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=-7.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no 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 AC7BAC43460 for ; Wed, 12 May 2021 13:19:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 739BC6112D for ; Wed, 12 May 2021 13:19:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231144AbhELNUl (ORCPT ); Wed, 12 May 2021 09:20:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46214 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230037AbhELNUk (ORCPT ); Wed, 12 May 2021 09:20:40 -0400 Received: from mail-wr1-x42a.google.com (mail-wr1-x42a.google.com [IPv6:2a00:1450:4864:20::42a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2095EC061574; Wed, 12 May 2021 06:19:30 -0700 (PDT) Received: by mail-wr1-x42a.google.com with SMTP id a4so23612124wrr.2; Wed, 12 May 2021 06:19:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=50s22QAFIe8Pgp5SC5xJu65yAnW54h9Wui8ifLw1Ctk=; b=FG/cft1gz7AGT8Ob/5BaAtTR6JqzvPxU04ZcAbFc+2GIA6JXxOMiUNvlG3ax3x8LfT A6PhHFM3omwjV2mzmpbiRYBuX2CFianIVYx+EffLzokUWDcmdYJf7YfnX7mT/wpKmkQz oE4m8JBeTGtTppPzLrlAbiTHfnhaAaUGsV/hmegZS2FK8Kj1hLqj5+fuMHufp3tZrnr2 pf65d44hzFMV0Kfhrm1cmIvE+asgz8wkAzxAA/iLSpn3Z2U4wdxjALHOZo6qJsSYcxOA +OzQ5z+Iw+Q2zytlO/STm0ddPqGqT1Qv9t+BDgx+bZvmJSMK/wliT6NYEF0tUhkDoayi hUEg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=50s22QAFIe8Pgp5SC5xJu65yAnW54h9Wui8ifLw1Ctk=; b=reze5+2wXWUOviEUDaqZsc5F7QKKdMwSyO6zz5a52qInytvI+hin37T+neM73U6mZN grUGdqi4u9J6HE5QrpuSod9Tt+HiFNDLipbKV7EzB8pABX81acIKpbpagQGdl/koYfc9 UwOQwDogD9Y2mjMYmvz/7LpEGrGYV/6L80k/Cd1k2SXaA2GaaYSk0SP7l+WJlj8NL+jN CzAAosBVQqC990VSLclZ6WYyPJ9ZnlH0db/RLV3ePID8U2/lTF91juYvTwr1q2jA0ivp vWVeM3dZFk0yA0tzY3bPx92py0zwD82l54koz9qeqBSM+Cnz5WbYzwIHaMZx+mEVPzvL ZtVA== X-Gm-Message-State: AOAM531+/pVPSXCRAhs60qcKPsSU921PET79LJBk8jhX1NZCEauTmDYe zC6wQthS0PXwYS3JPjYn6Q== X-Google-Smtp-Source: ABdhPJxcdyYrKcu9Mgjt4Emzl9xKlLaTbn2JleyHQWz2V4oYOxZ2rTS8LE3uP5EkdkQum6xL+3LEeA== X-Received: by 2002:adf:a4c4:: with SMTP id h4mr2897902wrb.330.1620825568910; Wed, 12 May 2021 06:19:28 -0700 (PDT) Received: from localhost.localdomain ([46.53.248.42]) by smtp.gmail.com with ESMTPSA id m11sm30480029wri.44.2021.05.12.06.19.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 12 May 2021 06:19:28 -0700 (PDT) Date: Wed, 12 May 2021 16:19:26 +0300 From: Alexey Dobriyan To: Marcelo Henrique Cerri Cc: linux-fsdevel@vger.kernel.org, David Disseldorp , Thadeu Lima de Souza Cascardo , Andrew Morton , Christian Brauner , Michel Lespinasse , Helge Deller , Oleg Nesterov , Lorenzo Stoakes , linux-kernel@vger.kernel.org Subject: Re: [PATCH] proc: Avoid mixing integer types in mem_rw() Message-ID: References: <20210512125215.3348316-1-marcelo.cerri@canonical.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20210512125215.3348316-1-marcelo.cerri@canonical.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, May 12, 2021 at 09:52:12AM -0300, Marcelo Henrique Cerri wrote: > Use size_t when capping the count argument received by mem_rw(). Since > count is size_t, using min_t(int, ...) can lead to a negative value > that will later be passed to access_remote_vm(), which can cause > unexpected behavior. > > Since we are capping the value to at maximum PAGE_SIZE, the conversion > from size_t to int when passing it to access_remote_vm() as "len" > shouldn't be a problem. > --- a/fs/proc/base.c > +++ b/fs/proc/base.c > @@ -854,7 +854,7 @@ static ssize_t mem_rw(struct file *file, char __user *buf, > flags = FOLL_FORCE | (write ? FOLL_WRITE : 0); > > while (count > 0) { > - int this_len = min_t(int, count, PAGE_SIZE); > + size_t this_len = min_t(size_t, count, PAGE_SIZE); As much as I don't like signed integers, VFS caps read/write lengths at INT_MAX & PAGE_MASK, so casting doesn't change values.