blob: 9e1b6544bfa8e6263fc6a9db58d68b345692e591 [file] [log] [blame]
// SPDX-License-Identifier: GPL-2.0
/*
* This file contains core hardware tag-based KASAN code.
*
* Copyright (c) 2020 Google, Inc.
* Author: Andrey Konovalov <andreyknvl@google.com>
*/
#define pr_fmt(fmt) "kasan: " fmt
#include <linux/init.h>
#include <linux/kasan.h>
#include <linux/kernel.h>
#include <linux/memory.h>
#include <linux/mm.h>
#include <linux/static_key.h>
#include <linux/string.h>
#include <linux/types.h>
#include "kasan.h"
enum kasan_arg {
KASAN_ARG_DEFAULT,
KASAN_ARG_OFF,
KASAN_ARG_ON,
};
enum kasan_arg_mode {
KASAN_ARG_MODE_DEFAULT,
KASAN_ARG_MODE_SYNC,
KASAN_ARG_MODE_ASYNC,
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,
KASAN_ARG_STACKTRACE_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_stacktrace kasan_arg_stacktrace __initdata;
/*
* Whether KASAN is enabled at all.
* The value remains false until KASAN is initialized by kasan_init_hw_tags().
*/
DEFINE_STATIC_KEY_FALSE(kasan_flag_enabled);
EXPORT_SYMBOL(kasan_flag_enabled);
/*
* Whether the selected mode is synchronous, asynchronous, or asymmetric.
* Defaults to KASAN_MODE_SYNC.
*/
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);
/* kasan=off/on */
static int __init early_kasan_flag(char *arg)
{
if (!arg)
return -EINVAL;
if (!strcmp(arg, "off"))
kasan_arg = KASAN_ARG_OFF;
else if (!strcmp(arg, "on"))
kasan_arg = KASAN_ARG_ON;
else
return -EINVAL;
return 0;
}
early_param("kasan", early_kasan_flag);
/* kasan.mode=sync/async/asymm */
static int __init early_kasan_mode(char *arg)
{
if (!arg)
return -EINVAL;
if (!strcmp(arg, "sync"))
kasan_arg_mode = KASAN_ARG_MODE_SYNC;
else if (!strcmp(arg, "async"))
kasan_arg_mode = KASAN_ARG_MODE_ASYNC;
else if (!strcmp(arg, "asymm"))
kasan_arg_mode = KASAN_ARG_MODE_ASYMM;
else
return -EINVAL;
return 0;
}
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)
{
if (!arg)
return -EINVAL;
if (!strcmp(arg, "off"))
kasan_arg_stacktrace = KASAN_ARG_STACKTRACE_OFF;
else if (!strcmp(arg, "on"))
kasan_arg_stacktrace = KASAN_ARG_STACKTRACE_ON;
else
return -EINVAL;
return 0;
}
early_param("kasan.stacktrace", early_kasan_flag_stacktrace);
static inline const char *kasan_mode_info(void)
{
if (kasan_mode == KASAN_MODE_ASYNC)
return "async";
else if (kasan_mode == KASAN_MODE_ASYMM)
return "asymm";
else
return "sync";
}
/*
* kasan_init_hw_tags_cpu() is called for each CPU.
* Not marked as __init as a CPU can be hot-plugged after boot.
*/
void kasan_init_hw_tags_cpu(void)
{
/*
* There's no need to check that the hardware is MTE-capable here,
* as this function is only called for MTE-capable hardware.
*/
/*
* If KASAN is disabled via command line, don't initialize it.
* When this function is called, kasan_flag_enabled is not yet
* set by kasan_init_hw_tags(). Thus, check kasan_arg instead.
*/
if (kasan_arg == KASAN_ARG_OFF)
return;
/*
* Enable async or asymm modes only when explicitly requested
* through the command line.
*/
kasan_enable_tagging();
}
/* kasan_init_hw_tags() is called once on boot CPU. */
void __init kasan_init_hw_tags(void)
{
/* If hardware doesn't support MTE, don't initialize KASAN. */
if (!system_supports_mte())
return;
/* If KASAN is disabled via command line, don't initialize it. */
if (kasan_arg == KASAN_ARG_OFF)
return;
switch (kasan_arg_mode) {
case KASAN_ARG_MODE_DEFAULT:
/* Default is specified by kasan_mode definition. */
break;
case KASAN_ARG_MODE_SYNC:
kasan_mode = KASAN_MODE_SYNC;
break;
case KASAN_ARG_MODE_ASYNC:
kasan_mode = KASAN_MODE_ASYNC;
break;
case KASAN_ARG_MODE_ASYMM:
kasan_mode = KASAN_MODE_ASYMM;
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. */
break;
case KASAN_ARG_STACKTRACE_OFF:
static_branch_disable(&kasan_flag_stacktrace);
break;
case KASAN_ARG_STACKTRACE_ON:
static_branch_enable(&kasan_flag_stacktrace);
break;
}
/* 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",
kasan_mode_info(),
kasan_vmalloc_enabled() ? "on" : "off",
kasan_stack_collection_enabled() ? "on" : "off");
}
#ifdef CONFIG_KASAN_VMALLOC
static void unpoison_vmalloc_pages(const void *addr, u8 tag)
{
struct vm_struct *area;
int i;
/*
* As hardware tag-based KASAN only tags VM_ALLOC vmalloc allocations
* (see the comment in __kasan_unpoison_vmalloc), all of the pages
* should belong to a single area.
*/
area = find_vm_area((void *)addr);
if (WARN_ON(!area))
return;
for (i = 0; i < area->nr_pages; i++) {
struct page *page = area->pages[i];
page_kasan_tag_set(page, tag);
}
}
void *__kasan_unpoison_vmalloc(const void *start, unsigned long size,
kasan_vmalloc_flags_t flags)
{
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;
/*
* Skip unpoisoning and assigning a pointer tag for non-VM_ALLOC
* mappings as:
*
* 1. Unlike the software KASAN modes, hardware tag-based KASAN only
* supports tagging physical memory. Therefore, it can only tag a
* single mapping of normal physical pages.
* 2. Hardware tag-based KASAN can only tag memory mapped with special
* mapping protection bits, see arch_vmalloc_pgprot_modify().
* As non-VM_ALLOC mappings can be mapped outside of vmalloc code,
* providing these bits would require tracking all non-VM_ALLOC
* mappers.
*
* Thus, for VM_ALLOC mappings, hardware tag-based KASAN only tags
* the first virtual mapping, which is created by vmalloc().
* Tagging the page_alloc memory backing that vmalloc() allocation is
* skipped, see ___GFP_SKIP_KASAN_UNPOISON.
*
* For non-VM_ALLOC allocations, page_alloc memory is tagged as usual.
*/
if (!(flags & KASAN_VMALLOC_VM_ALLOC))
return (void *)start;
/*
* Don't tag executable memory.
* The kernel doesn't tolerate having the PC register tagged.
*/
if (!(flags & KASAN_VMALLOC_PROT_NORMAL))
return (void *)start;
tag = kasan_random_tag();
start = set_tag(start, tag);
/* Unpoison and initialize memory up to size. */
kasan_unpoison(start, size, flags & KASAN_VMALLOC_INIT);
/*
* Explicitly poison and initialize the in-page vmalloc() redzone.
* Unlike software KASAN modes, hardware tag-based KASAN doesn't
* unpoison memory when populating shadow for vmalloc() space.
*/
redzone_start = round_up((unsigned long)start + size,
KASAN_GRANULE_SIZE);
redzone_size = round_up(redzone_start, PAGE_SIZE) - redzone_start;
kasan_poison((void *)redzone_start, redzone_size, KASAN_TAG_INVALID,
flags & KASAN_VMALLOC_INIT);
/*
* Set per-page tag flags to allow accessing physical memory for the
* vmalloc() mapping through page_address(vmalloc_to_page()).
*/
unpoison_vmalloc_pages(start, tag);
return (void *)start;
}
void __kasan_poison_vmalloc(const void *start, unsigned long size)
{
/*
* No tagging here.
* The physical pages backing the vmalloc() allocation are poisoned
* through the usual page_alloc paths.
*/
}
#endif
void kasan_enable_tagging(void)
{
if (kasan_arg_mode == KASAN_ARG_MODE_ASYNC)
hw_enable_tagging_async();
else if (kasan_arg_mode == KASAN_ARG_MODE_ASYMM)
hw_enable_tagging_asymm();
else
hw_enable_tagging_sync();
}
#if IS_ENABLED(CONFIG_KASAN_KUNIT_TEST)
EXPORT_SYMBOL_GPL(kasan_enable_tagging);
void kasan_force_async_fault(void)
{
hw_force_async_tag_fault();
}
EXPORT_SYMBOL_GPL(kasan_force_async_fault);
#endif