out_azure_blob: fixed double free

Signed-off-by: Leonardo Alminana <leonardo.alminana@chronosphere.io>

Author: leonardo-albertovich

plugins/out_azure_blob/azure_blob.c

@@ -366,6 +366,14 @@ static int send_blob(struct flb_config *config,
 
     if (blob_type == AZURE_BLOB_APPENDBLOB) {
         uri = azb_append_blob_uri(ctx, tag);
+
+        block_id = flb_sds_create_len("\0", 1);
+
+        if (block_id == NULL) {
+            cfl_sds_destroy(ref_name);
+
+            return FLB_RETRY;
+        }
     }
     else if (blob_type == AZURE_BLOB_BLOCKBLOB) {
         if (event_type == FLB_EVENT_TYPE_LOGS) {
@@ -388,8 +396,12 @@ static int send_blob(struct flb_config *config,
     }
 
     if (!uri) {
-        flb_free(block_id);
+        if (block_id != NULL) {
+            flb_free(block_id);
+        }
+
         flb_sds_destroy(ref_name);
+
         return FLB_RETRY;
     }
 
@@ -403,7 +415,11 @@ static int send_blob(struct flb_config *config,
                                 &payload_buf, &payload_size);
         if (ret != 0) {
             flb_sds_destroy(uri);
-            flb_free(block_id);
+
+            if (block_id != NULL) {
+                flb_free(block_id);
+            }
+
             flb_sds_destroy(ref_name);
             return FLB_ERROR;
         }
@@ -420,7 +436,6 @@ static int send_blob(struct flb_config *config,
         /* For Logs type, we need to commit the block right away */
         if (event_type == FLB_EVENT_TYPE_LOGS) {
             ret = azb_block_blob_commit_block(ctx, block_id, tag, ms);
-            flb_free(block_id);
         }
     }
     else if (ret == CREATE_BLOB) {
@@ -436,7 +451,10 @@ static int send_blob(struct flb_config *config,
     }
 
     flb_sds_destroy(uri);
-    flb_free(block_id);
+
+    if (block_id != NULL) {
+        flb_free(block_id);
+    }
 
     return ret;
 }
@@ -593,13 +611,13 @@ static int ensure_container(struct flb_azure_blob *ctx)
     else if (status == 200) {
         flb_plg_info(ctx->ins, "container '%s' already exists", ctx->container_name);
         return FLB_TRUE;
-    } 
+    }
     else if (status == 403) {
         flb_plg_error(ctx->ins, "failed getting container '%s', access denied",
                       ctx->container_name);
         return FLB_FALSE;
     }
-    
+
     flb_plg_error(ctx->ins, "get container request failed, status=%i",
                   status);