kasan: fill in cache and object in complete_report_info

Add cache and object fields to kasan_report_info and fill them in in
complete_report_info() instead of fetching them in the middle of the
report printing code.

This allows the reporting code to get access to the object information
before starting printing the report.  One of the following patches uses
this information to determine the bug type with the tag-based modes.

Link: https://lkml.kernel.org/r/23264572cb2cbb8f0efbb51509b6757eb3cc1fc9.1662411799.git.andreyknvl@google.comSigned-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Peter Collingbourne <pcc@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/kasan/kasan.h

@@ -162,6 +162,8 @@ struct kasan_report_info {
 
 	/* Filled in by the common reporting code. */
 	void *first_bad_addr;
+	struct kmem_cache *cache;
+	void *object;
 };
 
 /* Do not change the struct layout: compiler ABI. */

mm/kasan/report.c

@@ -287,19 +287,16 @@ static inline bool init_task_stack_addr(const void *addr)
 			sizeof(init_thread_union.stack));
 }
 
-static void print_address_description(void *addr, u8 tag)
+static void print_address_description(void *addr, u8 tag,
+				      struct kasan_report_info *info)
 {
 	struct page *page = addr_to_page(addr);
-	struct slab *slab = kasan_addr_to_slab(addr);
 
 	dump_stack_lvl(KERN_ERR);
 	pr_err("\n");
 
-	if (slab) {
-		struct kmem_cache *cache = slab->slab_cache;
-		void *object = nearest_obj(cache, slab,	addr);
-
-		describe_object(cache, object, addr, tag);
+	if (info->cache && info->object) {
+		describe_object(info->cache, info->object, addr, tag);
 		pr_err("\n");
 	}
 
@@ -406,7 +403,7 @@ static void print_report(struct kasan_report_info *info)
 	pr_err("\n");
 
 	if (addr_has_metadata(addr)) {
-		print_address_description(addr, tag);
+		print_address_description(addr, tag, info);
 		print_memory_metadata(info->first_bad_addr);
 	} else {
 		dump_stack_lvl(KERN_ERR);
@@ -416,12 +413,20 @@ static void print_report(struct kasan_report_info *info)
 static void complete_report_info(struct kasan_report_info *info)
 {
 	void *addr = kasan_reset_tag(info->access_addr);
+	struct slab *slab;
 
 	if (info->type == KASAN_REPORT_ACCESS)
 		info->first_bad_addr = kasan_find_first_bad_addr(
 					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);
+	} else
+		info->cache = info->object = NULL;
 }
 
 void kasan_report_invalid_free(void *ptr, unsigned long ip, enum kasan_report_type type)