[mirror_ubuntu-jammy-kernel.git] / mm / kasan / common.c

// 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"

depot_stack_handle_t kasan_save_stack(gfp_t flags)
{
        unsigned long entries[KASAN_STACK_DEPTH];
        unsigned int nr_entries;

        nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 0);
        nr_entries = filter_irq_stacks(entries, nr_entries);
        return stack_depot_save(entries, nr_entries, flags);
}

void kasan_set_track(struct kasan_track *track, gfp_t flags)
{
        track->pid = current->pid;
        track->stack = kasan_save_stack(flags);
}

#if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
void kasan_enable_current(void)
{
        current->kasan_depth++;
}

void kasan_disable_current(void)
{
        current->kasan_depth--;
}
#endif /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */

void kasan_unpoison_range(const void *address, size_t size)
{
        unpoison_range(address, size);
}

static void __kasan_unpoison_stack(struct task_struct *task, const void *sp)
{
        void *base = task_stack_page(task);
        size_t size = sp - base;

        unpoison_range(base, size);
}

/* Unpoison the entire stack for a task. */
void kasan_unpoison_task_stack(struct task_struct *task)
{
        __kasan_unpoison_stack(task, task_stack_page(task) + THREAD_SIZE);
}

/* 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));

        unpoison_range(base, watermark - base);
}

void kasan_alloc_pages(struct page *page, unsigned int order)
{
        u8 tag;
        unsigned long i;

        if (unlikely(PageHighMem(page)))
                return;

        tag = random_tag();
        for (i = 0; i < (1 << order); i++)
                page_kasan_tag_set(page + i, tag);
        unpoison_range(page_address(page), PAGE_SIZE << order);
}

void kasan_free_pages(struct page *page, unsigned int order)
{
        if (likely(!PageHighMem(page)))
                poison_range(page_address(page),
                                PAGE_SIZE << order,
                                KASAN_FREE_PAGE);
}

/*
 * Adaptive redzone policy taken from the userspace AddressSanitizer runtime.
 * For larger allocations larger redzones are used.
 */
static inline unsigned int optimal_redzone(unsigned int object_size)
{
        if (!IS_ENABLED(CONFIG_KASAN_GENERIC))
                return 0;

        return
                object_size <= 64        - 16   ? 16 :
                object_size <= 128       - 32   ? 32 :
                object_size <= 512       - 64   ? 64 :
                object_size <= 4096      - 128  ? 128 :
                object_size <= (1 << 14) - 256  ? 256 :
                object_size <= (1 << 15) - 512  ? 512 :
                object_size <= (1 << 16) - 1024 ? 1024 : 2048;
}

void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
                        slab_flags_t *flags)
{
        unsigned int orig_size = *size;
        unsigned int redzone_size;
        int redzone_adjust;

        /* Add alloc meta. */
        cache->kasan_info.alloc_meta_offset = *size;
        *size += sizeof(struct kasan_alloc_meta);

        /* Add free meta. */
        if (IS_ENABLED(CONFIG_KASAN_GENERIC) &&
            (cache->flags & SLAB_TYPESAFE_BY_RCU || cache->ctor ||
             cache->object_size < sizeof(struct kasan_free_meta))) {
                cache->kasan_info.free_meta_offset = *size;
                *size += sizeof(struct kasan_free_meta);
        }

        redzone_size = optimal_redzone(cache->object_size);
        redzone_adjust = redzone_size - (*size - cache->object_size);
        if (redzone_adjust > 0)
                *size += redzone_adjust;

        *size = min_t(unsigned int, KMALLOC_MAX_SIZE,
                        max(*size, cache->object_size + redzone_size));

        /*
         * If the metadata doesn't fit, don't enable KASAN at all.
         */
        if (*size <= cache->kasan_info.alloc_meta_offset ||
                        *size <= cache->kasan_info.free_meta_offset) {
                cache->kasan_info.alloc_meta_offset = 0;
                cache->kasan_info.free_meta_offset = 0;
                *size = orig_size;
                return;
        }

        *flags |= SLAB_KASAN;
}

size_t kasan_metadata_size(struct kmem_cache *cache)
{
        return (cache->kasan_info.alloc_meta_offset ?
                sizeof(struct kasan_alloc_meta) : 0) +
                (cache->kasan_info.free_meta_offset ?
                sizeof(struct kasan_free_meta) : 0);
}

struct kasan_alloc_meta *kasan_get_alloc_meta(struct kmem_cache *cache,
                                              const void *object)
{
        return (void *)reset_tag(object) + cache->kasan_info.alloc_meta_offset;
}

struct kasan_free_meta *kasan_get_free_meta(struct kmem_cache *cache,
                                            const void *object)
{
        BUILD_BUG_ON(sizeof(struct kasan_free_meta) > 32);
        return (void *)reset_tag(object) + cache->kasan_info.free_meta_offset;
}

void kasan_poison_slab(struct page *page)
{
        unsigned long i;

        for (i = 0; i < compound_nr(page); i++)
                page_kasan_tag_reset(page + i);
        poison_range(page_address(page), page_size(page),
                     KASAN_KMALLOC_REDZONE);
}

void kasan_unpoison_object_data(struct kmem_cache *cache, void *object)
{
        unpoison_range(object, cache->object_size);
}

void kasan_poison_object_data(struct kmem_cache *cache, void *object)
{
        poison_range(object,
                        round_up(cache->object_size, KASAN_GRANULE_SIZE),
                        KASAN_KMALLOC_REDZONE);
}

/*
 * 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 u8 assign_tag(struct kmem_cache *cache, const void *object,
                        bool init, bool keep_tag)
{
        /*
         * 1. When an object is kmalloc()'ed, two hooks are called:
         *    kasan_slab_alloc() and kasan_kmalloc(). We assign the
         *    tag only in the first one.
         * 2. We reuse the same tag for krealloc'ed objects.
         */
        if (keep_tag)
                return get_tag(object);

        /*
         * 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 : 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_page(object), (void *)object);
#else
        /*
         * For SLUB assign a random tag during slab creation, otherwise reuse
         * the already assigned tag.
         */
        return init ? random_tag() : get_tag(object);
#endif
}

void * __must_check kasan_init_slab_obj(struct kmem_cache *cache,
                                                const void *object)
{
        struct kasan_alloc_meta *alloc_meta;

        if (!(cache->flags & SLAB_KASAN))
                return (void *)object;

        alloc_meta = kasan_get_alloc_meta(cache, object);
        __memset(alloc_meta, 0, sizeof(*alloc_meta));

        if (IS_ENABLED(CONFIG_KASAN_SW_TAGS) || IS_ENABLED(CONFIG_KASAN_HW_TAGS))
                object = set_tag(object, assign_tag(cache, object, true, false));

        return (void *)object;
}

static bool __kasan_slab_free(struct kmem_cache *cache, void *object,
                              unsigned long ip, bool quarantine)
{
        u8 tag;
        void *tagged_object;
        unsigned long rounded_up_size;

        tag = get_tag(object);
        tagged_object = object;
        object = reset_tag(object);

        if (unlikely(nearest_obj(cache, virt_to_head_page(object), object) !=
            object)) {
                kasan_report_invalid_free(tagged_object, ip);
                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 (check_invalid_free(tagged_object)) {
                kasan_report_invalid_free(tagged_object, ip);
                return true;
        }

        rounded_up_size = round_up(cache->object_size, KASAN_GRANULE_SIZE);
        poison_range(object, rounded_up_size, KASAN_KMALLOC_FREE);

        if ((IS_ENABLED(CONFIG_KASAN_GENERIC) && !quarantine) ||
                        unlikely(!(cache->flags & SLAB_KASAN)))
                return false;

        kasan_set_free_info(cache, object, tag);

        quarantine_put(cache, object);

        return IS_ENABLED(CONFIG_KASAN_GENERIC);
}

bool kasan_slab_free(struct kmem_cache *cache, void *object, unsigned long ip)
{
        return __kasan_slab_free(cache, object, ip, true);
}

static void *__kasan_kmalloc(struct kmem_cache *cache, const void *object,
                                size_t size, gfp_t flags, bool keep_tag)
{
        unsigned long redzone_start;
        unsigned long redzone_end;
        u8 tag = 0xff;

        if (gfpflags_allow_blocking(flags))
                quarantine_reduce();

        if (unlikely(object == NULL))
                return NULL;

        redzone_start = round_up((unsigned long)(object + size),
                                KASAN_GRANULE_SIZE);
        redzone_end = round_up((unsigned long)object + cache->object_size,
                                KASAN_GRANULE_SIZE);

        if (IS_ENABLED(CONFIG_KASAN_SW_TAGS) || IS_ENABLED(CONFIG_KASAN_HW_TAGS))
                tag = assign_tag(cache, object, false, keep_tag);

        /* Tag is ignored in set_tag without CONFIG_KASAN_SW/HW_TAGS */
        unpoison_range(set_tag(object, tag), size);
        poison_range((void *)redzone_start, redzone_end - redzone_start,
                     KASAN_KMALLOC_REDZONE);

        if (cache->flags & SLAB_KASAN)
                kasan_set_track(&kasan_get_alloc_meta(cache, object)->alloc_track, flags);

        return set_tag(object, tag);
}

void * __must_check kasan_slab_alloc(struct kmem_cache *cache, void *object,
                                        gfp_t flags)
{
        return __kasan_kmalloc(cache, object, cache->object_size, flags, false);
}

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, true);
}
EXPORT_SYMBOL(kasan_kmalloc);

void * __must_check kasan_kmalloc_large(const void *ptr, size_t size,
                                                gfp_t flags)
{
        struct page *page;
        unsigned long redzone_start;
        unsigned long redzone_end;

        if (gfpflags_allow_blocking(flags))
                quarantine_reduce();

        if (unlikely(ptr == NULL))
                return NULL;

        page = virt_to_page(ptr);
        redzone_start = round_up((unsigned long)(ptr + size),
                                KASAN_GRANULE_SIZE);
        redzone_end = (unsigned long)ptr + page_size(page);

        unpoison_range(ptr, size);
        poison_range((void *)redzone_start, redzone_end - redzone_start,
                     KASAN_PAGE_REDZONE);

        return (void *)ptr;
}

void * __must_check kasan_krealloc(const void *object, size_t size, gfp_t flags)
{
        struct page *page;

        if (unlikely(object == ZERO_SIZE_PTR))
                return (void *)object;

        page = virt_to_head_page(object);

        if (unlikely(!PageSlab(page)))
                return kasan_kmalloc_large(object, size, flags);
        else
                return __kasan_kmalloc(page->slab_cache, object, size,
                                                flags, true);
}

void kasan_poison_kfree(void *ptr, unsigned long ip)
{
        struct page *page;

        page = virt_to_head_page(ptr);

        if (unlikely(!PageSlab(page))) {
                if (ptr != page_address(page)) {
                        kasan_report_invalid_free(ptr, ip);
                        return;
                }
                poison_range(ptr, page_size(page), KASAN_FREE_PAGE);
        } else {
                __kasan_slab_free(page->slab_cache, ptr, ip, false);
        }
}

void kasan_kfree_large(void *ptr, unsigned long ip)
{
        if (ptr != page_address(virt_to_head_page(ptr)))
                kasan_report_invalid_free(ptr, ip);
        /* The object will be poisoned by page_alloc. */
}