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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 50E7DC433F5 for ; Thu, 26 May 2022 13:11:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241615AbiEZNLv (ORCPT ); Thu, 26 May 2022 09:11:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52962 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244857AbiEZNLs (ORCPT ); Thu, 26 May 2022 09:11:48 -0400 Received: from mail-ej1-x631.google.com (mail-ej1-x631.google.com [IPv6:2a00:1450:4864:20::631]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 64E29D6817 for ; Thu, 26 May 2022 06:11:46 -0700 (PDT) Received: by mail-ej1-x631.google.com with SMTP id gi33so2974287ejc.3 for ; Thu, 26 May 2022 06:11:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=soleen.com; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=Nt+n2haklMuWStLRmgRtCfZgoN7afB/xjurnhlibBtA=; b=mdh4hUALSiiYooecz2d11OWfKfPev1AO99H5MjRa6BV8gFhSR5KjdOV7L8lCUi701X 3oE6KQ+1Pz6HNtSdOhN1ac/v1j7/wpJtJXG1c7Dh3jy9720CFNKoHEiAKmaYWREiK0ud YPTCe4Pc+4v24AnQM0uCl3U+MMV2GfyF3FlVlTaUgBDtnVSPu1My2a5HuiHpmoSOG1mv h2D8npJzXAq8jGEnX4q+C/5kLLFJGhzC4EXV/j+51zADBGxTb5cAvm9GkoMGrWR/n9dW F/fQMJIw96OTAOdjrFD8j/ghyoWQhiLQbiCcljv/HWdzPJ0F3RK7VneNeFgQnQq4WV71 GF3g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=Nt+n2haklMuWStLRmgRtCfZgoN7afB/xjurnhlibBtA=; b=VwSYozbtARaNQPQvWsqlhmbaPf6i5lLb6uSPKQ8ggCaq8H2J/GAnWvjBPvlLd6EORR gAQSFMb1LjeYw29gkkVc58IbG1DhbVOEMMMFkhzbaWRCIETyzMG+kf7v/Gfuf/9sW4TF 5GewGkje4X3MRZGuRgTqB4BlS2zfi/8Axp5Ba2N/JoUkC7RVt+o1uX4MsBUbUQ7VVkQ3 A64O1+YoV3/2mS3UlfGLj8q8x0vvrp/ad9GyvJOyS5cZVTzOn6Xee9llZVcAb6c1gktH /1U3i42qUTRBss8irFF/57WixUY/H2Z53rJtZsXQX8hik0IY+yNz0g9BSmnssguAxBUR kETQ== X-Gm-Message-State: AOAM5303TUtQ81Rv7pk7dldZaFzEERnzk+lleCFWxbOFFFtB8uIwLdIB pMHpnU9cljIdduFNsDaC/xyFYvQ40ZaMAyiJZSF7cw== X-Google-Smtp-Source: ABdhPJyVOJFJpwtgzyvTJVh+RCxHEKoowBQj8NU7m0i1XTs+8LBvYgl44pjc658B2YptHEliXFJqRdQ1QdhtiUwI7so= X-Received: by 2002:a17:907:86a9:b0:6ff:45d:c05b with SMTP id qa41-20020a17090786a900b006ff045dc05bmr11989570ejc.492.1653570704863; Thu, 26 May 2022 06:11:44 -0700 (PDT) MIME-Version: 1.0 References: <20220526113350.30806-1-linmiaohe@huawei.com> <09f38cf3-282a-61fa-9916-057b01b57d30@bytedance.com> In-Reply-To: <09f38cf3-282a-61fa-9916-057b01b57d30@bytedance.com> From: Pasha Tatashin Date: Thu, 26 May 2022 09:11:07 -0400 Message-ID: Subject: Re: [PATCH] mm/page_table_check: fix accessing unmapped ptep To: Qi Zheng Cc: Miaohe Lin , Andrew Morton , David Rientjes , linux-mm , LKML Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 26, 2022 at 9:04 AM Qi Zheng wrote: > > > > On 2022/5/26 7:33 PM, Miaohe Lin wrote: > > ptep is unmapped too early, so ptep will be accessed while it's unmapped. > > Fix it by deferring pte_unmap() until page table checking is done. > > In the beginning, page_table_check only supported x86_64, so there > is no problem. But then the commit 3fee229a8eb9 ("riscv/mm: enable > ARCH_SUPPORTS_PAGE_TABLE_CHECK") added support for riscv-32, it is > indeed a problem in this case. pte_unmap() is needed only with CONFIG_HIGHPTE. I do not see this config for riskv-32? Pasha > > So: > > Reviewed-by: Qi Zheng > > > > > Fixes: 80110bbfbba6 ("mm/page_table_check: check entries at pmd levels") > > Signed-off-by: Miaohe Lin > > --- > > mm/page_table_check.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/mm/page_table_check.c b/mm/page_table_check.c > > index 3692bea2ea2c..971c3129b0e3 100644 > > --- a/mm/page_table_check.c > > +++ b/mm/page_table_check.c > > @@ -234,11 +234,11 @@ void __page_table_check_pte_clear_range(struct mm_struct *mm, > > pte_t *ptep = pte_offset_map(&pmd, addr); > > unsigned long i; > > > > - pte_unmap(ptep); > > for (i = 0; i < PTRS_PER_PTE; i++) { > > __page_table_check_pte_clear(mm, addr, *ptep); > > addr += PAGE_SIZE; > > ptep++; > > } > > + pte_unmap(ptep); > > } > > } > > -- > Thanks, > Qi