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c=simple/simple; d=arm.com; s=foss; t=1788796239; bh=SlilMlpGicltaebBQ8I/GC+iE4frt6Y1f/gAHvySSDQ=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=iqQG57G5PDVhyw+vfLok9WQkjMSwIU3sN60egn04GlddymBAdaexzT4zstzK5PxY0 28Bg4YQ63K5zQ+At/Qb/iDsJW7qSK16xoEp8sCDBbDw6BZlhdLqg23swtYz/GX344K +AGPNAn1CqfVXdKotmnH1oNQu3GUWshCTEXPjLlQ= Message-ID: <37bfd819-2bd4-4893-9d58-48c7e10880a3@arm.com> Date: Mon, 7 Sep 2026 17:50:31 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC v9 11/25] mm: kpkeys: Introduce kpkeys_hardened_pgtables feature To: Mike Rapoport Cc: linux-hardening@vger.kernel.org, Andrew Morton , Andy Lutomirski , Catalin Marinas , Dave Hansen , "David Hildenbrand (Arm)" , Jann Horn , Jeff Xu , Joey Gouly , Kees Cook , Linu Cherian , Linus Walleij , Marc Zyngier , Mark Brown , Matthew Wilcox , Maxwell Bland , Peter Zijlstra , Pierre Langlois , =?UTF-8?Q?Pierre-Cl=C3=A9ment_Tosi?= , Quentin Perret , Rick Edgecombe , Ryan Roberts , Vlastimil Babka , Will Deacon , Yang Shi , Yeoreum Yun , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, x86@kernel.org, Ira Weiny , Lorenzo Stoakes , Thomas Gleixner References: <20260818-kpkeys-v9-0-743ad31b2c8f@arm.com> <20260818-kpkeys-v9-11-743ad31b2c8f@arm.com> <178877845406.3691569.11239630051799000768.b4-review@b4> From: Kevin Brodsky Content-Language: en-GB In-Reply-To: <178877845406.3691569.11239630051799000768.b4-review@b4> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Stat-Signature: 9smghc55rzn9a8dstjbz8odxsr5ku6yq X-Rspamd-Queue-Id: A12AA20008 X-Rspamd-Server: rspam06 X-HE-Tag: 1788796240-149237 X-HE-Meta: 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 sibVZxft D6gz13jgXRGmEs9j55Xgs0EDTbU+7TfQqVVo9bhJjunAYQicUJeo5N5MapBa1vDltr3bETNhZoGMKG++Inrbr8GqZic304hOTNeexzf8nYO0Fn+muLONel3OEGexRqaz/NBpHDaPrM9fHa/e9PcXrFL4V+8Npg4688FjXP6ZLEiGwutXF6FPUHVOfJkJiHXx79Ov4/RkFrh5DoDTMk0CmSt56MgQGXEHfNaBN1wXY/+PxX3EAonubWLi9r8puvLfwz2GWUp2yjV3UySaSuuLH4ymJKkLmnDR/ID4p Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 07/09/2026 12:54, Mike Rapoport wrote: > Hi Kevin, > >> kpkeys_hardened_pgtables is a hardening feature based on kpkeys. It >> aims to prevent the corruption of page tables by: 1. mapping all >> page table pages, both kernel and user, with a privileged pkey >> (KPKEYS_PKEY_PGTABLES), and 2. granting write access to that pkey >> only when running at in a privileged kpkeys context >> (KPKEYS_CTX_PGTABLES). This patch introduces basic infrastructure; >> the implementation of both aspects will follow. >> >> The feature is exposed as CONFIG_KPKEYS_HARDENED_PGTABLES; it >> requires explicit architecture opt-in by selecting >> ARCH_HAS_KPKEYS_HARDENED_PGTABLES, since much of the page table >> handling is arch-specific. >> >> Because this feature relies on kpkeys being supported and modifies >> attributes of the linear map, it must be inactive on boot. >> kpkeys_hardened_pgtables_init() enables it by toggling a static key; >> this function must be called by supported architectures in >> mem_init(), before any call to pagetable_alloc() is made. > Presuming other architecures will use kpkeys framework it's better to > call kpkeys_hardened_pgtables_init() from mm_core_init() rather than > stick into each arch's mem_init(). Ah yes I was wondering whether it was acceptable to stick another call directly in mm_core_init(), but I suppose it doesn't hurt. I can move the call to kpkeys_hardened_pgtables_init() just before memblock_free_all() and leave mem_init() alone. Thanks for chipping in! - Kevin