blob: 21e66d7f261de8808c536643525726551d3c9390 [file] [log] [blame]
// SPDX-License-Identifier: GPL-2.0
/*
* This file contains common KASAN code.
*
* Copyright (c) 2014 Samsung Electronics Co., Ltd.
* Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
*
* Some code borrowed from https://github.com/xairy/kasan-prototype by
* Andrey Konovalov <andreyknvl@gmail.com>
*/
#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/task_stack.h>
#include <linux/slab.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, bool can_alloc)
{
unsigned long entries[KASAN_STACK_DEPTH];
unsigned int nr_entries;
nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 0);
return __stack_depot_save(entries, nr_entries, 0, flags, can_alloc);
}
void kasan_set_track(struct kasan_track *track, gfp_t flags)
{
track->pid = current->pid;
track->stack = kasan_save_stack(flags, true);
}
#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)
{
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 */
void __kasan_unpoison_pages(struct page *page, unsigned int order, bool init)
{
u8 tag;
unsigned long i;
if (unlikely(PageHighMem(page)))
return;
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);
}
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_cache_create_kmalloc(struct kmem_cache *cache)
{
cache->kasan_info.is_kmalloc = true;
}
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_object_data(struct kmem_cache *cache, void *object)
{
kasan_unpoison(object, cache->object_size, false);
}
void __kasan_poison_object_data(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.
* 3. For SLAB allocator we can't preassign tags randomly since the freelist
* is stored as an array of indexes instead of a linked list. Assign tags
* based on objects indexes, so that objects that are next to each other
* get different tags.
*/
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: */
#ifdef CONFIG_SLAB
/* For SLAB assign tags based on the object index in the freelist. */
return (u8)obj_to_index(cache, virt_to_slab(object), (void *)object);
#else
/*
* For SLUB assign a random tag during slab creation, otherwise reuse
* the already assigned tag.
*/
return init ? kasan_random_tag() : get_tag(object);
#endif
}
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 ____kasan_slab_free(struct kmem_cache *cache, void *object,
unsigned long ip, bool quarantine, bool init)
{
void *tagged_object;
if (!kasan_arch_is_ready())
return false;
tagged_object = object;
object = kasan_reset_tag(object);
if (is_kfence_address(object))
return false;
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 ((IS_ENABLED(CONFIG_KASAN_GENERIC) && !quarantine))
return false;
if (kasan_stack_collection_enabled())
kasan_save_free_info(cache, tagged_object);
return kasan_quarantine_put(cache, object);
}
bool __kasan_slab_free(struct kmem_cache *cache, void *object,
unsigned long ip, bool init)
{
return ____kasan_slab_free(cache, object, ip, true, init);
}
static inline bool ____kasan_kfree_large(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;
}
/*
* The object will be poisoned by kasan_poison_pages() or
* kasan_slab_free_mempool().
*/
return false;
}
void __kasan_kfree_large(void *ptr, unsigned long ip)
{
____kasan_kfree_large(ptr, ip);
}
void __kasan_slab_free_mempool(void *ptr, unsigned long ip)
{
struct folio *folio;
folio = virt_to_folio(ptr);
/*
* Even though this function is only called for kmem_cache_alloc and
* kmalloc backed mempool allocations, those allocations can still be
* !PageSlab() when the size provided to kmalloc is larger than
* KMALLOC_MAX_SIZE, and kmalloc falls back onto page_alloc.
*/
if (unlikely(!folio_test_slab(folio))) {
if (____kasan_kfree_large(ptr, ip))
return;
kasan_poison(ptr, folio_size(folio), KASAN_PAGE_FREE, false);
} else {
struct slab *slab = folio_slab(folio);
____kasan_slab_free(slab->slab_cache, ptr, ip, false, false);
}
}
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 whole object.
* For kmalloc() allocations, kasan_kmalloc() will do precise poisoning.
*/
kasan_unpoison(tagged_object, cache->object_size, init);
/* Save alloc info (if possible) for non-kmalloc() allocations. */
if (kasan_stack_collection_enabled() && !cache->kasan_info.is_kmalloc)
kasan_save_alloc_info(cache, tagged_object, flags);
return tagged_object;
}
static inline void *____kasan_kmalloc(struct kmem_cache *cache,
const void *object, size_t size, gfp_t flags)
{
unsigned long redzone_start;
unsigned long redzone_end;
if (gfpflags_allow_blocking(flags))
kasan_quarantine_reduce();
if (unlikely(object == NULL))
return NULL;
if (is_kfence_address(kasan_reset_tag(object)))
return (void *)object;
/*
* The object has already been unpoisoned by kasan_slab_alloc() for
* kmalloc() or by kasan_krealloc() for krealloc().
*/
/*
* 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() && cache->kasan_info.is_kmalloc)
kasan_save_alloc_info(cache, (void *)object, flags);
/* Keep the tag that was set by kasan_slab_alloc(). */
return (void *)object;
}
void * __must_check __kasan_kmalloc(struct kmem_cache *cache, const void *object,
size_t size, gfp_t flags)
{
return ____kasan_kmalloc(cache, object, size, flags);
}
EXPORT_SYMBOL(__kasan_kmalloc);
void * __must_check __kasan_kmalloc_large(const void *ptr, size_t size,
gfp_t flags)
{
unsigned long redzone_start;
unsigned long redzone_end;
if (gfpflags_allow_blocking(flags))
kasan_quarantine_reduce();
if (unlikely(ptr == NULL))
return NULL;
/*
* The object has already been unpoisoned by kasan_unpoison_pages() for
* alloc_pages() or by kasan_krealloc() for krealloc().
*/
/*
* 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);
return (void *)ptr;
}
void * __must_check __kasan_krealloc(const void *object, size_t size, gfp_t flags)
{
struct slab *slab;
if (unlikely(object == ZERO_SIZE_PTR))
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))
return __kasan_kmalloc_large(object, size, flags);
else
return ____kasan_kmalloc(slab->slab_cache, object, size, flags);
}
bool __kasan_check_byte(const void *address, unsigned long ip)
{
if (!kasan_byte_accessible(address)) {
kasan_report((unsigned long)address, 1, false, ip);
return false;
}
return true;
}