telemetry: fix autotest on Alpine

[ upstream commit 6ffce64857216344f02ee88d92cb69ee241b3c7b ]

On Alpine linux, the telemetry_data_autotest was failing for the
test where we had dictionaries embedded in other dictionaries up
to three levels deep. Indications are that this issue is due to
excess data being stored on the stack, so replace stack-allocated
buffer data with dynamically allocated data in the case where we
are doing recursive processing of telemetry data structures into
json.

Bugzilla ID: 1177
Fixes: c933bb5 ("telemetry: support array values in data object")
Fixes: d2671e6 ("telemetry: support dict of dicts")

Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
Acked-by: Tyler Retzlaff <roretzla@linux.microsoft.com>

lib/telemetry/telemetry.c

@@ -197,7 +197,11 @@ container_to_json(const struct rte_tel_data *d, char *out_buf, size_t buf_len)
 				break;
 			case RTE_TEL_CONTAINER:
 			{
-				char temp[buf_len];
+				char *temp = malloc(buf_len);
+				if (temp == NULL)
+					break;
+				*temp = '\0';  /* ensure valid string */
+
 				const struct container *cont =
 						&v->value.container;
 				if (container_to_json(cont->data,
@@ -208,6 +212,7 @@ container_to_json(const struct rte_tel_data *d, char *out_buf, size_t buf_len)
 							v->name, temp);
 				if (!cont->keep)
 					rte_tel_data_free(cont->data);
+				free(temp);
 				break;
 			}
 			}
@@ -264,7 +269,11 @@ output_json(const char *cmd, const struct rte_tel_data *d, int s)
 				break;
 			case RTE_TEL_CONTAINER:
 			{
-				char temp[buf_len];
+				char *temp = malloc(buf_len);
+				if (temp == NULL)
+					break;
+				*temp = '\0';  /* ensure valid string */
+
 				const struct container *cont =
 						&v->value.container;
 				if (container_to_json(cont->data,
@@ -275,6 +284,7 @@ output_json(const char *cmd, const struct rte_tel_data *d, int s)
 							v->name, temp);
 				if (!cont->keep)
 					rte_tel_data_free(cont->data);
+				free(temp);
 			}
 			}
 		}
@@ -306,7 +316,11 @@ output_json(const char *cmd, const struct rte_tel_data *d, int s)
 						buf_len, used,
 						d->data.array[i].u64val);
 			else if (d->type == RTE_TEL_ARRAY_CONTAINER) {
-				char temp[buf_len];
+				char *temp = malloc(buf_len);
+				if (temp == NULL)
+					break;
+				*temp = '\0';  /* ensure valid string */
+
 				const struct container *rec_data =
 						&d->data.array[i].container;
 				if (container_to_json(rec_data->data,
@@ -316,6 +330,7 @@ output_json(const char *cmd, const struct rte_tel_data *d, int s)
 							buf_len, used, temp);
 				if (!rec_data->keep)
 					rte_tel_data_free(rec_data->data);
+				free(temp);
 			}
 		used += prefix_used;
 		used += strlcat(out_buf + used, "}", sizeof(out_buf) - used);