KEYS: fix length validation in keyctl_pkey_params_get_2()

KEYS: fix length validation in keyctl_pkey_params_get_2()

BugLink: https://bugs.launchpad.net/bugs/1969110
commit c51abd96837f600d8fd940b6ab8e2da578575504 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit fe8df44892407e301ed03027639b4d904f12694c)
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>