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=-6.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, 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 7811AC433EF for ; Tue, 14 Sep 2021 18:48:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4E3176113B for ; Tue, 14 Sep 2021 18:48:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229869AbhINStT (ORCPT ); Tue, 14 Sep 2021 14:49:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43550 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229937AbhINStS (ORCPT ); Tue, 14 Sep 2021 14:49:18 -0400 Received: from mail-pf1-x434.google.com (mail-pf1-x434.google.com [IPv6:2607:f8b0:4864:20::434]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EE699C061574 for ; Tue, 14 Sep 2021 11:48:00 -0700 (PDT) Received: by mail-pf1-x434.google.com with SMTP id q22so275864pfu.0 for ; Tue, 14 Sep 2021 11:48:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=u4/hZa5X5iiSrh9aM4nYzcLFV48vDhJpzjaofNxmELM=; b=kSvmUyBn95LRNcM6llDwG3+F1VjOFofJWmaLRoyYvU7KNVN9l1Iz9OnfHYkKJD0Hi3 CeJMoI5ctnU4Eba9OSWo+Phxe4/M/L+6RCYSi+YbNYGMEQBESgR1WFZMdoQ0QtrjvL8s DAbA37Pk5B9BaRHzasmS4ixeYYG7w5I4N3bs0= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=u4/hZa5X5iiSrh9aM4nYzcLFV48vDhJpzjaofNxmELM=; b=OT7mHU2OXTdiYtN0LuaHaqLKianykygwkDuqDRVs6DsNsMWjtuafhM0WOFyYVzPrsF kGqnL2rvpYtvlsfvYSCrekf3D84mPkMJM45OV9q7kHZdzJhvL7EJ0MmowGiRaXex16C7 z6S8B/Ihb/M4lpSb21bs7/mUERcZaklbMY5QagiLd4D8SDfAxlb4ATNuTAihphAf91bX xm/NaozECmD1LYewVFcV+hYf/3zgeJy7eOszN7JDbMn19yiVmFjwVRt7ew8QgFBPnss1 VlvyqlvMw3E+9F5BDOumBO7gHv9ACdpdSriMitny0tc79b+RLfNgDuRyEE/GZSc6zFxH PYSw== X-Gm-Message-State: AOAM532oPUbbbcsnTjlh21DMiRgeY9pn5KrpglZzXxDCZl5/Ez3LGZ7t mGCkMNGbngNcBF7rtcv5G3lTZPVSS9My7w== X-Google-Smtp-Source: ABdhPJxqbjG40g/47sryBDttm98oA7oQ4YOMO2XbIxC6H1EYNMN/YQ+DyO1bMFlOyEBbn2QKfqFtfQ== X-Received: by 2002:a05:6a00:170d:b0:3f3:bcdb:4883 with SMTP id h13-20020a056a00170d00b003f3bcdb4883mr6284406pfc.68.1631645280482; Tue, 14 Sep 2021 11:48:00 -0700 (PDT) Received: from www.outflux.net (smtp.outflux.net. [198.145.64.163]) by smtp.gmail.com with ESMTPSA id k190sm11477706pfd.211.2021.09.14.11.47.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 14 Sep 2021 11:47:59 -0700 (PDT) Date: Tue, 14 Sep 2021 11:47:58 -0700 From: Kees Cook To: Linus Torvalds Cc: Josef Bacik , Jens Axboe , Rasmus Villemoes , Nick Desaulniers , Greg Kroah-Hartman , Sasha Levin , llvm@lists.linux.dev, stable , Arnd Bergmann , Naresh Kamboju , Nathan Chancellor , Stephen Rothwell , Pavel Machek Subject: Re: [PATCH 5.10] overflow.h: use new generic division helpers to avoid / operator Message-ID: <202109141144.1AE2DDB@keescook> References: <20210913203201.1844253-1-ndesaulniers@google.com> <195b2f47-b92e-a00b-a2bc-d91bfdbd9d12@rasmusvillemoes.dk> <202109141031.AEFD06F03F@keescook> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Tue, Sep 14, 2021 at 11:30:03AM -0700, Linus Torvalds wrote: > case NBD_SET_SIZE_BLOCKS: > - if (check_mul_overflow((loff_t)arg, config->blksize, &bytesize)) > + bytesize = arg << config->blksize_bits; > + if (bytesize >> config->blksize_bits != arg) > return -EINVAL; FWIW, it's probably better to avoid open-coding the check. There are helpers for shift-left too. :) + if (check_shl_overflow(arg, config->blksize_bits, &bytesize)) -- Kees Cook