ASLR entropy is very low in mimalloc-secure #289
Description
The execution environment is ubuntu 18.04 latest.
// address range [0x40000802000 - 0x40000917021] is allocated at a rate of 0.570000
// address range [0x40000942000 - 0x40000a57021] is allocated at a rate of 0.430000
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <malloc.h>
void* p[256];
uintptr_t buf[256];
int main() {
p[0] = malloc(378200);
p[1] = malloc(1134626);
return 0;
}When executing the code above, the heap memory range is quite predictable. It is, by 100% either one of 0x40000802000 - 0x40000917021 or 0x40000942000 - 0x40000a57021, so it may be prone to heap spray attacks. The main reason is because the base address is fixed to 0x40000000000.