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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 48110CC6B1A for ; Wed, 14 Oct 2026 06:46:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=fyOVQO2Ag1zGISI6pO5VoA/zNNqmIYt5vkvpyI+5aQ4=; b=Lj+XVSaVZgMmvct58+70CKlT1y v1Hnjb3K3cqaJpA18rkhS83vohhMl9uS8D2qtBpKxBfMIqKPMO0V33pFKPOy1LkWqq+qUYAtUtaoe OnREsNfVVkSCgYpG9A3rCYOHhXM+uXmO5R6Gm7k2uRrBosB9+esmAQmUg0Kx79LD515Pg15zDIMOv ZGtxRkamYXuD6VD2c0LIhg9ZZRE00HuIrZz4LjZAi1X2QCcUB70jGjqnjb1ogdKERk4qTAs43+jj+ 6Vh+siphKpRJpyKrSROmVvO2OSqYeIdBW/fad+MeoVwdoq/1LA7oHvPxaPxJgP7HokQrJ7akLp0RZ x7AqbK/Q==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1xGsl7-0000000EeSg-2Um6; Wed, 14 Oct 2026 06:46:41 +0000 Received: from out-187.mta0.migadu.com ([2001:41d0:1004:224b::bb] helo=mta0.migadu.com) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1xGsl2-0000000EePo-2aFF for linux-arm-kernel@lists.infradead.org; Wed, 14 Oct 2026 06:46:41 +0000 X-Envelope-To: linux-arm-kernel@lists.infradead.org DKIM-Signature: a=rsa-sha256; bh=JLmTAoue8gGf1ERWgAb5UXzBAVBda1/ywkl4q8ms6rw=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1791960394; v=1; x=1792565194; b=XduXr+NWEQc2k1ced2e4wi+9s8WN76WAicldStKItAcufoJI3wVXZKFuaTRVUBF7ND96HqvN R0eN5dIVH8BZYV8hJprCPN82Jcgo77XC6FmBjysbkspL0JlH5jDAJN1pNq1vsLzkIQt/NFOchYo W3JiTblzWUaZR9iCpLyqRV+0= X-Envelope-To: linux-arm-kernel@lists.infradead.org Received: by smtp.migadu.com with ESMTPS id b9d4fb5be1186799; Wed, 14 Oct 2026 06:46:34 +0000 X-Mizu-Trace-ID: b9d4fb5be1186799 X-Migadu-Flow: FLOW_OUT Message-ID: Date: Wed, 14 Oct 2026 14:46:21 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] arm64/mm: restrict transparent contpte mappings to valid PTEs Content-Language: en-US To: Zhao Gongyi Cc: catalin.marinas@arm.com, will@kernel.org, ryan.roberts@arm.com, dev.jain@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> From: Lance Yang In-Reply-To: <516828fb-558d-4a20-9532-51f50d6ba042@bytedance.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20261013_234636_796790_F07BECA6 X-CRM114-Status: GOOD ( 17.39 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 2026/10/14 14:31, 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. Cheers! > 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)); > 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 for the quick fix! Nothing jumped out at me :) With that: Tested-by: Lance Yang