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=-19.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT 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 8905DC433DB for ; Mon, 8 Feb 2021 16:36:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3EF0664E9A for ; Mon, 8 Feb 2021 16:36:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234414AbhBHQf6 (ORCPT ); Mon, 8 Feb 2021 11:35:58 -0500 Received: from mail.kernel.org ([198.145.29.99]:56398 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232171AbhBHPNe (ORCPT ); Mon, 8 Feb 2021 10:13:34 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 1934364EBC; Mon, 8 Feb 2021 15:10:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1612797035; bh=Ol5TGqL9tdYPrnU3t8SzO77dUDoR2OOxgyzlD37EV2I=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=uUdRyj6XcUQXd1KOYiVnqoO6MaBsfnWvGdulJZgVgLY38oW1XSEf4mTscSwqfJVvR LsVsyPOw9nJxUmvPP3uFiVE3SyWl/A7/Ag2+yz/HWp+Tw4ANjdmdnsHOgLEtXYn3ff EJ1VGAfgX7Zf6LwTsNTK6Ql6ZVtKspiTkRiD6m7A= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Vishal Verma , Dave Jiang , Ira Weiny , Coly Li , Richard Palethorpe , Dan Williams Subject: [PATCH 5.4 36/65] libnvdimm/dimm: Avoid race between probe and available_slots_show() Date: Mon, 8 Feb 2021 16:01:08 +0100 Message-Id: <20210208145811.627989831@linuxfoundation.org> X-Mailer: git-send-email 2.30.0 In-Reply-To: <20210208145810.230485165@linuxfoundation.org> References: <20210208145810.230485165@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Dan Williams commit 7018c897c2f243d4b5f1b94bc6b4831a7eab80fb upstream. Richard reports that the following test: (while true; do cat /sys/bus/nd/devices/nmem*/available_slots 2>&1 > /dev/null done) & while true; do for i in $(seq 0 4); do echo nmem$i > /sys/bus/nd/drivers/nvdimm/bind done for i in $(seq 0 4); do echo nmem$i > /sys/bus/nd/drivers/nvdimm/unbind done done ...fails with a crash signature like: divide error: 0000 [#1] SMP KASAN PTI RIP: 0010:nd_label_nfree+0x134/0x1a0 [libnvdimm] [..] Call Trace: available_slots_show+0x4e/0x120 [libnvdimm] dev_attr_show+0x42/0x80 ? memset+0x20/0x40 sysfs_kf_seq_show+0x218/0x410 The root cause is that available_slots_show() consults driver-data, but fails to synchronize against device-unbind setting up a TOCTOU race to access uninitialized memory. Validate driver-data under the device-lock. Fixes: 4d88a97aa9e8 ("libnvdimm, nvdimm: dimm driver and base libnvdimm device-driver infrastructure") Cc: Cc: Vishal Verma Cc: Dave Jiang Cc: Ira Weiny Cc: Coly Li Reported-by: Richard Palethorpe Acked-by: Richard Palethorpe Signed-off-by: Dan Williams Signed-off-by: Greg Kroah-Hartman --- drivers/nvdimm/dimm_devs.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-) --- a/drivers/nvdimm/dimm_devs.c +++ b/drivers/nvdimm/dimm_devs.c @@ -344,16 +344,16 @@ static ssize_t state_show(struct device } static DEVICE_ATTR_RO(state); -static ssize_t available_slots_show(struct device *dev, - struct device_attribute *attr, char *buf) +static ssize_t __available_slots_show(struct nvdimm_drvdata *ndd, char *buf) { - struct nvdimm_drvdata *ndd = dev_get_drvdata(dev); + struct device *dev; ssize_t rc; u32 nfree; if (!ndd) return -ENXIO; + dev = ndd->dev; nvdimm_bus_lock(dev); nfree = nd_label_nfree(ndd); if (nfree - 1 > nfree) { @@ -365,6 +365,18 @@ static ssize_t available_slots_show(stru nvdimm_bus_unlock(dev); return rc; } + +static ssize_t available_slots_show(struct device *dev, + struct device_attribute *attr, char *buf) +{ + ssize_t rc; + + nd_device_lock(dev); + rc = __available_slots_show(dev_get_drvdata(dev), buf); + nd_device_unlock(dev); + + return rc; +} static DEVICE_ATTR_RO(available_slots); __weak ssize_t security_show(struct device *dev,