Messages in this thread | | | Date | Tue, 9 Aug 2016 13:36:29 +0300 | From | Jarkko Sakkinen <> | Subject | Re: [PATCH] tpm: fix a race condition tpm2_unseal_trusted() |
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On Thu, Jul 21, 2016 at 10:25:36AM -0600, Jason Gunthorpe wrote: > On Thu, Jul 21, 2016 at 12:02:45PM +0300, Jarkko Sakkinen wrote: > > On Wed, Jul 20, 2016 at 03:13:32PM -0600, Jason Gunthorpe wrote: > > > On Wed, Jul 20, 2016 at 11:53:14PM +0300, Jarkko Sakkinen wrote: > > > > > > > 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. > > > > > > Right, but that is just a reflection of what the in kernel users are > > > doing today, not necessarily what they should be doing. > > > > > > We should not break the put/get semantics.. > > > > > > > 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? > > > > > > The put/get is intended to allow a kapi user to hold a ref to tpm > > > without it geting destroyed. It is not intended to be an exclusive lock. > > > > These operations *are not* exposed to kapi. They are interal to the > > driver. That's why it does not make sense speak about kapi user. > > Right now yes, but look at other subsystems and you will see > operations like that, because that is typical design pattern. When I > wrote them I made sure they could be used in that typical way. > > We have issues in our kapi users with regards to hot plug and multiple > tpms. Fortunately that basically never happens, but it does indicate > the API is not sufficient..
Functionally my patch should not break anything. I understand the need for clean up of locking but why doing this now to make the driver non-racy would make clean up later on any harder?
I would rather think of clean up after the code is non-racy than doing a huge clean up for racy code. Correct functionality is more important than clean code because it has direct effect to users.
/Jarkko
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