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=-16.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 D2DCDC43462 for ; Thu, 15 Apr 2021 09:38:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9EBF56124B for ; Thu, 15 Apr 2021 09:38:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231947AbhDOJij (ORCPT ); Thu, 15 Apr 2021 05:38:39 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:40258 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231697AbhDOJii (ORCPT ); Thu, 15 Apr 2021 05:38:38 -0400 Received: from mail-ej1-f71.google.com ([209.85.218.71]) by youngberry.canonical.com with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1lWyRz-0005zk-4j for linux-i2c@vger.kernel.org; Thu, 15 Apr 2021 09:38:15 +0000 Received: by mail-ej1-f71.google.com with SMTP id p26-20020a170906a01ab0290373d37378f3so725261ejy.3 for ; Thu, 15 Apr 2021 02:38:15 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=4aRJNj2Va0WuSj7bZqa+mg+YnYSMlodN/I41H1ztfK0=; b=W5E/JUed4SOmaMqtXKJ1f0BV0gfAmPfqoSJvjGgK3e+HoMg5sUvvJuJHv2soFKtHdT xhEzjfxhecUSJJGpL7wxoBkvlVwpDyMI7xEf+/Qz8o9xS3pHQNp73Fr7zpKgkL6S+abQ 0X3cGpsZzokr4VB6OMnFxJ4DZig6Z8ja9vWr+XhYmvZ603ePQLwsToEp5WMO0FwvVpXf YwP04Y1J2SByfSPGSTTkIKh3yfI1c2jwidubRgNSXhiGDwXCban23FP6rK6iOLJliSmz Hrtdb+bOR9+oZrr8CUSR39toDHUlLk4Z8qCKHgNga34pe+Te1NT8wPu6CEA3Gs5ctzzm Lw1A== X-Gm-Message-State: AOAM5332B5KEJ0pTCCtjGrBnrYRvvefkBplYQxszaRLdHz1gYfr+dmd+ l+o1rl8PCnEAqPQcR/6H/ES39ocv/d0GaO60mmXD9ha8zoUFjHLw5USZxxzZj12yaHL1BttMOnU iKxjnNvKL7ywUuQMzw/pPMif31u4GZ0WCHMlYHg== X-Received: by 2002:a05:6402:12c3:: with SMTP id k3mr3104014edx.86.1618479494847; Thu, 15 Apr 2021 02:38:14 -0700 (PDT) X-Google-Smtp-Source: ABdhPJw8hCXucMNCy2MFa0IAxrCmDHgzWOO5+IZIekrpsC964e9WmaUDMs8NNfahxQW97g1nkmD62A== X-Received: by 2002:a05:6402:12c3:: with SMTP id k3mr3103999edx.86.1618479494737; Thu, 15 Apr 2021 02:38:14 -0700 (PDT) Received: from localhost.localdomain (xdsl-188-155-192-147.adslplus.ch. [188.155.192.147]) by smtp.gmail.com with ESMTPSA id cq26sm1954088edb.60.2021.04.15.02.38.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 15 Apr 2021 02:38:14 -0700 (PDT) From: Krzysztof Kozlowski To: Krzysztof Kozlowski , linux-i2c@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Marek Szyprowski , Sylwester Nawrocki , Alim Akhtar , Andrzej Hajda Subject: [RFT 2/2] i2c: s3c2410: fix possible NULL pointer deref on read message after write Date: Thu, 15 Apr 2021 11:38:03 +0200 Message-Id: <20210415093803.162673-2-krzysztof.kozlowski@canonical.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210415093803.162673-1-krzysztof.kozlowski@canonical.com> References: <20210415093803.162673-1-krzysztof.kozlowski@canonical.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-i2c@vger.kernel.org Interrupt handler processes multiple message write requests one after another, till the driver message queue is drained. However if driver encounters a read message without preceding START, it stops the I2C transfer as it is an invalid condition for the controller. At least the comment describes a requirement "the controller forces us to send a new START when we change direction". This stop results in clearing the message queue (i2c->msg = NULL). The code however immediately jumped back to label "retry_write" which dereferenced the "i2c->msg" making it a possible NULL pointer dereference. The Coverity analysis: 1. Condition !is_msgend(i2c), taking false branch. if (!is_msgend(i2c)) { 2. Condition !is_lastmsg(i2c), taking true branch. } else if (!is_lastmsg(i2c)) { 3. Condition i2c->msg->flags & 1, taking true branch. if (i2c->msg->flags & I2C_M_RD) { 4. write_zero_model: Passing i2c to s3c24xx_i2c_stop, which sets i2c->msg to NULL. s3c24xx_i2c_stop(i2c, -EINVAL); 5. Jumping to label retry_write. goto retry_write; All previous calls to s3c24xx_i2c_stop() in this interrupt service routine are followed by jumping to end of function (acknowledging the interrupt and returning). This seems a reasonable choice also here since message buffer was entirely emptied. Addresses-Coverity: Explicit null dereferenced Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Krzysztof Kozlowski --- drivers/i2c/busses/i2c-s3c2410.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/i2c/busses/i2c-s3c2410.c b/drivers/i2c/busses/i2c-s3c2410.c index ab928613afba..4d82761e1585 100644 --- a/drivers/i2c/busses/i2c-s3c2410.c +++ b/drivers/i2c/busses/i2c-s3c2410.c @@ -480,7 +480,10 @@ static int i2c_s3c_irq_nextbyte(struct s3c24xx_i2c *i2c, unsigned long iicstat) * forces us to send a new START * when we change direction */ + dev_dbg(i2c->dev, + "missing START before write->read\n"); s3c24xx_i2c_stop(i2c, -EINVAL); + break; } goto retry_write; -- 2.25.1