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=-18.8 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, 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 4BC2AC433DB for ; Mon, 1 Mar 2021 21:31:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 06DAF60240 for ; Mon, 1 Mar 2021 21:31:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238297AbhCAVbX (ORCPT ); Mon, 1 Mar 2021 16:31:23 -0500 Received: from mail.kernel.org ([198.145.29.99]:36604 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238035AbhCARS3 (ORCPT ); Mon, 1 Mar 2021 12:18:29 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 1EC9C64EBE; Mon, 1 Mar 2021 16:46:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1614617205; bh=GoN/ez8d53JBJoTOnaBAX2eFBXESWRbKo7b1nIeshwA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Z4WpotnvuNlDy+I2ufMpzAKKc0qcrCejZ2RBHimQvFqFYrWP4TKmYBq6ARRbBNXqM a7jpVsUoPo19sw+KNQM8L1Ye2KJ3FIF+T2H3iKhGA1t0UwBZ3Ttf58eC/SxkwbYYLA YKQjfqxCOSP7wDcEZnWvPWotPiPXQFzNJQQ8PENk= 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 , Sudip Mukherjee Subject: [PATCH 4.19 222/247] libnvdimm/dimm: Avoid race between probe and available_slots_show() Date: Mon, 1 Mar 2021 17:14:02 +0100 Message-Id: <20210301161042.551402638@linuxfoundation.org> X-Mailer: git-send-email 2.30.1 In-Reply-To: <20210301161031.684018251@linuxfoundation.org> References: <20210301161031.684018251@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 [sudip: use device_lock()] Signed-off-by: Sudip Mukherjee 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 @@ -359,16 +359,16 @@ 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) { @@ -380,6 +380,18 @@ 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; + + device_lock(dev); + rc = __available_slots_show(dev_get_drvdata(dev), buf); + device_unlock(dev); + + return rc; +} static DEVICE_ATTR_RO(available_slots); static struct attribute *nvdimm_attributes[] = {