fix %c $string substitution

Fix udev_rules_apply_format() to give error messages for unknown
format elements and pass such elements to the output string
unmodified.

When truncating the substitution string to the length specified in the
format string, head[len] = '\0' could write outside the buffer if that
length was too large.

diff --git a/udev_rules.c b/udev_rules.c
index edaaa71d12c7793c9716cb332ce5edaed41a2598..d1c3f042c390ce5dd4c913a664159ffce350f1c2 100644 (file)
--- a/udev_rules.c
+++ b/udev_rules.c
@@ -364,6 +364,8 @@ void udev_rules_apply_format(struct udevice *udev, char *string, size_t maxsize)
                                                goto found;
                                        }
                                }
+                               head[0] = '$';
+                               err("unknown format variable '%s'", head);
                        } else if (head[0] == '%') {
                                /* substitute format char */
                                if (head[1] == '\0')
@@ -385,6 +387,8 @@ void udev_rules_apply_format(struct udevice *udev, char *string, size_t maxsize)
                                                goto found;
                                        }
                                }
+                               head[0] = '%';
+                               err("unknown format char '%c'", tail[0]);
                        }
                        head++;
                }
@@ -554,7 +558,7 @@ found:
                        break;
                }
                /* possibly truncate to format-char specified length */
-               if (len != -1) {
+               if (len >= 0 && len < (int)strlen(head)) {
                        head[len] = '\0';
                        dbg("truncate to %i chars, subtitution string becomes '%s'", len, head);
                }