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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 543B8C433F5 for ; Fri, 5 Nov 2021 16:58:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 31782610D0 for ; Fri, 5 Nov 2021 16:58:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233723AbhKERBa (ORCPT ); Fri, 5 Nov 2021 13:01:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33572 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229763AbhKERB3 (ORCPT ); Fri, 5 Nov 2021 13:01:29 -0400 Received: from mail-pj1-x1029.google.com (mail-pj1-x1029.google.com [IPv6:2607:f8b0:4864:20::1029]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0A010C061714; Fri, 5 Nov 2021 09:58:50 -0700 (PDT) Received: by mail-pj1-x1029.google.com with SMTP id gn3so3462829pjb.0; Fri, 05 Nov 2021 09:58:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=message-id:date:mime-version:user-agent:subject:content-language:to :cc:references:from:in-reply-to:content-transfer-encoding; bh=Dm/tkXe8vrCYnsbfNrGgeQZgPuQ1rWi9SOlQuOERJiI=; b=UlgE/YQSPQJWMfUCwYhCOqMFMyTOzpcRoFGeVLHrFwMjU1iG9rKTvQzHGlDVFkLOif nz2oGZJ1mrmILyfc7DAGyBmoFpWLwE0snPV1E61vYv2HKle3i6L0B/nWriJgQhTwrmTl TF0QAerEaUNMjLFqoXZRVALTfh9NDSHa1TYrtBzJrspT16kiXkysTx2ZbisaMpJ9RTSz IImS8hwU48HL1JpMLXPxI1xKjNop82xMh9LoIIiFRHSnVNOtxVU++8lGU47O9fpN6Mtv FVnrIkBVcs0aBL1B+y04O2oLdA70zx0tvk6GMz8LM1cIKWxAQa2O1KD6vDo15qloWAPN zbXg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:message-id:date:mime-version:user-agent:subject :content-language:to:cc:references:from:in-reply-to :content-transfer-encoding; bh=Dm/tkXe8vrCYnsbfNrGgeQZgPuQ1rWi9SOlQuOERJiI=; b=otzEm1PISloyZN7zf0gwW2o00zcBBKQ+rs9y1NKaANJq8vIMtw/sGQ85tdkllsK/FH i1Ha9ZD4+Gp8f5Nykx4yFX0PMSANHscXf9p+CpOMbrD1ZL43FTgX2Y5RvdQb7uxSL2Fm A35CDhkE+5WJ+Xm96DV/LFFvS39mXpiVAHPzIlEEk/D8GWeNLo0hhh1pRe7TYTA8+zgM 4KACmPESBEiEh6y88DwceTHwInl+8P41a/0vS6Kfvjo88NkBNZYLMZmsszhWyFLmHqOU PjWfyobFIGaJA0Y2yH78GvnHebJUK5pT7kOyrbd9VA7D2cbL+2rtWVw5I2iOzR1q8v1g Hoyw== X-Gm-Message-State: AOAM531U1scfbZ03zT/FUHfQ45hUYGb7Rm79XpGbwuSDMFtlzWrIzxcA aECn6px0cuKzLzxy59ONBxA= X-Google-Smtp-Source: ABdhPJxM2R0qJcfJqVo7o/snSZySDmo6F9vZuLLmqo8/DfMX02pan77bXrd9rpIJGITUbEsvFUv7iQ== X-Received: by 2002:a17:90b:4d84:: with SMTP id oj4mr26973402pjb.90.1636131529539; Fri, 05 Nov 2021 09:58:49 -0700 (PDT) Received: from [192.168.1.194] ([50.39.237.102]) by smtp.gmail.com with ESMTPSA id mz7sm4659568pjb.7.2021.11.05.09.58.48 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 05 Nov 2021 09:58:48 -0700 (PDT) Message-ID: <136709ac-1fbe-80d0-f49f-8a0399106ad8@gmail.com> Date: Fri, 5 Nov 2021 09:58:47 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:91.0) Gecko/20100101 Thunderbird/91.2.1 Subject: Re: [PATCH] landlock: Initialize kernel stack variables properly Content-Language: en-US To: Austin Kim , =?UTF-8?Q?Micka=c3=abl_Sala=c3=bcn?= Cc: "Serge E. Hallyn" , linux-security-module , Linux Kernel Mailing List References: <20211103071427.GA13854@raspberrypi> <7a71215c-58f4-081b-6a2e-030073f2737e@digikod.net> From: J Freyensee In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: On 11/4/21 4:41 AM, Austin Kim wrote: > 2021년 11월 3일 (수) 오후 9:14, Mickaël Salaün 님이 작성: >> Hi Austin, >> >> On 03/11/2021 08:14, Austin Kim wrote: >>> In case kernel stack variables are not initialized properly, there might >>> be a little chance of kernel information disclosure. So it is better for >>> kernel stack variables to be initialized with null characters. >>> >>> Signed-off-by: Austin Kim >>> --- >>> security/landlock/syscalls.c | 2 ++ >>> 1 file changed, 2 insertions(+) >>> >>> diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c >>> index 32396962f04d..50a6f7091428 100644 >>> --- a/security/landlock/syscalls.c >>> +++ b/security/landlock/syscalls.c >>> @@ -320,6 +320,8 @@ SYSCALL_DEFINE4(landlock_add_rule, >>> if (rule_type != LANDLOCK_RULE_PATH_BENEATH) >>> return -EINVAL; >>> >>> + memset(&path_beneath_attr, 0, sizeof(path_beneath_attr)); >>> + >> This memset is already done with the copy_from_user() call just below. >> > It seems that memset() is done inside copy_from_user(). > Thanks for feedback. If you are really sensitive of what information may be disclosed in this case you can consider memzero_explicit() to use instead: https://www.kernel.org/doc/htmldocs/kernel-api/API-memzero-explicit.html Jay > > BR, > Austin Kim > >>> /* Copies raw user space buffer, only one type for now. */ >>> res = copy_from_user(&path_beneath_attr, rule_attr, >>> sizeof(path_beneath_attr)); >>>