[PATCH v3 4/9] kasan: simplify address description logic

From: Andrey Konovalov
Date: Mon Mar 06 2017 - 11:01:15 EST


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

Makes the code easier to follow.

Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
---
mm/kasan/report.c | 36 ++++++++++++++++++++----------------
1 file changed, 20 insertions(+), 16 deletions(-)

diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index 382d4d2b9052..f77341979dae 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -188,11 +188,17 @@ 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);

@@ -211,34 +217,32 @@ 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)
--
2.12.0.rc1.440.g5b76565f74-goog