// SPDX-License-Identifier: GPL-2.0
/*
 * This file contains generic KASAN specific error reporting 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/bitops.h>
#include <linux/ftrace.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/printk.h>
#include <linux/sched.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/kasan.h>
#include <linux/module.h>

#include <asm/sections.h>

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

const void *kasan_find_first_bad_addr(const void *addr, size_t size)
{
        const void *p = addr;

        if (!addr_has_metadata(p))
                return p;

        while (p < addr + size && !(*(u8 *)kasan_mem_to_shadow(p)))
                p += KASAN_GRANULE_SIZE;

        return p;
}

size_t kasan_get_alloc_size(void *object, struct kmem_cache *cache)
{
        size_t size = 0;
        u8 *shadow;

        /*
         * Skip the addr_has_metadata check, as this function only operates on
         * slab memory, which must have metadata.
         */

        /*
         * The loop below returns 0 for freed objects, for which KASAN cannot
         * calculate the allocation size based on the metadata.
         */
        shadow = (u8 *)kasan_mem_to_shadow(object);
        while (size < cache->object_size) {
                if (*shadow == 0)
                        size += KASAN_GRANULE_SIZE;
                else if (*shadow >= 1 && *shadow <= KASAN_GRANULE_SIZE - 1)
                        return size + *shadow;
                else
                        return size;
                shadow++;
        }

        return cache->object_size;
}

static const char *get_shadow_bug_type(struct kasan_report_info *info)
{
        const char *bug_type = "unknown-crash";
        u8 *shadow_addr;

        shadow_addr = (u8 *)kasan_mem_to_shadow(info->first_bad_addr);

        /*
         * If shadow byte value is in [0, KASAN_GRANULE_SIZE) we can look
         * at the next shadow byte to determine the type of the bad access.
         */
        if (*shadow_addr > 0 && *shadow_addr <= KASAN_GRANULE_SIZE - 1)
                shadow_addr++;

        switch (*shadow_addr) {
        case 0 ... KASAN_GRANULE_SIZE - 1:
                /*
                 * In theory it's still possible to see these shadow values
                 * due to a data race in the kernel code.
                 */
                bug_type = "out-of-bounds";
                break;
        case KASAN_PAGE_REDZONE:
        case KASAN_SLAB_REDZONE:
                bug_type = "slab-out-of-bounds";
                break;
        case KASAN_GLOBAL_REDZONE:
                bug_type = "global-out-of-bounds";
                break;
        case KASAN_STACK_LEFT:
        case KASAN_STACK_MID:
        case KASAN_STACK_RIGHT:
        case KASAN_STACK_PARTIAL:
                bug_type = "stack-out-of-bounds";
                break;
        case KASAN_PAGE_FREE:
                bug_type = "use-after-free";
                break;
        case KASAN_SLAB_FREE:
        case KASAN_SLAB_FREE_META:
                bug_type = "slab-use-after-free";
                break;
        case KASAN_ALLOCA_LEFT:
        case KASAN_ALLOCA_RIGHT:
                bug_type = "alloca-out-of-bounds";
                break;
        case KASAN_VMALLOC_INVALID:
                bug_type = "vmalloc-out-of-bounds";
                break;
        }

        return bug_type;
}

static const char *get_wild_bug_type(struct kasan_report_info *info)
{
        const char *bug_type = "unknown-crash";

        if ((unsigned long)info->access_addr < PAGE_SIZE)
                bug_type = "null-ptr-deref";
        else if ((unsigned long)info->access_addr < TASK_SIZE)
                bug_type = "user-memory-access";
        else
                bug_type = "wild-memory-access";

        return bug_type;
}

static const char *get_bug_type(struct kasan_report_info *info)
{
        /*
         * If access_size is a negative number, then it has reason to be
         * defined as out-of-bounds bug type.
         *
         * Casting negative numbers to size_t would indeed turn up as
         * a large size_t and its value will be larger than ULONG_MAX/2,
         * so that this can qualify as out-of-bounds.
         */
        if (info->access_addr + info->access_size < info->access_addr)
                return "out-of-bounds";

        if (addr_has_metadata(info->access_addr))
                return get_shadow_bug_type(info);
        return get_wild_bug_type(info);
}

void kasan_complete_mode_report_info(struct kasan_report_info *info)
{
        struct kasan_alloc_meta *alloc_meta;
        struct kasan_free_meta *free_meta;

        if (!info->bug_type)
                info->bug_type = get_bug_type(info);

        if (!info->cache || !info->object)
                return;

        alloc_meta = kasan_get_alloc_meta(info->cache, info->object);
        if (alloc_meta)
                memcpy(&info->alloc_track, &alloc_meta->alloc_track,
                       sizeof(info->alloc_track));

        if (*(u8 *)kasan_mem_to_shadow(info->object) == KASAN_SLAB_FREE_META) {
                /* Free meta must be present with KASAN_SLAB_FREE_META. */
                free_meta = kasan_get_free_meta(info->cache, info->object);
                memcpy(&info->free_track, &free_meta->free_track,
                       sizeof(info->free_track));
        }
}

void kasan_metadata_fetch_row(char *buffer, void *row)
{
        memcpy(buffer, kasan_mem_to_shadow(row), META_BYTES_PER_ROW);
}

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

        alloc_meta = kasan_get_alloc_meta(cache, object);
        if (!alloc_meta)
                return;

        if (alloc_meta->aux_stack[0]) {
                pr_err("Last potentially related work creation:\n");
                stack_depot_print(alloc_meta->aux_stack[0]);
                pr_err("\n");
        }
        if (alloc_meta->aux_stack[1]) {
                pr_err("Second to last potentially related work creation:\n");
                stack_depot_print(alloc_meta->aux_stack[1]);
                pr_err("\n");
        }
}

#ifdef CONFIG_KASAN_STACK
static bool __must_check tokenize_frame_descr(const char **frame_descr,
                                              char *token, size_t max_tok_len,
                                              unsigned long *value)
{
        const char *sep = strchr(*frame_descr, ' ');

        if (sep == NULL)
                sep = *frame_descr + strlen(*frame_descr);

        if (token != NULL) {
                const size_t tok_len = sep - *frame_descr;

                if (tok_len + 1 > max_tok_len) {
                        pr_err("internal error: frame description too long: %s\n",
                               *frame_descr);
                        return false;
                }

                /* Copy token (+ 1 byte for '\0'). */
                strscpy(token, *frame_descr, tok_len + 1);
        }

        /* Advance frame_descr past separator. */
        *frame_descr = sep + 1;

        if (value != NULL && kstrtoul(token, 10, value)) {
                pr_err("internal error: not a valid number: %s\n", token);
                return false;
        }

        return true;
}

static void print_decoded_frame_descr(const char *frame_descr)
{
        /*
         * We need to parse the following string:
         *    "n alloc_1 alloc_2 ... alloc_n"
         * where alloc_i looks like
         *    "offset size len name"
         * or "offset size len name:line".
         */

        char token[64];
        unsigned long num_objects;

        if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
                                  &num_objects))
                return;

        pr_err("\n");
        pr_err("This frame has %lu %s:\n", num_objects,
               num_objects == 1 ? "object" : "objects");

        while (num_objects--) {
                unsigned long offset;
                unsigned long size;

                /* access offset */
                if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
                                          &offset))
                        return;
                /* access size */
                if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
                                          &size))
                        return;
                /* name length (unused) */
                if (!tokenize_frame_descr(&frame_descr, NULL, 0, NULL))
                        return;
                /* object name */
                if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
                                          NULL))
                        return;

                /* Strip line number; without filename it's not very helpful. */
                strreplace(token, ':', '\0');

                /* Finally, print object information. */
                pr_err(" [%lu, %lu) '%s'", offset, offset + size, token);
        }
}

/* Returns true only if the address is on the current task's stack. */
static bool __must_check get_address_stack_frame_info(const void *addr,
                                                      unsigned long *offset,
                                                      const char **frame_descr,
                                                      const void **frame_pc)
{
        unsigned long aligned_addr;
        unsigned long mem_ptr;
        const u8 *shadow_bottom;
        const u8 *shadow_ptr;
        const unsigned long *frame;

        BUILD_BUG_ON(IS_ENABLED(CONFIG_STACK_GROWSUP));

        aligned_addr = round_down((unsigned long)addr, sizeof(long));
        mem_ptr = round_down(aligned_addr, KASAN_GRANULE_SIZE);
        shadow_ptr = kasan_mem_to_shadow((void *)aligned_addr);
        shadow_bottom = kasan_mem_to_shadow(end_of_stack(current));

        while (shadow_ptr >= shadow_bottom && *shadow_ptr != KASAN_STACK_LEFT) {
                shadow_ptr--;
                mem_ptr -= KASAN_GRANULE_SIZE;
        }

        while (shadow_ptr >= shadow_bottom && *shadow_ptr == KASAN_STACK_LEFT) {
                shadow_ptr--;
                mem_ptr -= KASAN_GRANULE_SIZE;
        }

        if (shadow_ptr < shadow_bottom)
                return false;

        frame = (const unsigned long *)(mem_ptr + KASAN_GRANULE_SIZE);
        if (frame[0] != KASAN_CURRENT_STACK_FRAME_MAGIC) {
                pr_err("internal error: frame has invalid marker: %lu\n",
                       frame[0]);
                return false;
        }

        *offset = (unsigned long)addr - (unsigned long)frame;
        *frame_descr = (const char *)frame[1];
        *frame_pc = (void *)frame[2];

        return true;
}

void kasan_print_address_stack_frame(const void *addr)
{
        unsigned long offset;
        const char *frame_descr;
        const void *frame_pc;

        if (WARN_ON(!object_is_on_stack(addr)))
                return;

        pr_err("The buggy address belongs to stack of task %s/%d\n",
               current->comm, task_pid_nr(current));

        if (!get_address_stack_frame_info(addr, &offset, &frame_descr,
                                          &frame_pc))
                return;

        pr_err(" and is located at offset %lu in frame:\n", offset);
        pr_err(" %pS\n", frame_pc);

        if (!frame_descr)
                return;

        print_decoded_frame_descr(frame_descr);
}
#endif /* CONFIG_KASAN_STACK */

#define DEFINE_ASAN_REPORT_LOAD(size)                     \
void __asan_report_load##size##_noabort(void *addr) \
{                                                         \
        kasan_report(addr, size, false, _RET_IP_);        \
}                                                         \
EXPORT_SYMBOL(__asan_report_load##size##_noabort)

#define DEFINE_ASAN_REPORT_STORE(size)                     \
void __asan_report_store##size##_noabort(void *addr) \
{                                                          \
        kasan_report(addr, size, true, _RET_IP_);          \
}                                                          \
EXPORT_SYMBOL(__asan_report_store##size##_noabort)

DEFINE_ASAN_REPORT_LOAD(1);
DEFINE_ASAN_REPORT_LOAD(2);
DEFINE_ASAN_REPORT_LOAD(4);
DEFINE_ASAN_REPORT_LOAD(8);
DEFINE_ASAN_REPORT_LOAD(16);
DEFINE_ASAN_REPORT_STORE(1);
DEFINE_ASAN_REPORT_STORE(2);
DEFINE_ASAN_REPORT_STORE(4);
DEFINE_ASAN_REPORT_STORE(8);
DEFINE_ASAN_REPORT_STORE(16);

void __asan_report_load_n_noabort(void *addr, ssize_t size)
{
        kasan_report(addr, size, false, _RET_IP_);
}
EXPORT_SYMBOL(__asan_report_load_n_noabort);

void __asan_report_store_n_noabort(void *addr, ssize_t size)
{
        kasan_report(addr, size, true, _RET_IP_);
}
EXPORT_SYMBOL(__asan_report_store_n_noabort);