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 45576C433EF for ; Tue, 5 Oct 2021 22:55:41 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id CE87961029 for ; Tue, 5 Oct 2021 22:55:40 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org CE87961029 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=chromium.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 2F1BD900002; Tue, 5 Oct 2021 18:55:40 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 27A0C6B0071; Tue, 5 Oct 2021 18:55:40 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 11BCC900002; Tue, 5 Oct 2021 18:55:40 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0144.hostedemail.com [216.40.44.144]) by kanga.kvack.org (Postfix) with ESMTP id F20886B006C for ; Tue, 5 Oct 2021 18:55:39 -0400 (EDT) Received: from smtpin13.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 983DD181CC438 for ; Tue, 5 Oct 2021 22:55:39 +0000 (UTC) X-FDA: 78663892398.13.A4A490C Received: from mail-pg1-f172.google.com (mail-pg1-f172.google.com [209.85.215.172]) by imf21.hostedemail.com (Postfix) with ESMTP id 549AED03A3BB for ; Tue, 5 Oct 2021 22:55:39 +0000 (UTC) Received: by mail-pg1-f172.google.com with SMTP id s11so701743pgr.11 for ; Tue, 05 Oct 2021 15:55:39 -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=NE4Laz5ALb4pvgu+vNF3w9xn0H066FG9o1tnJaYX8As=; b=P7c3vg4GSo8CCeXXOp9VGjo+USLZGrrIukf4LblS8cuKZlyk2U6dY5qDg4bGz07T/b 8Ws1O1H2CjaS8XRUjjK7Mi/ICAj11daol3bce/RqiGrblKOAY4+zZt4N3E8+Q1F/cHmN BuaLLGKAYWp7QQR7Z1cHiFmlzRkWuoKWorP2Q= 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=NE4Laz5ALb4pvgu+vNF3w9xn0H066FG9o1tnJaYX8As=; b=tMBcTp6sbQwGShdvAVC4NRgebbp7hXJFXAyo53hkf0mYJbrQ/wQUnjRZEk9sVjhcQs 0+XwUdF1+DkJiDHmPc7Fy0rNQuJOCWTdzgV7s2C2vlq0OTe2UCTxlEkiHHTs6KejOwPM pibF89mGOEaCPSRUNklMP0ATnpvlWIqK9tYFOgCgvD3lj/4SiU9Pq0QVCtfT3mB2/hhA nLFq9Cv0kpmN2qsOj4bxk944aAB/Cb/nYsm4adgIXkrKNlbK6oJDuGeb0lHSI7PRkM0D M9wPqYd6fweZHsfsIGR6bqOO3fnaW8hG2wdBojR1MSrzChNjxMyxYRJF7mm9rOpcwW7W aMvQ== X-Gm-Message-State: AOAM533Vpo5GpEYt13NbdSHpe9KBZb6n3zT3eyJI/rKXVpSKZb1TCWHu eULQZoI974hh7FYFr2xaYQ4X/w== X-Google-Smtp-Source: ABdhPJyj+oSvq1U9jBLn3e0f0mB7xhCQRARwgQ5UKkcDxRrLeXP+YeiT3BDaVHB8+uduicgNNTR8+Q== X-Received: by 2002:a63:c4b:: with SMTP id 11mr3447542pgm.214.1633474538305; Tue, 05 Oct 2021 15:55:38 -0700 (PDT) Received: from www.outflux.net (smtp.outflux.net. [198.145.64.163]) by smtp.gmail.com with ESMTPSA id o11sm2820126pjp.0.2021.10.05.15.55.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 05 Oct 2021 15:55:38 -0700 (PDT) Date: Tue, 5 Oct 2021 15:55:37 -0700 From: Kees Cook To: Matthew Wilcox Cc: linux-mm@kvack.org, Thomas Gleixner Subject: Re: [PATCH 3/3] mm/usercopy: Detect compound page overruns Message-ID: <202110051555.72347C41@keescook> References: <20211004224224.4137992-1-willy@infradead.org> <20211004224224.4137992-4-willy@infradead.org> <202110051425.ABFA413@keescook> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 549AED03A3BB X-Stat-Signature: 8gx3urketfjpb6578ix9ztkup77chpdg Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=chromium.org header.s=google header.b=P7c3vg4G; dmarc=pass (policy=none) header.from=chromium.org; spf=pass (imf21.hostedemail.com: domain of keescook@chromium.org designates 209.85.215.172 as permitted sender) smtp.mailfrom=keescook@chromium.org X-HE-Tag: 1633474539-344553 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Oct 05, 2021 at 11:12:47PM +0100, Matthew Wilcox wrote: > On Tue, Oct 05, 2021 at 02:26:37PM -0700, Kees Cook wrote: > > On Mon, Oct 04, 2021 at 11:42:23PM +0100, Matthew Wilcox (Oracle) wrote: > > > + } else if (PageHead(page)) { > > > + /* A compound allocation */ > > > + if (ptr + n > page_address(page) + page_size(page)) > > > + usercopy_abort("page alloc", NULL, to_user, 0, n); > > > > "0" could be "ptr - page_address(page)", I think? With that: > > > > Acked-by: Kees Cook > > Right, so that can be: > > } else if (PageHead(page)) { > /* A compound allocation */ > unsigned long offset = ptr - page_address(page); > if (offset + n > page_size(page)) > usercopy_abort("page alloc", NULL, to_user, offset, n); > > which saves us calling page_address() twice. Probably GCC is smart > enough to CSE it anyway, but it also avoids splitting at the 80 column > boundary ;-) Perfect, yes! -- Kees Cook