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=-13.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,FAKE_REPLY_C,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 18C03C3526C for ; Sat, 19 Dec 2020 17:52:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D11AE2388E for ; Sat, 19 Dec 2020 17:52:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727250AbgLSRwf (ORCPT ); Sat, 19 Dec 2020 12:52:35 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56980 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725562AbgLSRwe (ORCPT ); Sat, 19 Dec 2020 12:52:34 -0500 Received: from mail-oi1-x233.google.com (mail-oi1-x233.google.com [IPv6:2607:f8b0:4864:20::233]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 83A41C0613CF for ; Sat, 19 Dec 2020 09:51:54 -0800 (PST) Received: by mail-oi1-x233.google.com with SMTP id l207so6713593oib.4 for ; Sat, 19 Dec 2020 09:51:54 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:mime-version :content-disposition:user-agent; bh=Bi9+8PWR8xRsIKhCEM2h2bE5clfk/H11A/Yp12L9OEg=; b=jUN8UuEPAlu4QHUtm9xoZZ67pzyNPhGzGpDj2V6xRqEC6O3ZlaBmHGUCQsTr1uRQau pz6EmwkOmdmXM9uyX//H+T5MK/0+g6LEmbX80m1GomCWr7koxLQ2kONoZ38tPc4X2GHS COdJrIG2ti9YGjuHKFlEuSQaPIRWZoit2fHnA8zaIqwmEU1WL+a7iFCFoKl5tua3q7dJ X7G4c5FFcTEF5XSQa6YDMnRt/hGFrzvyFO00Bp+xF1zq9KBl2HCg5cBeaz+6v4qM26RE 3S4bDPBbQmvnLngkpt60QJFcAwRcfJS8L60PcJDex2ycz+7l29Lk6Wc1eNB4PPzbKFvE h+zg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :mime-version:content-disposition:user-agent; bh=Bi9+8PWR8xRsIKhCEM2h2bE5clfk/H11A/Yp12L9OEg=; b=h+kFZoStE8JGaz8ZAMptog0Sp9jb795SbFo2PkGKLefyqUGlFXKmc1+jkRCAqVjxHx dnZJfVv1y9CHuO9rG4aJKpopEuEsy2Z9jZ/8uQtNbAqbfRSIXpPeJqLG6fSK/RWQ3wgE /1VJhKGvuJVkweQTyDHSdLyZNKmbTsxgVooP6k5MASWqEpBU6YTEc7tu88irYKzXRyOQ KwyceIq3zvNVK/1pMN1s1PR3l0bqKERHzTe7g3YMhPexbo/bxTsO8+UZXK2UoUhSmpXH xiv3k+TSH/s/yhWFX7lEPc5nyd3ztGhAvt0Td16dPnN75Kbkms1Nu4AZFOJFQvBY10pw rvUw== X-Gm-Message-State: AOAM533j803XyZ5QuJKzN6ludNXldwIF+ZGrqBAGtMmLjbikhWKpzujq ZUr7/RHusIsLPgbgTOMYeFU= X-Google-Smtp-Source: ABdhPJzl302HbXKhes494AXjy7KLvhTnVIsw6QClQhMrOYYsnFCPU+SnUD4zmIduRPFM3liguu82tw== X-Received: by 2002:a54:4787:: with SMTP id o7mr6496342oic.113.1608400313506; Sat, 19 Dec 2020 09:51:53 -0800 (PST) Received: from localhost ([2600:1700:e321:62f0:329c:23ff:fee3:9d7c]) by smtp.gmail.com with ESMTPSA id r15sm2498257oie.33.2020.12.19.09.51.52 (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Sat, 19 Dec 2020 09:51:52 -0800 (PST) Sender: Guenter Roeck Date: Sat, 19 Dec 2020 09:51:51 -0800 From: Guenter Roeck To: Kalesh Singh Cc: surenb@google.com, minchan@kernel.org, joelaf@google.com, lokeshgidra@google.com, kernel-team@android.com, Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: mremap - Fix extent calculation Message-ID: <20201219175151.GA6542@roeck-us.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.9.4 (2018-02-28) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Dec 19, 2020 at 05:04:33PM +0000, Kalesh Singh wrote: > When `next < old_addr`, `next - old_addr` arithmetic underflows > causing `extent` to be incorrect. > > Make `extent` the smaller of `next - old_addr` or `old_end - old_addr`. > > Reported-by: Guenter Roeck > Signed-off-by: Kalesh Singh This patch fixes the problem I had observed when booting 'parisc' images. Tested-by: Guenter Roeck Guenter > --- > mm/mremap.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/mm/mremap.c b/mm/mremap.c > index c5590afe7165..f554320281cc 100644 > --- a/mm/mremap.c > +++ b/mm/mremap.c > @@ -358,7 +358,9 @@ static unsigned long get_extent(enum pgt_entry entry, unsigned long old_addr, > > next = (old_addr + size) & mask; > /* even if next overflowed, extent below will be ok */ > - extent = (next > old_end) ? old_end - old_addr : next - old_addr; > + extent = next - old_addr; > + if (extent > old_end - old_addr) > + extent = old_end - old_addr; > next = (new_addr + size) & mask; > if (extent > next - new_addr) > extent = next - new_addr; > -- > 2.29.2.729.g45daf8777d-goog >