[failures] kasan-hw-tags-introduce-kasanwrite_only-option.patch removed from -mm tree

[Andrew Morton <akpm@linux-foundation.org>]

The quilt patch titled
     Subject: kasan/hw-tags: introduce kasan.write_only option
has been removed from the -mm tree.  Its filename was
     kasan-hw-tags-introduce-kasanwrite_only-option.patch

This patch was dropped because it had testing failures

------------------------------------------------------
From: Yeoreum Yun <yeoreum.yun@arm.com>
Subject: kasan/hw-tags: introduce kasan.write_only option
Date: Sat, 16 Aug 2025 12:00:17 +0100

Patch series "introduce kasan.write_only option in hw-tags", v3.

Hardware tag based KASAN is implemented using the Memory Tagging Extension
(MTE) feature.

MTE is built on top of the ARMv8.0 virtual address tagging TBI (Top Byte
Ignore) feature and allows software to access a 4-bit allocation tag for
each 16-byte granule in the physical address space.  A logical tag is
derived from bits 59-56 of the virtual address used for the memory access.
A CPU with MTE enabled will compare the logical tag against the
allocation tag and potentially raise an tag check fault on mismatch,
subject to system registers configuration.

Since ARMv8.9, FEAT_MTE_STORE_ONLY can be used to restrict raise of tag
check fault on store operation only.

Using this feature (FEAT_MTE_STORE_ONLY), introduce KASAN write-only mode
which restricts KASAN check write (store) operation only.  This mode omits
KASAN check for read (fetch/load) operation.  Therefore, it might be used
not only debugging purpose but also in normal environment.


This patch (of 2):

Since Armv8.9, FEATURE_MTE_STORE_ONLY feature is introduced to restrict
raise of tag check fault on store operation only.  Introcude KASAN write
only mode based on this feature.

KASAN write only mode restricts KASAN checks operation for write only and
omits the checks for fetch/read operations when accessing memory.  So it
might be used not only debugging environment but also normal environment
to check memory safety.

This features can be controlled with "kasan.write_only" arguments.  When
"kasan.write_only=on", KASAN checks write operation only otherwise KASAN
checks all operations.

This changes the MTE_STORE_ONLY feature as BOOT_CPU_FEATURE like
ARM64_MTE_ASYMM so that makes it initialise in kasan_init_hw_tags() with
other function together.

Link: https://lkml.kernel.org/r/20250816110018.4055617-1-yeoreum.yun@arm.com
Link: https://lkml.kernel.org/r/20250816110018.4055617-2-yeoreum.yun@arm.com
Signed-off-by: Yeoreum Yun <yeoreum.yun@arm.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Breno Leitao <leitao@debian.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Dmitriy Vyukov <dvyukov@google.com>
Cc: D Scott Phillips <scott@os.amperecomputing.com>
Cc: Hardevsinh Palaniya <hardevsinh.palaniya@siliconsignals.io>
Cc: James Morse <james.morse@arm.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kalesh Singh <kaleshsingh@google.com>
Cc: levi.yun <yeoreum.yun@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Brown <broonie@kernel.org>
Cc: Oliver Upton <oliver.upton@linux.dev>
Cc: Pankaj Gupta <pankaj.gupta@amd.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yang Shi <yang@os.amperecomputing.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 Documentation/dev-tools/kasan.rst  |    3 +
 arch/arm64/include/asm/memory.h    |    1 
 arch/arm64/include/asm/mte-kasan.h |    6 +++
 arch/arm64/kernel/cpufeature.c     |    2 -
 arch/arm64/kernel/mte.c            |   18 +++++++++
 mm/kasan/hw_tags.c                 |   54 ++++++++++++++++++++++++++-
 mm/kasan/kasan.h                   |    7 +++
 7 files changed, 88 insertions(+), 3 deletions(-)

--- a/arch/arm64/include/asm/memory.h~kasan-hw-tags-introduce-kasanwrite_only-option
+++ a/arch/arm64/include/asm/memory.h
@@ -308,6 +308,7 @@ static inline const void *__tag_set(cons
 #define arch_enable_tag_checks_sync()		mte_enable_kernel_sync()
 #define arch_enable_tag_checks_async()		mte_enable_kernel_async()
 #define arch_enable_tag_checks_asymm()		mte_enable_kernel_asymm()
+#define arch_enable_tag_checks_write_only()	mte_enable_kernel_store_only()
 #define arch_suppress_tag_checks_start()	mte_enable_tco()
 #define arch_suppress_tag_checks_stop()		mte_disable_tco()
 #define arch_force_async_tag_fault()		mte_check_tfsr_exit()
--- a/arch/arm64/include/asm/mte-kasan.h~kasan-hw-tags-introduce-kasanwrite_only-option
+++ a/arch/arm64/include/asm/mte-kasan.h
@@ -200,6 +200,7 @@ static inline void mte_set_mem_tag_range
 void mte_enable_kernel_sync(void);
 void mte_enable_kernel_async(void);
 void mte_enable_kernel_asymm(void);
+int mte_enable_kernel_store_only(void);
 
 #else /* CONFIG_ARM64_MTE */
 
@@ -251,6 +252,11 @@ static inline void mte_enable_kernel_asy
 {
 }
 
+static inline int mte_enable_kernel_store_only(void)
+{
+	return -EINVAL;
+}
+
 #endif /* CONFIG_ARM64_MTE */
 
 #endif /* __ASSEMBLY__ */
--- a/arch/arm64/kernel/cpufeature.c~kasan-hw-tags-introduce-kasanwrite_only-option
+++ a/arch/arm64/kernel/cpufeature.c
@@ -2920,7 +2920,7 @@ static const struct arm64_cpu_capabiliti
 	{
 		.desc = "Store Only MTE Tag Check",
 		.capability = ARM64_MTE_STORE_ONLY,
-		.type = ARM64_CPUCAP_SYSTEM_FEATURE,
+		.type = ARM64_CPUCAP_BOOT_CPU_FEATURE,
 		.matches = has_cpuid_feature,
 		ARM64_CPUID_FIELDS(ID_AA64PFR2_EL1, MTESTOREONLY, IMP)
 	},
--- a/arch/arm64/kernel/mte.c~kasan-hw-tags-introduce-kasanwrite_only-option
+++ a/arch/arm64/kernel/mte.c
@@ -157,6 +157,24 @@ void mte_enable_kernel_asymm(void)
 		mte_enable_kernel_sync();
 	}
 }
+
+int mte_enable_kernel_store_only(void)
+{
+	/*
+	 * If the CPU does not support MTE store only,
+	 * the kernel checks all operations.
+	 */
+	if (!cpus_have_cap(ARM64_MTE_STORE_ONLY))
+		return -EINVAL;
+
+	sysreg_clear_set(sctlr_el1, SCTLR_EL1_TCSO_MASK,
+			 SYS_FIELD_PREP(SCTLR_EL1, TCSO, 1));
+	isb();
+
+	pr_info_once("MTE: enabled stonly mode at EL1\n");
+
+	return 0;
+}
 #endif
 
 #ifdef CONFIG_KASAN_HW_TAGS
--- a/Documentation/dev-tools/kasan.rst~kasan-hw-tags-introduce-kasanwrite_only-option
+++ a/Documentation/dev-tools/kasan.rst
@@ -143,6 +143,9 @@ disabling KASAN altogether or controllin
   Asymmetric mode: a bad access is detected synchronously on reads and
   asynchronously on writes.
 
+- ``kasan.write_only=off`` or ``kasan.write_only=on`` controls whether KASAN
+  checks the write (store) accesses only or all accesses (default: ``off``)
+
 - ``kasan.vmalloc=off`` or ``=on`` disables or enables tagging of vmalloc
   allocations (default: ``on``).
 
--- a/mm/kasan/hw_tags.c~kasan-hw-tags-introduce-kasanwrite_only-option
+++ a/mm/kasan/hw_tags.c
@@ -41,9 +41,16 @@ enum kasan_arg_vmalloc {
 	KASAN_ARG_VMALLOC_ON,
 };
 
+enum kasan_arg_write_only {
+	KASAN_ARG_WRITE_ONLY_DEFAULT,
+	KASAN_ARG_WRITE_ONLY_OFF,
+	KASAN_ARG_WRITE_ONLY_ON,
+};
+
 static enum kasan_arg kasan_arg __ro_after_init;
 static enum kasan_arg_mode kasan_arg_mode __ro_after_init;
 static enum kasan_arg_vmalloc kasan_arg_vmalloc __initdata;
+static enum kasan_arg_write_only kasan_arg_write_only __ro_after_init;
 
 /*
  * Whether KASAN is enabled at all.
@@ -67,6 +74,8 @@ DEFINE_STATIC_KEY_FALSE(kasan_flag_vmall
 #endif
 EXPORT_SYMBOL_GPL(kasan_flag_vmalloc);
 
+static bool kasan_flag_write_only;
+
 #define PAGE_ALLOC_SAMPLE_DEFAULT	1
 #define PAGE_ALLOC_SAMPLE_ORDER_DEFAULT	3
 
@@ -141,6 +150,23 @@ static int __init early_kasan_flag_vmall
 }
 early_param("kasan.vmalloc", early_kasan_flag_vmalloc);
 
+/* kasan.write_only=off/on */
+static int __init early_kasan_flag_write_only(char *arg)
+{
+	if (!arg)
+		return -EINVAL;
+
+	if (!strcmp(arg, "off"))
+		kasan_arg_write_only = KASAN_ARG_WRITE_ONLY_OFF;
+	else if (!strcmp(arg, "on"))
+		kasan_arg_write_only = KASAN_ARG_WRITE_ONLY_ON;
+	else
+		return -EINVAL;
+
+	return 0;
+}
+early_param("kasan.write_only", early_kasan_flag_write_only);
+
 static inline const char *kasan_mode_info(void)
 {
 	if (kasan_mode == KASAN_MODE_ASYNC)
@@ -257,15 +283,26 @@ void __init kasan_init_hw_tags(void)
 		break;
 	}
 
+	switch (kasan_arg_write_only) {
+	case KASAN_ARG_WRITE_ONLY_DEFAULT:
+	case KASAN_ARG_WRITE_ONLY_OFF:
+		kasan_flag_write_only = false;
+		break;
+	case KASAN_ARG_WRITE_ONLY_ON:
+		kasan_flag_write_only = true;
+		break;
+	}
+
 	kasan_init_tags();
 
 	/* KASAN is now initialized, enable it. */
 	static_branch_enable(&kasan_flag_enabled);
 
-	pr_info("KernelAddressSanitizer initialized (hw-tags, mode=%s, vmalloc=%s, stacktrace=%s)\n",
+	pr_info("KernelAddressSanitizer initialized (hw-tags, mode=%s, vmalloc=%s, stacktrace=%s, write_only=%s\n",
 		kasan_mode_info(),
 		str_on_off(kasan_vmalloc_enabled()),
-		str_on_off(kasan_stack_collection_enabled()));
+		str_on_off(kasan_stack_collection_enabled()),
+		str_on_off(kasan_arg_write_only));
 }
 
 #ifdef CONFIG_KASAN_VMALLOC
@@ -392,6 +429,13 @@ void kasan_enable_hw_tags(void)
 		hw_enable_tag_checks_asymm();
 	else
 		hw_enable_tag_checks_sync();
+
+	if (kasan_arg_mode == KASAN_ARG_WRITE_ONLY_ON &&
+	    hw_enable_tag_checks_write_only()) {
+		kasan_arg_mode == KASAN_ARG_WRITE_ONLY_OFF;
+		kasan_flag_write_only = false;
+		pr_warn_once("System doesn't support write-only option. Disable it\n");
+	}
 }
 
 #if IS_ENABLED(CONFIG_KASAN_KUNIT_TEST)
@@ -404,4 +448,10 @@ VISIBLE_IF_KUNIT void kasan_force_async_
 }
 EXPORT_SYMBOL_IF_KUNIT(kasan_force_async_fault);
 
+VISIBLE_IF_KUNIT bool kasan_write_only_enabled(void)
+{
+	return kasan_flag_write_only;
+}
+EXPORT_SYMBOL_IF_KUNIT(kasan_write_only_enabled);
+
 #endif
--- a/mm/kasan/kasan.h~kasan-hw-tags-introduce-kasanwrite_only-option
+++ a/mm/kasan/kasan.h
@@ -428,6 +428,7 @@ static inline const void *arch_kasan_set
 #define hw_enable_tag_checks_sync()		arch_enable_tag_checks_sync()
 #define hw_enable_tag_checks_async()		arch_enable_tag_checks_async()
 #define hw_enable_tag_checks_asymm()		arch_enable_tag_checks_asymm()
+#define hw_enable_tag_checks_write_only()	arch_enable_tag_checks_write_only()
 #define hw_suppress_tag_checks_start()		arch_suppress_tag_checks_start()
 #define hw_suppress_tag_checks_stop()		arch_suppress_tag_checks_stop()
 #define hw_force_async_tag_fault()		arch_force_async_tag_fault()
@@ -437,11 +438,17 @@ static inline const void *arch_kasan_set
 			arch_set_mem_tag_range((addr), (size), (tag), (init))
 
 void kasan_enable_hw_tags(void);
+bool kasan_write_only_enabled(void);
 
 #else /* CONFIG_KASAN_HW_TAGS */
 
 static inline void kasan_enable_hw_tags(void) { }
 
+static inline bool kasan_write_only_enabled(void)
+{
+	return false;
+}
+
 #endif /* CONFIG_KASAN_HW_TAGS */
 
 #if defined(CONFIG_KASAN_SW_TAGS) || defined(CONFIG_KASAN_HW_TAGS)
_

Patches currently in -mm which might be from yeoreum.yun@arm.com are

kunit-kasan_test-disable-fortify-string-checker-on-kasan_strings-test.patch
kasan-apply-write-only-mode-in-kasan-kunit-testcases.patch