uasync: replace raw socket_node pointer with index-based handle — fix UAF after realloc

lib/u_async.c

@@ -675,14 +675,16 @@ void* uasync_add_socket(struct UASYNC* ua, int fd, socket_callback_t read_cbk, s
     }
 #endif
     
-    // Return pointer to the socket node as ID
-    return &ua->sockets->sockets[index];
+    // Return index-based handle
+    return (void*)(uintptr_t)(index + 1);
 }
 
 err_t uasync_remove_socket(struct UASYNC* ua, void* s_id) {
     if (!ua || !s_id) return ERR_FAIL;
     
-    struct socket_node* node = (struct socket_node*)s_id;
+    int i = (int)(uintptr_t)s_id - 1;
+    if (i < 0 || i >= ua->sockets->capacity) return ERR_FAIL;
+    struct socket_node* node = &ua->sockets->sockets[i];
     if (!node->active || node->fd < 0) return ERR_FAIL;
     
     int fd = node->fd;
@@ -736,7 +738,7 @@ void* uasync_add_socket_t(struct UASYNC* ua, socket_t sock, socket_t_callback_t
     }
 #endif
     
-    return &ua->sockets->sockets[index];
+    return (void*)(uintptr_t)(index + 1);   /* +1: index 0 ≠ NULL */
 }
 
 // Remove socket by socket_t
@@ -774,7 +776,9 @@ err_t uasync_remove_socket_t(struct UASYNC* ua, socket_t sock) {
 err_t uasync_set_socket_read(struct UASYNC* ua, void* s_id, int enable) {
     if (!ua || !s_id) return ERR_FAIL;
 
-    struct socket_node* node = (struct socket_node*)s_id;
+    int i = (int)(uintptr_t)s_id - 1;
+    if (i < 0 || i >= ua->sockets->capacity) return ERR_FAIL;
+    struct socket_node* node = &ua->sockets->sockets[i];
     if (!node->active || node->fd < 0) return ERR_FAIL;
 
     int val = enable ? 1 : 0;
@@ -811,7 +815,9 @@ err_t uasync_set_socket_read(struct UASYNC* ua, void* s_id, int enable) {
 err_t uasync_set_socket_write(struct UASYNC* ua, void* s_id, int enable) {
     if (!ua || !s_id) return ERR_FAIL;
 
-    struct socket_node* node = (struct socket_node*)s_id;
+    int i = (int)(uintptr_t)s_id - 1;
+    if (i < 0 || i >= ua->sockets->capacity) return ERR_FAIL;
+    struct socket_node* node = &ua->sockets->sockets[i];
     if (!node->active || node->fd < 0) return ERR_FAIL;
 
     int val = enable ? 1 : 0;