diff --git a/tools/power/x86/intel-speed-select/isst-display.c b/tools/power/x86/intel-speed-select/isst-display.c
index e105fece47b6..f32ce0362eb7 100644
--- a/tools/power/x86/intel-speed-select/isst-display.c
+++ b/tools/power/x86/intel-speed-select/isst-display.c
@@ -25,10 +25,14 @@ static void printcpulist(int str_len, char *str, int mask_size,
 			index = snprintf(&str[curr_index],
 					 str_len - curr_index, ",");
 			curr_index += index;
+			if (curr_index >= str_len)
+				break;
 		}
 		index = snprintf(&str[curr_index], str_len - curr_index, "%d",
 				 i);
 		curr_index += index;
+		if (curr_index >= str_len)
+			break;
 		first = 0;
 	}
 }
@@ -64,10 +68,14 @@ static void printcpumask(int str_len, char *str, int mask_size,
 		index = snprintf(&str[curr_index], str_len - curr_index, "%08x",
 				 mask[i]);
 		curr_index += index;
+		if (curr_index >= str_len)
+			break;
 		if (i) {
 			strncat(&str[curr_index], ",", str_len - curr_index);
 			curr_index++;
 		}
+		if (curr_index >= str_len)
+			break;
 	}
 
 	free(mask);
@@ -185,7 +193,7 @@ static void _isst_pbf_display_information(int cpu, FILE *outf, int level,
 					  int disp_level)
 {
 	char header[256];
-	char value[256];
+	char value[512];
 
 	snprintf(header, sizeof(header), "speed-select-base-freq-properties");
 	format_and_print(outf, disp_level, header, NULL);
@@ -349,7 +357,7 @@ void isst_ctdp_display_information(int cpu, FILE *outf, int tdp_level,
 				   struct isst_pkg_ctdp *pkg_dev)
 {
 	char header[256];
-	char value[256];
+	char value[512];
 	static int level;
 	int i;