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    SubjectRe: [PATCH 1/4] integrity: TPM internel kernel interface
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    Christoph Hellwig <hch@infradead.org> wrote on 08/09/2008 02:46:22 PM:

    > > +{
    > > + struct tpm_chip *pos;
    > > +
    > > + spin_lock(&driver_lock);
    > > + list_for_each_entry(pos, &tpm_chip_list, list) {
    > > + if ((chip_num == TPM_ANY_NUM || pos->dev_num == chip_num)
    > > + && (chip_typ == TPM_ANY_TYPE)) {
    > > + spin_unlock(&driver_lock);
    > > + return pos;
    > > + }
    > > + }
    > > +
    > > + spin_unlock(&driver_lock);
    >
    > besides the usual coding style issues, what protects the chip from going
    > away afer you dropped the lock?
    >

    I assume the concern here is that between looking up the chip and actually

    using the chip, the TPM chip is disabled/deactivated. Based on
    discussions
    with Kenneth Goldman, the TCG main specification part2: structures,
    require
    that even if the TPM is disabled/deactivated, the command to extend the
    PCR
    will succeed, but the command to read the PCR will fail with an
    appropriate
    error code.

    Mimi


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