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]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id E7501CC6B1D for ; Wed, 14 Oct 2026 10:45:41 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id DC3886B0088; Wed, 14 Oct 2026 06:45:40 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D74236B008A; Wed, 14 Oct 2026 06:45:40 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id CB2016B008C; Wed, 14 Oct 2026 06:45:40 -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 ACB236B0088 for ; Wed, 14 Oct 2026 06:45:40 -0400 (EDT) Received: from smtpin06.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 53C66A8015 for ; Wed, 14 Oct 2026 10:45:40 +0000 (UTC) X-FDA: 85320900840.06.6B07BB2 Received: from mta1.migadu.com (out-241.mta1.migadu.com [95.215.58.241]) by imf21.hostedemail.com (Postfix) with ESMTP id 05FF51C0003 for ; Wed, 14 Oct 2026 10:45:37 +0000 (UTC) Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=FYzHg0Xn; spf=pass (imf21.hostedemail.com: domain of lance.yang@linux.dev designates 95.215.58.241 as permitted sender) smtp.mailfrom=lance.yang@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1791974738; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=blI+0pSqSuATt3s7ccT3kLKAD9SFsP3tmGqnNgFKm2c=; b=X/AgR6nzoRWOUg+lhZPYgefA5m3mMlSeIbFnekJ3eSzOhuyGFeY3OmeCPnFGWtSG6o1ugQ ZSEbdCHaZAaqOW39fX/z09uu+NTlAUIFuOLu0TbZm+v7RSeNDf4A/JjJn8JFWKhmzp9Ur/ c4n5AEpgRc9uhlRuSuyiGc7drxBCQOQ= ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1791974738; b=wWVWclnJDv6mb0pCbL5sZpYy3x+oQx0k6kzJAzyMk4ySx6eO8yAnxDqFMBWwdCFDhk1LLo UO0bsEfIpSQuXurugyuv/EYOeCK0Iw48HR/At8Qt/G8XdGEZ1qhECD+kqxyH3ENjon8TLd RxdEpgVBE4wsGqjsaX+DMT1PEc91CLE= ARC-Authentication-Results: i=1; imf21.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=FYzHg0Xn; spf=pass (imf21.hostedemail.com: domain of lance.yang@linux.dev designates 95.215.58.241 as permitted sender) smtp.mailfrom=lance.yang@linux.dev; dmarc=pass (policy=none) header.from=linux.dev X-Envelope-To: linux-mm@kvack.org DKIM-Signature: a=rsa-sha256; bh=4j71whs7pU+NnCMQt6l/U/Btk6pFemJHjPQ5tC3+JVI=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1791974733; v=1; x=1792579533; b=FYzHg0XnYGEUQq4gQZ5cIbHAgUUe4PpGS1L3xemdo1QSXQzcIC76202IsBVcUhpf6mVVskX/ XK4ZbrCHKtKxf26lrd1wGSJh0rbd9KbjJDTAkElHSfV7oM+6YU8/nTeRR4QAv4kDQFKqJpC0wiE r0uD1vFxp4NgP+ne0cKlS/C8= X-Envelope-To: linux-mm@kvack.org Received: by smtp.migadu.com with ESMTPS id 767be9f59756f718; Wed, 14 Oct 2026 10:45:21 +0000 X-Mizu-Trace-ID: 767be9f59756f718 X-Migadu-Flow: FLOW_OUT Message-ID: <44aba42f-0355-4643-826f-0c7abec4499c@linux.dev> Date: Wed, 14 Oct 2026 18:45:11 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] arm64/mm: restrict transparent contpte mappings to valid PTEs To: Dev Jain , Zhao Gongyi Cc: catalin.marinas@arm.com, will@kernel.org, ryan.roberts@arm.com, baolin.wang@linux.alibaba.com, mark.rutland@arm.com, akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20261013093600.54995-1-zhaogongyi@bytedance.com> <20261013153953.77575-1-lance.yang@linux.dev> <516828fb-558d-4a20-9532-51f50d6ba042@bytedance.com> <0bbbe312-47a4-4eeb-8299-1f20daf4e949@arm.com> Content-Language: en-US From: Lance Yang In-Reply-To: <0bbbe312-47a4-4eeb-8299-1f20daf4e949@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 05FF51C0003 X-Stat-Signature: ifzuwskurg6693w8hfos4roy5ys5gwr5 X-HE-Tag: 1791974737-130894 X-HE-Meta: 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 kszXyQFW u6UROzdVU+vIJouB6ybQNLZVBlFXmwheTYOf4Piw8RYXTaqEJSGyuL8fKy+DHeTfk3TMjVDManvAIxxj4edJujV376mCZ0m9oKENqA5c+BpNtTYLBttCuE48h1d6kB4zeBh7oWKidD+IkonQLdTHboidZ4bFODSAUc+It6BdoRrWVo55csgTX0nMNl/pVx7qpqN38pZRelnbOlDtS1HGHuUVvL106pBi/Qygtxxd9sdCga66rOLJK5GvBOvmuTp1oOmvBd50qA0HwAavefP3CYO/FsA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2026/10/14 18:03, Dev Jain wrote: > > > On 14/10/26 12:01 pm, Zhao Gongyi wrote: >> On 10/13/26 11:39 PM, Lance Yang wrote: >>>> >>>> + /* >>>> + * Keep the producer-side invariant documented in pgtable.h true even >>>> + * if a direct caller passes an invalid descriptor with PTE_CONT set. >>>> + */ >>>> + if (!pte_valid(pte)) >>>> + return __set_ptes(mm, addr, ptep, pte_mknoncont(pte), nr); >>> >>> set_ptes() is the only in-tree caller, and it already clears PTE_CONT >>> before we get here ... no? Why not fold !pte_valid(pte) into the >>> !mm_is_user(mm) check below and return __set_ptes() directly? >>> >>> if (!mm_is_user(mm) || !pte_valid(pte)) >>> return __set_ptes(mm, addr, ptep, pte, nr); >>> >>> If a direct caller does pass a !pte_valid PTE with PTE_CONT set, I'd >>> rather add a VM_WARN_ON() to catch that. Silently clearing the bit would >>> hide a caller bug :) >>> >> >> Hi Lance, >> >> Thanks for taking a look. >> >> Yes, you are right. The public set_ptes() wrapper already strips PTE_CONT >> before calling contpte_set_ptes(), so the pte_mknoncont() in the invalid >> path is unnecessary for the current in-tree path. >> >> The issue I was trying to avoid is not that the incoming pte already has >> PTE_CONT set, but that contpte_set_ptes() rebuilds the pte from pfn/prot >> and then adds PTE_CONT again based on alignment. For an invalid descriptor, >> that transparent contiguous encoding should be skipped entirely. >> >> So your suggested shape makes sense to me. I will change this to return >> through __set_ptes() directly for invalid descriptors, and add a warning >> for any unexpected direct caller that passes an invalid PTE with PTE_CONT >> set, e.g.: >> >> if (!mm_is_user(mm) || !pte_valid(pte)) { >> VM_WARN_ON_ONCE(!pte_valid(pte) && pte_cont(pte)); > > set_ptes does pte_mknoncont(), so the warning will *never* fire I think? YES. Just a sanity check to catch a future direct caller passing a !pte_valid PTE with PTE_CONT set, rather than silently clearing the bit :) Cheers, Lance > >> return __set_ptes(mm, addr, ptep, pte, nr); >> } >> >> That keeps the fix focused on not creating new invalid contpte entries, >> while still catching a bad direct caller instead of silently sanitizing it. >> >> Thanks, >> Zhao >