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From: Peter Collingbourne <pcc@google.com>
To: Will Deacon <will@kernel.org>
Cc: Peter Collingbourne <pcc@google.com>,
	Marc Zyngier <maz@kernel.org>,
	linux-arm-kernel@lists.infradead.org,
	Catalin Marinas <catalin.marinas@arm.com>,
	stable@vger.kernel.org
Subject: [PATCH] arm64: set UXN on swapper page tables
Date: Tue, 19 Jul 2022 16:49:09 -0700	[thread overview]
Message-ID: <20220719234909.1398992-1-pcc@google.com> (raw)

On a system that implements FEAT_EPAN, read/write access to the idmap
is denied because UXN is not set on the swapper PTEs. As a result,
idmap_kpti_install_ng_mappings panics the kernel when accessing
__idmap_kpti_flag. Fix it by setting UXN on these PTEs.

Fixes: 18107f8a2df6 ("arm64: Support execute-only permissions with Enhanced PAN")
Cc: <stable@vger.kernel.org> # 5.15
Link: https://linux-review.googlesource.com/id/Ic452fa4b4f74753e54f71e61027e7222a0fae1b1
Signed-off-by: Peter Collingbourne <pcc@google.com>
---
This fix is no longer needed since commit c3cee924bd85 ("arm64: head:
cover entire kernel image in initial ID map"), which moved __idmap_kpti_flag
to .data, but that commit is currently only present in next.

 arch/arm64/include/asm/kernel-pgtable.h | 4 ++--
 arch/arm64/kernel/head.S                | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/kernel-pgtable.h b/arch/arm64/include/asm/kernel-pgtable.h
index 96dc0f7da258..a971d462f531 100644
--- a/arch/arm64/include/asm/kernel-pgtable.h
+++ b/arch/arm64/include/asm/kernel-pgtable.h
@@ -103,8 +103,8 @@
 /*
  * Initial memory map attributes.
  */
-#define SWAPPER_PTE_FLAGS	(PTE_TYPE_PAGE | PTE_AF | PTE_SHARED)
-#define SWAPPER_PMD_FLAGS	(PMD_TYPE_SECT | PMD_SECT_AF | PMD_SECT_S)
+#define SWAPPER_PTE_FLAGS	(PTE_TYPE_PAGE | PTE_AF | PTE_SHARED | PTE_UXN)
+#define SWAPPER_PMD_FLAGS	(PMD_TYPE_SECT | PMD_SECT_AF | PMD_SECT_S | PMD_SECT_UXN)
 
 #if ARM64_KERNEL_USES_PMD_MAPS
 #define SWAPPER_MM_MMUFLAGS	(PMD_ATTRINDX(MT_NORMAL) | SWAPPER_PMD_FLAGS)
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 6a98f1a38c29..8a93a0a7489b 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -285,7 +285,7 @@ SYM_FUNC_START_LOCAL(__create_page_tables)
 	subs	x1, x1, #64
 	b.ne	1b
 
-	mov	x7, SWAPPER_MM_MMUFLAGS
+	mov_q	x7, SWAPPER_MM_MMUFLAGS
 
 	/*
 	 * Create the identity mapping.
-- 
2.37.0.170.g444d1eabd0-goog


WARNING: multiple messages have this Message-ID (diff)
From: Peter Collingbourne <pcc@google.com>
To: Will Deacon <will@kernel.org>
Cc: Peter Collingbourne <pcc@google.com>,
	Marc Zyngier <maz@kernel.org>,
	linux-arm-kernel@lists.infradead.org,
	 Catalin Marinas <catalin.marinas@arm.com>,
	stable@vger.kernel.org
Subject: [PATCH] arm64: set UXN on swapper page tables
Date: Tue, 19 Jul 2022 16:49:09 -0700	[thread overview]
Message-ID: <20220719234909.1398992-1-pcc@google.com> (raw)

On a system that implements FEAT_EPAN, read/write access to the idmap
is denied because UXN is not set on the swapper PTEs. As a result,
idmap_kpti_install_ng_mappings panics the kernel when accessing
__idmap_kpti_flag. Fix it by setting UXN on these PTEs.

Fixes: 18107f8a2df6 ("arm64: Support execute-only permissions with Enhanced PAN")
Cc: <stable@vger.kernel.org> # 5.15
Link: https://linux-review.googlesource.com/id/Ic452fa4b4f74753e54f71e61027e7222a0fae1b1
Signed-off-by: Peter Collingbourne <pcc@google.com>
---
This fix is no longer needed since commit c3cee924bd85 ("arm64: head:
cover entire kernel image in initial ID map"), which moved __idmap_kpti_flag
to .data, but that commit is currently only present in next.

 arch/arm64/include/asm/kernel-pgtable.h | 4 ++--
 arch/arm64/kernel/head.S                | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/kernel-pgtable.h b/arch/arm64/include/asm/kernel-pgtable.h
index 96dc0f7da258..a971d462f531 100644
--- a/arch/arm64/include/asm/kernel-pgtable.h
+++ b/arch/arm64/include/asm/kernel-pgtable.h
@@ -103,8 +103,8 @@
 /*
  * Initial memory map attributes.
  */
-#define SWAPPER_PTE_FLAGS	(PTE_TYPE_PAGE | PTE_AF | PTE_SHARED)
-#define SWAPPER_PMD_FLAGS	(PMD_TYPE_SECT | PMD_SECT_AF | PMD_SECT_S)
+#define SWAPPER_PTE_FLAGS	(PTE_TYPE_PAGE | PTE_AF | PTE_SHARED | PTE_UXN)
+#define SWAPPER_PMD_FLAGS	(PMD_TYPE_SECT | PMD_SECT_AF | PMD_SECT_S | PMD_SECT_UXN)
 
 #if ARM64_KERNEL_USES_PMD_MAPS
 #define SWAPPER_MM_MMUFLAGS	(PMD_ATTRINDX(MT_NORMAL) | SWAPPER_PMD_FLAGS)
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 6a98f1a38c29..8a93a0a7489b 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -285,7 +285,7 @@ SYM_FUNC_START_LOCAL(__create_page_tables)
 	subs	x1, x1, #64
 	b.ne	1b
 
-	mov	x7, SWAPPER_MM_MMUFLAGS
+	mov_q	x7, SWAPPER_MM_MMUFLAGS
 
 	/*
 	 * Create the identity mapping.
-- 
2.37.0.170.g444d1eabd0-goog


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             reply	other threads:[~2022-07-19 23:49 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-07-19 23:49 Peter Collingbourne [this message]
2022-07-19 23:49 ` [PATCH] arm64: set UXN on swapper page tables Peter Collingbourne
2022-07-20  9:56 ` Will Deacon
2022-07-20  9:56   ` Will Deacon
2022-07-20 19:04 ` Catalin Marinas
2022-07-20 19:04   ` Catalin Marinas
2022-07-21 16:19   ` Catalin Marinas
2022-07-21 16:19     ` Catalin Marinas

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