linux-kernel - [PATCH mm 07/11] kasan: respect CONFIG_KASAN_VMALLOC for kasan_flag

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Message-Id: <3e5c933c8f6b59bd587efb05c407964be951772c.1703188911.git.andreyknvl@google.com>
Date: Thu, 21 Dec 2023 21:04:49 +0100
From: andrey.konovalov@...ux.dev
To: Marco Elver <elver@...gle.com>
Cc: Andrey Konovalov <andreyknvl@...il.com>,
	Alexander Potapenko <glider@...gle.com>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	Andrey Ryabinin <ryabinin.a.a@...il.com>,
	kasan-dev@...glegroups.com,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Andrey Konovalov <andreyknvl@...gle.com>
Subject: [PATCH mm 07/11] kasan: respect CONFIG_KASAN_VMALLOC for kasan_flag_vmalloc

From: Andrey Konovalov <andreyknvl@...gle.com>

Never enable the kasan_flag_vmalloc static branch unless
CONFIG_KASAN_VMALLOC is enabled.

This does not fix any observable bugs (vmalloc annotations for the
HW_TAGS mode are no-op with CONFIG_KASAN_VMALLOC disabled) but rather
just cleans up the code.

Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
---
 mm/kasan/hw_tags.c | 7 +++++++
 mm/kasan/kasan.h   | 1 +
 2 files changed, 8 insertions(+)

diff --git a/mm/kasan/hw_tags.c b/mm/kasan/hw_tags.c
index 06141bbc1e51..80f11a3eccd5 100644
--- a/mm/kasan/hw_tags.c
+++ b/mm/kasan/hw_tags.c
@@ -57,7 +57,11 @@ enum kasan_mode kasan_mode __ro_after_init;
 EXPORT_SYMBOL_GPL(kasan_mode);
 
 /* Whether to enable vmalloc tagging. */
+#ifdef CONFIG_KASAN_VMALLOC
 DEFINE_STATIC_KEY_TRUE(kasan_flag_vmalloc);
+#else
+DEFINE_STATIC_KEY_FALSE(kasan_flag_vmalloc);
+#endif
 
 #define PAGE_ALLOC_SAMPLE_DEFAULT	1
 #define PAGE_ALLOC_SAMPLE_ORDER_DEFAULT	3
@@ -119,6 +123,9 @@ static int __init early_kasan_flag_vmalloc(char *arg)
 	if (!arg)
 		return -EINVAL;
 
+	if (!IS_ENABLED(CONFIG_KASAN_VMALLOC))
+		return 0;
+
 	if (!strcmp(arg, "off"))
 		kasan_arg_vmalloc = KASAN_ARG_VMALLOC_OFF;
 	else if (!strcmp(arg, "on"))
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index 5fbcc1b805bc..dee105ba32dd 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -49,6 +49,7 @@ DECLARE_PER_CPU(long, kasan_page_alloc_skip);
 
 static inline bool kasan_vmalloc_enabled(void)
 {
+	/* Static branch is never enabled with CONFIG_KASAN_VMALLOC disabled. */
 	return static_branch_likely(&kasan_flag_vmalloc);
 }
 
-- 
2.25.1