[PATCH v7 2/4] kasan: record and print the free track
From: Walter Wu
Date: Mon Jun 01 2020 - 01:10:38 EST
Move free track from kasan_alloc_meta to kasan_free_meta in order
to make struct kasan_alloc_meta and kasan_free_meta size are both
16 bytes. It is a good size because it is the minimal redzone size
and a good number of alignment.
For free track, we make some modifications as shown below:
1) Remove the free_track from struct kasan_alloc_meta.
2) Add the free_track into struct kasan_free_meta.
3) Add a macro KASAN_KMALLOC_FREETRACK in order to check whether
it can print free stack in KASAN report.
[1]https://bugzilla.kernel.org/show_bug.cgi?id=198437
Signed-off-by: Walter Wu <walter-zh.wu@xxxxxxxxxxxx>
Suggested-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Co-developed-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Reviewed-and-tested-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Reviewed-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Cc: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
---
mm/kasan/common.c | 22 ++--------------------
mm/kasan/generic.c | 22 ++++++++++++++++++++++
mm/kasan/generic_report.c | 1 +
mm/kasan/kasan.h | 13 +++++++++++--
mm/kasan/quarantine.c | 1 +
mm/kasan/report.c | 26 ++++----------------------
mm/kasan/tags.c | 37 +++++++++++++++++++++++++++++++++++++
7 files changed, 78 insertions(+), 44 deletions(-)
diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 8bc618289bb1..47b53912f322 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -51,7 +51,7 @@ depot_stack_handle_t kasan_save_stack(gfp_t flags)
return stack_depot_save(entries, nr_entries, flags);
}
-static inline void set_track(struct kasan_track *track, gfp_t flags)
+void kasan_set_track(struct kasan_track *track, gfp_t flags)
{
track->pid = current->pid;
track->stack = kasan_save_stack(flags);
@@ -299,24 +299,6 @@ struct kasan_free_meta *get_free_info(struct kmem_cache *cache,
return (void *)object + cache->kasan_info.free_meta_offset;
}
-
-static void kasan_set_free_info(struct kmem_cache *cache,
- void *object, u8 tag)
-{
- struct kasan_alloc_meta *alloc_meta;
- u8 idx = 0;
-
- alloc_meta = get_alloc_info(cache, object);
-
-#ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY
- idx = alloc_meta->free_track_idx;
- alloc_meta->free_pointer_tag[idx] = tag;
- alloc_meta->free_track_idx = (idx + 1) % KASAN_NR_FREE_STACKS;
-#endif
-
- set_track(&alloc_meta->free_track[idx], GFP_NOWAIT);
-}
-
void kasan_poison_slab(struct page *page)
{
unsigned long i;
@@ -492,7 +474,7 @@ static void *__kasan_kmalloc(struct kmem_cache *cache, const void *object,
KASAN_KMALLOC_REDZONE);
if (cache->flags & SLAB_KASAN)
- set_track(&get_alloc_info(cache, object)->alloc_track, flags);
+ kasan_set_track(&get_alloc_info(cache, object)->alloc_track, flags);
return set_tag(object, tag);
}
diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c
index 8acf48882ba2..4b3cbad7431b 100644
--- a/mm/kasan/generic.c
+++ b/mm/kasan/generic.c
@@ -346,3 +346,25 @@ void kasan_record_aux_stack(void *addr)
alloc_info->aux_stack[1] = alloc_info->aux_stack[0];
alloc_info->aux_stack[0] = kasan_save_stack(GFP_NOWAIT);
}
+
+void kasan_set_free_info(struct kmem_cache *cache,
+ void *object, u8 tag)
+{
+ struct kasan_free_meta *free_meta;
+
+ free_meta = get_free_info(cache, object);
+ kasan_set_track(&free_meta->free_track, GFP_NOWAIT);
+
+ /*
+ * the object was freed and has free track set
+ */
+ *(u8 *)kasan_mem_to_shadow(object) = KASAN_KMALLOC_FREETRACK;
+}
+
+struct kasan_track *kasan_get_free_track(struct kmem_cache *cache,
+ void *object, u8 tag)
+{
+ if (*(u8 *)kasan_mem_to_shadow(object) != KASAN_KMALLOC_FREETRACK)
+ return NULL;
+ return &get_free_info(cache, object)->free_track;
+}
diff --git a/mm/kasan/generic_report.c b/mm/kasan/generic_report.c
index e200acb2d292..a38c7a9e192a 100644
--- a/mm/kasan/generic_report.c
+++ b/mm/kasan/generic_report.c
@@ -80,6 +80,7 @@ static const char *get_shadow_bug_type(struct kasan_access_info *info)
break;
case KASAN_FREE_PAGE:
case KASAN_KMALLOC_FREE:
+ case KASAN_KMALLOC_FREETRACK:
bug_type = "use-after-free";
break;
case KASAN_ALLOCA_LEFT:
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index a7391bc83070..ef655a1c6e15 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -17,15 +17,17 @@
#define KASAN_PAGE_REDZONE 0xFE /* redzone for kmalloc_large allocations */
#define KASAN_KMALLOC_REDZONE 0xFC /* redzone inside slub object */
#define KASAN_KMALLOC_FREE 0xFB /* object was freed (kmem_cache_free/kfree) */
+#define KASAN_KMALLOC_FREETRACK 0xFA /* object was freed and has free track set */
#else
#define KASAN_FREE_PAGE KASAN_TAG_INVALID
#define KASAN_PAGE_REDZONE KASAN_TAG_INVALID
#define KASAN_KMALLOC_REDZONE KASAN_TAG_INVALID
#define KASAN_KMALLOC_FREE KASAN_TAG_INVALID
+#define KASAN_KMALLOC_FREETRACK KASAN_TAG_INVALID
#endif
-#define KASAN_GLOBAL_REDZONE 0xFA /* redzone for global variable */
-#define KASAN_VMALLOC_INVALID 0xF9 /* unallocated space in vmapped page */
+#define KASAN_GLOBAL_REDZONE 0xF9 /* redzone for global variable */
+#define KASAN_VMALLOC_INVALID 0xF8 /* unallocated space in vmapped page */
/*
* Stack redzone shadow values
@@ -127,6 +129,9 @@ struct kasan_free_meta {
* Otherwise it might be used for the allocator freelist.
*/
struct qlist_node quarantine_link;
+#ifdef CONFIG_KASAN_GENERIC
+ struct kasan_track free_track;
+#endif
};
struct kasan_alloc_meta *get_alloc_info(struct kmem_cache *cache,
@@ -168,6 +173,10 @@ void kasan_report_invalid_free(void *object, unsigned long ip);
struct page *kasan_addr_to_page(const void *addr);
depot_stack_handle_t kasan_save_stack(gfp_t flags);
+void kasan_set_track(struct kasan_track *track, gfp_t flags);
+void kasan_set_free_info(struct kmem_cache *cache, void *object, u8 tag);
+struct kasan_track *kasan_get_free_track(struct kmem_cache *cache,
+ void *object, u8 tag);
#if defined(CONFIG_KASAN_GENERIC) && \
(defined(CONFIG_SLAB) || defined(CONFIG_SLUB))
diff --git a/mm/kasan/quarantine.c b/mm/kasan/quarantine.c
index 978bc4a3eb51..4c5375810449 100644
--- a/mm/kasan/quarantine.c
+++ b/mm/kasan/quarantine.c
@@ -145,6 +145,7 @@ static void qlink_free(struct qlist_node *qlink, struct kmem_cache *cache)
if (IS_ENABLED(CONFIG_SLAB))
local_irq_save(flags);
+ *(u8 *)kasan_mem_to_shadow(object) = KASAN_KMALLOC_FREE;
___cache_free(cache, object, _THIS_IP_);
if (IS_ENABLED(CONFIG_SLAB))
diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index 2421a4bd9227..fed3c8fdfd25 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -164,26 +164,6 @@ static void describe_object_addr(struct kmem_cache *cache, void *object,
(void *)(object_addr + cache->object_size));
}
-static struct kasan_track *kasan_get_free_track(struct kmem_cache *cache,
- void *object, u8 tag)
-{
- struct kasan_alloc_meta *alloc_meta;
- int i = 0;
-
- alloc_meta = get_alloc_info(cache, object);
-
-#ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY
- for (i = 0; i < KASAN_NR_FREE_STACKS; i++) {
- if (alloc_meta->free_pointer_tag[i] == tag)
- break;
- }
- if (i == KASAN_NR_FREE_STACKS)
- i = alloc_meta->free_track_idx;
-#endif
-
- return &alloc_meta->free_track[i];
-}
-
static void describe_object(struct kmem_cache *cache, void *object,
const void *addr, u8 tag)
{
@@ -195,8 +175,10 @@ static void describe_object(struct kmem_cache *cache, void *object,
print_track(&alloc_info->alloc_track, "Allocated");
pr_err("\n");
free_track = kasan_get_free_track(cache, object, tag);
- print_track(free_track, "Freed");
- pr_err("\n");
+ if (free_track) {
+ print_track(free_track, "Freed");
+ pr_err("\n");
+ }
#ifdef CONFIG_KASAN_GENERIC
if (alloc_info->aux_stack[0]) {
diff --git a/mm/kasan/tags.c b/mm/kasan/tags.c
index 25b7734e7013..201dee5d6ae0 100644
--- a/mm/kasan/tags.c
+++ b/mm/kasan/tags.c
@@ -162,3 +162,40 @@ void __hwasan_tag_memory(unsigned long addr, u8 tag, unsigned long size)
kasan_poison_shadow((void *)addr, size, tag);
}
EXPORT_SYMBOL(__hwasan_tag_memory);
+
+void kasan_set_free_info(struct kmem_cache *cache,
+ void *object, u8 tag)
+{
+ struct kasan_alloc_meta *alloc_meta;
+ u8 idx = 0;
+
+ alloc_meta = get_alloc_info(cache, object);
+
+#ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY
+ idx = alloc_meta->free_track_idx;
+ alloc_meta->free_pointer_tag[idx] = tag;
+ alloc_meta->free_track_idx = (idx + 1) % KASAN_NR_FREE_STACKS;
+#endif
+
+ kasan_set_track(&alloc_meta->free_track[idx], GFP_NOWAIT);
+}
+
+struct kasan_track *kasan_get_free_track(struct kmem_cache *cache,
+ void *object, u8 tag)
+{
+ struct kasan_alloc_meta *alloc_meta;
+ int i = 0;
+
+ alloc_meta = get_alloc_info(cache, object);
+
+#ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY
+ for (i = 0; i < KASAN_NR_FREE_STACKS; i++) {
+ if (alloc_meta->free_pointer_tag[i] == tag)
+ break;
+ }
+ if (i == KASAN_NR_FREE_STACKS)
+ i = alloc_meta->free_track_idx;
+#endif
+
+ return &alloc_meta->free_track[i];
+}
--
2.18.0