KEYS: fix length validation in keyctl_pkey_params_get_2()

KEYS: fix length validation in keyctl_pkey_params_get_2()

In many cases, keyctl_pkey_params_get_2() is validating the user buffer
lengths against the wrong algorithm properties.  Fix it to check against
the correct properties.

Probably this wasn't noticed before because for all asymmetric keys of
the "public_key" subtype, max_data_size == max_sig_size == max_enc_size
== max_dec_size.  However, this isn't necessarily true for the
"asym_tpm" subtype (it should be, but it's not strictly validated).  Of
course, future key types could have different values as well.

Fixes: 00d60fd3b932 ("KEYS: Provide keyctls to drive the new key type ops for asymmetric keys [ver #2]")
Cc: <stable@vger.kernel.org> # v4.20+
Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>