Re: [PATCH v5] tpm: infineon: add bounds check in tpm_inf_recv

Paul Menzel
2025-10-10T08:03:02Z

Dear Shahriyar,

Thank you for the improved version.

Am 10.10.25 um 09:49 schrieb Shahriyar Jalayeri:
> 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.
> 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.
>
> Fixes: ebb81fdb3dd0 ("[PATCH] tpm: Support for Infineon TPM")
> Signed-off-by: Shahriyar Jalayeri <shahriyar@posteo.de>
> ---
> Changelog:
> v5:
> - replaced space indentation with tabs before the header comment
> v4:
> - removed the curly braces around one line statements
> v3:
> - removed dev_err() logs
> - added missing "fixes" tag
> - described header structure
> - fixed commit message length
> - removed use of local variable as constant
> - fixed check to account for off-by-six bytes
> v2:
> - added complete changes in the commit message
> - dev_err() logged expected sizes and stated operation is aborted
>
> drivers/char/tpm/tpm_infineon.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/drivers/char/tpm/tpm_infineon.c b/drivers/char/tpm/tpm_infineon.c
> index 7638b65b8..d76aae08b 100644
> --- a/drivers/char/tpm/tpm_infineon.c
> +++ b/drivers/char/tpm/tpm_infineon.c
> @@ -250,6 +250,10 @@ static int tpm_inf_recv(struct tpm_chip *chip, u8 * buf, size_t count)
> number_of_wtx = 0;
>
> recv_begin:
> + /* expect at least 1-byte VL header, 1-byte ctrl-tag, 2-byte data size */
> + if (count < 4)
> + return -EIO;
> +
> /* start receiving header */
> for (i = 0; i < 4; i++) {
> ret = wait(chip, STAT_RDA);
> @@ -268,6 +272,9 @@ 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 + 6 > count)
> + return -EIO;
> +
> for (i = 0; i < size; i++) {
> wait(chip, STAT_RDA);
> buf[i] = tpm_data_in(RDFIFO);

Reviewed-by: Paul Menzel <pmenzel@molgen.mpg.de>

Kind regards,

Paul