From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Pali=20Roh=C3=A1r?= <pali.rohar@gmail.com>
Date: Thu, 22 Jun 2017 14:33:17 +0200
Subject: [PATCH] udf: Fix reading label, lvd.ident is dstring

UDF dstring has stored length in the last byte of buffer. Therefore last
byte is not part of recorded characters. And empty string in dstring is
encoded as empty buffer, including first byte (compression id).
---
 grub-core/fs/udf.c | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/grub-core/fs/udf.c b/grub-core/fs/udf.c
index 839bff88963..2587456336e 100644
--- a/grub-core/fs/udf.c
+++ b/grub-core/fs/udf.c
@@ -860,6 +860,25 @@ read_string (const grub_uint8_t *raw, grub_size_t sz, char *outbuf)
   return outbuf;
 }
 
+static char *
+read_dstring (const grub_uint8_t *raw, grub_size_t sz)
+{
+  grub_size_t len;
+
+  if (raw[0] == 0) {
+      char *outbuf = grub_malloc (1);
+      if (!outbuf)
+	return NULL;
+      outbuf[0] = 0;
+      return outbuf;
+    }
+
+  len = raw[sz - 1];
+  if (len > sz - 1)
+    len = sz - 1;
+  return read_string (raw, len, NULL);
+}
+
 static int
 grub_udf_iterate_dir (grub_fshelp_node_t dir,
 		      grub_fshelp_iterate_dir_hook_t hook, void *hook_data)
@@ -1197,7 +1216,7 @@ grub_udf_label (grub_device_t device, char **label)
 
   if (data)
     {
-      *label = read_string (data->lvd.ident, sizeof (data->lvd.ident), 0);
+      *label = read_dstring (data->lvd.ident, sizeof (data->lvd.ident));
       grub_free (data);
     }
   else