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=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL 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 530C9C433E0 for ; Thu, 4 Jun 2020 20:30:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2ECC9206E6 for ; Thu, 4 Jun 2020 20:30:00 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="N9f0DBz1" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729828AbgFDU37 (ORCPT ); Thu, 4 Jun 2020 16:29:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52946 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728869AbgFDU35 (ORCPT ); Thu, 4 Jun 2020 16:29:57 -0400 Received: from mail-pf1-x444.google.com (mail-pf1-x444.google.com [IPv6:2607:f8b0:4864:20::444]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 117DCC08C5C6 for ; Thu, 4 Jun 2020 13:29:57 -0700 (PDT) Received: by mail-pf1-x444.google.com with SMTP id f3so3779838pfd.11 for ; Thu, 04 Jun 2020 13:29:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=bnsaMm5xHsmGTKM8crY5633RBfnrE452zASAiUrFU6c=; b=N9f0DBz11v8qKCu5VA9JXvurX/AQtTOXbiTH5jmNKefXzNsIFm+M7WPzmoaUlp4aH2 r+jMi/YmukLuVqYctzsJtxcn0mVNYhMsSNT9VA6N7PnsQg5yUlK9mfLk/5/Ruh0U/Pwu PDPRxMt4IzbnxQDI/neSyUM1ytXRkW/vLuLZKE80o7Nj5PUF2JyDsoKL+PvQ95dTnNfZ KgrObLpuy2lSQ1b3DD2riryZUDl8/MGtuP3prwyWT2YzcrBoR4Z0ygA8w4IwkVOIQfT2 XknAaA0BFuOmwbwTbgOy7UCAxJmRzkJu3RwBQHvX6d2dQvm2RBoWXIh1YpGHB5SsL5b+ hRAg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=bnsaMm5xHsmGTKM8crY5633RBfnrE452zASAiUrFU6c=; b=Qyb2JOSu7ZKto+kbXgGvp8nxo+B4EgkKnd6N2seA27Zjj969SNxSN47NAHZ7yBgiOT nbelLrsU7Soj/KFMzc0sDNBUxFR5tnp8CV9vNXFo4pt9AzSKs+nXtDTSoJmqLTG5ggPo TcF2RYNaM4s4dAxxDb11eS7V0yZ4NGJCZLyPGKTrMrH5ZnsSA7fcT3I7hlr1iHoys8WH FIaANucGwEfw7RQyN3JCGu2z0EfX3Qzydap8WJV0xSPDQ3fjcUz2mPk2gbOz0iXV/U/n 5nby5SFWND4GUThqgMExFKPNPs9AE+lrBypGme3NSVWOQiUInTXdybmdOH4tcJv+N8Oi EpPQ== X-Gm-Message-State: AOAM532YqmEeqVX8rhSkVo63t4K24D9nufHNEX6qOd4rVsZoErXzTr5M KsKoC694ReCFGUOq67zADrpO7eAneNUUXPqLTKVQvA== X-Google-Smtp-Source: ABdhPJy84Bpyo9gVnHDmhNZ0Cl7JJ5pAaUOhbP1nHyEJIJ3dMgwhwkaPgsD+FnKg2zDZj7i1oTdj2nlsRsGHJYRwQ7w= X-Received: by 2002:a63:f00d:: with SMTP id k13mr6286936pgh.263.1591302596138; Thu, 04 Jun 2020 13:29:56 -0700 (PDT) MIME-Version: 1.0 References: <20200603233203.1695403-1-keescook@chromium.org> <20200603233203.1695403-6-keescook@chromium.org> <202006041318.B0EA9059C7@keescook> In-Reply-To: <202006041318.B0EA9059C7@keescook> From: Nick Desaulniers Date: Thu, 4 Jun 2020 13:29:44 -0700 Message-ID: Subject: Re: [PATCH 05/10] ide: Remove uninitialized_var() usage To: Kees Cook Cc: LKML , Linus Torvalds , Miguel Ojeda , Alexander Potapenko , Joe Perches , Andy Whitcroft , "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , drbd-dev@lists.linbit.com, linux-block@vger.kernel.org, b43-dev@lists.infradead.org, Network Development , linux-wireless , linux-ide@vger.kernel.org, linux-clk@vger.kernel.org, linux-spi@vger.kernel.org, Linux Memory Management List , clang-built-linux , Sebastian Andrzej Siewior , Saravana Kannan Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jun 4, 2020 at 1:20 PM Kees Cook wrote: > > On Thu, Jun 04, 2020 at 12:29:17PM -0700, Nick Desaulniers wrote: > > On Wed, Jun 3, 2020 at 4:32 PM Kees Cook wrote: > > > > > > Using uninitialized_var() is dangerous as it papers over real bugs[1] > > > (or can in the future), and suppresses unrelated compiler warnings (e.g. > > > "unused variable"). If the compiler thinks it is uninitialized, either > > > simply initialize the variable or make compiler changes. As a precursor > > > to removing[2] this[3] macro[4], just remove this variable since it was > > > actually unused: > > > > > > drivers/ide/ide-taskfile.c:232:34: warning: unused variable 'flags' [-Wunused-variable] > > > unsigned long uninitialized_var(flags); > > > ^ > > > > > > [1] https://lore.kernel.org/lkml/20200603174714.192027-1-glider@google.com/ > > > [2] https://lore.kernel.org/lkml/CA+55aFw+Vbj0i=1TGqCR5vQkCzWJ0QxK6CernOU6eedsudAixw@mail.gmail.com/ > > > [3] https://lore.kernel.org/lkml/CA+55aFwgbgqhbp1fkxvRKEpzyR5J8n1vKT1VZdz9knmPuXhOeg@mail.gmail.com/ > > > [4] https://lore.kernel.org/lkml/CA+55aFz2500WfbKXAx8s67wrm9=yVJu65TpLgN_ybYNv0VEOKA@mail.gmail.com/ > > > > > > Signed-off-by: Kees Cook > > > > Reviewed-by: Nick Desaulniers > > Thanks for the reviews! > > > Fixes ce1e518190ea ("ide: don't disable interrupts during kmap_atomic()") > > I originally avoided adding Fixes tags because I didn't want these > changes backported into a -stable without -Wmaybe-uninitialized > disabled, but in these cases (variable removal), that actually does make > sense. Thanks! Saravana showed me a cool trick for quickly finding commits that removed a particular identifier that I find faster than `git blame` or vim-fugitive for the purpose of Fixes tags: $ git log -S I've added it to our wiki: https://github.com/ClangBuiltLinux/linux/wiki/Command-line-tips-and-tricks#for-finding-which-commit-may-have-removed-a-string-try. I should update the first tip; what was your suggestion for constraining the search to the current remote? -- Thanks, ~Nick Desaulniers