From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 4CB5BCA45 for ; Thu, 2 Jul 2026 05:18:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782969509; cv=none; b=BKEAV88rR0HCIa6Okcyh+DMaFwsiZ2DjNvLqqrfHH8NQGEBBm9jg5jVwlPTSX/oyy4tDqHHGDVOjx1yJCYIq8YsrX4Dx4IAtCHhheNSR5IIYyLkc3hA8pzKj4MlFEVpex5hLAIKryuiWJYVO3poRHYvc65mzlQIirO5Klz3dx3w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782969509; c=relaxed/simple; bh=HWcuQG3VbY7dExFtBga22lhrQAg518lTINsmOAVnKPs=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=BC76OSJ7cAaw+Y5ZmiD/l0YG8e5V9AUr26pMg6Ow/5Be4xxstxGFlyOvTkWM6CWMEDEg4LOlblCJZIOSfDwLn5jVYzmxfd6SYm4qX9Cqe8DTazbM2YsQYHbkbq74RxoHlc3dPRQ3rAm9joBDqLMLS5RCUfDPd/6QrtBZ7bImI88= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=scqO3kWI; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="scqO3kWI" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 3C5C61AC1; Wed, 1 Jul 2026 22:18:22 -0700 (PDT) Received: from [10.164.19.15] (unknown [10.164.19.15]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id AEB2A3F85F; Wed, 1 Jul 2026 22:18:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1782969506; bh=HWcuQG3VbY7dExFtBga22lhrQAg518lTINsmOAVnKPs=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=scqO3kWII+PhHw+GblRSZz1AJhAi5sK6iwxlRL9BdhBlWJQIXjm7cbkSYsl1gR0Kc nkntpx2oBLcqlKnTu9EZMUIWuFOHrXhX5KTZiMfAGbNG6JgNyJmLyFT9+UteYyap87 s35t4wy9yqBND0lQNNEmDM9zAyYhbCFKZmFpSItE= Message-ID: <555ccf16-3abf-4f82-9ebd-5df970e9de53@arm.com> Date: Thu, 2 Jul 2026 10:48:14 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 6/6] mm/mprotect: use huge_ptep_get() for hugetlb To: muchun.song@linux.dev, osalvador@suse.de, akpm@linux-foundation.org, ljs@kernel.org, david@kernel.org, liam@infradead.org Cc: riel@surriel.com, vbabka@kernel.org, harry@kernel.org, jannh@google.com, lance.yang@linux.dev, kas@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, rcampbell@nvidia.com, apopple@nvidia.com, ziy@nvidia.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, gourry@gourry.net, ying.huang@linux.alibaba.com, j-nomura@ce.jp.nec.com, nao.horiguchi@gmail.com, ak@linux.intel.com, mel@csn.ul.ie, pfalcato@suse.de, jpoimboe@kernel.org, dave.hansen@intel.com, tglx@kernel.org, catalin.marinas@arm.com, will@kernel.org, linux-arm-kernel@lists.infradead.org, ryan.roberts@arm.com, anshuman.khandual@arm.com References: <20260702051341.126509-1-dev.jain@arm.com> <20260702051341.126509-7-dev.jain@arm.com> Content-Language: en-US From: Dev Jain In-Reply-To: <20260702051341.126509-7-dev.jain@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 02/07/26 10:43 am, Dev Jain wrote: > prot_none_hugetlb_entry() is the hugetlb callback for the early > mprotect(PROT_NONE) PFN permission walk on x86. > > The callback passes the decoded PFN to pfn_modify_allowed(). For a > hugetlb callback, the pte pointer refers to a hugetlb entry. On > architectures where hugetlb entries need huge_ptep_get(), reading that > entry with ptep_get() can make the permission check use the wrong PFN. > > Use huge_ptep_get() before decoding the hugetlb PFN. > > Currently there is no path which can trigger a bug: huge_ptep_get() is a > simple ptep_get() for x86, and the prot_none walk occurs only for x86. > > So no need to backport - use the correct helper anyways. > > Fixes: 42e4089c7890 ("x86/speculation/l1tf: Disallow non privileged high MMIO PROT_NONE mappings") > Signed-off-by: Dev Jain > --- @Muchun, I did not do the change you suggested: if we do #ifdef around the hugetlb callback, then for CONFIG_HUGETLB_PAGE=n, prot_none_hugetlb_entry() is defined but not used, giving compile error. > mm/mprotect.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/mm/mprotect.c b/mm/mprotect.c > index 9cbf932b028cf..23779632d18bf 100644 > --- a/mm/mprotect.c > +++ b/mm/mprotect.c > @@ -699,14 +699,20 @@ static int prot_none_pte_entry(pte_t *pte, unsigned long addr, > 0 : -EACCES; > } > > +#ifdef CONFIG_HUGETLB_PAGE > static int prot_none_hugetlb_entry(pte_t *pte, unsigned long hmask, > unsigned long addr, unsigned long next, > struct mm_walk *walk) > { > - return pfn_modify_allowed(pte_pfn(ptep_get(pte)), > + pte_t entry = huge_ptep_get(walk->mm, addr, pte); > + > + return pfn_modify_allowed(pte_pfn(entry), > *(pgprot_t *)(walk->private)) ? > 0 : -EACCES; > } > +#else > +#define prot_none_hugetlb_entry NULL > +#endif > > static int prot_none_test(unsigned long addr, unsigned long next, > struct mm_walk *walk)