// SPDX-License-Identifier: GPL-2.0
/*
* This file contains common KASAN code.
*
* Copyright (c) 2014 Samsung Electronics Co., Ltd.
* Author: Andrey Ryabinin <[email protected]>
*
* Some code borrowed from https://github.com/xairy/kasan-prototype by
* Andrey Konovalov <[email protected]>
*/
#include <linux/export.h>
#include <linux/init.h>
#include <linux/kasan.h>
#include <linux/kernel.h>
#include <linux/linkage.h>
#include <linux/memblock.h>
#include <linux/memory.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/printk.h>
#include <linux/sched.h>
#include <linux/sched/clock.h>
#include <linux/sched/task_stack.h>
#include <linux/slab.h>
#include <linux/stackdepot.h>
#include <linux/stacktrace.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/bug.h>
#include "kasan.h"
#include "../slab.h"
struct slab *kasan_addr_to_slab(const void *addr)
{
if (virt_addr_valid(addr))
return virt_to_slab(addr);
return NULL;
}
depot_stack_handle_t kasan_save_stack(gfp_t flags, depot_flags_t depot_flags)
{
unsigned long entries[KASAN_STACK_DEPTH];
unsigned int nr_entries;
nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 0);
return stack_depot_save_flags(entries, nr_entries, flags, depot_flags);
}
void kasan_set_track(struct kasan_track *track, depot_stack_handle_t stack)
{
#ifdef CONFIG_KASAN_EXTRA_INFO
u32 cpu = raw_smp_processor_id();
u64 ts_nsec = local_clock();
track->cpu = cpu;
track->timestamp = ts_nsec >> 9;
#endif /* CONFIG_KASAN_EXTRA_INFO */
track->pid = current->pid;
track->stack = stack;
}
void kasan_save_track(struct kasan_track *track, gfp_t flags)
{
depot_stack_handle_t stack;
stack = kasan_save_stack(flags, STACK_DEPOT_FLAG_CAN_ALLOC);
kasan_set_track(track, stack);
}
#if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
void kasan_enable_current(void)
{
current->kasan_depth++;
}
EXPORT_SYMBOL(kasan_enable_current);
void kasan_disable_current(void)
{
current->kasan_depth--;
}
EXPORT_SYMBOL(kasan_disable_current);
#endif /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */
void __kasan_unpoison_range(const void *address, size_t size)
{
if (is_kfence_address(address))
return;
kasan_unpoison(address, size, false);
}
#ifdef CONFIG_KASAN_STACK
/* Unpoison the entire stack for a task. */
void kasan_unpoison_task_stack(struct task_struct *task)
{
void *base = task_stack_page(task);
kasan_unpoison(base, THREAD_SIZE, false);
}
/* Unpoison the stack for the current task beyond a watermark sp value. */
asmlinkage void kasan_unpoison_task_stack_below(const void *watermark)
{
/*
* Calculate the task stack base address. Avoid using 'current'
* because this function is called by early resume code which hasn't
* yet set up the percpu register (%gs).
*/
void *base = (void *)((unsigned long)watermark & ~(THREAD_SIZE - 1));
kasan_unpoison(base, watermark - base, false);
}
#endif /* CONFIG_KASAN_STACK */
bool __kasan_unpoison_pages(struct page *page, unsigned int order, bool init)
{
u8 tag;
unsigned long i;
if (unlikely(PageHighMem(page)))
return false;
if (!kasan_sample_page_alloc(order))
return false;
tag = kasan_random_tag();
kasan_unpoison(set_tag(page_address(page), tag),
PAGE_SIZE << order, init);
for (i = 0; i < (1 << order); i++)
page_kasan_tag_set(page + i, tag);
return true;
}
void __kasan_poison_pages(struct page *page, unsigned int order, bool init)
{
if (likely(!PageHighMem(page)))
kasan_poison(page_address(page), PAGE_SIZE << order,
KASAN_PAGE_FREE, init);
}
void __kasan_poison_slab(struct slab *slab)
{
struct page *page = slab_page(slab);
unsigned long i;
for (i = 0; i < compound_nr(page); i++)
page_kasan_tag_reset(page + i);
kasan_poison(page_address(page), page_size(page),
KASAN_SLAB_REDZONE, false);
}
void __kasan_unpoison_new_object(struct kmem_cache *cache, void *object)
{
kasan_unpoison(object, cache->object_size, false);
}
void __kasan_poison_new_object(struct kmem_cache *cache, void *object)
{
kasan_poison(object, round_up(cache->object_size, KASAN_GRANULE_SIZE),
KASAN_SLAB_REDZONE, false);
}
/*
* This function assigns a tag to an object considering the following:
* 1. A cache might have a constructor, which might save a pointer to a slab
* object somewhere (e.g. in the object itself). We preassign a tag for
* each object in caches with constructors during slab creation and reuse
* the same tag each time a particular object is allocated.
* 2. A cache might be SLAB_TYPESAFE_BY_RCU, which means objects can be
* accessed after being freed. We preassign tags for objects in these
* caches as well.
*/
static inline u8 assign_tag(struct kmem_cache *cache,
const void *object, bool init)
{
if (IS_ENABLED(CONFIG_KASAN_GENERIC))
return 0xff;
/*
* If the cache neither has a constructor nor has SLAB_TYPESAFE_BY_RCU
* set, assign a tag when the object is being allocated (init == false).
*/
if (!cache->ctor && !(cache->flags & SLAB_TYPESAFE_BY_RCU))
return init ? KASAN_TAG_KERNEL : kasan_random_tag();
/*
* For caches that either have a constructor or SLAB_TYPESAFE_BY_RCU,
* assign a random tag during slab creation, otherwise reuse
* the already assigned tag.
*/
return init ? kasan_random_tag() : get_tag(object);
}
void * __must_check __kasan_init_slab_obj(struct kmem_cache *cache,
const void *object)
{
/* Initialize per-object metadata if it is present. */
if (kasan_requires_meta())
kasan_init_object_meta(cache, object);
/* Tag is ignored in set_tag() without CONFIG_KASAN_SW/HW_TAGS */
object = set_tag(object, assign_tag(cache, object, true));
return (void *)object;
}
static inline bool poison_slab_object(struct kmem_cache *cache, void *object,
unsigned long ip, bool init)
{
void *tagged_object;
if (!kasan_arch_is_ready())
return false;
tagged_object = object;
object = kasan_reset_tag(object);
if (unlikely(nearest_obj(cache, virt_to_slab(object), object) != object)) {
kasan_report_invalid_free(tagged_object, ip, KASAN_REPORT_INVALID_FREE);
return true;
}
/* RCU slabs could be legally used after free within the RCU period. */
if (unlikely(cache->flags & SLAB_TYPESAFE_BY_RCU))
return false;
if (!kasan_byte_accessible(tagged_object)) {
kasan_report_invalid_free(tagged_object, ip, KASAN_REPORT_DOUBLE_FREE);
return true;
}
kasan_poison(object, round_up(cache->object_size, KASAN_GRANULE_SIZE),
KASAN_SLAB_FREE, init);
if (kasan_stack_collection_enabled())
kasan_save_free_info(cache, tagged_object);
return false;
}
bool __kasan_slab_free(struct kmem_cache *cache, void *object,
unsigned long ip, bool init)
{
if (is_kfence_address(object))
return false;
/*
* If the object is buggy, do not let slab put the object onto the
* freelist. The object will thus never be allocated again and its
* metadata will never get released.
*/
if (poison_slab_object(cache, object, ip, init))
return true;
/*
* If the object is put into quarantine, do not let slab put the object
* onto the freelist for now. The object's metadata is kept until the
* object gets evicted from quarantine.
*/
if (kasan_quarantine_put(cache, object))
return true;
/*
* Note: Keep per-object metadata to allow KASAN print stack traces for
* use-after-free-before-realloc bugs.
*/
/* Let slab put the object onto the freelist. */
return false;
}
static inline bool check_page_allocation(void *ptr, unsigned long ip)
{
if (!kasan_arch_is_ready())
return false;
if (ptr != page_address(virt_to_head_page(ptr))) {
kasan_report_invalid_free(ptr, ip, KASAN_REPORT_INVALID_FREE);
return true;
}
if (!kasan_byte_accessible(ptr)) {
kasan_report_invalid_free(ptr, ip, KASAN_REPORT_DOUBLE_FREE);
return true;
}
return false;
}
void __kasan_kfree_large(void *ptr, unsigned long ip)
{
check_page_allocation(ptr, ip);
/* The object will be poisoned by kasan_poison_pages(). */
}
static inline void unpoison_slab_object(struct kmem_cache *cache, void *object,
gfp_t flags, bool init)
{
/*
* Unpoison the whole object. For kmalloc() allocations,
* poison_kmalloc_redzone() will do precise poisoning.
*/
kasan_unpoison(object, cache->object_size, init);
/* Save alloc info (if possible) for non-kmalloc() allocations. */
if (kasan_stack_collection_enabled() && !is_kmalloc_cache(cache))
kasan_save_alloc_info(cache, object, flags);
}
void * __must_check __kasan_slab_alloc(struct kmem_cache *cache,
void *object, gfp_t flags, bool init)
{
u8 tag;
void *tagged_object;
if (gfpflags_allow_blocking(flags))
kasan_quarantine_reduce();
if (unlikely(object == NULL))
return NULL;
if (is_kfence_address(object))
return (void *)object;
/*
* Generate and assign random tag for tag-based modes.
* Tag is ignored in set_tag() for the generic mode.
*/
tag = assign_tag(cache, object, false);
tagged_object = set_tag(object, tag);
/* Unpoison the object and save alloc info for non-kmalloc() allocations. */
unpoison_slab_object(cache, tagged_object, flags, init);
return tagged_object;
}
static inline void poison_kmalloc_redzone(struct kmem_cache *cache,
const void *object, size_t size, gfp_t flags)
{
unsigned long redzone_start;
unsigned long redzone_end;
/*
* The redzone has byte-level precision for the generic mode.
* Partially poison the last object granule to cover the unaligned
* part of the redzone.
*/
if (IS_ENABLED(CONFIG_KASAN_GENERIC))
kasan_poison_last_granule((void *)object, size);
/* Poison the aligned part of the redzone. */
redzone_start = round_up((unsigned long)(object + size),
KASAN_GRANULE_SIZE);
redzone_end = round_up((unsigned long)(object + cache->object_size),
KASAN_GRANULE_SIZE);
kasan_poison((void *)redzone_start, redzone_end - redzone_start,
KASAN_SLAB_REDZONE, false);
/*
* Save alloc info (if possible) for kmalloc() allocations.
* This also rewrites the alloc info when called from kasan_krealloc().
*/
if (kasan_stack_collection_enabled() && is_kmalloc_cache(cache))
kasan_save_alloc_info(cache, (void *)object, flags);
}
void * __must_check __kasan_kmalloc(struct kmem_cache *cache, const void *object,
size_t size, gfp_t flags)
{
if (gfpflags_allow_blocking(flags))
kasan_quarantine_reduce();
if (unlikely(object == NULL))
return NULL;
if (is_kfence_address(object))
return (void *)object;
/* The object has already been unpoisoned by kasan_slab_alloc(). */
poison_kmalloc_redzone(cache, object, size, flags);
/* Keep the tag that was set by kasan_slab_alloc(). */
return (void *)object;
}
EXPORT_SYMBOL(__kasan_kmalloc);
static inline void poison_kmalloc_large_redzone(const void *ptr, size_t size,
gfp_t flags)
{
unsigned long redzone_start;
unsigned long redzone_end;
/*
* The redzone has byte-level precision for the generic mode.
* Partially poison the last object granule to cover the unaligned
* part of the redzone.
*/
if (IS_ENABLED(CONFIG_KASAN_GENERIC))
kasan_poison_last_granule(ptr, size);
/* Poison the aligned part of the redzone. */
redzone_start = round_up((unsigned long)(ptr + size), KASAN_GRANULE_SIZE);
redzone_end = (unsigned long)ptr + page_size(virt_to_page(ptr));
kasan_poison((void *)redzone_start, redzone_end - redzone_start,
KASAN_PAGE_REDZONE, false);
}
void * __must_check __kasan_kmalloc_large(const void *ptr, size_t size,
gfp_t flags)
{
if (gfpflags_allow_blocking(flags))
kasan_quarantine_reduce();
if (unlikely(ptr == NULL))
return NULL;
/* The object has already been unpoisoned by kasan_unpoison_pages(). */
poison_kmalloc_large_redzone(ptr, size, flags);
/* Keep the tag that was set by alloc_pages(). */
return (void *)ptr;
}
void * __must_check __kasan_krealloc(const void *object, size_t size, gfp_t flags)
{
struct slab *slab;
if (gfpflags_allow_blocking(flags))
kasan_quarantine_reduce();
if (unlikely(object == ZERO_SIZE_PTR))
return (void *)object;
if (is_kfence_address(object))
return (void *)object;
/*
* Unpoison the object's data.
* Part of it might already have been unpoisoned, but it's unknown
* how big that part is.
*/
kasan_unpoison(object, size, false);
slab = virt_to_slab(object);
/* Piggy-back on kmalloc() instrumentation to poison the redzone. */
if (unlikely(!slab))
poison_kmalloc_large_redzone(object, size, flags);
else
poison_kmalloc_redzone(slab->slab_cache, object, size, flags);
return (void *)object;
}
bool __kasan_mempool_poison_pages(struct page *page, unsigned int order,
unsigned long ip)
{
unsigned long *ptr;
if (unlikely(PageHighMem(page)))
return true;
/* Bail out if allocation was excluded due to sampling. */
if (!IS_ENABLED(CONFIG_KASAN_GENERIC) &&
page_kasan_tag(page) == KASAN_TAG_KERNEL)
return true;
ptr = page_address(page);
if (check_page_allocation(ptr, ip))
return false;
kasan_poison(ptr, PAGE_SIZE << order, KASAN_PAGE_FREE, false);
return true;
}
void __kasan_mempool_unpoison_pages(struct page *page, unsigned int order,
unsigned long ip)
{
__kasan_unpoison_pages(page, order, false);
}
bool __kasan_mempool_poison_object(void *ptr, unsigned long ip)
{
struct folio *folio = virt_to_folio(ptr);
struct slab *slab;
/*
* This function can be called for large kmalloc allocation that get
* their memory from page_alloc. Thus, the folio might not be a slab.
*/
if (unlikely(!folio_test_slab(folio))) {
if (check_page_allocation(ptr, ip))
return false;
kasan_poison(ptr, folio_size(folio), KASAN_PAGE_FREE, false);
return true;
}
if (is_kfence_address(ptr))
return false;
slab = folio_slab(folio);
return !poison_slab_object(slab->slab_cache, ptr, ip, false);
}
void __kasan_mempool_unpoison_object(void *ptr, size_t size, unsigned long ip)
{
struct slab *slab;
gfp_t flags = 0; /* Might be executing under a lock. */
slab = virt_to_slab(ptr);
/*
* This function can be called for large kmalloc allocation that get
* their memory from page_alloc.
*/
if (unlikely(!slab)) {
kasan_unpoison(ptr, size, false);
poison_kmalloc_large_redzone(ptr, size, flags);
return;
}
if (is_kfence_address(ptr))
return;
/* Unpoison the object and save alloc info for non-kmalloc() allocations. */
unpoison_slab_object(slab->slab_cache, ptr, flags, false);
/* Poison the redzone and save alloc info for kmalloc() allocations. */
if (is_kmalloc_cache(slab->slab_cache))
poison_kmalloc_redzone(slab->slab_cache, ptr, size, flags);
}
bool __kasan_check_byte(const void *address, unsigned long ip)
{
if (!kasan_byte_accessible(address)) {
kasan_report(address, 1, false, ip);
return false;
}
return true;
}
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