3 files changed, 128 insertions, 66 deletions

diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c
index 4b20061102f6..c81549d5c833 100644
--- a/mm/kasan/kasan.c
+++ b/mm/kasan/kasan.c
@@ -577,7 +577,8 @@ bool kasan_slab_free(struct kmem_cache *cache, void *object)
 
 	shadow_byte = READ_ONCE(*(s8 *)kasan_mem_to_shadow(object));
 	if (shadow_byte < 0 || shadow_byte >= KASAN_SHADOW_SCALE_SIZE) {
-		kasan_report_double_free(cache, object, shadow_byte);
+		kasan_report_double_free(cache, object,
+				__builtin_return_address(1));
 		return true;
 	}
 
@@ -690,7 +691,7 @@ int kasan_module_alloc(void *addr, size_t size)
 
 	ret = __vmalloc_node_range(shadow_size, 1, shadow_start,
 			shadow_start + shadow_size,
-			GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO,
+			GFP_KERNEL | __GFP_ZERO,
 			PAGE_KERNEL, VM_NO_GUARD, NUMA_NO_NODE,
 			__builtin_return_address(0));
 
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index dd2dea8eb077..1229298cce64 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -99,7 +99,7 @@ static inline const void *kasan_shadow_to_mem(const void *shadow_addr)
 void kasan_report(unsigned long addr, size_t size,
 		bool is_write, unsigned long ip);
 void kasan_report_double_free(struct kmem_cache *cache, void *object,
-			s8 shadow);
+					void *ip);
 
 #if defined(CONFIG_SLAB) || defined(CONFIG_SLUB)
 void quarantine_put(struct kasan_free_meta *info, struct kmem_cache *cache);
diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index ab42a0803f16..beee0e980e2d 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -51,7 +51,13 @@ static const void *find_first_bad_addr(const void *addr, size_t size)
 	return first_bad_addr;
 }
 
-static void print_error_description(struct kasan_access_info *info)
+static bool addr_has_shadow(struct kasan_access_info *info)
+{
+	return (info->access_addr >=
+		kasan_shadow_to_mem((void *)KASAN_SHADOW_START));
+}
+
+static const char *get_shadow_bug_type(struct kasan_access_info *info)
 {
 	const char *bug_type = "unknown-crash";
 	u8 *shadow_addr;
@@ -98,12 +104,39 @@ static void print_error_description(struct kasan_access_info *info)
 		break;
 	}
 
-	pr_err("BUG: KASAN: %s in %pS at addr %p\n",
-		bug_type, (void *)info->ip,
-		info->access_addr);
-	pr_err("%s of size %zu by task %s/%d\n",
-		info->is_write ? "Write" : "Read",
-		info->access_size, current->comm, task_pid_nr(current));
+	return bug_type;
+}
+
+const char *get_wild_bug_type(struct kasan_access_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_access_info *info)
+{
+	if (addr_has_shadow(info))
+		return get_shadow_bug_type(info);
+	return get_wild_bug_type(info);
+}
+
+static void print_error_description(struct kasan_access_info *info)
+{
+	const char *bug_type = get_bug_type(info);
+
+	pr_err("BUG: KASAN: %s in %pS\n",
+		bug_type, (void *)info->ip);
+	pr_err("%s of size %zu at addr %p by task %s/%d\n",
+		info->is_write ? "Write" : "Read", info->access_size,
+		info->access_addr, current->comm, task_pid_nr(current));
 }
 
 static inline bool kernel_or_module_addr(const void *addr)
@@ -144,9 +177,9 @@ static void kasan_end_report(unsigned long *flags)
 	kasan_enable_current();
 }
 
-static void print_track(struct kasan_track *track)
+static void print_track(struct kasan_track *track, const char *prefix)
 {
-	pr_err("PID = %u\n", track->pid);
+	pr_err("%s by task %u:\n", prefix, track->pid);
 	if (track->stack) {
 		struct stack_trace trace;
 
@@ -157,59 +190,84 @@ static void print_track(struct kasan_track *track)
 	}
 }
 
-static void kasan_object_err(struct kmem_cache *cache, void *object)
+static struct page *addr_to_page(const void *addr)
 {
-	struct kasan_alloc_meta *alloc_info = get_alloc_info(cache, object);
+	if ((addr >= (void *)PAGE_OFFSET) &&
+			(addr < high_memory))
+		return virt_to_head_page(addr);
+	return NULL;
+}
 
-	dump_stack();
-	pr_err("Object at %p, in cache %s size: %d\n", object, cache->name,
-		cache->object_size);
+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;
 
-	if (!(cache->flags & SLAB_KASAN))
+	pr_err("The buggy address belongs to the object at %p\n"
+	       " which belongs to the cache %s of size %d\n",
+		object, cache->name, cache->object_size);
+
+	if (!addr)
 		return;
 
-	pr_err("Allocated:\n");
-	print_track(&alloc_info->alloc_track);
-	pr_err("Freed:\n");
-	print_track(&alloc_info->free_track);
+	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 [%p, %p)\n",
+		rel_bytes, rel_type, cache->object_size, (void *)object_addr,
+		(void *)(object_addr + cache->object_size));
 }
 
-void kasan_report_double_free(struct kmem_cache *cache, void *object,
-			s8 shadow)
+static void describe_object(struct kmem_cache *cache, void *object,
+				const void *addr)
 {
-	unsigned long flags;
+	struct kasan_alloc_meta *alloc_info = get_alloc_info(cache, object);
 
-	kasan_start_report(&flags);
-	pr_err("BUG: Double free or freeing an invalid pointer\n");
-	pr_err("Unexpected shadow byte: 0x%hhX\n", shadow);
-	kasan_object_err(cache, object);
-	kasan_end_report(&flags);
+	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 void print_address_description(struct kasan_access_info *info)
+static void print_address_description(void *addr)
 {
-	const void *addr = info->access_addr;
+	struct page *page = addr_to_page(addr);
 
-	if ((addr >= (void *)PAGE_OFFSET) &&
-		(addr < high_memory)) {
-		struct page *page = virt_to_head_page(addr);
-
-		if (PageSlab(page)) {
-			void *object;
-			struct kmem_cache *cache = page->slab_cache;
-			object = nearest_obj(cache, page,
-						(void *)info->access_addr);
-			kasan_object_err(cache, object);
-			return;
-		}
-		dump_page(page, "kasan: bad access detected");
+	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)) {
-		if (!init_task_stack_addr(addr))
-			pr_err("Address belongs to variable %pS\n", 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");
 	}
-	dump_stack();
 }
 
 static bool row_is_guilty(const void *row, const void *guilty)
@@ -264,31 +322,34 @@ static void print_shadow_for_address(const void *addr)
 	}
 }
 
+void kasan_report_double_free(struct kmem_cache *cache, void *object,
+				void *ip)
+{
+	unsigned long flags;
+
+	kasan_start_report(&flags);
+	pr_err("BUG: KASAN: double-free or invalid-free in %pS\n", ip);
+	pr_err("\n");
+	print_address_description(object);
+	pr_err("\n");
+	print_shadow_for_address(object);
+	kasan_end_report(&flags);
+}
+
 static void kasan_report_error(struct kasan_access_info *info)
 {
 	unsigned long flags;
-	const char *bug_type;
 
 	kasan_start_report(&flags);
 
-	if (info->access_addr <
-			kasan_shadow_to_mem((void *)KASAN_SHADOW_START)) {
-		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";
-		pr_err("BUG: KASAN: %s on address %p\n",
-			bug_type, info->access_addr);
-		pr_err("%s of size %zu by task %s/%d\n",
-			info->is_write ? "Write" : "Read",
-			info->access_size, current->comm,
-			task_pid_nr(current));
+	print_error_description(info);
+	pr_err("\n");
+
+	if (!addr_has_shadow(info)) {
 		dump_stack();
 	} else {
-		print_error_description(info);
-		print_address_description(info);
+		print_address_description((void *)info->access_addr);
+		pr_err("\n");
 		print_shadow_for_address(info->first_bad_addr);
 	}