fix all cases of strcpy on overlapping strings.

libbb/lineedit.c

@@ -1552,7 +1552,7 @@ int FAST_FUNC read_line_input(const char *prompt, char *command, int maxsize, li
 		vi_case(CTRL('U')|vbit:)
 			/* Control-U -- Clear line before cursor */
 			if (cursor) {
-				strcpy(command, command + cursor);
+				overlapping_strcpy(command, command + cursor);
 				command_len -= cursor;
 				redraw(cmdedit_y, command_len);
 			}

libbb/parse_config.c

@@ -161,7 +161,7 @@ int FAST_FUNC config_read(parser_t *parser, char **tokens, unsigned flags, const
 			int n = strspn(line, delims);
 			if (n) {
 				ii -= n;
-				strcpy(line, line + n);
+				overlapping_strcpy(line, line + n);
 			}
 			// cut trailing
 			if (ii) {

libbb/safe_strncpy.c

@@ -16,3 +16,12 @@ char* FAST_FUNC safe_strncpy(char *dst, const char *src, size_t size)
 	dst[--size] = '\0';
 	return strncpy(dst, src, size);
 }
+
+/* Like strcpy but can copy overlapping strings. */
+void FAST_FUNC overlapping_strcpy(char *dst, const char *src)
+{
+	while ((*dst = *src) != '\0') {
+		dst++;
+		src++;
+	}
+}