linux-kernel - [RFC PATCH 13/16] arm64: mm: Reset pkey in __tlb_remove

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Message-ID: <20241206101110.1646108-14-kevin.brodsky@arm.com>
Date: Fri,  6 Dec 2024 10:11:07 +0000
From: Kevin Brodsky <kevin.brodsky@....com>
To: linux-hardening@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
	Kevin Brodsky <kevin.brodsky@....com>,
	aruna.ramakrishna@...cle.com,
	broonie@...nel.org,
	catalin.marinas@....com,
	dave.hansen@...ux.intel.com,
	jannh@...gle.com,
	jeffxu@...omium.org,
	joey.gouly@....com,
	kees@...nel.org,
	maz@...nel.org,
	pierre.langlois@....com,
	qperret@...gle.com,
	ryan.roberts@....com,
	will@...nel.org,
	linux-arm-kernel@...ts.infradead.org,
	x86@...nel.org
Subject: [RFC PATCH 13/16] arm64: mm: Reset pkey in __tlb_remove_table()

Page table pages are typically freed via tlb_remove_table() and
friends. Ensure that the linear mapping for those pages is reset to
the default pkey when CONFIG_KPKEYS_HARDENED_PGTABLES is enabled.

This patch is a no-op if CONFIG_KPKEYS_HARDENED_PGTABLES is disabled
(default).

Signed-off-by: Kevin Brodsky <kevin.brodsky@....com>
---
 arch/arm64/include/asm/tlb.h | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/tlb.h b/arch/arm64/include/asm/tlb.h
index a947c6e784ed..d1611ffa6d91 100644
--- a/arch/arm64/include/asm/tlb.h
+++ b/arch/arm64/include/asm/tlb.h
@@ -10,10 +10,14 @@
 
 #include <linux/pagemap.h>
 #include <linux/swap.h>
+#include <linux/kpkeys.h>
 
 static inline void __tlb_remove_table(void *_table)
 {
-	free_page_and_swap_cache((struct page *)_table);
+	struct page *page = (struct page *)_table;
+
+	kpkeys_unprotect_pgtable_memory((unsigned long)page_address(page), 1);
+	free_page_and_swap_cache(page);
 }
 
 #define tlb_flush tlb_flush
-- 
2.47.0