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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5095CC433F5 for ; Thu, 26 May 2022 13:17:55 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 958478D0003; Thu, 26 May 2022 09:17:54 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 906708D0002; Thu, 26 May 2022 09:17:54 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7CC718D0003; Thu, 26 May 2022 09:17:54 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 6DB698D0002 for ; Thu, 26 May 2022 09:17:54 -0400 (EDT) Received: from smtpin21.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 3737C4D2 for ; Thu, 26 May 2022 13:17:54 +0000 (UTC) X-FDA: 79507946868.21.CEE5D55 Received: from mail-ej1-f42.google.com (mail-ej1-f42.google.com [209.85.218.42]) by imf16.hostedemail.com (Postfix) with ESMTP id 0DC5B180053 for ; Thu, 26 May 2022 13:17:38 +0000 (UTC) Received: by mail-ej1-f42.google.com with SMTP id gh17so2989213ejc.6 for ; Thu, 26 May 2022 06:17:53 -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=/Tums9sSBFm64JACZICEeaJP4n2qB4OZ4M0MNbuB31s=; b=F04feQsX0xtaTMBBAIJ0ZM+soGiLto1TlYo8OhYxfKtXyZTXTedLY95EAHuqpAQ2Rw vhGMZLsQ0F1Xm8sCodqH/nso/UcewPDGeJPOFABGTeR2sloWV0vVUaiys3f89CFFwhJC p8yE4d5bu5QX+rSvVTcsbQLgksjy/MZlCeJaPrpFmZMCs1Muzb1smSiB9AMbSuJQJ1ut K+eyrNWUC79mn8xF3N5bNPxOBF9ucs4YO3II8PQESLvWiB3303TXV6YMPuAaQA/lKzl1 L1vRRV+dKBtm8nPyGLuSBEO0MrJ/MjIHWhLUO8CfCiKO91o0XgLpoYaSo8W3MnkbAmmc JwkQ== 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=/Tums9sSBFm64JACZICEeaJP4n2qB4OZ4M0MNbuB31s=; b=GEsqxqpkmT6Uhn/UE+Q69NS5UC08Pz+dAXz28PStMxFXswlJEF9N4Gf+d1Tbww3yM+ Bnlz1U3C6iEQzHxbneSxjCDaCXVLsg6KzX5WMQqTLJXhtIEArw2vKbm+BFZHbWdOjMNX lrYoE7z0ci+iux/hy/apw4OM/U76yDXAVHsa0Owi9NajrMFy4i9PSr+zsbLStYqSYWXo y/6icn478JziJ4ui41k97JwyssPkKGTLsyfWa6gWzURqL1yuMghQKXqn7UzwEf78PK0O 5itcSmkOWxPvVcOxDGYvOqXSP+o6YMewGxm87HNH1TmRff4VuLc8UbOoBwT7FFDTBPod tW+Q== X-Gm-Message-State: AOAM530ViI9FQERRQPoBwOemaE/X8W10LCbp1XxNtkRLavHhML0XWX6I j8A6RCtubNYunBEvEbuqMfG/q7Qq9IY6ZSJXQj6AyA== X-Google-Smtp-Source: ABdhPJwt2DDvHgTg3x1ZOOEX1n+YPivbXaH4Zo/aUAeNSS2EIe9RQvn5zW/kTp+wlypm6G+UT4rkqjenFUrrI+C6Cwc= X-Received: by 2002:a17:907:86a9:b0:6ff:45d:c05b with SMTP id qa41-20020a17090786a900b006ff045dc05bmr12015950ejc.492.1653571072192; Thu, 26 May 2022 06:17:52 -0700 (PDT) MIME-Version: 1.0 References: <20220526113350.30806-1-linmiaohe@huawei.com> In-Reply-To: <20220526113350.30806-1-linmiaohe@huawei.com> From: Pasha Tatashin Date: Thu, 26 May 2022 09:17:14 -0400 Message-ID: Subject: Re: [PATCH] mm/page_table_check: fix accessing unmapped ptep To: Miaohe Lin Cc: Andrew Morton , David Rientjes , linux-mm , LKML Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: 0DC5B180053 X-Stat-Signature: ptmhb3bi17n3zkojw93ssnb9n1sdfnfd Authentication-Results: imf16.hostedemail.com; dkim=pass header.d=soleen.com header.s=google header.b=F04feQsX; dmarc=none; spf=pass (imf16.hostedemail.com: domain of pasha.tatashin@soleen.com designates 209.85.218.42 as permitted sender) smtp.mailfrom=pasha.tatashin@soleen.com X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1653571058-582040 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 Thu, May 26, 2022 at 7:33 AM 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. I would re-word this as a cleanup. While pte_unmap() is currently unused, it is still better to call it after we are done with *ptep in case of future changes in other architectures. > > Fixes: 80110bbfbba6 ("mm/page_table_check: check entries at pmd levels") This is more a clean-up, there is no existing bug, so no need to backport to stable. Please remove the above. > Signed-off-by: Miaohe Lin With the above changes: Acked-by: Pasha Tatashin > --- > 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); > } > } > -- > 2.23.0 >