esp_netif: list lock/unlock

[Uto1963]

ESP-IDF V4.2

Two threads call esp_netif_new(), that calls esp_netif_get_handle_from_ifkey(), that calls esp_netif_list_lock()
The first thread creates and takes the semaphore; the second waits for xSemaphoreTake() returning.
The first threads gives the semaphore then delete it, beeing s_esp_netif_counter still zero.
When the second thread calls esp_netif_unlock() assert(s_list_lock) fails beeing the semaphore handle NULL.
The semaphore cannot protect itself.

Code from esp_netif_objects.c

Code: [Select all] [Expand/Collapse]

1.  
2.  static size_t s_esp_netif_counter = 0;
3.  
4.  
5. esp_netif_t *esp_netif_new(const esp_netif_config_t *esp_netif_config)
6. {
7.     // mandatory configuration must be provided when creating esp_netif object
8.     if (esp_netif_config == NULL ||
9.         esp_netif_config->base->if_key == NULL ||
10.         NULL != esp_netif_get_handle_from_ifkey(esp_netif_config->base->if_key)) {
11.         ESP_LOGE(TAG, "%s: Failed to configure netif with config=%p (config or if_key is NULL or duplicate key)",
12.         __func__,  esp_netif_config);
13.         return NULL;
14.     }
15.  
16.    …
17.  
18. }
19.  
20.  
21. esp_netif_t *esp_netif_get_handle_from_ifkey(const char *if_key)
22. {
23.     esp_err_t ret;
24.     if ((ret = esp_netif_list_lock()) != ESP_OK) {
25.         ESP_LOGE(TAG, "Failed to lock esp-netif list with %d", ret);
26.         return NULL;
27.     }
28.  
29.     esp_netif_t *esp_netif = esp_netif_next_unsafe(NULL);
30.     do {
31.         if (esp_netif && strcmp(if_key, esp_netif_get_ifkey(esp_netif))==0) {
32.             esp_netif_list_unlock();
33.             return esp_netif;
34.         }
35.     } while (NULL != (esp_netif = esp_netif_next_unsafe(esp_netif)));
36.     esp_netif_list_unlock();
37.     return NULL;
38. }
39.  
40. void esp_netif_list_unlock(void)
41. {
42.     assert(s_list_lock);
43.     xSemaphoreGive(s_list_lock);
44.     if(s_esp_netif_counter == 0) {
45.       vQueueDelete(s_list_lock);
46.       s_list_lock = NULL;
47.     }
48. }
49.  
50. esp_err_t esp_netif_list_lock(void)
51. {
52.     if (s_list_lock == NULL) {
53.         s_list_lock = xSemaphoreCreateMutex();
54.         if (s_list_lock == NULL) {
55.             return ESP_ERR_NO_MEM;
56.         }
57.     }
58.     xSemaphoreTake(s_list_lock, portMAX_DELAY);
59.     return ESP_OK;
60. }

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