Commit e4b7818b authored by Walter Wu's avatar Walter Wu Committed by Linus Torvalds
Browse files

kasan: record and print the free track 

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

[walter-zh.wu@mediatek.com: build fix]
  Link: http://lkml.kernel.org/r/20200710162440.23887-1-walter-zh.wu@mediatek.com



Suggested-by: default avatarDmitry Vyukov <dvyukov@google.com>
Co-developed-by: default avatarDmitry Vyukov <dvyukov@google.com>
Signed-off-by: default avatarWalter Wu <walter-zh.wu@mediatek.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Tested-by: default avatarDmitry Vyukov <dvyukov@google.com>
Reviewed-by: default avatarDmitry Vyukov <dvyukov@google.com>
Reviewed-by: default avatarAndrey Konovalov <andreyknvl@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Cc: "Paul E . McKenney" <paulmck@kernel.org>
Link: http://lkml.kernel.org/r/20200601051022.1230-1-walter-zh.wu@mediatek.com


Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 26e760c9

mm/kasan/common.c

+2 −20
Original line number Diff line number Diff line
@@ -50,7 +50,7 @@ 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);
@@ -298,24 +298,6 @@ 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;
@@ -491,7 +473,7 @@ 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);

}

mm/kasan/generic.c

+22 −0
Original line number Diff line number Diff line
@@ -345,3 +345,25 @@ 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;

}

mm/kasan/generic_report.c

+1 −0
Original line number Diff line number Diff line
@@ -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:

mm/kasan/kasan.h

+13 −3
Original line number Diff line number Diff line
@@ -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
@@ -110,8 +112,9 @@ struct kasan_alloc_meta { 
	 * The free stack is stored into struct kasan_free_meta.

	 */

	depot_stack_handle_t aux_stack[2];

#endif

#else

	struct kasan_track free_track[KASAN_NR_FREE_STACKS];

#endif

#ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY

	u8 free_pointer_tag[KASAN_NR_FREE_STACKS];

	u8 free_track_idx;
@@ -126,6 +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,
@@ -167,6 +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))

mm/kasan/quarantine.c

+1 −0
Original line number Diff line number Diff line
@@ -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))