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    Subject[PATCH 5.15 57/66] tpm: Fix buffer access in tpm2_get_tpm_pt()
    Date
    From: Stefan Mahnke-Hartmann <stefan.mahnke-hartmann@infineon.com>

    commit e57b2523bd37e6434f4e64c7a685e3715ad21e9a upstream.

    Under certain conditions uninitialized memory will be accessed.
    As described by TCG Trusted Platform Module Library Specification,
    rev. 1.59 (Part 3: Commands), if a TPM2_GetCapability is received,
    requesting a capability, the TPM in field upgrade mode may return a
    zero length list.
    Check the property count in tpm2_get_tpm_pt().

    Fixes: 2ab3241161b3 ("tpm: migrate tpm2_get_tpm_pt() to use struct tpm_buf")
    Cc: stable@vger.kernel.org
    Signed-off-by: Stefan Mahnke-Hartmann <stefan.mahnke-hartmann@infineon.com>
    Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
    Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/char/tpm/tpm2-cmd.c | 11 ++++++++++-
    1 file changed, 10 insertions(+), 1 deletion(-)

    --- a/drivers/char/tpm/tpm2-cmd.c
    +++ b/drivers/char/tpm/tpm2-cmd.c
    @@ -400,7 +400,16 @@ ssize_t tpm2_get_tpm_pt(struct tpm_chip
    if (!rc) {
    out = (struct tpm2_get_cap_out *)
    &buf.data[TPM_HEADER_SIZE];
    - *value = be32_to_cpu(out->value);
    + /*
    + * To prevent failing boot up of some systems, Infineon TPM2.0
    + * returns SUCCESS on TPM2_Startup in field upgrade mode. Also
    + * the TPM2_Getcapability command returns a zero length list
    + * in field upgrade mode.
    + */
    + if (be32_to_cpu(out->property_cnt) > 0)
    + *value = be32_to_cpu(out->value);
    + else
    + rc = -ENODATA;
    }
    tpm_buf_destroy(&buf);
    return rc;

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