From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from wtarreau.pck.nerim.net ([62.212.114.60]:36256 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934672AbbEOIQJ (ORCPT ); Fri, 15 May 2015 04:16:09 -0400 Message-Id: <20150515080531.940427223@1wt.eu> Date: Fri, 15 May 2015 10:06:09 +0200 From: Willy Tarreau To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Ian Abbott , Mark Brown , Ben Hutchings , Willy Tarreau Subject: [ 39/48] spi: spidev: fix possible arithmetic overflow for multi-transfer message MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 In-Reply-To: <9c2783dfae10ef2d1e9b08bcc1e562c5@local> Sender: stable-owner@vger.kernel.org List-ID: 2.6.32-longterm 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 [Ian Abbott: Note: original commit compares the lengths to INT_MAX instead of bufsiz due to changes in earlier commits.] Signed-off-by: Ben Hutchings (cherry picked from commit 7499401e4a0b01ee43cff768de4ca630dcd0bc64) Signed-off-by: Willy Tarreau --- 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 5d23983..4dd8e2a 100644 --- a/drivers/spi/spidev.c +++ b/drivers/spi/spidev.c @@ -241,7 +241,10 @@ 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; } -- 1.7.12.2.21.g234cd45.dirty