fix(replace): improve ETA string handling in device replace status

Author: DocMAX

cmds/replace.c

@@ -46,6 +46,8 @@ static char *progress2string(char *buf, size_t s, int progress_1000);
 
 /* Used to separate internal errors from actual dev replace ioctl results. */
 #define BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_RESULT		-1
+/* Buffer size for ETA string display */
+#define ETA_STR_SIZE						80
 
 static const char *replace_dev_result2string(__u64 result)
 {
@@ -422,7 +424,8 @@ static int print_replace_status(int fd, const char *path, int once)
 	char string1[80];
 	char string2[80];
 	char string3[80];
-	char eta_str[80];
+	char eta_str[ETA_STR_SIZE];
+	struct tm eta_tm_buf;
 
 	for (;;) {
 		args.cmd = BTRFS_IOCTL_DEV_REPLACE_CMD_STATUS;
@@ -470,10 +473,10 @@ static int print_replace_status(int fd, const char *path, int once)
 					/* Only show ETA if we have a reasonable estimate */
 					if (remaining_time > 0 && total_time > elapsed_time) {
 						eta_time = current_time + remaining_time;
-						struct tm eta_tm_buf;
 						struct tm *eta_tm = localtime_r(&eta_time, &eta_tm_buf);
-						strftime(eta_str, sizeof(eta_str), "ETA: %a %b %d %H:%M:%S %Y", eta_tm);
-						num_chars += printf(", %s", eta_str);
+						if (strftime(eta_str, sizeof(eta_str), "ETA: %a %b %d %H:%M:%S %Y", eta_tm) > 0) {
+							num_chars += printf(", %s", eta_str);
+						}
 					}
 				}
 			}