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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D6B47C77B75 for ; Tue, 16 May 2023 20:37:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229705AbjEPUhU (ORCPT ); Tue, 16 May 2023 16:37:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53378 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229591AbjEPUhT (ORCPT ); Tue, 16 May 2023 16:37:19 -0400 Received: from mail-pf1-x436.google.com (mail-pf1-x436.google.com [IPv6:2607:f8b0:4864:20::436]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 868CA1FFE for ; Tue, 16 May 2023 13:37:18 -0700 (PDT) Received: by mail-pf1-x436.google.com with SMTP id d2e1a72fcca58-643990c5373so14918533b3a.1 for ; Tue, 16 May 2023 13:37:18 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; t=1684269438; x=1686861438; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=+Mgv2eOlGj/h9MwpBTlxreNYaXJNzFwMprpBEmpknKc=; b=TdlKCzKhDFUQTd31/qkSmmjb0xhqD5H36cEE70QK4cpplWptxDkNCZK29F6tr8HEqu GdakMB9csehTVAPg9SiLLLNjckM1jm2i9qFgagCLvsbHwAoQaSUztcg4MOEwEh4wnpHQ Trz90IS4j3mClG0eYjmpdpBVXP/5g2CEq4lxQ= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1684269438; x=1686861438; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=+Mgv2eOlGj/h9MwpBTlxreNYaXJNzFwMprpBEmpknKc=; b=L19S9rBgshcmp0Q7ZmIrNVXsL3jg7hrBGI+E2KvXrcjsWXRY9ZKXpk4nTF2DkqrALR U3LSK/c0/IK8w6KEDZMQOItzstzP7zmbMOgDVx7SE/OxLGYuM3KQ1t552Rw0IPKBWuWv 4D4NgFnPC7Ltgx3Eue0jfryPRIHTV/yOGNlq8eCOVSyajadWqTXdsJKG0Q2bbb3A4mbH bl65zF2TBgRH7cFeu0MfXvpGoGqn4/sDPcVB6SVKGq3ki/2la5B5AinOX+S/QYEMgwIE mhG8q0SM3MV+vf2mpddjG/4WWXY5jeqz+usQCJ1XIDm4U/spGLZrGGTdgOXiiLFOPkoa ysyA== X-Gm-Message-State: AC+VfDy0wfm2hLbkMzv1mBJTCetbplLkFET2hePOmEbf73DBZANGw1av 3DRJQDEslfd2113rV0wuEnpWHA== X-Google-Smtp-Source: ACHHUZ5jfYMLOvkx/dOXiqrfkGj2bp4cesBk6e+Y7hEdcYwmUwJUiReJK1XuEvKsidvpAxfkoLesqg== X-Received: by 2002:a05:6a00:10cd:b0:645:fc7b:63d6 with SMTP id d13-20020a056a0010cd00b00645fc7b63d6mr37919796pfu.6.1684269438040; Tue, 16 May 2023 13:37:18 -0700 (PDT) Received: from www.outflux.net (198-0-35-241-static.hfc.comcastbusiness.net. [198.0.35.241]) by smtp.gmail.com with ESMTPSA id b19-20020aa78713000000b00643355ff6a6sm14268576pfo.99.2023.05.16.13.37.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 16 May 2023 13:37:17 -0700 (PDT) Date: Tue, 16 May 2023 13:37:16 -0700 From: Kees Cook To: Christian Brauner Cc: Azeem Shaikh , linux-hardening@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Alexander Viro Subject: Re: [PATCH] vfs: Replace all non-returning strlcpy with strscpy Message-ID: <202305161331.6BA62FD@keescook> References: <20230510221119.3508930-1-azeemshaikh38@gmail.com> <20230515-seenotrettung-variieren-10995fad7802@brauner> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230515-seenotrettung-variieren-10995fad7802@brauner> Precedence: bulk List-ID: X-Mailing-List: linux-hardening@vger.kernel.org On Mon, May 15, 2023 at 09:50:25AM +0200, Christian Brauner wrote: > On Wed, 10 May 2023 22:11:19 +0000, Azeem Shaikh wrote: > > strlcpy() reads the entire source buffer first. > > This read may exceed the destination size limit. > > This is both inefficient and can lead to linear read > > overflows if a source string is not NUL-terminated [1]. > > In an effort to remove strlcpy() completely [2], replace > > strlcpy() here with strscpy(). > > No return values were used, so direct replacement is safe. > > > > [...] > > I sincerely hope we'll be done with swapping out various string > functions for one another at some point. Such patches always seems > benign and straightforward but the potential for subtle bugs is > feels rather high... Agreed. The long-term goal is to remove "strlcpy"[1] and "strncpy"[2] completely from the kernel, leaving only "strscpy". From there, I hope to do a treewide change to scrub the kernel of the pattern: strscpy(fixed-sized-dest, fixed-sized-source, sizeof(fixed-size-dest)) and replace it with a much stricter "strcpy" that refuses to work on dynamically sized arguments. This will get us away from the pointless exercise of duplicating sizeof() arguments when the compiler can very happily do it itself. But doing the return value transitions (and padding checks) for strlcpy and strncpy need to happen first. It's a long road. > Applied to the vfs.misc branch of the vfs/vfs.git tree. > Patches in the vfs.misc branch should appear in linux-next soon. Thanks! -Kees [1] https://github.com/KSPP/linux/issues/89 [2] https://github.com/KSPP/linux/issues/90 -- Kees Cook