// SPDX-License-Identifier: GPL-2.0
/*
 * This file contains common 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>
 */

#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 <linux/uaccess.h>
#include <trace/events/error_report.h>

#include <asm/sections.h>

#include <kunit/test.h>

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

static unsigned long kasan_flags;

#define KASAN_BIT_REPORTED      0
#define KASAN_BIT_MULTI_SHOT    1

enum kasan_arg_fault {
        KASAN_ARG_FAULT_DEFAULT,
        KASAN_ARG_FAULT_REPORT,
        KASAN_ARG_FAULT_PANIC,
};

static enum kasan_arg_fault kasan_arg_fault __ro_after_init = KASAN_ARG_FAULT_DEFAULT;

/* kasan.fault=report/panic */
static int __init early_kasan_fault(char *arg)
{
        if (!arg)
                return -EINVAL;

        if (!strcmp(arg, "report"))
                kasan_arg_fault = KASAN_ARG_FAULT_REPORT;
        else if (!strcmp(arg, "panic"))
                kasan_arg_fault = KASAN_ARG_FAULT_PANIC;
        else
                return -EINVAL;

        return 0;
}
early_param("kasan.fault", early_kasan_fault);

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",
                kasan_get_bug_type(info), (void *)info->ip);
        if (info->access_size)
                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));
        else
                pr_err("%s at addr %px by task %s/%d\n",
                        info->is_write ? "Write" : "Read",
                        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, unsigned long addr)
{
        if (!kasan_async_mode_enabled())
                trace_error_report_end(ERROR_DETECTOR_KASAN, addr);
        pr_err("==================================================================\n");
        add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
        spin_unlock_irqrestore(&report_lock, *flags);
        if (panic_on_warn && !test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags)) {
                /*
                 * This thread may hit another WARN() in the panic path.
                 * Resetting this prevents additional WARN() from panicking the
                 * system on this thread.  Other threads are blocked by the
                 * panic_mutex in panic().
                 */
                panic_on_warn = 0;
                panic("panic_on_warn set ...\n");
        }
        if (kasan_arg_fault == KASAN_ARG_FAULT_PANIC)
                panic("kasan.fault=panic set ...\n");
        kasan_enable_current();
}

static void print_stack(depot_stack_handle_t stack)
{
        unsigned long *entries;
        unsigned int nr_entries;

        nr_entries = stack_depot_fetch(stack, &entries);
        stack_trace_print(entries, nr_entries, 0);
}

static void print_track(struct kasan_track *track, const char *prefix)
{
        pr_err("%s by task %u:\n", prefix, track->pid);
        if (track->stack) {
                print_stack(track->stack);
        } else {
                pr_err("(stack is not available)\n");
        }
}

struct page *kasan_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_stacks(struct kmem_cache *cache, void *object,
                                        const void *addr, u8 tag)
{
        struct kasan_alloc_meta *alloc_meta;
        struct kasan_track *free_track;

        alloc_meta = kasan_get_alloc_meta(cache, object);
        if (alloc_meta) {
                print_track(&alloc_meta->alloc_track, "Allocated");
                pr_err("\n");
        }

        free_track = kasan_get_free_track(cache, object, tag);
        if (free_track) {
                print_track(free_track, "Freed");
                pr_err("\n");
        }

#ifdef CONFIG_KASAN_GENERIC
        if (!alloc_meta)
                return;
        if (alloc_meta->aux_stack[0]) {
                pr_err("Last potentially related work creation:\n");
                print_stack(alloc_meta->aux_stack[0]);
                pr_err("\n");
        }
        if (alloc_meta->aux_stack[1]) {
                pr_err("Second to last potentially related work creation:\n");
                print_stack(alloc_meta->aux_stack[1]);
                pr_err("\n");
        }
#endif
}

static void describe_object(struct kmem_cache *cache, void *object,
                                const void *addr, u8 tag)
{
        if (kasan_stack_collection_enabled())
                describe_object_stacks(cache, object, addr, tag);
        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 void print_address_description(void *addr, u8 tag)
{
        struct page *page = kasan_addr_to_page(addr);

        dump_stack_lvl(KERN_ERR);
        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, tag);
        }

        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");
        }

        kasan_print_address_stack_frame(addr);
}

static bool meta_row_is_guilty(const void *row, const void *addr)
{
        return (row <= addr) && (addr < row + META_MEM_BYTES_PER_ROW);
}

static int meta_pointer_offset(const void *row, const void *addr)
{
        /*
         * Memory state around the buggy address:
         *  ff00ff00ff00ff00: 00 00 00 05 fe fe fe fe fe fe fe fe fe fe fe fe
         *  ...
         *
         * The length of ">ff00ff00ff00ff00: " is
         *    3 + (BITS_PER_LONG / 8) * 2 chars.
         * The length of each granule metadata is 2 bytes
         *    plus 1 byte for space.
         */
        return 3 + (BITS_PER_LONG / 8) * 2 +
                (addr - row) / KASAN_GRANULE_SIZE * 3 + 1;
}

static void print_memory_metadata(const void *addr)
{
        int i;
        void *row;

        row = (void *)round_down((unsigned long)addr, META_MEM_BYTES_PER_ROW)
                        - META_ROWS_AROUND_ADDR * META_MEM_BYTES_PER_ROW;

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

        for (i = -META_ROWS_AROUND_ADDR; i <= META_ROWS_AROUND_ADDR; i++) {
                char buffer[4 + (BITS_PER_LONG / 8) * 2];
                char metadata[META_BYTES_PER_ROW];

                snprintf(buffer, sizeof(buffer),
                                (i == 0) ? ">%px: " : " %px: ", row);

                /*
                 * We should not pass a shadow pointer to generic
                 * function, because generic functions may try to
                 * access kasan mapping for the passed address.
                 */
                kasan_metadata_fetch_row(&metadata[0], row);

                print_hex_dump(KERN_ERR, buffer,
                        DUMP_PREFIX_NONE, META_BYTES_PER_ROW, 1,
                        metadata, META_BYTES_PER_ROW, 0);

                if (meta_row_is_guilty(row, addr))
                        pr_err("%*c\n", meta_pointer_offset(row, addr), '^');

                row += META_MEM_BYTES_PER_ROW;
        }
}

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

#if IS_ENABLED(CONFIG_KUNIT)
static void kasan_update_kunit_status(struct kunit *cur_test)
{
        struct kunit_resource *resource;
        struct kunit_kasan_expectation *kasan_data;

        resource = kunit_find_named_resource(cur_test, "kasan_data");

        if (!resource) {
                kunit_set_failure(cur_test);
                return;
        }

        kasan_data = (struct kunit_kasan_expectation *)resource->data;
        WRITE_ONCE(kasan_data->report_found, true);
        kunit_put_resource(resource);
}
#endif /* IS_ENABLED(CONFIG_KUNIT) */

void kasan_report_invalid_free(void *object, unsigned long ip)
{
        unsigned long flags;
        u8 tag = get_tag(object);

        object = kasan_reset_tag(object);

#if IS_ENABLED(CONFIG_KUNIT)
        if (current->kunit_test)
                kasan_update_kunit_status(current->kunit_test);
#endif /* IS_ENABLED(CONFIG_KUNIT) */

        start_report(&flags);
        pr_err("BUG: KASAN: double-free or invalid-free in %pS\n", (void *)ip);
        kasan_print_tags(tag, object);
        pr_err("\n");
        print_address_description(object, tag);
        pr_err("\n");
        print_memory_metadata(object);
        end_report(&flags, (unsigned long)object);
}

#ifdef CONFIG_KASAN_HW_TAGS
void kasan_report_async(void)
{
        unsigned long flags;

#if IS_ENABLED(CONFIG_KUNIT)
        if (current->kunit_test)
                kasan_update_kunit_status(current->kunit_test);
#endif /* IS_ENABLED(CONFIG_KUNIT) */

        start_report(&flags);
        pr_err("BUG: KASAN: invalid-access\n");
        pr_err("Asynchronous mode enabled: no access details available\n");
        pr_err("\n");
        dump_stack_lvl(KERN_ERR);
        end_report(&flags, 0);
}
#endif /* CONFIG_KASAN_HW_TAGS */

static 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 IS_ENABLED(CONFIG_KUNIT)
        if (current->kunit_test)
                kasan_update_kunit_status(current->kunit_test);
#endif /* IS_ENABLED(CONFIG_KUNIT) */

        disable_trace_on_warning();

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

        info.access_addr = tagged_addr;
        if (addr_has_metadata(untagged_addr))
                info.first_bad_addr =
                        kasan_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_metadata(untagged_addr))
                kasan_print_tags(get_tag(tagged_addr), info.first_bad_addr);
        pr_err("\n");

        if (addr_has_metadata(untagged_addr)) {
                print_address_description(untagged_addr, get_tag(tagged_addr));
                pr_err("\n");
                print_memory_metadata(info.first_bad_addr);
        } else {
                dump_stack_lvl(KERN_ERR);
        }

        end_report(&flags, addr);
}

bool kasan_report(unsigned long addr, size_t size, bool is_write,
                        unsigned long ip)
{
        unsigned long flags = user_access_save();
        bool ret = false;

        if (likely(report_enabled())) {
                __kasan_report(addr, size, is_write, ip);
                ret = true;
        }

        user_access_restore(flags);

        return ret;
}

#ifdef CONFIG_KASAN_INLINE
/*
 * With CONFIG_KASAN_INLINE, accesses to bogus pointers (outside the high
 * canonical half of the address space) cause out-of-bounds shadow memory reads
 * before the actual access. For addresses in the low canonical half of the
 * address space, as well as most non-canonical addresses, that out-of-bounds
 * shadow memory access lands in the non-canonical part of the address space.
 * Help the user figure out what the original bogus pointer was.
 */
void kasan_non_canonical_hook(unsigned long addr)
{
        unsigned long orig_addr;
        const char *bug_type;

        if (addr < KASAN_SHADOW_OFFSET)
                return;

        orig_addr = (addr - KASAN_SHADOW_OFFSET) << KASAN_SHADOW_SCALE_SHIFT;
        /*
         * For faults near the shadow address for NULL, we can be fairly certain
         * that this is a KASAN shadow memory access.
         * For faults that correspond to shadow for low canonical addresses, we
         * can still be pretty sure - that shadow region is a fairly narrow
         * chunk of the non-canonical address space.
         * But faults that look like shadow for non-canonical addresses are a
         * really large chunk of the address space. In that case, we still
         * print the decoded address, but make it clear that this is not
         * necessarily what's actually going on.
         */
        if (orig_addr < PAGE_SIZE)
                bug_type = "null-ptr-deref";
        else if (orig_addr < TASK_SIZE)
                bug_type = "probably user-memory-access";
        else
                bug_type = "maybe wild-memory-access";
        pr_alert("KASAN: %s in range [0x%016lx-0x%016lx]\n", bug_type,
                 orig_addr, orig_addr + KASAN_GRANULE_SIZE - 1);
}
#endif