ksmbd: replace hardcoded hdr2_len with offsetof() in smb2_calc_max_out_buf_len()

After this commit (e2b76ab "ksmbd: add support for read compound"),
response buffer management was changed to use dynamic iov array.
In the new design, smb2_calc_max_out_buf_len() expects the second
argument (hdr2_len) to be the offset of ->Buffer field in the
response structure, not a hardcoded magic number.
Fix the remaining call sites to use the correct offsetof() value.

Cc: [email protected]
Fixes: e2b76ab ("ksmbd: add support for read compound")
Signed-off-by: Namjae Jeon <[email protected]>
Signed-off-by: Steve French <[email protected]>

Author: namjaejeon

fs/smb/server/smb2pdu.c

@@ -4452,8 +4452,9 @@ int smb2_query_dir(struct ksmbd_work *work)
 	d_info.wptr = (char *)rsp->Buffer;
 	d_info.rptr = (char *)rsp->Buffer;
 	d_info.out_buf_len =
-		smb2_calc_max_out_buf_len(work, 8,
-					  le32_to_cpu(req->OutputBufferLength));
+		smb2_calc_max_out_buf_len(work,
+				offsetof(struct smb2_query_directory_rsp, Buffer),
+				le32_to_cpu(req->OutputBufferLength));
 	if (d_info.out_buf_len < 0) {
 		rc = -EINVAL;
 		goto err_out;
@@ -4720,8 +4721,9 @@ static int smb2_get_ea(struct ksmbd_work *work, struct ksmbd_file *fp,
 	}
 
 	buf_free_len =
-		smb2_calc_max_out_buf_len(work, 8,
-					  le32_to_cpu(req->OutputBufferLength));
+		smb2_calc_max_out_buf_len(work,
+				offsetof(struct smb2_query_info_rsp, Buffer),
+				le32_to_cpu(req->OutputBufferLength));
 	if (buf_free_len < 0)
 		return -EINVAL;
 
@@ -5047,8 +5049,9 @@ static int get_file_stream_info(struct ksmbd_work *work,
 	file_info = (struct smb2_file_stream_info *)rsp->Buffer;
 
 	buf_free_len =
-		smb2_calc_max_out_buf_len(work, 8,
-					  le32_to_cpu(req->OutputBufferLength));
+		smb2_calc_max_out_buf_len(work,
+				offsetof(struct smb2_query_info_rsp, Buffer),
+				le32_to_cpu(req->OutputBufferLength));
 	if (buf_free_len < 0)
 		goto out;
 
@@ -8206,8 +8209,9 @@ int smb2_ioctl(struct ksmbd_work *work)
 	buffer = (char *)req + le32_to_cpu(req->InputOffset);
 
 	cnt_code = le32_to_cpu(req->CtlCode);
-	ret = smb2_calc_max_out_buf_len(work, 48,
-					le32_to_cpu(req->MaxOutputResponse));
+	ret = smb2_calc_max_out_buf_len(work,
+			offsetof(struct smb2_ioctl_rsp, Buffer),
+			le32_to_cpu(req->MaxOutputResponse));
 	if (ret < 0) {
 		rsp->hdr.Status = STATUS_INVALID_PARAMETER;
 		goto out;