From patchwork Fri May 8 23:53:19 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Andrew Morton X-Patchwork-Id: 226056 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=-3.7 required=3.0 tests=DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS, LOTS_OF_MONEY, MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 C7EE6C47255 for ; Fri, 8 May 2020 23:53:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A7A7B2063A for ; Fri, 8 May 2020 23:53:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588982002; bh=Q+zg/S+1Gx4065xyCGOd2vJrhliJjaxxiPkQceLl/fM=; h=Date:From:To:Subject:In-Reply-To:List-ID:From; b=bDY8gZaXV2HXrNumYbTYRFSZnx2sLf2MkIeGRSLdH78Ar803Vhj3j1dqE/80gB6i5 Kdq0PiWmu0u9LQsKi0ROPgNipZGgaiLCW6Yd4H1255pY2DP5BuuQR6mkcWJTJ2ms12 nvPIxmdrE/kGH2zkfAksOj+hfORNjCBahoO0BbSQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728379AbgEHXxV (ORCPT ); Fri, 8 May 2020 19:53:21 -0400 Received: from mail.kernel.org ([198.145.29.99]:55836 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727878AbgEHXxV (ORCPT ); Fri, 8 May 2020 19:53:21 -0400 Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 3FB262063A; Fri, 8 May 2020 23:53:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588982000; bh=Q+zg/S+1Gx4065xyCGOd2vJrhliJjaxxiPkQceLl/fM=; h=Date:From:To:Subject:In-Reply-To:From; b=W2CClFWnASUjWS3FjpdC+13aANTdykKUpo1+WB7WWdgN4ditEx5p5vZsiXCufifz+ YUneyH0/haAWWK4a5VVmTNlaNkc0tXVkMD+yQUVUrMqv9sDI+Pd7ERs3/1lEUwxtIt 1nQLNWv/NVP/skh719Bp4srlvKkwvwPXBF9AYHeI= Date: Fri, 08 May 2020 16:53:19 -0700 From: Andrew Morton To: akpm@linux-foundation.org, dan.j.williams@intel.com, dave.jiang@intel.com, david@redhat.com, mm-commits@vger.kernel.org, pasha.tatashin@soleen.com, stable@vger.kernel.org, vishal.l.verma@intel.com Subject: + device-dax-dont-leak-kernel-memory-to-user-space-after-unloading-kmem.patch added to -mm tree Message-ID: <20200508235319.0NmZ0DltL%akpm@linux-foundation.org> In-Reply-To: <20200507183509.c5ef146c5aaeb118a25a39a8@linux-foundation.org> User-Agent: s-nail v14.8.16 MIME-Version: 1.0 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org The patch titled Subject: device-dax: don't leak kernel memory to user space after unloading kmem has been added to the -mm tree. Its filename is device-dax-dont-leak-kernel-memory-to-user-space-after-unloading-kmem.patch This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/device-dax-dont-leak-kernel-memory-to-user-space-after-unloading-kmem.patch and later at http://ozlabs.org/~akpm/mmotm/broken-out/device-dax-dont-leak-kernel-memory-to-user-space-after-unloading-kmem.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: David Hildenbrand Subject: device-dax: don't leak kernel memory to user space after unloading kmem Assume we have kmem configured and loaded: [root@localhost ~]# cat /proc/iomem ... 140000000-33fffffff : Persistent Memory$ 140000000-1481fffff : namespace0.0 150000000-33fffffff : dax0.0 150000000-33fffffff : System RAM Assume we try to unload kmem. This force-unloading will work, even if memory cannot get removed from the system. [root@localhost ~]# rmmod kmem [ 86.380228] removing memory fails, because memory [0x0000000150000000-0x0000000157ffffff] is onlined ... [ 86.431225] kmem dax0.0: DAX region [mem 0x150000000-0x33fffffff] cannot be hotremoved until the next reboot Now, we can reconfigure the namespace: [root@localhost ~]# ndctl create-namespace --force --reconfig=namespace0.0 --mode=devdax [ 131.409351] nd_pmem namespace0.0: could not reserve region [mem 0x140000000-0x33fffffff]dax [ 131.410147] nd_pmem: probe of namespace0.0 failed with error -16namespace0.0 --mode=devdax ... This fails as expected due to the busy memory resource, and the memory cannot be used. However, the dax0.0 device is removed, and along its name. The name of the memory resource now points at freed memory (name of the device). [root@localhost ~]# cat /proc/iomem ... 140000000-33fffffff : Persistent Memory 140000000-1481fffff : namespace0.0 150000000-33fffffff : �_�^7_��/_��wR��WQ���^��� ... 150000000-33fffffff : System RAM We have to make sure to duplicate the string. While at it, remove the superfluous setting of the name and fixup a stale comment. Link: http://lkml.kernel.org/r/20200508084217.9160-2-david@redhat.com Fixes: 9f960da72b25 ("device-dax: "Hotremove" persistent memory that is used like normal RAM") Signed-off-by: David Hildenbrand Cc: Dan Williams Cc: Vishal Verma Cc: Dave Jiang Cc: Pavel Tatashin Cc: Andrew Morton Cc: [5.3] Signed-off-by: Andrew Morton --- drivers/dax/kmem.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) --- a/drivers/dax/kmem.c~device-dax-dont-leak-kernel-memory-to-user-space-after-unloading-kmem +++ a/drivers/dax/kmem.c @@ -22,6 +22,7 @@ int dev_dax_kmem_probe(struct device *de resource_size_t kmem_size; resource_size_t kmem_end; struct resource *new_res; + const char *new_res_name; int numa_node; int rc; @@ -48,11 +49,16 @@ int dev_dax_kmem_probe(struct device *de kmem_size &= ~(memory_block_size_bytes() - 1); kmem_end = kmem_start + kmem_size; - /* Region is permanently reserved. Hot-remove not yet implemented. */ - new_res = request_mem_region(kmem_start, kmem_size, dev_name(dev)); + new_res_name = kstrdup(dev_name(dev), GFP_KERNEL); + if (!new_res_name) + return -ENOMEM; + + /* Region is permanently reserved if hotremove fails. */ + new_res = request_mem_region(kmem_start, kmem_size, new_res_name); if (!new_res) { dev_warn(dev, "could not reserve region [%pa-%pa]\n", &kmem_start, &kmem_end); + kfree(new_res_name); return -EBUSY; } @@ -63,12 +69,12 @@ int dev_dax_kmem_probe(struct device *de * unknown to us that will break add_memory() below. */ new_res->flags = IORESOURCE_SYSTEM_RAM; - new_res->name = dev_name(dev); rc = add_memory(numa_node, new_res->start, resource_size(new_res)); if (rc) { release_resource(new_res); kfree(new_res); + kfree(new_res_name); return rc; } dev_dax->dax_kmem_res = new_res; @@ -83,6 +89,7 @@ static int dev_dax_kmem_remove(struct de struct resource *res = dev_dax->dax_kmem_res; resource_size_t kmem_start = res->start; resource_size_t kmem_size = resource_size(res); + const char *res_name = res->name; int rc; /* @@ -102,6 +109,7 @@ static int dev_dax_kmem_remove(struct de /* Release and free dax resources */ release_resource(res); kfree(res); + kfree(res_name); dev_dax->dax_kmem_res = NULL; return 0;