From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-181.mta1.migadu.com (out-181.mta1.migadu.com [95.215.58.181]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 83F7133A00C for ; Thu, 2 Jul 2026 08:30:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.181 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782981059; cv=none; b=YolR4Lg4i5mCaTNh4HOYh2FCP4+99auuSzLq2cXQyz2vrG4kgMqEe6JTbQXkPlLAAGrmKjxWWKvf2MqdcPlf0JchMK/BP/MEEtwBxyYboKPad5gZER7eiio2vk3fERzM6kcBUXNTDW0DLrX6/i4JoLJM/3tocaBr+1IJUZgMlEA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782981059; c=relaxed/simple; bh=adgjMTckmpxpZCcJHdKndp5zeblz2lkQJtQUpi5yLqw=; h=Content-Type:Mime-Version:Subject:From:In-Reply-To:Date:Cc: Message-Id:References:To; b=bQVKenBi2lehUrTymN5+J2+eecomwLSyyKajEIwduUkL/wR4kyxXHIFQeN4buRKgZDoDEFvun2fCrpi2NAM55eVYkJUoBKN0qiNee9rTUNoUF54+3uj7RVGVAuH02kZybi935F6xltzwtK7Pi+CdckblnP8qc4go8emXTh0s7kE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=lCL8SUoR; arc=none smtp.client-ip=95.215.58.181 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="lCL8SUoR" Content-Type: text/plain; charset=us-ascii DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1782981054; h=from:from: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; bh=adgjMTckmpxpZCcJHdKndp5zeblz2lkQJtQUpi5yLqw=; b=lCL8SUoRvBuYJjOANyVkEtDxtMP+lrtMd+JM22wKEQg/9vL02SI2jmIv/0K6w18ZXSfRmW pyYqOtyzNMKo9IlWryGti6xTNZDxKuT4/OiXQMIgcEuP/lkaMwrX5LmL40mqzRK/is1qNv 824p2/q8qxoAqbhxxZiPgnYNnOVND+E= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3864.600.51.1.1\)) Subject: Re: [PATCH v2 6/6] mm/mprotect: use huge_ptep_get() for hugetlb X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Muchun Song In-Reply-To: <555ccf16-3abf-4f82-9ebd-5df970e9de53@arm.com> Date: Thu, 2 Jul 2026 16:29:59 +0800 Cc: osalvador@suse.de, akpm@linux-foundation.org, ljs@kernel.org, david@kernel.org, liam@infradead.org, 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 Content-Transfer-Encoding: quoted-printable Message-Id: <69EA5792-0152-4ACA-9BB0-1971180F40F0@linux.dev> References: <20260702051341.126509-1-dev.jain@arm.com> <20260702051341.126509-7-dev.jain@arm.com> <555ccf16-3abf-4f82-9ebd-5df970e9de53@arm.com> To: Dev Jain X-Migadu-Flow: FLOW_OUT > On Jul 2, 2026, at 13:18, Dev Jain wrote: >=20 >=20 >=20 > 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. >>=20 >> 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. >>=20 >> Use huge_ptep_get() before decoding the hugetlb PFN. >>=20 >> 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. >>=20 >> So no need to backport - use the correct helper anyways. >>=20 >> Fixes: 42e4089c7890 ("x86/speculation/l1tf: Disallow non privileged = high MMIO PROT_NONE mappings") >> Signed-off-by: Dev Jain >> --- >=20 > @Muchun, I did not do the change you suggested: if we do #ifdef around > the hugetlb callback, then for CONFIG_HUGETLB_PAGE=3Dn, = prot_none_hugetlb_entry() > is defined but not used, giving compile error. >=20 Got it. Thanks for your explanation.