socks_proxy: defer conn free to fix UAF from synchronous write_queue flush

src/proxy/socks_proxy.c

@@ -28,6 +28,8 @@ static void on_read_cb(struct ll_queue* q, void* arg);
 static void on_fin_cb(struct tcp_conn* tc, void* arg);
 static void on_error_cb(struct tcp_conn* tc, int err, void* arg);
 static void on_closed_cb(struct tcp_conn* tc, void* arg);
+static void socks_proxy_conn_free_deferred(void* arg);
+static void socks_proxy_conn_free_soon(struct socks_proxy_conn* c);
 static void tx_waiter_cb(struct ll_queue* q, void* arg);
 static void tx_retry_timer_cb(void* arg);
 static void socks_issue_dns(struct socks_proxy_conn* c, const char* host, uint8_t kind);
@@ -119,8 +121,8 @@ static int write_to_client(struct socks_proxy_conn* c, const uint8_t* data, uint
     }
     memcpy(buf, data, len);
     e->dgram = buf; e->len = len;
-    queue_data_put(c->tc->write_queue, e);
     c->bytes_to_client += len;
+    queue_data_put(c->tc->write_queue, e);
     return 0;
 }
 
@@ -556,7 +558,7 @@ static void on_error_cb(struct tcp_conn* tc, int err, void* arg) {
     struct UTUN_INSTANCE* inst = c->inst;
     uint64_t via = c->via_node_id;
     uint32_t sid = c->stream_id;
-    socks_proxy_conn_free(c);
+    socks_proxy_conn_free_soon(c);
     if (notify && inst) send_msg(inst, TOPO_GROUP_UTUN, via, TCP_PROXY_SUBCMD_ERROR, sid, NULL, 0, 1);
 }
 
@@ -565,7 +567,7 @@ static void on_closed_cb(struct tcp_conn* tc, void* arg) {
     DEBUG_INFO(DEBUG_CATEGORY_PROXY, "socks_proxy: tcp closed sid=%08x state=%d fm_r=%d fm_l=%d rem_cl=%d bytes_client=%u bytes_exit=%u",
               c->stream_id, c->state, tc->fin_remote, tc->fin_local, c->rem_closed, c->bytes_to_client, c->bytes_from_exit);
     if (!c->close_sent && !c->close_pending) send_close(c);
-    socks_proxy_conn_free(c);
+    socks_proxy_conn_free_soon(c);
 }
 
 // ====================================================================
@@ -627,8 +629,8 @@ int socks_proxy_handle_etcp(struct socks_proxy_conn** head, int* count,
             uint8_t* buf = memory_pool_alloc(c->tc->data_pool);
             if (e && buf) {
                 memcpy(buf, data, data_len); e->dgram = buf; e->len = (uint16_t)data_len;
-                queue_data_put(c->tc->write_queue, e);
                 c->bytes_to_client += (uint32_t)data_len;
+                queue_data_put(c->tc->write_queue, e);
             } else {
                 DEBUG_ERROR(DEBUG_CATEGORY_PROXY, "socks_proxy: handle_data alloc failed sid=%08x wq=%d bytes_in=%u bytes_out=%u",
                            stream_id, c->tc->write_queue->count, c->bytes_from_exit, c->bytes_to_client);
@@ -665,10 +667,22 @@ int socks_proxy_handle_etcp(struct socks_proxy_conn** head, int* count,
     return 1;
 }
 
+static void socks_proxy_conn_free_deferred(void* arg) {
+    struct socks_proxy_conn* c = (struct socks_proxy_conn*)arg;
+    c->free_soon_id = NULL;
+    socks_proxy_conn_free(c);
+}
+
+static void socks_proxy_conn_free_soon(struct socks_proxy_conn* c) {
+    if (!c || c->free_soon_id) return;
+    c->free_soon_id = uasync_call_soon(c->ua, c, socks_proxy_conn_free_deferred);
+}
+
 void socks_proxy_conn_free(struct socks_proxy_conn* c) {
     if (!c) return;
     if (c->freed) return;
     c->freed = 1;
+    if (c->free_soon_id) { uasync_call_soon_cancel(c->ua, c->free_soon_id); c->free_soon_id = NULL; }
     struct socks_proxy_conn** head = c->head; int* count = c->count;
     DEBUG_INFO(DEBUG_CATEGORY_PROXY, "socks_proxy: FREE sid=%08x state=%d total=%d", c->stream_id, c->state, count ? *count : 0);
     if (c->close_pending && c->inst) {

src/proxy/socks_proxy.h

@@ -52,6 +52,7 @@ struct socks_proxy_conn {
     uint8_t             is_http;
     uint8_t             state;
     uint8_t             freed;
+    void*               free_soon_id;  // handle отложенного освобождения (uasync_call_soon)
     uint8_t             buf[1024];
     uint16_t            buf_len;
     uint8_t*            tx_buf;    // буфер при backpressure (retry в tx_waiter_cb)