Fix winChkName() to match when the last slot contains nothing but the

terminating zero (it was treated as length missmatch). The mtools create
such slots if the name len is the product of 13 (max number of unicode
chars fitting in directory slot).

MFC after:	1 week

1 files changed, 8 insertions, 1 deletions

diff --git a/sys/fs/msdosfs/msdosfs_conv.c b/sys/fs/msdosfs/msdosfs_conv.c
index 32138c5..7b3591e 100644
--- a/sys/fs/msdosfs/msdosfs_conv.c
+++ b/sys/fs/msdosfs/msdosfs_conv.c
@@ -780,7 +780,14 @@ winChkName(un, unlen, wep, chksum, u2w_loaded, u2w, ul_loaded, ul)
 	 */
 	i = ((wep->weCnt&WIN_CNT) - 1) * WIN_CHARS;
 	un += i;
-	if ((unlen -= i) <= 0)
+	unlen -= i;
+
+	/*
+	 * unlen being zero must not be treated as length missmatch. It is
+	 * possible if the entry is WIN_LAST and contains nothing but the
+	 * terminating 0.
+	 */
+	if (unlen < 0)
 		return -1;
 	if ((wep->weCnt&WIN_LAST) && unlen > WIN_CHARS)
 		return -1;