Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751810AbbEGJqx (ORCPT ); Thu, 7 May 2015 05:46:53 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:47295 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751314AbbEGJqo (ORCPT ); Thu, 7 May 2015 05:46:44 -0400 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Ian Abbott , Mark Brown , Luis Henriques Subject: [PATCH 3.16.y-ckt 002/180] spi: spidev: fix possible arithmetic overflow for multi-transfer message Date: Thu, 7 May 2015 10:43:31 +0100 Message-Id: <1430991989-23170-3-git-send-email-luis.henriques@canonical.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1430991989-23170-1-git-send-email-luis.henriques@canonical.com> References: <1430991989-23170-1-git-send-email-luis.henriques@canonical.com> X-Extended-Stable: 3.16 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2097 Lines: 51 3.16.7-ckt11 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Ian Abbott commit f20fbaad7620af2df36a1f9d1c9ecf48ead5b747 upstream. `spidev_message()` sums the lengths of the individual SPI transfers to determine the overall SPI message length. It restricts the total length, returning an error if too long, but it does not check for arithmetic overflow. For example, if the SPI message consisted of two transfers and the first has a length of 10 and the second has a length of (__u32)(-1), the total length would be seen as 9, even though the second transfer is actually very long. If the second transfer specifies a null `rx_buf` and a non-null `tx_buf`, the `copy_from_user()` could overrun the spidev's pre-allocated tx buffer before it reaches an invalid user memory address. Fix it by checking that neither the total nor the individual transfer lengths exceed the maximum allowed value. Thanks to Dan Carpenter for reporting the potential integer overflow. Signed-off-by: Ian Abbott Signed-off-by: Mark Brown [ luis: backported to 3.16: used backport provided by Ian ] Signed-off-by: Luis Henriques --- drivers/spi/spidev.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/drivers/spi/spidev.c b/drivers/spi/spidev.c index e3bc23bb5883..621df17214a5 100644 --- a/drivers/spi/spidev.c +++ b/drivers/spi/spidev.c @@ -244,7 +244,10 @@ static int spidev_message(struct spidev_data *spidev, k_tmp->len = u_tmp->len; total += k_tmp->len; - if (total > bufsiz) { + /* Check total length of transfers. Also check each + * transfer length to avoid arithmetic overflow. + */ + if (total > bufsiz || k_tmp->len > bufsiz) { status = -EMSGSIZE; goto done; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/