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Re: [PATCH] tpm: fix a race condition in tpm2_unseal_trusted()

From Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Newsgroups linux.kernel
Subject Re: [PATCH] tpm: fix a race condition in tpm2_unseal_trusted()
Date 2016-08-28 21:00 +0200
Message-ID <sbdtg-5lr-3@gated-at.bofh.it> (permalink)
References <sb1V8-6BZ-21@gated-at.bofh.it>
Organization linux.* mail to news gateway

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On Sun, Aug 28, 2016 at 08:36:52AM +0200, Jarkko Sakkinen wrote:
>  
> @@ -576,7 +576,8 @@ static int tpm2_load(struct tpm_chip *chip,
>  		goto out;
>  	}
>  
> -	rc = tpm_transmit_cmd(chip, buf.data, PAGE_SIZE, "loading blob");
> +	rc = tpm_transmit_cmd(chip, buf.data, PAGE_SIZE, TPM_TRANSMIT_UNLOCKED,
> +			      "loading blob");

I still don't like this, required mutex's should not be split outside the
function that needs them without more a more obvious indication:

> +	mutex_lock(&chip->tpm_mutex);
>  	rc = tpm2_load(chip, payload, options, &blob_handle);
>  	if (rc)
> -		return rc;

I recommend you stick with the idiom and do this:

        mutex_lock(&chip->tpm_mutex);
  	rc = tpm2_load(chip, payload, options, &blob_handle, TPM_TRANSMIT_UNLOCKED);

Which makes it easy to see we are doing it right everywhere.

Jason

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Thread

[PATCH] tpm: fix a race condition in tpm2_unseal_trusted() Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com> - 2016-08-28 08:40 +0200
  Re: [PATCH] tpm: fix a race condition in tpm2_unseal_trusted() Jason Gunthorpe <jgunthorpe@obsidianresearch.com> - 2016-08-28 21:00 +0200
    Re: [PATCH] tpm: fix a race condition in tpm2_unseal_trusted() Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com> - 2016-08-29 17:30 +0200
      Re: [PATCH] tpm: fix a race condition in tpm2_unseal_trusted() Jason Gunthorpe <jgunthorpe@obsidianresearch.com> - 2016-08-29 21:30 +0200
        Re: [PATCH] tpm: fix a race condition in tpm2_unseal_trusted() Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com> - 2016-08-29 21:50 +0200
          Re: [PATCH] tpm: fix a race condition in tpm2_unseal_trusted() Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com> - 2016-08-29 22:10 +0200
            Re: [PATCH] tpm: fix a race condition in tpm2_unseal_trusted() Jason Gunthorpe <jgunthorpe@obsidianresearch.com> - 2016-08-29 22:10 +0200

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