From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from bedivere.hansenpartnership.com ([66.63.167.143]:59584 "EHLO bedivere.hansenpartnership.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752054AbeBHUbR (ORCPT ); Thu, 8 Feb 2018 15:31:17 -0500 Message-ID: <1518121876.21828.16.camel@HansenPartnership.com> Subject: [PATCH v2 4/5] tpm_i2c_nuvoton: fix potential buffer overruns caused by bit glitches on the bus From: James Bottomley To: linux-integrity@vger.kernel.org Cc: Jeremy Boone , Jarkko Sakkinen Date: Thu, 08 Feb 2018 12:31:16 -0800 In-Reply-To: <1518121576.21828.10.camel@HansenPartnership.com> References: <1518121576.21828.10.camel@HansenPartnership.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Sender: linux-integrity-owner@vger.kernel.org List-ID: From: Jeremy Boone Discrete TPMs are often connected over slow serial buses which, on some platforms, can have glitches causing bit flips. In all the driver _recv() functions, we need to use a u32 to unmarshal the response size, otherwise a bit flip of the 31st bit would cause the expected variable to go negative, which would then try to read a huge amount of data. Also sanity check that the expected amount of data is large enough for the TPM header. Signed-off-by: Jeremy Boone Cc: stable@vger.kernel.org Signed-off-by: James Bottomley --- drivers/char/tpm/tpm_i2c_nuvoton.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/char/tpm/tpm_i2c_nuvoton.c b/drivers/char/tpm/tpm_i2c_nuvoton.c index c6428771841f..17cf7af9a2c5 100644 --- a/drivers/char/tpm/tpm_i2c_nuvoton.c +++ b/drivers/char/tpm/tpm_i2c_nuvoton.c @@ -281,7 +281,8 @@ static int i2c_nuvoton_recv(struct tpm_chip *chip, u8 *buf, size_t count) struct device *dev = chip->dev.parent; struct i2c_client *client = to_i2c_client(dev); s32 rc; - int expected, status, burst_count, retries, size = 0; + int status, burst_count, retries, size = 0; + u32 expected; if (count < TPM_HEADER_SIZE) { i2c_nuvoton_ready(chip); /* return to idle */ @@ -323,7 +324,7 @@ static int i2c_nuvoton_recv(struct tpm_chip *chip, u8 *buf, size_t count) * to machine native */ expected = be32_to_cpu(*(__be32 *) (buf + 2)); - if (expected > count) { + if (expected > count || expected < size) { dev_err(dev, "%s() expected > count\n", __func__); size = -EIO; continue; -- 2.12.3