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 0B237CCA470 for ; Wed, 1 Oct 2025 17:22:39 +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=KtHH5slsD8Ox5MoPLqaiqd9jBeTgdv0YVlgjsuTd720=; b=zbrWBpfH7XkAXmKjAvZH2U+9am Elx6B7fMUn+XPu8wnpzL7gymrs939QI4PcdUDyehAwQ5PnoflabZDnOW84IEJTMsVqBh+/aUbH4zM zhDXEREguYtafeuIrMaiIKWGhDV4Bjg8U5349oDt3l9MhK+zY32shWEjo+xssvMHl1+Rv9EIVk/uu Ak4HHsDIbe3fM2NcsIoEbATvxX3gJH+y7lVUYFvGYLehxI4Ndd+YKqMyvwa/2qLme7rY9x6NRPFk/ gT9ofrG6Rse9KbBEJh3vqQBJjnuLJ0g/SqjbthPAitLEU/EEHMoNfUBUPbVvNukgaIMctJR2+PaMD SIuAxcng==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1v40XB-00000008dXA-0wbn; Wed, 01 Oct 2025 17:22:33 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1v40X8-00000008dVJ-3fvc for linux-arm-kernel@lists.infradead.org; Wed, 01 Oct 2025 17:22:32 +0000 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 DDF2116F8; Wed, 1 Oct 2025 10:22:19 -0700 (PDT) Received: from [10.57.66.40] (unknown [10.57.66.40]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 30AE33F59E; Wed, 1 Oct 2025 10:22:22 -0700 (PDT) Message-ID: <69b1c489-b4cb-4bee-aff1-6c76fc48cf29@arm.com> Date: Wed, 1 Oct 2025 19:22:20 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH v5 13/18] mm: Map page tables with privileged pkey To: David Hildenbrand , linux-hardening@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Andrew Morton , Andy Lutomirski , Catalin Marinas , Dave Hansen , Ira Weiny , Jann Horn , Jeff Xu , Joey Gouly , Kees Cook , Linus Walleij , Lorenzo Stoakes , Marc Zyngier , Mark Brown , Matthew Wilcox , Maxwell Bland , "Mike Rapoport (IBM)" , Peter Zijlstra , Pierre Langlois , Quentin Perret , Rick Edgecombe , Ryan Roberts , Thomas Gleixner , Vlastimil Babka , Will Deacon , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, x86@kernel.org References: <20250815085512.2182322-1-kevin.brodsky@arm.com> <20250815085512.2182322-14-kevin.brodsky@arm.com> <48ed62b1-cceb-4bce-923c-25c11dbccc37@redhat.com> Content-Language: en-GB From: Kevin Brodsky In-Reply-To: <48ed62b1-cceb-4bce-923c-25c11dbccc37@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251001_102231_024423_6ED06562 X-CRM114-Status: GOOD ( 21.91 ) 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 01/10/2025 17:28, David Hildenbrand wrote: > On 15.08.25 10:55, Kevin Brodsky wrote: > > Just wondering, should the patch subject be: > > "mm: protect page tables with privileged pkey" ? > > At least patch #2 tells me that set_memory_pkey() will set the > protection key, and the function is called > "kpkeys_protect_pgtable_memory"? > > Just trying to connect the dots here :) That's fair! I suppose I meant "map with privileged pkey" in the sense of "modify the mapping/PTE to set the pkey". But I see how that can be confusing, as we're not creating any mapping. I'll reword that in v6. > >> If CONFIG_KPKEYS_HARDENED_PGTABLES is enabled, map allocated page >> table pages using a privileged pkey (KPKEYS_PKEY_PGTABLES), so that >> page tables can only be written under guard(kpkeys_hardened_pgtables). >> >> This patch is a no-op if CONFIG_KPKEYS_HARDENED_PGTABLES is disabled >> (default). >> >> Signed-off-by: Kevin Brodsky >> --- >>   include/linux/mm.h | 4 ++++ >>   1 file changed, 4 insertions(+) >> >> diff --git a/include/linux/mm.h b/include/linux/mm.h >> index d9371d992033..4880cb7a4cb9 100644 >> --- a/include/linux/mm.h >> +++ b/include/linux/mm.h >> @@ -34,6 +34,7 @@ >>   #include >>   #include >>   #include >> +#include >>     struct mempolicy; >>   struct anon_vma; >> @@ -2979,6 +2980,8 @@ static inline bool __pagetable_ctor(struct >> ptdesc *ptdesc) >>         __folio_set_pgtable(folio); >>       lruvec_stat_add_folio(folio, NR_PAGETABLE); >> +    if (kpkeys_protect_pgtable_memory(folio)) >> +        return false; >>       return true; >>   } >>   @@ -2989,6 +2992,7 @@ static inline void pagetable_dtor(struct >> ptdesc *ptdesc) >>       ptlock_free(ptdesc); >>       __folio_clear_pgtable(folio); >>       lruvec_stat_sub_folio(folio, NR_PAGETABLE); >> +    kpkeys_unprotect_pgtable_memory(folio); > > This is all rather nasty. Not your fault. > > In the near future page tables will not be folios, and the whole > ptdesc_folio() conversion will not make any sense. Ah, interesting. Any patches/series I should be aware of? > > Likely you should make kpkeys_protect_pgtable_memory() etc. consume an > address range, or a page range right from the start. Got it. That said, as per the discussion on the cover letter [1], it's quite likely that we'll have to change the approach completely anyway (i.e. allocate PTPs from a dedicated pool where the pkey is already set). - Kevin [1] lore.kernel.org/r/aMwd7IJVECEy8mzf@willie-the-truck