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b=Jb+0DT4W1wA4KEIVY4FoTtbFdUSZtISD7worO4gRLlYY13CxQryM6AF6d0YWZbYzF LyX3FSawfZ0kMCSA4gRZSBZHETiCihTbBLv/EP9F1CduZHloB/MmIg5Ui7E/EouNKn TeHzhu0uercSUy9wjPxl5S4QDwqFdGmdvmn6wfms/pbWEDnjVLyCz2CpziNgPzIJ6U 9lyu2kDRnQ8Q38D98pATzyqu4XMt0IBR4d44V2436QrK3tQsQUdmouWn62qrqXx3kE btgIr4R3pdICtncO7p14CMOiRN4I88Pu2GDKcg/lLWRmMr8FkvK1VZqsV94h3ZAIFU /EQQgy7FE+paQ== Message-ID: Date: Wed, 15 Apr 2026 15:00:46 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 01/30] mm: Introduce kpkeys To: Kevin Brodsky , 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 , Yang Shi , Yeoreum Yun , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, x86@kernel.org References: <20260227175518.3728055-1-kevin.brodsky@arm.com> <20260227175518.3728055-2-kevin.brodsky@arm.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Queue-Id: 28C24140027 X-Stat-Signature: bdup1kahuxgpbu4hpxac6depam9aii7t X-Rspamd-Server: rspam06 X-HE-Tag: 1776258060-781169 X-HE-Meta: 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 p4w0AmW9 II4hXcQw9pN2V8mS1UpKaPJc8eqsZzYFW/A571hs+NzZhl2YgYj0cnwKEo3aGBk9e4Ua+BmPOb8SgsjTqUh9Z4i8URyxkH4hsRHP2zR0+qQfzYphmmVCTkIbYPpJm+cakiASNoFVM5w+D+i4cPqnB8KnQEeBvXZGJML7RoyXpg4jysevWFRk91IQnocFRS4HV7xYndrc+kXSfYvEWL68zxqiS7aNwj9tX45WQ96bjDNNqLi4QLDuWYwS6BSj352iAisDz Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2/27/26 18:54, Kevin Brodsky wrote: > kpkeys is a simple framework to enable the use of protection keys > (pkeys) to harden the kernel itself. This patch introduces the basic > API in : a couple of functions to set and restore > the pkey register and macros to define guard objects. > > kpkeys introduces a new concept on top of pkeys: the kpkeys level. > Each level is associated to a set of permissions for the pkeys > managed by the kpkeys framework. kpkeys_set_level(lvl) sets those > permissions according to lvl, and returns the original pkey > register, to be later restored by kpkeys_restore_pkey_reg(). To > start with, only KPKEYS_LVL_DEFAULT is available, which is meant > to grant RW access to KPKEYS_PKEY_DEFAULT (i.e. all memory since > this is the only available pkey for now). > > Because each architecture implementing pkeys uses a different > representation for the pkey register, and may reserve certain pkeys > for specific uses, support for kpkeys must be explicitly indicated > by selecting ARCH_HAS_KPKEYS and defining the following functions in > , in addition to the macros provided in > : I don't quite understand the reason for using levels. Levels sounds like it would all be in some ordered fashion, where higher levels have access to lower levels. Think of that as a key that can unlock all "lower" locks, not just a single lock. Then, the question is about the ordering once we introduce new keys/locks. With two, it obviously doesn't matter :) So naturally I wonder whether levels is really the right abstraction here, and why we are not simply using "distinct" keys, like KPKEY_DEFAULT KPKEY_PGTABLE KPKEY_SUPER_SECRET1 KPKEY_SUPER_SECRET2 Is it because you want KPKEY_PGTABLE also be able to write to KPKEY_DEFAULT? But how would you handle KPKEY_SUPER_SECRET1 and KPKEY_SUPER_SECRET2 then? -- Cheers, David