻击者利用来执行恶意代码。实际上,只要是释放指向堆内存的指针都有可能产生Double Free漏洞。Double Free的原理和堆溢出类似,都是通过unlink这个双向链表删除的宏来利用的。不同之处在于,Double Free需要攻击者自己伪造整个chunk并且欺骗操作系统。在一些情况下,攻击者可以通过Double Free漏洞来泄露libc基址,从而进一步攻击系统。
相关问题
C++ double free
Double free is a type of memory error that occurs when a program tries to free (or deallocate) a block of memory that has already been freed. This can lead to corrupt memory, crashes, or other unexpected behavior.
In C, memory is allocated using functions like malloc() and calloc(), and deallocated using the free() function. Double free can happen when a program calls free() on the same memory block more than once, or if it calls free() on a pointer that was not actually allocated using malloc() or calloc().
To avoid double free errors, it's important to keep track of which blocks of memory have been allocated and freed, and to only call free() once for each block. One way to do this is to use NULL pointers to mark freed memory, so that the program can check whether a pointer is NULL before calling free() on it.
Here's an example of double free in C:
```c
#include <stdlib.h>
int main() {
int* ptr = malloc(sizeof(int));
free(ptr);
free(ptr); // double free error
return 0;
}
```
In this example, the program allocates memory for an integer using malloc(), then frees it using free(). However, it then tries to free the same memory block again, causing a double free error.
double free or corruption
double free or corruption是一种内存错误,通常发生在程序试图释放已经被释放的内存或者试图释放不是通过malloc系列函数分配的内存时。这种错误可能会导致程序崩溃或者出现其他不可预测的行为。在C/C++中,程序员需要手动分配和释放内存,如果不正确地使用这些函数,就会出现double free or corruption错误。为了避免这种错误,程序员需要仔细检查他们的代码,确保正确地分配和释放内存,并避免重复释放已经被释放的内存。