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=-19.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_RED,USER_AGENT_GIT autolearn=unavailable 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 3F9F3C4332E for ; Mon, 15 Mar 2021 14:50:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1DB1764FC3 for ; Mon, 15 Mar 2021 14:50:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238030AbhCOOtz (ORCPT ); Mon, 15 Mar 2021 10:49:55 -0400 Received: from mail.kernel.org ([198.145.29.99]:49008 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232682AbhCOOYz (ORCPT ); Mon, 15 Mar 2021 10:24:55 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 6224B6506D; Mon, 15 Mar 2021 14:24:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1615818291; bh=qlgasr3+ZRpAg9iQcYqf+dX55vEfBbKD0Qm7BuwN1TI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=B49mjBUJguCHsNOewLCrKgJNHP4g9IrY63bYBspU/poJSPNs+ugOkxc4HQx1C9D1f EVjviIy514qLBOcMbEps2xC8e3LJthrjgxrwI9Zqdp+oKpmo81fZ3APM10oPbM6HAo q1KzbfL4fc5wGTlm7WhlASAuciTf7Yqa3YjKnMqI= From: gregkh@linuxfoundation.org To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, OGAWA Hirofumi , Matthew Wilcox , Andrew Morton , Linus Torvalds Subject: [PATCH 5.11 300/306] mm/highmem.c: fix zero_user_segments() with start > end Date: Mon, 15 Mar 2021 15:24:25 +0100 Message-Id: <20210315135517.847546877@linuxfoundation.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210315135517.556638562@linuxfoundation.org> References: <20210315135507.611436477@linuxfoundation.org> <20210315135517.556638562@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Greg Kroah-Hartman From: OGAWA Hirofumi commit 184cee516f3e24019a08ac8eb5c7cf04c00933cb upstream. zero_user_segments() is used from __block_write_begin_int(), for example like the following zero_user_segments(page, 4096, 1024, 512, 918) But new the zero_user_segments() implementation for for HIGHMEM + TRANSPARENT_HUGEPAGE doesn't handle "start > end" case correctly, and hits BUG_ON(). (we can fix __block_write_begin_int() instead though, it is the old and multiple usage) Also it calls kmap_atomic() unnecessarily while start == end == 0. Link: https://lkml.kernel.org/r/87v9ab60r4.fsf@mail.parknet.co.jp Fixes: 0060ef3b4e6d ("mm: support THPs in zero_user_segments") Signed-off-by: OGAWA Hirofumi Cc: Matthew Wilcox Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/highmem.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) --- a/mm/highmem.c +++ b/mm/highmem.c @@ -368,20 +368,24 @@ void zero_user_segments(struct page *pag BUG_ON(end1 > page_size(page) || end2 > page_size(page)); + if (start1 >= end1) + start1 = end1 = 0; + if (start2 >= end2) + start2 = end2 = 0; + for (i = 0; i < compound_nr(page); i++) { void *kaddr = NULL; - if (start1 < PAGE_SIZE || start2 < PAGE_SIZE) - kaddr = kmap_atomic(page + i); - if (start1 >= PAGE_SIZE) { start1 -= PAGE_SIZE; end1 -= PAGE_SIZE; } else { unsigned this_end = min_t(unsigned, end1, PAGE_SIZE); - if (end1 > start1) + if (end1 > start1) { + kaddr = kmap_atomic(page + i); memset(kaddr + start1, 0, this_end - start1); + } end1 -= this_end; start1 = 0; } @@ -392,8 +396,11 @@ void zero_user_segments(struct page *pag } else { unsigned this_end = min_t(unsigned, end2, PAGE_SIZE); - if (end2 > start2) + if (end2 > start2) { + if (!kaddr) + kaddr = kmap_atomic(page + i); memset(kaddr + start2, 0, this_end - start2); + } end2 -= this_end; start2 = 0; }