linux-kernel - Re: [PATCH v2] tpm: Clean up TPM space after command failure

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Message-Id: <D3HDPTAXDU8P.5CUQ1ECMIG2X@kernel.org>
Date: Fri, 16 Aug 2024 16:44:01 +0300
From: "Jarkko Sakkinen" <jarkko@...nel.org>
To: "Jonathan McDowell" <noodles@...th.li>, "Peter Huewe"
 <peterhuewe@....de>, "Jason Gunthorpe" <jgg@...pe.ca>, "James Bottomley"
 <James.Bottomley@...senpartnership.com>, <linux-integrity@...r.kernel.org>,
 <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] tpm: Clean up TPM space after command failure

On Fri Aug 16, 2024 at 2:55 PM EEST, Jonathan McDowell wrote:
> From: Jonathan McDowell <noodles@...a.com>
>
> tpm_dev_transmit prepares the TPM space before attempting command
> transmission. However if the command fails no rollback of this
> preparation is done. This can result in transient handles being leaked
> if the device is subsequently closed with no further commands performed.
>
> Fix this by flushing the space in the event of command transmission
> failure.
>
> Fixes: 745b361e989a ("tpm: infrastructure for TPM spaces")
> Signed-off-by: Jonathan McDowell <noodles@...a.com>
> ---
> v2:
>  - Add 'Fixes:'
>  - Cc James as one of the original authors
>  - Add space sanity check in tpm2_flush_space
>
>  drivers/char/tpm/tpm-dev-common.c | 2 ++
>  drivers/char/tpm/tpm2-space.c     | 3 +++
>  2 files changed, 5 insertions(+)
>
> diff --git a/drivers/char/tpm/tpm-dev-common.c b/drivers/char/tpm/tpm-dev-common.c
> index 30b4c288c1bb..c3fbbf4d3db7 100644
> --- a/drivers/char/tpm/tpm-dev-common.c
> +++ b/drivers/char/tpm/tpm-dev-common.c
> @@ -47,6 +47,8 @@ static ssize_t tpm_dev_transmit(struct tpm_chip *chip, struct tpm_space *space,
>  
>  	if (!ret)
>  		ret = tpm2_commit_space(chip, space, buf, &len);
> +	else
> +		tpm2_flush_space(chip);
>  
>  out_rc:
>  	return ret ? ret : len;
> diff --git a/drivers/char/tpm/tpm2-space.c b/drivers/char/tpm/tpm2-space.c
> index 4892d491da8d..25a66870c165 100644
> --- a/drivers/char/tpm/tpm2-space.c
> +++ b/drivers/char/tpm/tpm2-space.c
> @@ -169,6 +169,9 @@ void tpm2_flush_space(struct tpm_chip *chip)
>  	struct tpm_space *space = &chip->work_space;
>  	int i;
>  
> +	if (!space)
> +		return;
> +
>  	for (i = 0; i < ARRAY_SIZE(space->context_tbl); i++)
>  		if (space->context_tbl[i] && ~space->context_tbl[i])
>  			tpm2_flush_context(chip, space->context_tbl[i]);

I'll pick this for 6.12: I think it is a legit fix but not worth of
disturbing the in-progress release cycle (which is going almost rc4
already):

Reviewed-by: Jarkko Sakkinen <jarkko@...nel.org>

Thank you.

BR, Jarkko