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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 550D4C2BA15 for ; Sun, 5 Apr 2020 16:40:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 20E8820675 for ; Sun, 5 Apr 2020 16:40:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1586104811; bh=tRkkXO+PEc/JrqWheuKG1whPIrxpx6mFXjlo4ozKhNw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=PZ7F5JBFwlLj9vTc4Ds6hxluD9nRtyI/tkRlAwUq6G7dvUmrynPJJ8FK5UYNN5V7n SRIK457C1wfwi9RutzQiHNLAy6c7fPOlPF5LYdvno+pR1QJsjHqN1QaTnrPY9IOxZP wOg/9zctDXc2ETh4oGHEjuKrs94+k3sbXi/IQrIQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727349AbgDEQkK (ORCPT ); Sun, 5 Apr 2020 12:40:10 -0400 Received: from mail.kernel.org ([198.145.29.99]:54746 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726667AbgDEQkJ (ORCPT ); Sun, 5 Apr 2020 12:40:09 -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 CD33420675; Sun, 5 Apr 2020 16:40:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1586104809; bh=tRkkXO+PEc/JrqWheuKG1whPIrxpx6mFXjlo4ozKhNw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=jnfgp1DKwXMsHdHtFBSb419gEpYl3xaXybe04XzGLilluGFkO/IyJSj4Fo7+WxIcD fWJgt3dMpy84fwtijWeRReDHRsQ+oKGboxD6fpuFaUg6pzM1HS8gLRa+KmsggIUsuD 6CiqndUfJHhHDUROUe8aX0q6ZoGnsnqrHh51aTRk= Date: Sun, 5 Apr 2020 18:40:06 +0200 From: Greg KH To: zhangfeionline@gmail.com Cc: rafael@kernel.org, linux-kernel@vger.kernel.org, songmuchun@bytedance.com Subject: Re: [PATCH] driver core: Fix possible use after free on name Message-ID: <20200405164006.GA1582475@kroah.com> References: <1586102749-3364-1-git-send-email-zhangfeionline@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1586102749-3364-1-git-send-email-zhangfeionline@gmail.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Apr 05, 2020 at 09:05:49AM -0700, zhangfeionline@gmail.com wrote: > From: PengfeiZhang > > __class_create() copies the pointer to the name passed as an > argument only to be used later. But there's a chance the caller > could immediately free the passed string(e.g., local variable). > This could trigger a use after free when we use class name(e.g., > dev_uevent_name()called by device_destroy(),class_create_release()). > > To be on the safe side: duplicate the string with kstrdup_const() > so that if an unaware user passes an address to a stack-allocated > buffer, we won't get the arbitrary name and crash. Where are you seeing this happen? > > Signed-off-by: PengfeiZhang > --- > drivers/base/class.c | 17 +++++++++++++++-- > 1 file changed, 15 insertions(+), 2 deletions(-) > > diff --git a/drivers/base/class.c b/drivers/base/class.c > index bcd410e..770b3b3 100644 > --- a/drivers/base/class.c > +++ b/drivers/base/class.c > @@ -206,6 +206,7 @@ void class_unregister(struct class *cls) > static void class_create_release(struct class *cls) > { > pr_debug("%s called for %s\n", __func__, cls->name); > + kfree_const(cls->name); > kfree(cls); > } > > @@ -227,7 +228,10 @@ struct class *__class_create(struct module *owner, const char *name, > struct lock_class_key *key) > { > struct class *cls; > - int retval; > + int retval = -EINVAL; > + > + if (!name) > + goto done; This is a new change, who calls this function with name not being set? > > cls = kzalloc(sizeof(*cls), GFP_KERNEL); > if (!cls) { > @@ -235,18 +239,27 @@ struct class *__class_create(struct module *owner, const char *name, > goto error; > } > > + name = kstrdup_const(name, GFP_KERNEL); > + if (!name) { > + retval = -ENOMEM; > + goto error; > + } and overwriting the pointer like that is bad-form, try doing something else here instead. > + > cls->name = name; > cls->owner = owner; > cls->class_release = class_create_release; > > retval = __class_register(cls, key); > if (retval) > - goto error; > + goto error_class_register; > > return cls; > > +error_class_register: > + kfree(cls->name); kfree_const()? thanks, greg k-h