linux-kernel - [RFC PATCH 2/8] mm: kpkeys: Introduce unrestricted level

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Message-ID: <20250203102809.1223255-3-kevin.brodsky@arm.com>
Date: Mon,  3 Feb 2025 10:28:03 +0000
From: Kevin Brodsky <kevin.brodsky@....com>
To: linux-hardening@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
	Kevin Brodsky <kevin.brodsky@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mark Brown <broonie@...nel.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	David Howells <dhowells@...hat.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Jann Horn <jannh@...gle.com>,
	Jeff Xu <jeffxu@...omium.org>,
	Joey Gouly <joey.gouly@....com>,
	Kees Cook <kees@...nel.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Andy Lutomirski <luto@...nel.org>,
	Marc Zyngier <maz@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Pierre Langlois <pierre.langlois@....com>,
	Quentin Perret <qperret@...gle.com>,
	"Mike Rapoport (IBM)" <rppt@...nel.org>,
	Ryan Roberts <ryan.roberts@....com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Will Deacon <will@...nel.org>,
	Matthew Wilcox <willy@...radead.org>,
	Qi Zheng <zhengqi.arch@...edance.com>,
	linux-arm-kernel@...ts.infradead.org,
	linux-mm@...ck.org,
	x86@...nel.org
Subject: [RFC PATCH 2/8] mm: kpkeys: Introduce unrestricted level

Highly privileged components, such as allocators, may require write
access to arbitrary data. To that end, introduce a kpkeys level that
grants write access to all kpkeys.

Signed-off-by: Kevin Brodsky <kevin.brodsky@....com>
---
 arch/arm64/include/asm/kpkeys.h | 4 +++-
 include/linux/kpkeys.h          | 3 ++-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/kpkeys.h b/arch/arm64/include/asm/kpkeys.h
index 3f16584d495a..ab2305ca24b7 100644
--- a/arch/arm64/include/asm/kpkeys.h
+++ b/arch/arm64/include/asm/kpkeys.h
@@ -19,7 +19,9 @@ static inline u64 por_set_kpkeys_level(u64 por, int level)
 {
 	por = por_set_pkey_perms(por, KPKEYS_PKEY_DEFAULT, POE_RXW);
 	por = por_set_pkey_perms(por, KPKEYS_PKEY_PGTABLES,
-				 level == KPKEYS_LVL_PGTABLES ? POE_RW : POE_R);
+				 level == KPKEYS_LVL_PGTABLES ||
+				 level == KPKEYS_LVL_UNRESTRICTED
+				 ? POE_RW : POE_R);
 
 	return por;
 }
diff --git a/include/linux/kpkeys.h b/include/linux/kpkeys.h
index 645eaf00096c..9d9feec83ccf 100644
--- a/include/linux/kpkeys.h
+++ b/include/linux/kpkeys.h
@@ -10,9 +10,10 @@ struct folio;
 
 #define KPKEYS_LVL_DEFAULT	0
 #define KPKEYS_LVL_PGTABLES	1
+#define KPKEYS_LVL_UNRESTRICTED	2
 
 #define KPKEYS_LVL_MIN		KPKEYS_LVL_DEFAULT
-#define KPKEYS_LVL_MAX		KPKEYS_LVL_PGTABLES
+#define KPKEYS_LVL_MAX		KPKEYS_LVL_UNRESTRICTED
 
 #define __KPKEYS_GUARD(name, set_level, restore_pkey_reg, set_arg, ...)	\
 	__DEFINE_CLASS_IS_CONDITIONAL(name, false);			\
-- 
2.47.0