quoted

IMHO that should just fail then, ie, a "locked down" kernel should not want to
*pass* a firmware signature if such thing could not be done.

Its no different than trying to verify a signed module on a "locked down" for
which it has no signature.

But perhaps I'm not understanding the issue well, let me know.

My point is quite simple:
my_deviceA_init() {
        err = request_firmware(&fw, "deviceA"); <--- (a)
        if (err)
                goto err_request;

        err = verify_firmware(fw);  <--- (b)
        if (err)
                goto err_verify;

        load_fw_to_deviceA(fw);     <--- (c)
        ...
}

As legacy device drivers does not have (b), there is no chance to
prevent loading a firmware at (c) for locked-down kernel.

If you allow me to bring in yet another function, say
request_firmware_signable(), which should be used in place of (a)
for all verification-aware drivers, that would be fine.

I really don't understand why you need a new function.??The
request_firmware() eventually calls kernel_read_file_from_path(),
which already calls the pre and post LSM hooks.

IMA-appraisal is already on these hooks verifying the requested
firmware's signature. ?For systems with "lockdown" enabled, but
without IMA-appraisal enabled, define a small, builtin LSM that sits
on these LSM hooks and denies the unsigned firmware requests.

Mimi

In this case, all the invocation of request_firmware() in legacy code
could be forced to fail in locked-down kernel.

But I think that "signable" should be allowed to be combined with other
features of request_firmware variants like _(no)wait or _direct.

-Takahiro AKASHI

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