ksmbd: fix wrong DataOffset validation of create context

ksmbd: fix wrong DataOffset validation of create context

BugLink: https://bugs.launchpad.net/bugs/2039884
commit 17d5b135bb720832364e8f55f6a887a3c7ec8fdb upstream.

If ->DataOffset of create context is 0, DataBuffer size is not correctly
validated. This patch change wrong validation code and consider tag
length in request.

Cc: stable@vger.kernel.org
Reported-by: zdi-disclosures@trendmicro.com # ZDI-CAN-21824
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>