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Subject[PATCH v4 6/9] kasan: improve slab object description
Date
Changes slab object description from:

Object at ffff880068388540, in cache kmalloc-128 size: 128

to:

Object at ffff88006a2d5a80 belongs to cache kmalloc-128 of size 128
accessed at offset 123

This adds information about relative offset of the accessed address to
the start of the object.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
mm/kasan/report.c | 38 +++++++++++++++++++++++++++-----------
1 file changed, 27 insertions(+), 11 deletions(-)

diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index 156f998199e2..06e27a342d1d 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -194,18 +194,34 @@ static struct page *addr_to_page(const void *addr)
return NULL;
}

-static void describe_object(struct kmem_cache *cache, void *object)
+static void describe_object_addr(struct kmem_cache *cache, void *object,
+ const void *addr)
{
- struct kasan_alloc_meta *alloc_info = get_alloc_info(cache, object);
+ unsigned long access_addr = (unsigned long)addr;
+ unsigned long object_addr = (unsigned long)object;
+ const char *rel_type;
+ int rel_bytes;

- pr_err("Object at %p, in cache %s size: %d\n", object, cache->name,
- cache->object_size);
+ pr_err("Object at %p belongs to cache %s of size %d\n",
+ object, cache->name, cache->object_size);

- if (!(cache->flags & SLAB_KASAN))
+ if (!addr)
return;

- print_track(&alloc_info->alloc_track, "Allocated");
- print_track(&alloc_info->free_track, "Freed");
+ pr_err(" accessed at offset %d\n", access_addr - object_addr);
+}
+
+static void describe_object(struct kmem_cache *cache, void *object,
+ const void *addr)
+{
+ struct kasan_alloc_meta *alloc_info = get_alloc_info(cache, object);
+
+ if (cache->flags & SLAB_KASAN) {
+ print_track(&alloc_info->alloc_track, "Allocated");
+ print_track(&alloc_info->free_track, "Freed");
+ }
+
+ describe_object_addr(cache, object, addr);
}

void kasan_report_double_free(struct kmem_cache *cache, void *object,
@@ -217,13 +233,13 @@ void kasan_report_double_free(struct kmem_cache *cache, void *object,
pr_err("BUG: Double free or freeing an invalid pointer\n");
pr_err("Unexpected shadow byte: 0x%hhX\n", shadow);
dump_stack();
- describe_object(cache, object);
+ describe_object(cache, object, NULL);
kasan_end_report(&flags);
}

static void print_address_description(struct kasan_access_info *info)
{
- const void *addr = info->access_addr;
+ void *addr = (void *)info->access_addr;
struct page *page = addr_to_page(addr);

if (page)
@@ -233,9 +249,9 @@ static void print_address_description(struct kasan_access_info *info)

if (page && PageSlab(page)) {
struct kmem_cache *cache = page->slab_cache;
- void *object = nearest_obj(cache, page, (void *)addr);
+ void *object = nearest_obj(cache, page, addr);

- describe_object(cache, object);
+ describe_object(cache, object, addr);
}

if (kernel_or_module_addr(addr)) {
--
2.12.1.578.ge9c3154ca4-goog
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