1 files changed, 662 insertions, 0 deletions

diff --git a/mm/kasan/report.c b/mm/kasan/report.c
new file mode 100644
index 0000000000..6e3cb118d2
--- /dev/null
+++ b/mm/kasan/report.c
@@ -0,0 +1,662 @@
+// 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 <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/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) || IS_ENABLED(CONFIG_KASAN_MODULE_TEST)
+
+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);
+
+#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;
+
+void kasan_kunit_test_suite_start(void)
+{
+	WRITE_ONCE(kasan_kunit_executing, true);
+}
+EXPORT_SYMBOL_GPL(kasan_kunit_test_suite_start);
+
+void kasan_kunit_test_suite_end(void)
+{
+	WRITE_ONCE(kasan_kunit_executing, false);
+}
+EXPORT_SYMBOL_GPL(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_SPINLOCK(report_lock);
+
+static void start_report(unsigned long *flags, bool sync)
+{
+	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();
+	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");
+	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)
+{
+	pr_err("%s by task %u:\n", prefix, track->pid);
+	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)) {
+		struct vm_struct *va = find_vm_area(addr);
+
+		if (va) {
+			pr_err("The buggy address belongs to the virtual mapping at\n"
+			       " [%px, %px) created by:\n"
+			       " %pS\n",
+			       va->addr, va->addr + va->size, va->caller);
+			pr_err("\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, true);
+
+	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, true);
+
+	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, false);
+	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 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