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Message-ID: <aOEUAOUolS6mlf1n@kernel.org>
Date: Sat, 4 Oct 2025 15:33:04 +0300
From: Jarkko Sakkinen <jarkko@...nel.org>
To: Shahriyar Jalayeri <shahriyar@...teo.de>
Cc: Paul Menzel <pmenzel@...gen.mpg.de>, peterhuewe@....de, 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
On Sat, Oct 04, 2025 at 09:04:17AM +0000, Shahriyar Jalayeri wrote:
> Add two buffer size validations to prevent buffer
> overflows in tpm_inf_recv():
>
> 1. Validate that the provided buffer can hold at
> least the 4-byte header before attempting to
> read it.
What is this 4 byte header? Please describe what it is.
> 2. Validate that the buffer is large enough to
> hold the data size reported by the TPM before
> reading the payload.
>
> Without these checks, a malicious or malfunctioning
> TPM could cause buffer overflows by reporting data
> sizes larger than the provided buffer, leading to
> memory corruption.
>
> The error messages include both the expected and
> actual buffer sizes to indicate that the operation
> is aborted.
Paragraphs should be 75 chars per line.
>
> Signed-off-by: Shahriyar Jalayeri <shahriyar@...teo.de>
> ---
Please version your patches e.g., "git format-patch -v2"
And before diff stat it would be good to have a changelog.
> drivers/char/tpm/tpm_infineon.c | 19 ++++++++++++++++++-
> 1 file changed, 18 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/char/tpm/tpm_infineon.c b/drivers/char/tpm/tpm_infineon.c
> index 7638b65b8..385bac46a 100644
> --- a/drivers/char/tpm/tpm_infineon.c
> +++ b/drivers/char/tpm/tpm_infineon.c
> @@ -247,11 +247,20 @@ static int tpm_inf_recv(struct tpm_chip *chip, u8 * buf, size_t count)
> int i;
> int ret;
> u32 size = 0;
> + u32 header_size = 4;
Please don't use local variable for a constant.
> number_of_wtx = 0;
>
> recv_begin:
> + if (count < header_size) {
> + dev_err(&chip->dev,
> + "Buffer too small (count=%zd, header_size=%u), "
> + "operation aborted\n",
> + count, header_size);
> + return -EIO;
> + }
> +
> /* start receiving header */
> - for (i = 0; i < 4; i++) {
> + for (i = 0; i < header_size; i++) {
> ret = wait(chip, STAT_RDA);
> if (ret)
> return -EIO;
> @@ -268,6 +277,14 @@ 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 "
> + "(count=%zd, size=%u), operation aborted\n",
> + count, size);
> + return -EIO;
> + }
> +
> for (i = 0; i < size; i++) {
> wait(chip, STAT_RDA);
> buf[i] = tpm_data_in(RDFIFO);
> --
> 2.43.0
>
Other than that, same comments apply as for the previous version.
BR, Jarkko
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