From patchwork Wed Nov 8 09:13:00 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Li Tuo X-Patchwork-Id: 96803 Received: from vger.kernel.org ([23.128.96.18]) by www.linuxtv.org with esmtp (Exim 4.92) (envelope-from ) id 1r0ech-002d4w-PS; Wed, 08 Nov 2023 09:13:20 +0000 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235515AbjKHJNT (ORCPT + 1 other); Wed, 8 Nov 2023 04:13:19 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55686 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235408AbjKHJNS (ORCPT ); Wed, 8 Nov 2023 04:13:18 -0500 Received: from mail-pf1-x436.google.com (mail-pf1-x436.google.com [IPv6:2607:f8b0:4864:20::436]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C82EE9F; Wed, 8 Nov 2023 01:13:16 -0800 (PST) Received: by mail-pf1-x436.google.com with SMTP id d2e1a72fcca58-6be1bc5aa1cso6721387b3a.3; Wed, 08 Nov 2023 01:13:16 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1699434796; x=1700039596; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=HCAzZOLM6VBb1qJenEGSAomGqBz67B3OQEi+85kaQbs=; b=OyDyunivj2M6jQFCUaR36ZbZiivNlnFhIi9qbUl6qQ8LOzeTsRX50xPUOJq2KQRbCt 93mU5a+dozhTFgChgzL3IDNEnzYbDFnfvqn3TnmtwpMRD7zkqp3yai/UwRT9YVftGiLX GkJ6lSrz3FXpOgNaE2WTHZ5D7KvFu89AbmuwzcaK2VUtjdldS3WwNCbk0fwgiXkjvkSb F2hPXeAUgNOcpro/03JJmJ7q+N5zQBTjks5FZajpUSg4dzvYRqyPabyoDvGYMZIviYNl iB0FXlchmr3YSWATAgiq7nrXSdfyCZcepXRUYGeFIz6qvXoqrGnAq9Dw0qS9zRk6X62c Ieqw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1699434796; x=1700039596; 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=HCAzZOLM6VBb1qJenEGSAomGqBz67B3OQEi+85kaQbs=; b=g2zns5KbYkae2+UXarLh0LpM4u1of1FWo03aKBM5Gi6RJNYD7OftR4thsc76zXcNXp 460fL3BRCI1BlzdAJtdyR2Zi0vZrTqWdwUy6A2nXNUkF0OwVdHca422dLEDRp8Dn/lUp a64hyLMLPIOdW0S8Tu4tCyhpf6NjWIfYlg1SmtArBO6Ujo/+yrBz6aWoegVta7eKIQtg EoULIKs+DvlNJFm+UIYCtjVS1b4BTTm9RTU0kBDWVa6InSFo/rYysTJIVBT/3YZad8aV 0EQAFOGoclP98CNqQOMlF0CInzVMNuJ5pMf1I2bKaps1jHOcxwHQH6aRC7SgTLcVW/0d 4nZQ== X-Gm-Message-State: AOJu0YzcJBgEg1Fv+6h0VEBt1IPIqOQP7lDRBg7+ITCul5XY5UYCliBj RSEDqpcbEDMLI95q3mgF10Y= X-Google-Smtp-Source: AGHT+IGInqo4mT5vj74fw06D+iMd3Gssloh/EHnAdRCq2VbbTbYQORHEWwtfKd4KpysQJpOnVziVSg== X-Received: by 2002:a05:6a00:1881:b0:6be:9c0:7195 with SMTP id x1-20020a056a00188100b006be09c07195mr1233467pfh.20.1699434796137; Wed, 08 Nov 2023 01:13:16 -0800 (PST) Received: from oslab-pc.tsinghua.edu.cn ([166.111.139.134]) by smtp.gmail.com with ESMTPSA id p24-20020aa78618000000b006be5e537b6csm8585967pfn.63.2023.11.08.01.13.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 08 Nov 2023 01:13:15 -0800 (PST) From: Tuo Li To: mchehab@kernel.org, yongsuyoo0215@gmail.com 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: Wed, 8 Nov 2023 17:13:00 +0800 Message-Id: <20231108091300.3124649-1-islituo@gmail.com> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 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 | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/drivers/media/dvb-core/dvb_demux.c b/drivers/media/dvb-core/dvb_demux.c index 7c4d86bfdd6c..791db667e2ed 100644 --- a/drivers/media/dvb-core/dvb_demux.c +++ b/drivers/media/dvb-core/dvb_demux.c @@ -1141,8 +1141,11 @@ 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; + } p = memdup_user(buf, count); if (IS_ERR(p))