nfc: Ensure presence of required attributes in the activate_target handler

nfc: Ensure presence of required attributes in the activate_target handler

Check that the NFC_ATTR_TARGET_INDEX and NFC_ATTR_PROTOCOLS attributes (in
addition to NFC_ATTR_DEVICE_INDEX) are provided by the netlink client
prior to accessing them. This prevents potential unhandled NULL pointer
dereference exceptions which can be triggered by malicious user-mode
programs, if they omit one or both of these attributes.

Signed-off-by: Mateusz Jurczyk <[email protected]>
Acked-by: Kees Cook <[email protected]>
Signed-off-by: Samuel Ortiz <[email protected]>