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=-9.1 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 B0775C04AAF for ; Thu, 16 May 2019 14:24:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7671A20833 for ; Thu, 16 May 2019 14:24:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Zq2F9+Aw" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726909AbfEPOYL (ORCPT ); Thu, 16 May 2019 10:24:11 -0400 Received: from mail-pg1-f194.google.com ([209.85.215.194]:46539 "EHLO mail-pg1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726692AbfEPOYK (ORCPT ); Thu, 16 May 2019 10:24:10 -0400 Received: by mail-pg1-f194.google.com with SMTP id t187so1631509pgb.13; Thu, 16 May 2019 07:24:10 -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=pbiGxWp+6g8Ev1vPyMkDL0Yj0MpKYGjwYXWdffQT+X0=; b=Zq2F9+AwPqYiGFsLYwXUsUayVj+DYRUxovrZuhCckbgt3neqkzA5476vz9QvYBHHJ9 cmBQz7WpTNxXNfR5CBKLXJWTAvNkz75kzjVLSmEdvZsvVhZ7sFx8yWe38gkPLUWHePBn GvcqF64fgZlxB4aghH6KrBWjGYU3uVtC1GrCZiP6PN2yy8oHLd2q6QRv246u9E7NWaBJ pRQc1mbYjkIg9q5RmbQnKu/4kIch6ECX8TIAygzBIlCPZaR+gTt/BWhh+v/+b9QY0c2t 1G/45BQW3mPbhNbyIWPdHVK5gWtu3+8oH9kYiipg0+6XSj6aTxaFvfH5RKceG83dgStC +agQ== 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=pbiGxWp+6g8Ev1vPyMkDL0Yj0MpKYGjwYXWdffQT+X0=; b=kZ4vXEeoyb5PHqPHn9AUZodxD54LScLbIU0t+GsW94onq2JHCShteK854XR6mxjP1y d4Sx9/6DYCSaxdJO2+A8IX+06yFSxVAoAtK9gMqjMQ+Z8tr238c/HobC2MKYDml2LDeP Ca7tAycWLpB2ruofBJyY6Fm3ASBeYSBmmJ5ByKrsAUo6YE+oUfDkxdufKGxal9kVEn7j vBdjElDElKrMFi6G2EYRremFE0R3lIRHQaHGhy/LfvTAMhTPqPI1ngGOOeOW87NRnr88 ycfHoSpq0pIyVcIuRPvg7/wCxjqrPvbE+Ipl3zGQYx+sOp2VJW7koq4lNWLv0xqQZC2y 8Ovg== X-Gm-Message-State: APjAAAXIIZOysWZpKkq8zd5+HqVSQV7fCgv/aeBfWDxi0AgJ4+zNEbnN wHb5g9W3O356IL8CNC6evHc= X-Google-Smtp-Source: APXvYqzqUF7sYORxVtp1XKW8qb53iivcDATFMHlhkdQMRgw2+5O3yikymYytMK/4RZBJPrz8IT/DfA== X-Received: by 2002:a65:5241:: with SMTP id q1mr49877661pgp.298.1558016649724; Thu, 16 May 2019 07:24:09 -0700 (PDT) Received: from ubuntu.localdomain ([104.238.150.158]) by smtp.gmail.com with ESMTPSA id u6sm7080284pfm.10.2019.05.16.07.24.02 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 16 May 2019 07:24:09 -0700 (PDT) From: Muchun Song To: gregkh@linuxfoundation.org, rafael@kernel.org, benh@kernel.crashing.org, prsood@codeaurora.org, mojha@codeaurora.org, gkohli@codeaurora.org Cc: linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, zhaowuyun@wingtech.com Subject: [PATCH v4] driver core: Fix use-after-free and double free on glue directory Date: Thu, 16 May 2019 22:23:42 +0800 Message-Id: <20190516142342.28019-1-smuchun@gmail.com> X-Mailer: git-send-email 2.17.1 Sender: linux-arm-msm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@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 can ensure the lookup of the glue dir and creation of the child object(s) are done under a single instance of gdp_mutex so we never see a stale "empty" but still poentially used glue dir around. 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 --- 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. drivers/base/core.c | 108 +++++++++++++++++++++++++++++++++++++------- 1 file changed, 92 insertions(+), 16 deletions(-) diff --git a/drivers/base/core.c b/drivers/base/core.c index 4aeaa0c92bda..2251e391a352 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -1739,8 +1739,23 @@ class_dir_create_and_add(struct class *class, struct kobject *parent_kobj) static DEFINE_MUTEX(gdp_mutex); -static struct kobject *get_device_parent(struct device *dev, - struct device *parent) +/** + * __get_device_parent() - Get the parent device kobject. + * @dev: Pointer to the device structure. + * @parent: Pointer to the parent device structure. + * @lock: When we live in a glue directory, should we hold the + * gdp_mutex lock when this function returns? If @lock + * is true, this function returns with the gdp_mutex + * holed. Otherwise it will not. + * + * Note: Only when we live in a glue directory and @lock is + * true, the function will return with the gdp_mutex holed. + * In this case, The caller is responsible for releasing the + * gdp_mutex lock. + */ +static struct kobject *__get_device_parent(struct device *dev, + struct device *parent, + bool lock) { if (dev->class) { struct kobject *kobj = NULL; @@ -1778,16 +1793,32 @@ static struct kobject *get_device_parent(struct device *dev, break; } spin_unlock(&dev->class->p->glue_dirs.list_lock); - if (kobj) { - mutex_unlock(&gdp_mutex); - return kobj; - } - /* or create a new class-directory at the parent device */ - k = class_dir_create_and_add(dev->class, parent_kobj); - /* do not emit an uevent for this simple "glue" directory */ - mutex_unlock(&gdp_mutex); - return k; + /** + * If not found, create a new class-directory at the + * parent device and do not emit an uevent for this + * simple "glue" directory. + */ + if (!kobj) + kobj = class_dir_create_and_add(dev->class, + parent_kobj); + + /** + * If the caller want to add/move a new directory + * under the glue directory next. We should leave + * the function with the gdp_mutex holed. And then + * release the gdp_mutex lock after adding/moving + * the new directory. + * + * Because we should ensure the lookup of the glue + * dir and creation of the child object(s) are done + * under a single instance of gdp_mutex so we never + * see a stale "empty" but still poentially used + * glue dir around. + */ + if (!lock) + mutex_unlock(&gdp_mutex); + return kobj; } /* subsystems can specify a default root directory for their devices */ @@ -1799,6 +1830,36 @@ static struct kobject *get_device_parent(struct device *dev, return NULL; } +static inline struct kobject *get_device_parent(struct device *dev, + struct device *parent) +{ + return __get_device_parent(dev, parent, false); +} + +/** + * Note: When this function returns successfully, the gdp_mutex + * lock may be held (when we live in a glue directory). The caller + * can determine wheather we hold the lock by live_in_glue_dir(). + * + * If true is returned by live_in_glue_dir(), the caller should + * drop the gdp_mutex lock. + */ +static inline struct kobject *get_device_parent_locked(struct device *dev, + struct device *parent) +{ + struct kobject *kobj = __get_device_parent(dev, parent, true); + + /** + * When we create a new glue directory fail, there + * is no need for us to leave the function with the + * the gdp_mutex holed. + */ + if (IS_ERR(kobj)) + mutex_unlock(&gdp_mutex); + + return kobj; +} + static inline bool live_in_glue_dir(struct kobject *kobj, struct device *dev) { @@ -2040,7 +2101,7 @@ int device_add(struct device *dev) pr_debug("device: '%s': %s\n", dev_name(dev), __func__); parent = get_device(dev->parent); - kobj = get_device_parent(dev, parent); + kobj = get_device_parent_locked(dev, parent); if (IS_ERR(kobj)) { error = PTR_ERR(kobj); goto parent_error; @@ -2055,10 +2116,17 @@ int device_add(struct device *dev) /* first, register with generic layer. */ /* we require the name to be set before, and pass NULL */ error = kobject_add(&dev->kobj, dev->kobj.parent, NULL); - if (error) { - glue_dir = get_glue_dir(dev); + + glue_dir = get_glue_dir(dev); + /** + * Drops the mutex possibly acquired by get_device_parent_locked(). + * See the comment in __get_device_parent(). + */ + if (live_in_glue_dir(glue_dir, dev)) + mutex_unlock(&gdp_mutex); + + if (error) goto Error; - } /* notify platform of device entry */ error = device_platform_notify(dev, KOBJ_ADD); @@ -2972,7 +3040,7 @@ int device_move(struct device *dev, struct device *new_parent, device_pm_lock(); new_parent = get_device(new_parent); - new_parent_kobj = get_device_parent(dev, new_parent); + new_parent_kobj = get_device_parent_locked(dev, new_parent); if (IS_ERR(new_parent_kobj)) { error = PTR_ERR(new_parent_kobj); put_device(new_parent); @@ -2982,6 +3050,14 @@ int device_move(struct device *dev, struct device *new_parent, pr_debug("device: '%s': %s: moving to '%s'\n", dev_name(dev), __func__, new_parent ? dev_name(new_parent) : ""); error = kobject_move(&dev->kobj, new_parent_kobj); + + /** + * Drops the mutex possibly acquired by get_device_parent_locked(). + * See the comment in __get_device_parent(). + */ + if (live_in_glue_dir(new_parent_kobj, dev)) + mutex_unlock(&gdp_mutex); + if (error) { cleanup_glue_dir(dev, new_parent_kobj); put_device(new_parent); -- 2.17.1