// SPDX-License-Identifier: GPL-2.0
/*
 * This file contains common generic and tag-based KASAN 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>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 */

#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/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 <linux/sched/task_stack.h>

#include <asm/sections.h>

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

/* Shadow layout customization. */
#define SHADOW_BYTES_PER_BLOCK 1
#define SHADOW_BLOCKS_PER_ROW 16
#define SHADOW_BYTES_PER_ROW (SHADOW_BLOCKS_PER_ROW * SHADOW_BYTES_PER_BLOCK)
#define SHADOW_ROWS_AROUND_ADDR 2

static unsigned long kasan_flags;

#define KASAN_BIT_REPORTED      0
#define KASAN_BIT_MULTI_SHOT    1

bool kasan_save_enable_multi_shot(void)
{
        return test_and_set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
}
EXPORT_SYMBOL_GPL(kasan_save_enable_multi_shot);

void kasan_restore_multi_shot(bool enabled)
{
        if (!enabled)
                clear_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
}
EXPORT_SYMBOL_GPL(kasan_restore_multi_shot);

static int __init kasan_set_multi_shot(char *str)
{
        set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
        return 1;
}
__setup("kasan_multi_shot", kasan_set_multi_shot);

static void print_error_description(struct kasan_access_info *info)
{
        pr_err("BUG: KASAN: %s in %pS\n",
                get_bug_type(info), (void *)info->ip);
        pr_err("%s of size %zu at addr %px by task %s/%d\n",
                info->is_write ? "Write" : "Read", info->access_size,
                info->access_addr, current->comm, task_pid_nr(current));
}

static DEFINE_SPINLOCK(report_lock);

static void start_report(unsigned long *flags)
{
        /*
         * Make sure we don't end up in loop.
         */
        kasan_disable_current();
        spin_lock_irqsave(&report_lock, *flags);
        pr_err("==================================================================\n");
}

static void end_report(unsigned long *flags)
{
        pr_err("==================================================================\n");
        add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
        spin_unlock_irqrestore(&report_lock, *flags);
        if (panic_on_warn)
                panic("panic_on_warn set ...\n");
        kasan_enable_current();
}

static void print_track(struct kasan_track *track, const char *prefix)
{
        pr_err("%s by task %u:\n", prefix, track->pid);
        if (track->stack) {
                unsigned long *entries;
                unsigned int nr_entries;

                nr_entries = stack_depot_fetch(track->stack, &entries);
                stack_trace_print(entries, nr_entries, 0);
        } else {
                pr_err("(stack is not available)\n");
        }
}

static struct page *addr_to_page(const void *addr)
{
        if ((addr >= (void *)PAGE_OFFSET) &&
                        (addr < high_memory))
                return virt_to_head_page(addr);
        return NULL;
}

static void describe_object_addr(struct kmem_cache *cache, void *object,
                                const void *addr)
{
        unsigned long access_addr = (unsigned long)addr;
        unsigned long object_addr = (unsigned long)object;
        const char *rel_type;
        int rel_bytes;

        pr_err("The buggy address belongs to the object at %px\n"
               " which belongs to the cache %s of size %d\n",
                object, cache->name, cache->object_size);

        if (!addr)
                return;

        if (access_addr < object_addr) {
                rel_type = "to the left";
                rel_bytes = object_addr - access_addr;
        } else if (access_addr >= object_addr + cache->object_size) {
                rel_type = "to the right";
                rel_bytes = access_addr - (object_addr + cache->object_size);
        } else {
                rel_type = "inside";
                rel_bytes = access_addr - object_addr;
        }

        pr_err("The buggy address is located %d bytes %s of\n"
               " %d-byte region [%px, %px)\n",
                rel_bytes, rel_type, cache->object_size, (void *)object_addr,
                (void *)(object_addr + cache->object_size));
}

static void describe_object(struct kmem_cache *cache, void *object,
                                const void *addr)
{
        struct kasan_alloc_meta *alloc_info = get_alloc_info(cache, object);

        if (cache->flags & SLAB_KASAN) {
                print_track(&alloc_info->alloc_track, "Allocated");
                pr_err("\n");
                print_track(&alloc_info->free_track, "Freed");
                pr_err("\n");
        }

        describe_object_addr(cache, object, addr);
}

static inline bool kernel_or_module_addr(const void *addr)
{
        if (addr >= (void *)_stext && addr < (void *)_end)
                return true;
        if (is_module_address((unsigned long)addr))
                return true;
        return false;
}

static inline bool init_task_stack_addr(const void *addr)
{
        return addr >= (void *)&init_thread_union.stack &&
                (addr <= (void *)&init_thread_union.stack +
                        sizeof(init_thread_union.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("KASAN internal error: frame description too long: %s\n",
                               *frame_descr);
                        return false;
                }

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

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

        if (value != NULL && kstrtoul(token, 10, value)) {
                pr_err("KASAN 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);
        }
}

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));

        /*
         * NOTE: We currently only support printing frame information for
         * accesses to the task's own stack.
         */
        if (!object_is_on_stack(addr))
                return false;

        aligned_addr = round_down((unsigned long)addr, sizeof(long));
        mem_ptr = round_down(aligned_addr, KASAN_SHADOW_SCALE_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_SHADOW_SCALE_SIZE;
        }

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

        if (shadow_ptr < shadow_bottom)
                return false;

        frame = (const unsigned long *)(mem_ptr + KASAN_SHADOW_SCALE_SIZE);
        if (frame[0] != KASAN_CURRENT_STACK_FRAME_MAGIC) {
                pr_err("KASAN internal error: frame info validation failed; 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;
}

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

        if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
                return;

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

        /*
         * get_address_stack_frame_info only returns true if the given addr is
         * on the current task's stack.
         */
        pr_err("\n");
        pr_err("addr %px is located in stack of task %s/%d at offset %lu in frame:\n",
               addr, current->comm, task_pid_nr(current), offset);
        pr_err(" %pS\n", frame_pc);

        if (!frame_descr)
                return;

        print_decoded_frame_descr(frame_descr);
}

static void print_address_description(void *addr)
{
        struct page *page = addr_to_page(addr);

        dump_stack();
        pr_err("\n");

        if (page && PageSlab(page)) {
                struct kmem_cache *cache = page->slab_cache;
                void *object = nearest_obj(cache, page, addr);

                describe_object(cache, object, addr);
        }

        if (kernel_or_module_addr(addr) && !init_task_stack_addr(addr)) {
                pr_err("The buggy address belongs to the variable:\n");
                pr_err(" %pS\n", addr);
        }

        if (page) {
                pr_err("The buggy address belongs to the page:\n");
                dump_page(page, "kasan: bad access detected");
        }

        print_address_stack_frame(addr);
}

static bool row_is_guilty(const void *row, const void *guilty)
{
        return (row <= guilty) && (guilty < row + SHADOW_BYTES_PER_ROW);
}

static int shadow_pointer_offset(const void *row, const void *shadow)
{
        /* The length of ">ff00ff00ff00ff00: " is
         *    3 + (BITS_PER_LONG/8)*2 chars.
         */
        return 3 + (BITS_PER_LONG/8)*2 + (shadow - row)*2 +
                (shadow - row) / SHADOW_BYTES_PER_BLOCK + 1;
}

static void print_shadow_for_address(const void *addr)
{
        int i;
        const void *shadow = kasan_mem_to_shadow(addr);
        const void *shadow_row;

        shadow_row = (void *)round_down((unsigned long)shadow,
                                        SHADOW_BYTES_PER_ROW)
                - SHADOW_ROWS_AROUND_ADDR * SHADOW_BYTES_PER_ROW;

        pr_err("Memory state around the buggy address:\n");

        for (i = -SHADOW_ROWS_AROUND_ADDR; i <= SHADOW_ROWS_AROUND_ADDR; i++) {
                const void *kaddr = kasan_shadow_to_mem(shadow_row);
                char buffer[4 + (BITS_PER_LONG/8)*2];
                char shadow_buf[SHADOW_BYTES_PER_ROW];

                snprintf(buffer, sizeof(buffer),
                        (i == 0) ? ">%px: " : " %px: ", kaddr);
                /*
                 * We should not pass a shadow pointer to generic
                 * function, because generic functions may try to
                 * access kasan mapping for the passed address.
                 */
                memcpy(shadow_buf, shadow_row, SHADOW_BYTES_PER_ROW);
                print_hex_dump(KERN_ERR, buffer,
                        DUMP_PREFIX_NONE, SHADOW_BYTES_PER_ROW, 1,
                        shadow_buf, SHADOW_BYTES_PER_ROW, 0);

                if (row_is_guilty(shadow_row, shadow))
                        pr_err("%*c\n",
                                shadow_pointer_offset(shadow_row, shadow),
                                '^');

                shadow_row += SHADOW_BYTES_PER_ROW;
        }
}

static bool report_enabled(void)
{
        if (current->kasan_depth)
                return false;
        if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
                return true;
        return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags);
}

void kasan_report_invalid_free(void *object, unsigned long ip)
{
        unsigned long flags;

        start_report(&flags);
        pr_err("BUG: KASAN: double-free or invalid-free in %pS\n", (void *)ip);
        print_tags(get_tag(object), reset_tag(object));
        object = reset_tag(object);
        pr_err("\n");
        print_address_description(object);
        pr_err("\n");
        print_shadow_for_address(object);
        end_report(&flags);
}

void __kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip)
{
        struct kasan_access_info info;
        void *tagged_addr;
        void *untagged_addr;
        unsigned long flags;

        if (likely(!report_enabled()))
                return;

        disable_trace_on_warning();

        tagged_addr = (void *)addr;
        untagged_addr = reset_tag(tagged_addr);

        info.access_addr = tagged_addr;
        if (addr_has_shadow(untagged_addr))
                info.first_bad_addr = find_first_bad_addr(tagged_addr, size);
        else
                info.first_bad_addr = untagged_addr;
        info.access_size = size;
        info.is_write = is_write;
        info.ip = ip;

        start_report(&flags);

        print_error_description(&info);
        if (addr_has_shadow(untagged_addr))
                print_tags(get_tag(tagged_addr), info.first_bad_addr);
        pr_err("\n");

        if (addr_has_shadow(untagged_addr)) {
                print_address_description(untagged_addr);
                pr_err("\n");
                print_shadow_for_address(info.first_bad_addr);
        } else {
                dump_stack();
        }

        end_report(&flags);
}