From patchwork Mon Jun 26 02:44:29 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Li Tuo X-Patchwork-Id: 92725 Received: from vger.kernel.org ([23.128.96.18]) by www.linuxtv.org with esmtp (Exim 4.92) (envelope-from ) id 1qDcDz-0084Im-M8; Mon, 26 Jun 2023 02:45:08 +0000 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230104AbjFZCpF (ORCPT + 1 other); Sun, 25 Jun 2023 22:45:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44200 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231134AbjFZCoz (ORCPT ); Sun, 25 Jun 2023 22:44:55 -0400 Received: from mail-pj1-x1029.google.com (mail-pj1-x1029.google.com [IPv6:2607:f8b0:4864:20::1029]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 55BCFE7; Sun, 25 Jun 2023 19:44:54 -0700 (PDT) Received: by mail-pj1-x1029.google.com with SMTP id 98e67ed59e1d1-262e839647eso704604a91.2; Sun, 25 Jun 2023 19:44:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1687747494; x=1690339494; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=QcoEetkUYJEXKBOLQWwPPuBN/feg1Dag8bMvH33Pf/s=; b=NUTMwh3INPCVhHlFkUQxtTQ2i0zj8GT0N9HIgPMEu9lQX9MtpNsdqd1k9ARhmLJAnf 1mj38H0tths6ud0yl9vp/wHJ3w2gxxGOc1d28M+OO98WtTs/3ONFepL23oVd1Q3ISysA Vem6zUzO6wAM3q2AYfXHiCTewLHDbRvBX75pyd1W718RIuKB7lc9n/0balpf8BP7X4ds IXQ56jC+vxt0/USsYNJHi02K9TDwnp8NhSk3cEEAKtHMqZ8rgOQtsD6VyrseYJdHM4nr I8TIvlN6Ed8Gd1DDCLidrGZ2g3amzE3jcoDQpV38zkd1B31cFD8gfExpyGG45Ty0rxVt ub3A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1687747494; x=1690339494; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=QcoEetkUYJEXKBOLQWwPPuBN/feg1Dag8bMvH33Pf/s=; b=LQLSebeZUl0kZns1gE0DOmz/mJVRI0swzOE7WUYdL3IHHcx5V62x+KmPdwWXFomsSn E3zA0eUZAZHE/8/nTawwPyO73Yz3v+91q2u8pC/fnxAa/gXQWHLVfrQP72AEF82hJ8HA SUyGFfgXdGq4z0BDn+gmwBP/Bg0IZqjBMONMaeEGzijeVa/AXnsMqDeeKvJWNW/wbv8o uPGBQnsFAnPiqbaktzfoPFgCsa6ez/QT29SML7XR8MvbQzl2L5ck2SoEgkOy5SQWuQi8 LACZHu5STW/AClZdTx8Nxu7IFlZeM+geCorvhrxGjVHEcNP0i9fS3xdsk74NECBu0+Ak TVYQ== X-Gm-Message-State: AC+VfDwbYXqnvM//fE5s2I0Fezkhal51KrTPTNf/6i2ALTVhGiBEKPiK zc2pR3iaUcQ0pzlKD/lmorA= X-Google-Smtp-Source: ACHHUZ6JiHGb4Um9Iewl0YM9ptygQkUjOcrCWXlGbc6EiLUckuZKPIiBJTA3HDfRpMQtHM07UqDiWw== X-Received: by 2002:a17:90a:199:b0:25b:d8fe:2c92 with SMTP id 25-20020a17090a019900b0025bd8fe2c92mr24951784pjc.48.1687747493748; Sun, 25 Jun 2023 19:44:53 -0700 (PDT) Received: from oslab-pc.tsinghua.edu.cn ([166.111.139.122]) by smtp.gmail.com with ESMTPSA id p12-20020a17090a284c00b00256799877ffsm3486687pjf.47.2023.06.25.19.44.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 25 Jun 2023 19:44:53 -0700 (PDT) From: Tuo Li To: mchehab@kernel.org, yongsuyoo0215@gmail.com, tommaso.merciai@amarulasolutions.com, colin.i.king@gmail.com, hverkuil-cisco@xs4all.nl Cc: linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, baijiaju1990@outlook.com, Tuo Li , BassCheck Subject: [PATCH] media: dvb-core: Fix a possible null-pointer dereference due to data race in dvbdmx_write() Date: Mon, 26 Jun 2023 10:44:29 +0800 Message-Id: <20230626024429.994136-1-islituo@gmail.com> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_FROM, RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org X-LSpam-Score: -4.8 (----) X-LSpam-Report: No, score=-4.8 required=5.0 tests=BAYES_00=-1.9,DKIM_SIGNED=0.1,DKIM_VALID=-0.1,DKIM_VALID_AU=-0.1,FREEMAIL_FORGED_FROMDOMAIN=0.001,FREEMAIL_FROM=0.001,HEADER_FROM_DIFFERENT_DOMAINS=0.5,MAILING_LIST_MULTI=-1,RCVD_IN_DNSWL_MED=-2.3 autolearn=ham autolearn_force=no The struct field dmx_demux.frontend is often protected by the lock dvb_demux.mutex when is accessed. Here is an example in dvbdmx_connect_frontend(): mutex_lock(&dvbdemux->mutex); demux->frontend = frontend; mutex_unlock(&dvbdemux->mutex); However, the variable demux->frontend is accessed without holding the lock dvbdemux->mutex in dvbdmx_write(): if ((!demux->frontend) || (demux->frontend->source != DMX_MEMORY_FE)) In my opinion, this may be a harmful race, because if demux->fontend is set to NULL right after the first condition is checked, a null-pointer dereference can occur when accessing the field demux->frontend->source. To fix this possible null-pointer dereference caused by data race, a lock and unlock pair is added when accessing the variable demux->frontend. Reported-by: BassCheck Signed-off-by: Tuo Li --- drivers/media/dvb-core/dvb_demux.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/drivers/media/dvb-core/dvb_demux.c b/drivers/media/dvb-core/dvb_demux.c index 7c4d86bfdd6c..d26738e3310a 100644 --- a/drivers/media/dvb-core/dvb_demux.c +++ b/drivers/media/dvb-core/dvb_demux.c @@ -1140,9 +1140,13 @@ static int dvbdmx_write(struct dmx_demux *demux, const char __user *buf, size_t { struct dvb_demux *dvbdemux = (struct dvb_demux *)demux; void *p; - - if ((!demux->frontend) || (demux->frontend->source != DMX_MEMORY_FE)) + + mutex_lock(&dvbdemux->mutex); + if ((!demux->frontend) || (demux->frontend->source != DMX_MEMORY_FE)) { + mutex_unlock(&dvbdemux->mutex); return -EINVAL; + } + mutex_unlock(&dvbdemux->mutex); p = memdup_user(buf, count); if (IS_ERR(p))