// 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/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 <linux/vmalloc.h>

#include "kasan.h"
#include "../slab.h"

#if defined(CONFIG_ARCH_DEFER_KASAN) || defined(CONFIG_KASAN_HW_TAGS)
/*
 * Definition of the unified static key declared in kasan-enabled.h.
 * This provides consistent runtime enable/disable across KASAN modes.
 */
DEFINE_STATIC_KEY_FALSE(kasan_flag_enabled);
EXPORT_SYMBOL_GPL(kasan_flag_enabled);
#endif

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;
}

/* Returns true when freeing the object is not safe. */
static bool check_slab_allocation(struct kmem_cache *cache, void *object,
                                  unsigned long ip)
{
        void *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;
        }

        if (!kasan_byte_accessible(tagged_object)) {
                kasan_report_invalid_free(tagged_object, ip, KASAN_REPORT_DOUBLE_FREE);
                return true;
        }

        return false;
}

static inline void poison_slab_object(struct kmem_cache *cache, void *object,
                                      bool init)
{
        void *tagged_object = object;

        object = kasan_reset_tag(object);

        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);
}

bool __kasan_slab_pre_free(struct kmem_cache *cache, void *object,
                                unsigned long ip)
{
        if (is_kfence_address(object))
                return false;
        return check_slab_allocation(cache, object, ip);
}

bool __kasan_slab_free(struct kmem_cache *cache, void *object, bool init,
                       bool still_accessible, bool no_quarantine)
{
        if (is_kfence_address(object))
                return false;

        /*
         * If this point is reached with an object that must still be
         * accessible under RCU, we can't poison it; in that case, also skip the
         * quarantine. This should mostly only happen when CONFIG_SLUB_RCU_DEBUG
         * has been disabled manually.
         *
         * Putting the object on the quarantine wouldn't help catch UAFs (since
         * we can't poison it here), and it would mask bugs caused by
         * SLAB_TYPESAFE_BY_RCU users not being careful enough about object
         * reuse; so overall, putting the object into the quarantine here would
         * be counterproductive.
         */
        if (still_accessible)
                return false;

        poison_slab_object(cache, object, init);

        if (no_quarantine)
                return false;

        /*
         * 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 (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 page *page = virt_to_page(ptr);
        struct slab *slab;

        if (unlikely(PageLargeKmalloc(page))) {
                if (check_page_allocation(ptr, ip))
                        return false;
                kasan_poison(ptr, page_size(page), KASAN_PAGE_FREE, false);
                return true;
        }

        if (is_kfence_address(ptr))
                return true;

        slab = page_slab(page);

        if (check_slab_allocation(slab->slab_cache, ptr, ip))
                return false;

        poison_slab_object(slab->slab_cache, ptr, false);
        return true;
}

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;
}

#ifdef CONFIG_KASAN_VMALLOC
void __kasan_unpoison_vmap_areas(struct vm_struct **vms, int nr_vms,
                                 kasan_vmalloc_flags_t flags)
{
        unsigned long size;
        void *addr;
        int area;
        u8 tag;

        /*
         * If KASAN_VMALLOC_KEEP_TAG was set at this point, all vms[] pointers
         * would be unpoisoned with the KASAN_TAG_KERNEL which would disable
         * KASAN checks down the line.
         */
        if (WARN_ON_ONCE(flags & KASAN_VMALLOC_KEEP_TAG))
                return;

        size = vms[0]->size;
        addr = vms[0]->addr;
        vms[0]->addr = __kasan_unpoison_vmalloc(addr, size, flags);
        tag = get_tag(vms[0]->addr);

        for (area = 1 ; area < nr_vms ; area++) {
                size = vms[area]->size;
                addr = set_tag(vms[area]->addr, tag);
                vms[area]->addr =
                        __kasan_unpoison_vmalloc(addr, size, flags | KASAN_VMALLOC_KEEP_TAG);
        }
}

void __kasan_vrealloc(const void *addr, unsigned long old_size,
                unsigned long new_size)
{
        if (new_size < old_size) {
                kasan_poison_last_granule(addr, new_size);

                new_size = round_up(new_size, KASAN_GRANULE_SIZE);
                old_size = round_up(old_size, KASAN_GRANULE_SIZE);
                if (new_size < old_size)
                        __kasan_poison_vmalloc(addr + new_size,
                                        old_size - new_size);
        } else if (new_size > old_size) {
                old_size = round_down(old_size, KASAN_GRANULE_SIZE);
                __kasan_unpoison_vmalloc(addr + old_size,
                                        new_size - old_size,
                                        KASAN_VMALLOC_PROT_NORMAL |
                                        KASAN_VMALLOC_VM_ALLOC |
                                        KASAN_VMALLOC_KEEP_TAG);
        }
}
#endif