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=-5.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 F1492C0650F for ; Tue, 30 Jul 2019 16:46:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BFA3020693 for ; Tue, 30 Jul 2019 16:46:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1564505196; bh=Jv3sZV+amDx4LXh0EqyZi1UJfocfNlAOBczaY3hh4+I=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=py3lq8symFdz9VLCETc2PuT76vv2/4XYhnU0JrhujGoFIGfuKVITqzlndMKv8vIKL CsQ4E5kkMGPoQPNl2QcMhkogipby2sjjWj+csJxD8+n35w9UnRe1PkWFT5b4QP+usx DTnoahARZKlA1I5EZH7hZHUjAkLKrZB93r4nMkDQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728664AbfG3Qqf (ORCPT ); Tue, 30 Jul 2019 12:46:35 -0400 Received: from mail.kernel.org ([198.145.29.99]:57998 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725934AbfG3Qqf (ORCPT ); Tue, 30 Jul 2019 12:46:35 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (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 F400520693; Tue, 30 Jul 2019 16:46:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1564505194; bh=Jv3sZV+amDx4LXh0EqyZi1UJfocfNlAOBczaY3hh4+I=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=DvcMpS/tjf/d16GEeV1oqPaKk5i6GjYjrOCE5pjHrEeAAvXauPSobhCoVdXKM+7TK ZqQDdEQGMawOGnLEKlknWApv8DlL9oznPgYPhUgFo4FR9LTzvk2sMDtli9u2oDaSN/ SD9ZhxDKMEUuWFac8Ol58ZuF+3NH9cilG1gQzTfY= Date: Tue, 30 Jul 2019 18:46:31 +0200 From: Greg KH To: Muchun Song Cc: rafael@kernel.org, mojha@codeaurora.org, benh@kernel.crashing.org, prsood@codeaurora.org, gkohli@codeaurora.org, songmuchun@bytedance.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH v7] driver core: Fix use-after-free and double free on glue directory Message-ID: <20190730164631.GA17604@kroah.com> References: <20190727032122.24639-1-smuchun@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190727032122.24639-1-smuchun@gmail.com> User-Agent: Mutt/1.12.1 (2019-06-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Jul 27, 2019 at 11:21:22AM +0800, Muchun Song wrote: > There is a race condition between removing glue directory and adding a new > device under the glue dir. It can be reproduced in following test: > > CPU1: CPU2: > > device_add() > get_device_parent() > class_dir_create_and_add() > kobject_add_internal() > create_dir() // create glue_dir > > device_add() > get_device_parent() > kobject_get() // get glue_dir > > device_del() > cleanup_glue_dir() > kobject_del(glue_dir) > > kobject_add() > kobject_add_internal() > create_dir() // in glue_dir > sysfs_create_dir_ns() > kernfs_create_dir_ns(sd) > > sysfs_remove_dir() // glue_dir->sd=NULL > sysfs_put() // free glue_dir->sd > > // sd is freed > kernfs_new_node(sd) > kernfs_get(glue_dir) > kernfs_add_one() > kernfs_put() > > Before CPU1 remove last child device under glue dir, if CPU2 add a new > device under glue dir, the glue_dir kobject reference count will be > increase to 2 via kobject_get() in get_device_parent(). And CPU2 has > been called kernfs_create_dir_ns(), but not call kernfs_new_node(). > Meanwhile, CPU1 call sysfs_remove_dir() and sysfs_put(). This result in > glue_dir->sd is freed and it's reference count will be 0. Then CPU2 call > kernfs_get(glue_dir) will trigger a warning in kernfs_get() and increase > it's reference count to 1. Because glue_dir->sd is freed by CPU1, the next > call kernfs_add_one() by CPU2 will fail(This is also use-after-free) > and call kernfs_put() to decrease reference count. Because the reference > count is decremented to 0, it will also call kmem_cache_free() to free > the glue_dir->sd again. This will result in double free. > > In order to avoid this happening, we also should make sure that kernfs_node > for glue_dir is released in CPU1 only when refcount for glue_dir kobj is > 1 to fix this race. > > The following calltrace is captured in kernel 4.14 with the following patch > applied: > > commit 726e41097920 ("drivers: core: Remove glue dirs from sysfs earlier") > > -------------------------------------------------------------------------- > [ 3.633703] WARNING: CPU: 4 PID: 513 at .../fs/kernfs/dir.c:494 > Here is WARN_ON(!atomic_read(&kn->count) in kernfs_get(). > .... > [ 3.633986] Call trace: > [ 3.633991] kernfs_create_dir_ns+0xa8/0xb0 > [ 3.633994] sysfs_create_dir_ns+0x54/0xe8 > [ 3.634001] kobject_add_internal+0x22c/0x3f0 > [ 3.634005] kobject_add+0xe4/0x118 > [ 3.634011] device_add+0x200/0x870 > [ 3.634017] _request_firmware+0x958/0xc38 > [ 3.634020] request_firmware_into_buf+0x4c/0x70 > .... > [ 3.634064] kernel BUG at .../mm/slub.c:294! > Here is BUG_ON(object == fp) in set_freepointer(). > .... > [ 3.634346] Call trace: > [ 3.634351] kmem_cache_free+0x504/0x6b8 > [ 3.634355] kernfs_put+0x14c/0x1d8 > [ 3.634359] kernfs_create_dir_ns+0x88/0xb0 > [ 3.634362] sysfs_create_dir_ns+0x54/0xe8 > [ 3.634366] kobject_add_internal+0x22c/0x3f0 > [ 3.634370] kobject_add+0xe4/0x118 > [ 3.634374] device_add+0x200/0x870 > [ 3.634378] _request_firmware+0x958/0xc38 > [ 3.634381] request_firmware_into_buf+0x4c/0x70 > -------------------------------------------------------------------------- > > Fixes: 726e41097920 ("drivers: core: Remove glue dirs from sysfs earlier") > Signed-off-by: Muchun Song > Reviewed-by: Mukesh Ojha > Signed-off-by: Prateek Sood > --- > > Change in v7: > 1. Update commit message. > Change in v6: > 1. Remove hardcoding "1 " > Change in v5: > 1. Revert to the v1 fix. > 2. Add some comment to explain why we need do this in > cleanup_glue_dir(). > Change in v4: > 1. Add some kerneldoc comment. > 2. Remove unlock_if_glue_dir(). > 3. Rename get_device_parent_locked_if_glue_dir() to > get_device_parent_locked. > 4. Update commit message. > Change in v3: > Add change log. > Change in v2: > Fix device_move() also. Now queued up, thanks for sticking with this. greg k-h