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kasan: add kasan.vmalloc command line flag

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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: Andrey Konovalov <andreyknvl@google.com>
Acked-by: Marco 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Andrey Konovalov 2022-03-24 18:11:47 -07:00 committed by Linus Torvalds
parent 241944d162
commit 551b2bcb7e
2 changed files with 50 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

45
mm/kasan/hw_tags.c
View File

@ -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;

6
mm/kasan/kasan.h
View File

@ -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);