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    SubjectRe: [RFC PATCH] tpm: don't return -EINVAL if TPM command validation fails
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    On 11/17/2017 06:58 PM, Jason Gunthorpe wrote:
    > On Fri, Nov 17, 2017 at 06:56:09PM +0100, Javier Martinez Canillas wrote:
    >
    >> Yes, the problem with that is user-space not having enough information about
    >> what went wrong. Right now the TCTI layer just reports TSS2_BASE_RC_IO_ERROR
    >> in this case and can't be blamed.
    >
    > Well, if you care about the differnce between a transport failure and
    > a kernel rejection due to validation, then it needs to report a
    > different code :)
    >

    Fair enough, the hard part I guess would be to decide which errno codes to use
    that could better map to the actual TPM_RC_COMMAND_{CODE,SIZE} response codes.

    I'll give some thought to this and also discuss with the tpm2 tools/tss folks.

    >>> Regarding your specific issue, can you make the command you want to
    >>> use validate? Would that make sense?
    >>
    >> Sorry, I'm not sure to understand what you meant. Could you please elaborate?
    >
    > Make it so tpm_validate will accept the command being sent.
    >

    Right, that's what I understood indeed but wanted to be sure. The problem with
    that approach is that would not scale.

    Since this particular TPM2 doesn't have support for the TPM2_EncryptDecrypt2
    command, but some chips may not support others commands. So I rather prefer to
    have a consistent way for the kernel to report when a command is found to not
    be supported and user-space to understand it.

    > Jason
    >

    Best regards,
    --
    Javier Martinez Canillas
    Software Engineer - Desktop Hardware Enablement
    Red Hat

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