linux-kernel - Re: [PATCH] tpm: infineon: add bounds check in tpm_inf

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Message-ID: <c0a4d2bb-be78-4aac-b66b-c1eb766e7efd@molgen.mpg.de>
Date: Fri, 3 Oct 2025 13:22:11 +0200
From: Paul Menzel <pmenzel@...gen.mpg.de>
To: Shahriyar Jalayeri <shahriyar@...teo.de>
Cc: peterhuewe@....de, jarkko@...nel.org, jgg@...pe.ca,
 linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tpm: infineon: add bounds check in tpm_inf_recv

Dear Shahriyar,


Thank you for your patch.

Am 03.10.25 um 11:25 schrieb Shahriyar Jalayeri:
> Ensure tpm_inf_recv() does not overflow the provided buffer when
> the TPM reports more data than the caller expects.

Is it possible to enforce this situation to ensure your patch works?

> Signed-off-by: Shahriyar Jalayeri <shahriyar@...teo.de>
> ---
>   drivers/char/tpm/tpm_infineon.c | 12 ++++++++++++
>   1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/char/tpm/tpm_infineon.c b/drivers/char/tpm/tpm_infineon.c
> index 7638b65b8..eb6dd55ff 100644
> --- a/drivers/char/tpm/tpm_infineon.c
> +++ b/drivers/char/tpm/tpm_infineon.c
> @@ -250,6 +250,12 @@ static int tpm_inf_recv(struct tpm_chip *chip, u8 * buf, size_t count)
>   	number_of_wtx = 0;
>   
>   recv_begin:
> +	if (count < 4) {
> +		dev_err(&chip->dev,
> +			"count less than the header size!\n");

Mention both values count and 4?

> +		return -EIO;
> +	}
> +

This is not described in the commit message.

>   	/* start receiving header */
>   	for (i = 0; i < 4; i++) {
>   		ret = wait(chip, STAT_RDA);
> @@ -268,6 +274,12 @@ static int tpm_inf_recv(struct tpm_chip *chip, u8 * buf, size_t count)
>   		/* size of the data received */
>   		size = ((buf[2] << 8) | buf[3]);
>   
> +		if (size > count) {
> +			dev_err(&chip->dev,
> +				"Buffer too small for incoming data!\n");

I’d log both values, and also specify that the operation is aborted.

> +			return -EIO;
> +		}
> +
>   		for (i = 0; i < size; i++) {
>   			wait(chip, STAT_RDA);
>   			buf[i] = tpm_data_in(RDFIFO);


Kind regards,

Paul