Messages in this thread | | | Date | Wed, 20 Jul 2016 23:53:14 +0300 | From | Jarkko Sakkinen <> | Subject | Re: [PATCH] tpm: fix a race condition tpm2_unseal_trusted() |
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On Wed, Jul 20, 2016 at 10:48:18AM -0600, Jason Gunthorpe wrote: > On Wed, Jul 20, 2016 at 03:16:32AM +0300, Jarkko Sakkinen wrote: > > Unseal and load operations should be done as an atomic unit. This > > commit fixes the issue by moving TPM mutex handling to tpm_try_get_ops() > > and tpm_put_ops(), which is probably more logical place for it anyway. > > No.. > > 'get_ops' is to be used to hold a persisent kref to a single tpm. It > cannot block other tpm access. > > Eg a upper protocol might get_ops to for a long period to ensure it > consistently talks to the same TPM in a multi-tpm system. > > We need something else to solve whatever you are concerned with > here..
The only use cases I see at the moment for it work this way:
1. Call tpm_try_get_ops. 2. Send a TPM command. 3. Call tpm_put_ops.
I did not find any other form of use. The only use is to make sure that there are no transactions running before the ops are cleared. Or did I overlook something perhaps?
Trusted key unseal operation with TPM2 is broken into two operations:
1. Load the given key blob. 2. Unseal the data.
Without locking and unlocking mutex only once there is a race condition.
/Jarkko
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