cifsd: fix xfstests generic/504 test failure

If lock length in smb2 lock request from client is over
flock max length size, lock length is changed to flock max length
and don't return error response.
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifsd/smb2pdu.c

@@ -6422,7 +6422,7 @@ int smb2_lock(struct ksmbd_work *work)
 	int flags = 0;
 	int cmd = 0;
 	int err = 0, i;
-	u64 lock_length;
+	u64 lock_start, lock_length;
 	struct ksmbd_lock *smb_lock = NULL, *cmp_lock, *tmp;
 	int nolock = 0;
 	LIST_HEAD(lock_list);
@@ -6461,25 +6461,22 @@ int smb2_lock(struct ksmbd_work *work)
 
 		cmd = smb2_set_flock_flags(flock, flags);
 
-		flock->fl_start = le64_to_cpu(lock_ele[i].Offset);
-		if (flock->fl_start > OFFSET_MAX) {
+		lock_start = le64_to_cpu(lock_ele[i].Offset);
+		lock_length = le64_to_cpu(lock_ele[i].Length);
+		if (lock_start > U64_MAX - lock_length) {
 			ksmbd_err("Invalid lock range requested\n");
 			rsp->hdr.Status = STATUS_INVALID_LOCK_RANGE;
 			goto out;
 		}
 
+		if (lock_start > OFFSET_MAX)
+			flock->fl_start = OFFSET_MAX;
+		else
+			flock->fl_start = lock_start;
+
 		lock_length = le64_to_cpu(lock_ele[i].Length);
-		if (lock_length > 0) {
-			if (lock_length > OFFSET_MAX - flock->fl_start) {
-				ksmbd_debug(SMB,
-					"Invalid lock range requested\n");
-				lock_length = OFFSET_MAX - flock->fl_start;
-				rsp->hdr.Status = STATUS_INVALID_LOCK_RANGE;
-				goto out;
-			}
-		} else {
-			lock_length = 0;
-		}
+		if (lock_length > OFFSET_MAX - flock->fl_start)
+			lock_length = OFFSET_MAX - flock->fl_start;
 
 		flock->fl_end = flock->fl_start + lock_length;