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=-16.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=unavailable 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 603F0C433ED for ; Mon, 3 May 2021 04:55:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3450261376 for ; Mon, 3 May 2021 04:55:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232190AbhECE4X (ORCPT ); Mon, 3 May 2021 00:56:23 -0400 Received: from mail.kernel.org ([198.145.29.99]:47092 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229489AbhECEz7 (ORCPT ); Mon, 3 May 2021 00:55:59 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 11D4E606A5; Mon, 3 May 2021 04:54:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1620017696; bh=WO3o+LQZ/j0I9gGlRkfelt/09GbJDh2V9r0X25n8eDo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ufgz+jtlo4hzUgfJzbFK19b+gX6ulwT//TWHl7fRJSarXExjkakJXh67OB+YfcB1q X4MsjlzzGtw0kSY0t3WCkM+WDVtE670KHXKwk4c1E4VxA+h3jZf0AtEIC+JeNzrLfX dqckQ9fzSbvmkP2EwaT7N0tIUOMmWGKEbXdhPgK0= Date: Mon, 3 May 2021 06:54:54 +0200 From: Greg Kroah-Hartman To: Kees Cook Cc: Wenwen Wang , "Rafael J. Wysocki" , Len Brown , linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org Subject: Re: [PATCH] Revert "ACPI: custom_method: fix memory leaks" Message-ID: References: <20210502172326.2060025-1-keescook@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210502172326.2060025-1-keescook@chromium.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, May 02, 2021 at 10:23:26AM -0700, Kees Cook wrote: > This reverts commit 03d1571d9513369c17e6848476763ebbd10ec2cb. > > While /sys/kernel/debug/acpi/custom_method is already a privileged-only > API providing proxied arbitrary write access to kernel memory[1][2], > with existing race conditions[3] in buffer allocation and use that could > lead to memory leaks and use-after-free conditions, the above commit > appears to accidentally make the use-after-free conditions even easier > to accomplish. ("buf" is a global variable and prior kfree()s would set > buf back to NULL.) > > This entire interface needs to be reworked (if not entirely removed). > > [1] https://lore.kernel.org/lkml/20110222193250.GA23913@outflux.net/ > [2] https://lore.kernel.org/lkml/201906221659.B618D83@keescook/ > [3] https://lore.kernel.org/lkml/20170109231323.GA89642@beast/ > > Cc: Wenwen Wang > Signed-off-by: Kees Cook > --- > drivers/acpi/custom_method.c | 5 +---- > 1 file changed, 1 insertion(+), 4 deletions(-) > > diff --git a/drivers/acpi/custom_method.c b/drivers/acpi/custom_method.c > index 7b54dc95d36b..36d95a02cd30 100644 > --- a/drivers/acpi/custom_method.c > +++ b/drivers/acpi/custom_method.c > @@ -53,10 +53,8 @@ static ssize_t cm_write(struct file *file, const char __user * user_buf, > if ((*ppos > max_size) || > (*ppos + count > max_size) || > (*ppos + count < count) || > - (count > uncopied_bytes)) { > - kfree(buf); > + (count > uncopied_bytes)) > return -EINVAL; > - } > > if (copy_from_user(buf + (*ppos), user_buf, count)) { > kfree(buf); > @@ -76,7 +74,6 @@ static ssize_t cm_write(struct file *file, const char __user * user_buf, > add_taint(TAINT_OVERRIDDEN_ACPI_TABLE, LOCKDEP_NOW_UNRELIABLE); > } > > - kfree(buf); > return count; > } > > -- > 2.25.1 > Thanks for the revert, I'll queue it up on my larger "umn.edu reverts" branch that I'll be sending out for review in a day or so. greg k-h