kasan: simplify address description logic

Simplify logic for describing a memory address.  Add addr_to_page()
helper function.

Makes the code easier to follow.

Link: http://lkml.kernel.org/r/20170302134851.101218-5-andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Acked-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index 7d24363..a82d689 100644 (file)
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -190,11 +190,18 @@ static void print_track(struct kasan_track *track, const char *prefix)
        }
 }
 
-static void kasan_object_err(struct kmem_cache *cache, void *object)
+static struct page *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(struct kmem_cache *cache, void *object)
 {
        struct kasan_alloc_meta *alloc_info = get_alloc_info(cache, object);
 
-       dump_stack();
        pr_err("Object at %p, in cache %s size: %d\n", object, cache->name,
                cache->object_size);
 
@@ -213,34 +220,32 @@ void kasan_report_double_free(struct kmem_cache *cache, void *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);
+       dump_stack();
+       describe_object(cache, object);
        kasan_end_report(&flags);
 }
 
 static void print_address_description(struct kasan_access_info *info)
 {
        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;
-               }
+       if (page)
                dump_page(page, "kasan: bad access detected");
+
+       dump_stack();
+
+       if (page && PageSlab(page)) {
+               struct kmem_cache *cache = page->slab_cache;
+               void *object = nearest_obj(cache, page, (void *)addr);
+
+               describe_object(cache, object);
        }
 
        if (kernel_or_module_addr(addr)) {
                if (!init_task_stack_addr(addr))
                        pr_err("Address belongs to variable %pS\n", addr);
        }
-       dump_stack();
 }
 
 static bool row_is_guilty(const void *row, const void *guilty)