[CIFS] Fix oops when Windows server sent bad domain name null terminator

Fixes RedHat bug 211672

Windows sends one byte (instead of two) of null to terminate final Unicode
string (domain name) in session setup response in some cases - this caused
cifs to misalign some informational strings (making it hard to convert
from UCS16 to UTF8).

Thanks to Shaggy for his help and Akemi Yagi for debugging/testing
Signed-off-by: Shirish Pargaonkar <shirishp@us.ibm.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

fs/cifs/sess.c

@@ -182,11 +182,14 @@ static int decode_unicode_ssetup(char ** pbcc_area, int bleft, struct cifsSesInf
 	cFYI(1,("bleft %d",bleft));
 
 
-	/* word align, if bytes remaining is not even */
-	if(bleft % 2) {
-		bleft--;
+	/* SMB header is unaligned, so cifs servers word align start of
+	   Unicode strings */
 	data++;
-	}
+	bleft--; /* Windows servers do not always double null terminate
+		    their final Unicode string - in which case we
+		    now will not attempt to decode the byte of junk
+		    which follows it */
+		    
 	words_left = bleft / 2;
 
 	/* save off server operating system */