ksmbd: fix slab-out-of-bounds in smb2_allocate_rsp_buf

If ->ProtocolId is SMB2_TRANSFORM_PROTO_NUM, smb2 request size
validation could be skipped. if request size is smaller than
sizeof(struct smb2_query_info_req), slab-out-of-bounds read can happen in
smb2_allocate_rsp_buf(). This patch allocate response buffer after
decrypting transform request. smb3_decrypt_req() will validate transform
request size and avoid slab-out-of-bound in smb2_allocate_rsp_buf().

Reported-by: Norbert Szetei <norbert@doyensec.com>
Cc: stable@vger.kernel.org
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: namjaejeon

fs/smb/server/server.c

@@ -167,20 +167,17 @@ static void __handle_ksmbd_work(struct ksmbd_work *work,
 	int rc;
 	bool is_chained = false;
 
-	if (conn->ops->allocate_rsp_buf(work))
-		return;
-
 	if (conn->ops->is_transform_hdr &&
 	    conn->ops->is_transform_hdr(work->request_buf)) {
 		rc = conn->ops->decrypt_req(work);
-		if (rc < 0) {
-			conn->ops->set_rsp_status(work, STATUS_DATA_ERROR);
-			goto send;
-		}
-
+		if (rc < 0)
+			return;
 		work->encrypted = true;
 	}
 
+	if (conn->ops->allocate_rsp_buf(work))
+		return;
+
 	rc = conn->ops->init_rsp_hdr(work);
 	if (rc) {
 		/* either uid or tid is not correct */