Re: [PATCH] tpm: fix crash in tpm_tis

From	Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH] tpm: fix crash in tpm_tis
Date	2016-04-11 10:50 +0200
Message-ID	<rmFHJ-2Ui-31@gated-at.bofh.it> (permalink)
References	<rlhHt-3TE-29@gated-at.bofh.it> <rmFHJ-2Ui-33@gated-at.bofh.it>
Organization	Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo

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On Thu, Apr 07, 2016 at 07:36:54AM -0700, Jason Gunthorpe wrote:
>    I will have to look closer after the conference, but this does not look
>    right.
> 
>    I vaguely recall commenting on this before. Move the shutdown into the
>    core code to fix it.

This fix that I sent is not the right way to do it.

One example scenario:

1. TIS driver gets detached, which causes tpm_tis_remove() to be called.
2. Some in-kernel subsystem uses TPM, which should not be done since the
   hardware is already unitialized.
3. The devres subsystem sets ops to NULL.

Even though the fix is wrong I feel that it might put the rwsem into
question.

I'm just thinking that maybe there could be a release callback in
tpm_class_ops that could be called by tpm_del_char_device(). There can't
be clients for the chip at that point so no synchronization mechanism
is needed.

>    Jason

/Jarkko

Thread

[PATCH] tpm: fix crash in tpm_tis Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com> - 2016-04-07 15:00 +0200
  Re: [PATCH] tpm: fix crash in tpm_tis Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com> - 2016-04-11 10:50 +0200
    Re: [PATCH] tpm: fix crash in tpm_tis Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com> - 2016-04-11 13:20 +0200

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