On Fri, Oct 10, 2025 at 06:52:55AM +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.
> 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 <[email protected]>
> ---
> 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..0fe4193a3 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 */
This is definitely good enough :-)
But is that comment misaligned? Does VL come from "VLAN"?
> + 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 */
I'd delete the above comment.
> size = ((buf[2] << 8) | buf[3]);
And use here:
https://elixir.bootlin.com/linux/v6.17.1/source/include/linux/byteorder/generic.h#L108
Not exactly in scope but it would be good convention and make
the check after it more readable.
>
> + if (size + 6 > count)
> + return -EIO;
> +
> for (i = 0; i < size; i++) {
> wait(chip, STAT_RDA);
> buf[i] = tpm_data_in(RDFIFO);
> --
> 2.43.0
>
BR, Jarkko
