From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-17.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_2 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 799E2C64E7B for ; Fri, 27 Nov 2020 11:14:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 23AEC2224A for ; Fri, 27 Nov 2020 11:14:30 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="R5uRv8Im" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727737AbgK0LOT (ORCPT ); Fri, 27 Nov 2020 06:14:19 -0500 Received: from mail.kernel.org ([198.145.29.99]:53532 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725616AbgK0LOS (ORCPT ); Fri, 27 Nov 2020 06:14:18 -0500 Received: from coco.lan (ip5f5ad5a6.dynamic.kabel-deutschland.de [95.90.213.166]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id EA54721527; Fri, 27 Nov 2020 11:14:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1606475657; bh=UUHBLygREjHYXn3z1M033GRc6uSd/b7ObYwCOHWwod8=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=R5uRv8ImrJl1TIvMjjrXi8QUS5/ZkIsqaHATSP0jbwCGdIG8Q8vxZSarNQXImurFe JWekhIK4QpTFZolQrm1dzdBZ81/7MoQ/YtIDH33G8DZ3DCOPztbu/7/zld5/UtxzIx NXvscXKSJB6dHftOxfMyRxN4Z0vcc+7UBlacXV84= Date: Fri, 27 Nov 2020 12:14:12 +0100 From: Mauro Carvalho Chehab To: Jia-Ju Bai Cc: stanimir.varbanov@linaro.org, agross@kernel.org, bjorn.andersson@linaro.org, linux-media@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] media: venus: fix possible buffer overlow casued bad DMA value in venus_sfr_print() Message-ID: <20201127121412.2c982188@coco.lan> In-Reply-To: <20200530024117.24613-1-baijiaju1990@gmail.com> References: <20200530024117.24613-1-baijiaju1990@gmail.com> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.32; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org Em Sat, 30 May 2020 10:41:17 +0800 Jia-Ju Bai escreveu: > The value hdev->sfr.kva is stored in DMA memory, and it is assigned to > sfr, so sfr->buf_size can be modified at anytime by malicious hardware. > In this case, a buffer overflow may happen when the code > "sfr->data[sfr->buf_size - 1]" is executed. > > To fix this possible bug, sfr->buf_size is assigned to a local variable, > and then this variable is checked before being used. > > Signed-off-by: Jia-Ju Bai > --- > drivers/media/platform/qcom/venus/hfi_venus.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/drivers/media/platform/qcom/venus/hfi_venus.c b/drivers/media/platform/qcom/venus/hfi_venus.c > index 0d8855014ab3..4251a9e47a1b 100644 > --- a/drivers/media/platform/qcom/venus/hfi_venus.c > +++ b/drivers/media/platform/qcom/venus/hfi_venus.c > @@ -960,18 +960,23 @@ static void venus_sfr_print(struct venus_hfi_device *hdev) > { > struct device *dev = hdev->core->dev; > struct hfi_sfr *sfr = hdev->sfr.kva; > + u32 buf_size; > void *p; > > if (!sfr) > return; > > - p = memchr(sfr->data, '\0', sfr->buf_size); > + buf_size = sfr->buf_size; > + if (buf_size > 1) That seems plain wrong to me... I suspect you wanted to do, instead: if (buf_size < 1) or even: if (buf_size < 1 || buf_size >= maximum_size_of_data) > + return; > + > + p = memchr(sfr->data, '\0', buf_size); > /* > * SFR isn't guaranteed to be NULL terminated since SYS_ERROR indicates > * that Venus is in the process of crashing. > */ > if (!p) > - sfr->data[sfr->buf_size - 1] = '\0'; > + sfr->data[buf_size - 1] = '\0'; Well, a malicious hardware with DMA access could simply write 0 to some random address, without needing to rely on the value of sfr->buf_size. I can't see how a change like that would prevent that. A check like that only makes sense if the driver can ever call this function with an invalid value for sfr->buf_size. > > dev_err_ratelimited(dev, "SFR message from FW: %s\n", sfr->data); > } Thanks, Mauro