ksmbd: fix wrong data area length for smb2 lock request

When turning debug mode on, The following error message from
ksmbd_smb2_check_message() is coming.

ksmbd: cli req padded more than expected. Length 112 not 88 for cmd:10 mid:14

data area length calculation for smb2 lock request in smb2_get_data_area_len() is
incorrect.

Fixes: e2f3448 ("cifsd: add server-side procedures for SMB3")
Cc: stable@vger.kernel.org
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: namjaejeon

fs/ksmbd/smb2misc.c

@@ -149,15 +149,11 @@ static int smb2_get_data_area_len(unsigned int *off, unsigned int *len,
 		break;
 	case SMB2_LOCK:
 	{
-		int lock_count;
+		unsigned short lock_count;
 
-		/*
-		 * smb2_lock request size is 48 included single
-		 * smb2_lock_element structure size.
-		 */
-		lock_count = le16_to_cpu(((struct smb2_lock_req *)hdr)->LockCount) - 1;
+		lock_count = le16_to_cpu(((struct smb2_lock_req *)hdr)->LockCount);
 		if (lock_count > 0) {
-			*off = __SMB2_HEADER_STRUCTURE_SIZE + 48;
+			*off = offsetof(struct smb2_lock_req, locks);
 			*len = sizeof(struct smb2_lock_element) * lock_count;
 		}
 		break;