// 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 <kunit/test.h>
#include <kunit/visibility.h>
#include <linux/bitops.h>
#include <linux/ftrace.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/lockdep.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/vmalloc.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 "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,
        KASAN_ARG_FAULT_PANIC_ON_WRITE,
};

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 if (!strcmp(arg, "panic_on_write"))
                kasan_arg_fault = KASAN_ARG_FAULT_PANIC_ON_WRITE;
        else
                return -EINVAL;

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

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);

/*
 * This function is used to check whether KASAN reports are suppressed for
 * software KASAN modes via kasan_disable/enable_current() critical sections.
 *
 * This is done to avoid:
 * 1. False-positive reports when accessing slab metadata,
 * 2. Deadlocking when poisoned memory is accessed by the reporting code.
 *
 * Hardware Tag-Based KASAN instead relies on:
 * For #1: Resetting tags via kasan_reset_tag().
 * For #2: Suppression of tag checks via CPU, see report_suppress_start/end().
 */
static bool report_suppressed_sw(void)
{
#if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
        if (current->kasan_depth)
                return true;
#endif
        return false;
}

static void report_suppress_start(void)
{
#ifdef CONFIG_KASAN_HW_TAGS
        /*
         * Disable preemption for the duration of printing a KASAN report, as
         * hw_suppress_tag_checks_start() disables checks on the current CPU.
         */
        preempt_disable();
        hw_suppress_tag_checks_start();
#else
        kasan_disable_current();
#endif
}

static void report_suppress_stop(void)
{
#ifdef CONFIG_KASAN_HW_TAGS
        hw_suppress_tag_checks_stop();
        preempt_enable();
#else
        kasan_enable_current();
#endif
}

/*
 * Used to avoid reporting more than one KASAN bug unless kasan_multi_shot
 * is enabled. Note that KASAN tests effectively enable kasan_multi_shot
 * for their duration.
 */
static bool report_enabled(void)
{
        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_KASAN_KUNIT_TEST)

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

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

#endif

#if IS_ENABLED(CONFIG_KASAN_KUNIT_TEST)

/*
 * Whether the KASAN KUnit test suite is currently being executed.
 * Updated in kasan_test.c.
 */
static bool kasan_kunit_executing;

VISIBLE_IF_KUNIT void kasan_kunit_test_suite_start(void)
{
        WRITE_ONCE(kasan_kunit_executing, true);
}
EXPORT_SYMBOL_IF_KUNIT(kasan_kunit_test_suite_start);

VISIBLE_IF_KUNIT void kasan_kunit_test_suite_end(void)
{
        WRITE_ONCE(kasan_kunit_executing, false);
}
EXPORT_SYMBOL_IF_KUNIT(kasan_kunit_test_suite_end);

static bool kasan_kunit_test_suite_executing(void)
{
        return READ_ONCE(kasan_kunit_executing);
}

#else /* CONFIG_KASAN_KUNIT_TEST */

static inline bool kasan_kunit_test_suite_executing(void) { return false; }

#endif /* CONFIG_KASAN_KUNIT_TEST */

#if IS_ENABLED(CONFIG_KUNIT)

static void fail_non_kasan_kunit_test(void)
{
        struct kunit *test;

        if (kasan_kunit_test_suite_executing())
                return;

        test = current->kunit_test;
        if (test)
                kunit_set_failure(test);
}

#else /* CONFIG_KUNIT */

static inline void fail_non_kasan_kunit_test(void) { }

#endif /* CONFIG_KUNIT */

static DEFINE_RAW_SPINLOCK(report_lock);

static void start_report(unsigned long *flags)
{
        fail_non_kasan_kunit_test();
        /* Respect the /proc/sys/kernel/traceoff_on_warning interface. */
        disable_trace_on_warning();
        /* Do not allow LOCKDEP mangling KASAN reports. */
        lockdep_off();
        /* Make sure we don't end up in loop. */
        report_suppress_start();
        raw_spin_lock_irqsave(&report_lock, *flags);
        pr_err("==================================================================\n");
}

static void end_report(unsigned long *flags, const void *addr, bool is_write)
{
        if (addr)
                trace_error_report_end(ERROR_DETECTOR_KASAN,
                                       (unsigned long)addr);
        pr_err("==================================================================\n");
        raw_spin_unlock_irqrestore(&report_lock, *flags);
        if (!test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
                check_panic_on_warn("KASAN");
        switch (kasan_arg_fault) {
        case KASAN_ARG_FAULT_DEFAULT:
        case KASAN_ARG_FAULT_REPORT:
                break;
        case KASAN_ARG_FAULT_PANIC:
                panic("kasan.fault=panic set ...\n");
                break;
        case KASAN_ARG_FAULT_PANIC_ON_WRITE:
                if (is_write)
                        panic("kasan.fault=panic_on_write set ...\n");
                break;
        }
        add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
        lockdep_on();
        report_suppress_stop();
}

static void print_error_description(struct kasan_report_info *info)
{
        pr_err("BUG: KASAN: %s in %pS\n", info->bug_type, (void *)info->ip);

        if (info->type != KASAN_REPORT_ACCESS) {
                pr_err("Free of addr %px by task %s/%d\n",
                        info->access_addr, current->comm, task_pid_nr(current));
                return;
        }

        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 void print_track(struct kasan_track *track, const char *prefix)
{
#ifdef CONFIG_KASAN_EXTRA_INFO
        u64 ts_nsec = track->timestamp;
        unsigned long rem_usec;

        ts_nsec <<= 9;
        rem_usec = do_div(ts_nsec, NSEC_PER_SEC) / 1000;

        pr_err("%s by task %u on cpu %d at %lu.%06lus:\n",
                        prefix, track->pid, track->cpu,
                        (unsigned long)ts_nsec, rem_usec);
#else
        pr_err("%s by task %u:\n", prefix, track->pid);
#endif /* CONFIG_KASAN_EXTRA_INFO */
        if (track->stack)
                stack_depot_print(track->stack);
        else
                pr_err("(stack is not available)\n");
}

static inline struct page *addr_to_page(const void *addr)
{
        if (virt_addr_valid(addr))
                return virt_to_head_page(addr);
        return NULL;
}

static void describe_object_addr(const void *addr, struct kasan_report_info *info)
{
        unsigned long access_addr = (unsigned long)addr;
        unsigned long object_addr = (unsigned long)info->object;
        const char *rel_type, *region_state = "";
        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",
                info->object, info->cache->name, info->cache->object_size);

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

        /*
         * Tag-Based modes use the stack ring to infer the bug type, but the
         * memory region state description is generated based on the metadata.
         * Thus, defining the region state as below can contradict the metadata.
         * Fixing this requires further improvements, so only infer the state
         * for the Generic mode.
         */
        if (IS_ENABLED(CONFIG_KASAN_GENERIC)) {
                if (strcmp(info->bug_type, "slab-out-of-bounds") == 0)
                        region_state = "allocated ";
                else if (strcmp(info->bug_type, "slab-use-after-free") == 0)
                        region_state = "freed ";
        }

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

static void describe_object_stacks(struct kasan_report_info *info)
{
        if (info->alloc_track.stack) {
                print_track(&info->alloc_track, "Allocated");
                pr_err("\n");
        }

        if (info->free_track.stack) {
                print_track(&info->free_track, "Freed");
                pr_err("\n");
        }

        kasan_print_aux_stacks(info->cache, info->object);
}

static void describe_object(const void *addr, struct kasan_report_info *info)
{
        if (kasan_stack_collection_enabled())
                describe_object_stacks(info);
        describe_object_addr(addr, info);
}

static inline bool kernel_or_module_addr(const void *addr)
{
        if (is_kernel((unsigned long)addr))
                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 kasan_report_info *info)
{
        struct page *page = addr_to_page(addr);

        dump_stack_lvl(KERN_ERR);
        pr_err("\n");

        if (info->cache && info->object) {
                describe_object(addr, info);
                pr_err("\n");
        }

        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);
                pr_err("\n");
        }

        if (object_is_on_stack(addr)) {
                /*
                 * Currently, KASAN supports printing frame information only
                 * for accesses to the task's own stack.
                 */
                kasan_print_address_stack_frame(addr);
                pr_err("\n");
        }

        if (is_vmalloc_addr(addr)) {
                pr_err("The buggy address belongs to a");
                if (!vmalloc_dump_obj(addr))
                        pr_cont(" vmalloc virtual mapping\n");
                page = vmalloc_to_page(addr);
        }

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

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 void print_report(struct kasan_report_info *info)
{
        void *addr = kasan_reset_tag((void *)info->access_addr);
        u8 tag = get_tag((void *)info->access_addr);

        print_error_description(info);
        if (addr_has_metadata(addr))
                kasan_print_tags(tag, info->first_bad_addr);
        pr_err("\n");

        if (addr_has_metadata(addr)) {
                print_address_description(addr, tag, info);
                print_memory_metadata(info->first_bad_addr);
        } else {
                dump_stack_lvl(KERN_ERR);
        }
}

static void complete_report_info(struct kasan_report_info *info)
{
        void *addr = kasan_reset_tag((void *)info->access_addr);
        struct slab *slab;

        if (info->type == KASAN_REPORT_ACCESS)
                info->first_bad_addr = kasan_find_first_bad_addr(
                                        (void *)info->access_addr, info->access_size);
        else
                info->first_bad_addr = addr;

        slab = kasan_addr_to_slab(addr);
        if (slab) {
                info->cache = slab->slab_cache;
                info->object = nearest_obj(info->cache, slab, addr);

                /* Try to determine allocation size based on the metadata. */
                info->alloc_size = kasan_get_alloc_size(info->object, info->cache);
                /* Fallback to the object size if failed. */
                if (!info->alloc_size)
                        info->alloc_size = info->cache->object_size;
        } else
                info->cache = info->object = NULL;

        switch (info->type) {
        case KASAN_REPORT_INVALID_FREE:
                info->bug_type = "invalid-free";
                break;
        case KASAN_REPORT_DOUBLE_FREE:
                info->bug_type = "double-free";
                break;
        default:
                /* bug_type filled in by kasan_complete_mode_report_info. */
                break;
        }

        /* Fill in mode-specific report info fields. */
        kasan_complete_mode_report_info(info);
}

void kasan_report_invalid_free(void *ptr, unsigned long ip, enum kasan_report_type type)
{
        unsigned long flags;
        struct kasan_report_info info;

        /*
         * Do not check report_suppressed_sw(), as an invalid-free cannot be
         * caused by accessing poisoned memory and thus should not be suppressed
         * by kasan_disable/enable_current() critical sections.
         *
         * Note that for Hardware Tag-Based KASAN, kasan_report_invalid_free()
         * is triggered by explicit tag checks and not by the ones performed by
         * the CPU. Thus, reporting invalid-free is not suppressed as well.
         */
        if (unlikely(!report_enabled()))
                return;

        start_report(&flags);

        __memset(&info, 0, sizeof(info));
        info.type = type;
        info.access_addr = ptr;
        info.access_size = 0;
        info.is_write = false;
        info.ip = ip;

        complete_report_info(&info);

        print_report(&info);

        /*
         * Invalid free is considered a "write" since the allocator's metadata
         * updates involves writes.
         */
        end_report(&flags, ptr, true);
}

/*
 * kasan_report() is the only reporting function that uses
 * user_access_save/restore(): kasan_report_invalid_free() cannot be called
 * from a UACCESS region, and kasan_report_async() is not used on x86.
 */
bool kasan_report(const void *addr, size_t size, bool is_write,
                        unsigned long ip)
{
        bool ret = true;
        unsigned long ua_flags = user_access_save();
        unsigned long irq_flags;
        struct kasan_report_info info;

        if (unlikely(report_suppressed_sw()) || unlikely(!report_enabled())) {
                ret = false;
                goto out;
        }

        start_report(&irq_flags);

        __memset(&info, 0, sizeof(info));
        info.type = KASAN_REPORT_ACCESS;
        info.access_addr = addr;
        info.access_size = size;
        info.is_write = is_write;
        info.ip = ip;

        complete_report_info(&info);

        print_report(&info);

        end_report(&irq_flags, (void *)addr, is_write);

out:
        user_access_restore(ua_flags);

        return ret;
}

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

        /*
         * Do not check report_suppressed_sw(), as
         * kasan_disable/enable_current() critical sections do not affect
         * Hardware Tag-Based KASAN.
         */
        if (unlikely(!report_enabled()))
                return;

        start_report(&flags);
        pr_err("BUG: KASAN: invalid-access\n");
        pr_err("Asynchronous fault: no details available\n");
        pr_err("\n");
        dump_stack_lvl(KERN_ERR);
        /*
         * Conservatively set is_write=true, because no details are available.
         * In this mode, kasan.fault=panic_on_write is like kasan.fault=panic.
         */
        end_report(&flags, NULL, true);
}
#endif /* CONFIG_KASAN_HW_TAGS */

#if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
/*
 * With compiler-based KASAN modes, accesses to bogus pointers (outside of the
 * mapped kernel address space regions) cause faults when KASAN tries to check
 * the shadow memory before the actual memory access. This results in cryptic
 * GPF reports, which are hard for users to interpret. This hook helps users to
 * figure out what the original bogus pointer was.
 */
void kasan_non_canonical_hook(unsigned long addr)
{
        unsigned long orig_addr;
        const char *bug_type;

        /*
         * All addresses that came as a result of the memory-to-shadow mapping
         * (even for bogus pointers) must be >= KASAN_SHADOW_OFFSET.
         */
        if (addr < KASAN_SHADOW_OFFSET)
                return;

        orig_addr = (unsigned long)kasan_shadow_to_mem((void *)addr);

        /*
         * 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 the shadow for low or high canonical
         * addresses, we can still be pretty sure: these shadow regions are a
         * fairly narrow chunk of the address space.
         * But the shadow for non-canonical addresses is a really large chunk
         * of the address space. For this 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 if (addr_in_shadow((void *)addr))
                bug_type = "probably wild-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