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=-3.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 AEFA4C433FE for ; Mon, 7 Dec 2020 23:35:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6DA9F23A1C for ; Mon, 7 Dec 2020 23:35:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726869AbgLGXf2 (ORCPT ); Mon, 7 Dec 2020 18:35:28 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40746 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725885AbgLGXf2 (ORCPT ); Mon, 7 Dec 2020 18:35:28 -0500 Received: from mail-ej1-x643.google.com (mail-ej1-x643.google.com [IPv6:2a00:1450:4864:20::643]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C383AC061793 for ; Mon, 7 Dec 2020 15:34:47 -0800 (PST) Received: by mail-ej1-x643.google.com with SMTP id ce23so18239195ejb.8 for ; Mon, 07 Dec 2020 15:34:47 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=intel-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=sQn63EZOge/5u1O/zNYXVy9jWmczpwAodhP6G+HhrVU=; b=jeKo0g5j8gN4DEjE1aP2Z3RxD4Z8Ti4/W6nfcus+ybjPJw/Hcim9xy6YDaReHy+a0U 4p4YnHZCHpTjyCSDmP8zNjiCM29dFmsd+k5ToTTnI4dzuSDlHOIO3/Cb2pDuCGi7c0w0 lw+VwjuHL68EDXS5o40RPzwvwQn2cxw6a8Q2Rgs7ApmqyZi2gLEsilYdE0P+Dv5TnA2f 1obtLxrhRxgRFiIiahpyBhfX4uu5QLNQNAB2w6pNBFuAUvZkwUPLtuHC2r62PC9U8UzB gQ6IDVmxnXeye5t+35Ly8YNDeoVFzu0jiAg9wG8D1Ym4cnuryeECwcgIDmDfb7R2hb7E GJMQ== 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=sQn63EZOge/5u1O/zNYXVy9jWmczpwAodhP6G+HhrVU=; b=ga/jbZ4rFZZn9NMOqmB+79EM7bCbALKMYk9sn0o/3PGGRSlIuQED462ZXQIO9GqBKL NbUIoT7cdktnNkt+tW3yeclK2iRqQgxsH36ZvT/kljW1yKIfBqfo5XKIUy6o+/9Qv1uc 7Gr62NctlMfeNaoMFaZUtu6IxhMKeIFfGXqCsn+XQyGrIvjkGpzCF9B3JHhYTF6FOIxf Cd6TzIQL1RZJhUyeSP+kRYeLgkdac5wGOpwBG/6Tq9Amyazl0Cvy5mkWJGh7EsgwIV3P 2kDupJ/R1ne4Bc2QZI6F+pfEYM7vhfU9C91xZ2dmXcR9jAchw1CR/4NgB4WsQU1o1W41 3luw== X-Gm-Message-State: AOAM530EokaI8EQZXeHjWljQON7XEFBZBd5sHbGlGOSeN9GR4KiObx1F 7uXmrqBRMWSL1S4Qf3hgrLCuUnz1cYgQCzkfIIUXSg== X-Google-Smtp-Source: ABdhPJwtDWGIn9y4uZwDu0nJvWG+uG9TLnwXhaQxgiDb2wu16RgtjNOa1ODvOYd09Mye5ssRlwgTG2PqZG4KNaG6z5g= X-Received: by 2002:a17:906:edb2:: with SMTP id sa18mr20172741ejb.264.1607384086382; Mon, 07 Dec 2020 15:34:46 -0800 (PST) MIME-Version: 1.0 References: <20201207225703.2033611-1-ira.weiny@intel.com> <20201207225703.2033611-3-ira.weiny@intel.com> <20201207232649.GD7338@casper.infradead.org> In-Reply-To: <20201207232649.GD7338@casper.infradead.org> From: Dan Williams Date: Mon, 7 Dec 2020 15:34:44 -0800 Message-ID: Subject: Re: [PATCH V2 2/2] mm/highmem: Lift memcpy_[to|from]_page to core To: Matthew Wilcox Cc: "Weiny, Ira" , Thomas Gleixner , Andrew Morton , Dave Hansen , Christoph Hellwig , Al Viro , Eric Biggers , Joonas Lahtinen , Linux Kernel Mailing List , linux-fsdevel Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Dec 7, 2020 at 3:27 PM Matthew Wilcox wrote: > > On Mon, Dec 07, 2020 at 02:57:03PM -0800, ira.weiny@intel.com wrote: > > +static inline void memcpy_page(struct page *dst_page, size_t dst_off, > > + struct page *src_page, size_t src_off, > > + size_t len) > > +{ > > + char *dst = kmap_local_page(dst_page); > > + char *src = kmap_local_page(src_page); > > I appreciate you've only moved these, but please add: > > BUG_ON(dst_off + len > PAGE_SIZE || src_off + len > PAGE_SIZE); I imagine it's not outside the realm of possibility that some driver on CONFIG_HIGHMEM=n is violating this assumption and getting away with it because kmap_atomic() of contiguous pages "just works (TM)". Shouldn't this WARN rather than BUG so that the user can report the buggy driver and not have a dead system?