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

In the Linux kernel, the following vulnerability has been resolved:

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().