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=-8.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 32532C48BD6 for ; Wed, 26 Jun 2019 14:38:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F0D1F21670 for ; Wed, 26 Jun 2019 14:38:55 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="n7rtGwf9" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728004AbfFZOiy (ORCPT ); Wed, 26 Jun 2019 10:38:54 -0400 Received: from mail-pf1-f193.google.com ([209.85.210.193]:42697 "EHLO mail-pf1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726984AbfFZOiy (ORCPT ); Wed, 26 Jun 2019 10:38:54 -0400 Received: by mail-pf1-f193.google.com with SMTP id q10so1459198pff.9 for ; Wed, 26 Jun 2019 07:38:53 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id; bh=LITP8a5nu6BoMPhwbxTj2Lwn5C7IrnXB3v68VoPaQI4=; b=n7rtGwf9XW2vS3fQS7Mtr9T4HAYc6Dk3XIUN+o3T2PZFA/AE5HLF3XJ7THYW+wMdky owxcHFjtINWfDL8QHpSDqqvdp4ezLtQ+acGOqQXaw1UPrkUhJufCP8ytninnZ2E/uBRm M36yCieciWDUyDeFyNTARIz7ZSrqqycJ0eOvRLuSQAL2jcDCFu0gc57WQV1zK9ezmqaJ QrbeReRV8sxweueKmMskeN4kX0Syh7nIcqpVj1jnWAuCHBsMGB78Z5+0o3kFUi9R+XKo 09qGfdJGgSqI7u0Ltou1uDJJ6wAnAmSaVVBm1Ay8+GNzG1O/aQHfRGOx6YxscumkgLj3 ca5Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id; bh=LITP8a5nu6BoMPhwbxTj2Lwn5C7IrnXB3v68VoPaQI4=; b=d0OD+dINhV1jw8D99SVDbZ2bSIzkhbIV0nIckDUw91jQhNvm5Gq1lAaxxmPXkDjYtW hs//PruxjMtH2uEzYG7+FNgnSxCG6Q0B67IPbtUSrSz1vrnQr+NZM3SyVP79VFoblEJn P9uYV76+xUkhbjBmuE86F9NYR6lqH3IsXRtDO0SHWrtAovqI56qg733reJK6esU32gpq SyLoTMI9GVkvrWCezVk5LrriayW1Qhs9tVS1uj9cwqELSuQSVK382hAkI9WN3eX1FdAQ Gt54Ug030Z/q6eth/erfD0i7LNHyTHAvNa7WmyF5Rq8uovljJW0oWTKanTWNkhSTLgaD tkfg== X-Gm-Message-State: APjAAAXcUVueR/pdSglIQAOqLAXJzndHJOGKBz8V7EK7z1ydZCehhTkz zh0kzBTZwcBsHobQ9Bkzhkg= X-Google-Smtp-Source: APXvYqzR9EjMIANiupeq8oPDPbndhmZLsAdI1rL5XMUh+wP3dmNvVzkiZR/6Dss4yicsm5II+fecCA== X-Received: by 2002:a63:3d0f:: with SMTP id k15mr3284717pga.343.1561559933170; Wed, 26 Jun 2019 07:38:53 -0700 (PDT) Received: from ubuntu.localdomain ([104.238.150.158]) by smtp.gmail.com with ESMTPSA id 5sm17739909pfh.109.2019.06.26.07.38.40 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 26 Jun 2019 07:38:52 -0700 (PDT) From: Muchun Song To: gregkh@linuxfoundation.org, rafael@kernel.org Cc: benh@kernel.crashing.org, prsood@codeaurora.org, mojha@codeaurora.org, gkohli@codeaurora.org, linux-kernel@vger.kernel.org Subject: [PATCH v1 OPT1] driver core: Fix use-after-free and double free on glue directory Date: Wed, 26 Jun 2019 22:38:23 +0800 Message-Id: <20190626143823.7048-1-smuchun@gmail.com> X-Mailer: git-send-email 2.17.1 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org There is a race condition between removing glue directory and adding a new device under the glue directory. It can be reproduced in following test: path 1: Add the child device under glue dir device_add() get_device_parent() mutex_lock(&gdp_mutex); .... /*find parent from glue_dirs.list*/ list_for_each_entry(k, &dev->class->p->glue_dirs.list, entry) if (k->parent == parent_kobj) { kobj = kobject_get(k); break; } .... mutex_unlock(&gdp_mutex); .... .... kobject_add() kobject_add_internal() create_dir() sysfs_create_dir_ns() if (kobj->parent) parent = kobj->parent->sd; .... kernfs_create_dir_ns(parent) kernfs_new_node() kernfs_get(parent) .... /* link in */ rc = kernfs_add_one(kn); if (!rc) return kn; kernfs_put(kn) .... repeat: kmem_cache_free(kn) kn = parent; if (kn) { if (atomic_dec_and_test(&kn->count)) goto repeat; } .... path2: Remove last child device under glue dir device_del() cleanup_device_parent() cleanup_glue_dir() mutex_lock(&gdp_mutex); if (!kobject_has_children(glue_dir)) kobject_del(glue_dir); kobject_put(glue_dir); mutex_unlock(&gdp_mutex); Before path2 remove last child device under glue dir, If path1 add a new device under glue dir, the glue_dir kobject reference count will be increase to 2 via kobject_get(k) in get_device_parent(). And path1 has been called kernfs_new_node(), but not call kernfs_get(parent). Meanwhile, path2 call kobject_del(glue_dir) beacause 0 is returned by kobject_has_children(). This result in glue_dir->sd is freed and it's reference count will be 0. Then path1 call kernfs_get(parent) will trigger a warning in kernfs_get()(WARN_ON(!atomic_read(&kn->count))) and increase it's reference count to 1. Because glue_dir->sd is freed by path2, the next call kernfs_add_one() by path1 will fail(This is also use-after-free) and call atomic_dec_and_test() to decrease reference count. Because the reference count is decremented to 0, it will also call kmem_cache_free() to free glue_dir->sd again. This will result in double free. In order to avoid this happening, we should not call kobject_del() on path2 when the reference count of glue_dir is greater than 1. So we add a conditional statement to fix it. 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 --- Hi Greg, This fix patch is based on the refcount. It is also the original fix method. Another fix patch is based on the mutex lock. It can reference to: Subject: [PATCH v4 OPT2] driver core: Fix use-after-free and double free on glue directory I am hoping you would chose which solution you prefered here. Thanks. drivers/base/core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/base/core.c b/drivers/base/core.c index 4aeaa0c92bda..5ac5376ae9af 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -1825,7 +1825,7 @@ static void cleanup_glue_dir(struct device *dev, struct kobject *glue_dir) return; mutex_lock(&gdp_mutex); - if (!kobject_has_children(glue_dir)) + if (!kobject_has_children(glue_dir) && kref_read(&glue_dir->kref) == 1) kobject_del(glue_dir); kobject_put(glue_dir); mutex_unlock(&gdp_mutex); -- 2.17.1