Commit 551b2bcb authored by Andrey Konovalov's avatar Andrey Konovalov Committed by Linus Torvalds
Browse files

kasan: add kasan.vmalloc command line flag 

Allow disabling vmalloc() tagging for HW_TAGS KASAN via a kasan.vmalloc
command line switch.

This is a fail-safe switch intended for production systems that enable
HW_TAGS KASAN.  In case vmalloc() tagging ends up having an issue not
detected during testing but that manifests in production, kasan.vmalloc
allows to turn vmalloc() tagging off while leaving page_alloc/slab
tagging on.

Link: https://lkml.kernel.org/r/904f6d4dfa94870cc5fc2660809e093fd0d27c3b.1643047180.git.andreyknvl@google.com


Signed-off-by: default avatarAndrey Konovalov <andreyknvl@google.com>
Acked-by: default avatarMarco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Collingbourne <pcc@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 241944d1

mm/kasan/hw_tags.c

+44 −1
Original line number Diff line number Diff line
@@ -32,6 +32,12 @@ enum kasan_arg_mode { 
	KASAN_ARG_MODE_ASYMM,

};



enum kasan_arg_vmalloc {

	KASAN_ARG_VMALLOC_DEFAULT,

	KASAN_ARG_VMALLOC_OFF,

	KASAN_ARG_VMALLOC_ON,

};



enum kasan_arg_stacktrace {

	KASAN_ARG_STACKTRACE_DEFAULT,

	KASAN_ARG_STACKTRACE_OFF,
@@ -40,6 +46,7 @@ enum kasan_arg_stacktrace { 


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_stacktrace kasan_arg_stacktrace __initdata;



/*
@@ -56,6 +63,9 @@ EXPORT_SYMBOL(kasan_flag_enabled); 
enum kasan_mode kasan_mode __ro_after_init;

EXPORT_SYMBOL_GPL(kasan_mode);



/* Whether to enable vmalloc tagging. */

DEFINE_STATIC_KEY_TRUE(kasan_flag_vmalloc);



/* Whether to collect alloc/free stack traces. */

DEFINE_STATIC_KEY_TRUE(kasan_flag_stacktrace);
@@ -95,6 +105,23 @@ static int __init early_kasan_mode(char *arg) 
}

early_param("kasan.mode", early_kasan_mode);



/* kasan.vmalloc=off/on */

static int __init early_kasan_flag_vmalloc(char *arg)

{

	if (!arg)

		return -EINVAL;



	if (!strcmp(arg, "off"))

		kasan_arg_vmalloc = KASAN_ARG_VMALLOC_OFF;

	else if (!strcmp(arg, "on"))

		kasan_arg_vmalloc = KASAN_ARG_VMALLOC_ON;

	else

		return -EINVAL;



	return 0;

}

early_param("kasan.vmalloc", early_kasan_flag_vmalloc);



/* kasan.stacktrace=off/on */

static int __init early_kasan_flag_stacktrace(char *arg)

{
@@ -179,6 +206,18 @@ void __init kasan_init_hw_tags(void) 
		break;

	}



	switch (kasan_arg_vmalloc) {

	case KASAN_ARG_VMALLOC_DEFAULT:

		/* Default is specified by kasan_flag_vmalloc definition. */

		break;

	case KASAN_ARG_VMALLOC_OFF:

		static_branch_disable(&kasan_flag_vmalloc);

		break;

	case KASAN_ARG_VMALLOC_ON:

		static_branch_enable(&kasan_flag_vmalloc);

		break;

	}



	switch (kasan_arg_stacktrace) {

	case KASAN_ARG_STACKTRACE_DEFAULT:

		/* Default is specified by kasan_flag_stacktrace definition. */
@@ -194,8 +233,9 @@ void __init kasan_init_hw_tags(void) 
	/* KASAN is now initialized, enable it. */

	static_branch_enable(&kasan_flag_enabled);



	pr_info("KernelAddressSanitizer initialized (hw-tags, mode=%s, stacktrace=%s)\n",

	pr_info("KernelAddressSanitizer initialized (hw-tags, mode=%s, vmalloc=%s, stacktrace=%s)\n",

		kasan_mode_info(),

		kasan_vmalloc_enabled() ? "on" : "off",

		kasan_stack_collection_enabled() ? "on" : "off");

}
@@ -228,6 +268,9 @@ void *__kasan_unpoison_vmalloc(const void *start, unsigned long size, 
	u8 tag;

	unsigned long redzone_start, redzone_size;



	if (!kasan_vmalloc_enabled())

		return (void *)start;



	if (!is_vmalloc_or_module_addr(start))

		return (void *)start;

mm/kasan/kasan.h

+6 −0
Original line number Diff line number Diff line
@@ -12,6 +12,7 @@ 
#include <linux/static_key.h>

#include "../slab.h"



DECLARE_STATIC_KEY_TRUE(kasan_flag_vmalloc);

DECLARE_STATIC_KEY_TRUE(kasan_flag_stacktrace);



enum kasan_mode {
@@ -22,6 +23,11 @@ enum kasan_mode { 


extern enum kasan_mode kasan_mode __ro_after_init;



static inline bool kasan_vmalloc_enabled(void)

{

	return static_branch_likely(&kasan_flag_vmalloc);

}



static inline bool kasan_stack_collection_enabled(void)

{

	return static_branch_unlikely(&kasan_flag_stacktrace);