On Fri, May 12, 2017 at 04:40:58PM -0700, Josh Zimmerman wrote:
> If a TPM2 loses power without a TPM2_Shutdown command being issued, it
> may lose some state that has yet to be persisted to NVRam, and will
> increment the DA counter (meaning that after too many disorderly
> reboots, the TPM will lock the user out).
>
> This is a variant of https://patchwork.kernel.org/patch/9516631/.
> It differs in that:
> * It only changes behavior on TPM2 devices, to avoid invoking the
> unbounded-waiting sysfs codepath that was discussed on that patch, and
> to avoid racing on chip->ops.
> * It modifies tpm-chip rather than tpm_i2c_infineon, so that it can
> change behavior for all TPM2 devices.
>
> This patch is dependent on '[PATCH] Add "shutdown" to "struct class".'
> http://marc.info/?l=linux-kernel&m=149463235025420&w=2
Looks like it includes that patch. You need split this and send both
to Greg as he requested.
> +static void tpm_shutdown(struct device *dev)
> +{
> + struct tpm_chip *chip = container_of(dev, struct tpm_chip, dev);
> + // TPM 2.0 requires that the TPM2_Shutdown() command be issued prior to
> + // loss of power. If it is not, the DA counter will be incremented and,
> + // eventually, the user will be locked out of their TPM.
> + // XXX: This codepath relies on the fact that sysfs is not enabled for
> + // TPM2: sysfs uses an implicit lock on chip->ops, so this use could
> + // race if TPM2 has sysfs support enabled before TPM sysfs's implicit
> + // locking is fixed.
Please use the same block comment format as the rest of the file
> + if (chip->flags & TPM_CHIP_FLAG_TPM2) {
> + down_read(&chip->ops_sem);
This needs to be down_write
Jason
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