mirrors
/
linux-stable
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
1
0
Fork 0
Code Issues Releases Wiki Activity

kasan: stop leaking stack trace handles 

Commit 773688a6cb ("kasan: use stack_depot_put for Generic mode") added
support for stack trace eviction for Generic KASAN.

However, that commit didn't evict stack traces when the object is not put
into quarantine.  As a result, some stack traces are never evicted from
the stack depot.

In addition, with the "kasan: save mempool stack traces" series, the free
stack traces for mempool objects are also not properly evicted from the
stack depot.

Fix both issues by:

1. Evicting all stack traces when an object if freed if it was not put
   into quarantine;

2. Always evicting an existing free stack trace when a new one is saved.

Also do a few related clean-ups:

- Do not zero out free track when initializing/invalidating free meta:
  set a value in shadow memory instead;

- Rename KASAN_SLAB_FREETRACK to KASAN_SLAB_FREE_META;

- Drop the kasan_init_cache_meta function as it's not used by KASAN;

- Add comments for the kasan_alloc_meta and kasan_free_meta structs.

[akpm@linux-foundation.org: make release_free_meta() and release_alloc_meta() static]
Link: https://lkml.kernel.org/r/20231226225121.235865-1-andrey.konovalov@linux.dev
Fixes: 773688a6cb ("kasan: use stack_depot_put for Generic mode")
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Andrey Konovalov 2023-12-26 23:51:21 +01:00 committed by Andrew Morton
parent 7eb2d01a1b
commit 63b85ac56a
5 changed files with 97 additions and 41 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

27
mm/kasan/common.c
View File

@ -255,14 +255,33 @@ static inline bool poison_slab_object(struct kmem_cache *cache, void *object,
bool __kasan_slab_free(struct kmem_cache *cache, void *object,
unsigned long ip, bool init)
{
bool buggy_object;
if (is_kfence_address(object))
return false;
buggy_object = poison_slab_object(cache, object, ip, init);
/*
* If the object is buggy, do not let slab put the object onto the
* freelist. The object will thus never be allocated again and its
* metadata will never get released.
*/
if (poison_slab_object(cache, object, ip, init))
return true;
return buggy_object ? true : kasan_quarantine_put(cache, object);
/*
* If the object is put into quarantine, do not let slab put the object
* onto the freelist for now. The object's metadata is kept until the
* object gets evicted from quarantine.
*/
if (kasan_quarantine_put(cache, object))
return true;
/*
* If the object is not put into quarantine, it will likely be quickly
* reallocated. Thus, release its metadata now.
*/
kasan_release_object_meta(cache, object);
/* Let slab put the object onto the freelist. */
return false;
}
static inline bool check_page_allocation(void *ptr, unsigned long ip)

60
mm/kasan/generic.c
View File

@ -480,10 +480,10 @@ struct kasan_free_meta *kasan_get_free_meta(struct kmem_cache *cache,
void kasan_init_object_meta(struct kmem_cache *cache, const void *object)
{
struct kasan_alloc_meta *alloc_meta;
struct kasan_free_meta *free_meta;
alloc_meta = kasan_get_alloc_meta(cache, object);
if (alloc_meta) {
/* Zero out alloc meta to mark it as invalid. */
__memset(alloc_meta, 0, sizeof(*alloc_meta));
/*
@ -495,9 +495,50 @@ void kasan_init_object_meta(struct kmem_cache *cache, const void *object)
raw_spin_lock_init(&alloc_meta->aux_lock);
kasan_enable_current();
}
/*
* Explicitly marking free meta as invalid is not required: the shadow
* value for the first 8 bytes of a newly allocated object is not
* KASAN_SLAB_FREE_META.
*/
}
static void release_alloc_meta(struct kasan_alloc_meta *meta)
{
/* Evict the stack traces from stack depot. */
stack_depot_put(meta->alloc_track.stack);
stack_depot_put(meta->aux_stack[0]);
stack_depot_put(meta->aux_stack[1]);
/* Zero out alloc meta to mark it as invalid. */
__memset(meta, 0, sizeof(*meta));
}
static void release_free_meta(const void *object, struct kasan_free_meta *meta)
{
/* Check if free meta is valid. */
if (*(u8 *)kasan_mem_to_shadow(object) != KASAN_SLAB_FREE_META)
return;
/* Evict the stack trace from the stack depot. */
stack_depot_put(meta->free_track.stack);
/* Mark free meta as invalid. */
*(u8 *)kasan_mem_to_shadow(object) = KASAN_SLAB_FREE;
}
void kasan_release_object_meta(struct kmem_cache *cache, const void *object)
{
struct kasan_alloc_meta *alloc_meta;
struct kasan_free_meta *free_meta;
alloc_meta = kasan_get_alloc_meta(cache, object);
if (alloc_meta)
release_alloc_meta(alloc_meta);
free_meta = kasan_get_free_meta(cache, object);
if (free_meta)
__memset(free_meta, 0, sizeof(*free_meta));
release_free_meta(object, free_meta);
}
size_t kasan_metadata_size(struct kmem_cache *cache, bool in_object)
@ -573,11 +614,8 @@ void kasan_save_alloc_info(struct kmem_cache *cache, void *object, gfp_t flags)
if (!alloc_meta)
return;
/* Evict previous stack traces (might exist for krealloc). */
stack_depot_put(alloc_meta->alloc_track.stack);
stack_depot_put(alloc_meta->aux_stack[0]);
stack_depot_put(alloc_meta->aux_stack[1]);
__memset(alloc_meta, 0, sizeof(*alloc_meta));
/* Evict previous stack traces (might exist for krealloc or mempool). */
release_alloc_meta(alloc_meta);
kasan_save_track(&alloc_meta->alloc_track, flags);
}
@ -590,7 +628,11 @@ void kasan_save_free_info(struct kmem_cache *cache, void *object)
if (!free_meta)
return;
/* Evict previous stack trace (might exist for mempool). */
release_free_meta(object, free_meta);
kasan_save_track(&free_meta->free_track, 0);
/* The object was freed and has free track set. */
*(u8 *)kasan_mem_to_shadow(object) = KASAN_SLAB_FREETRACK;
/* Mark free meta as valid. */
*(u8 *)kasan_mem_to_shadow(object) = KASAN_SLAB_FREE_META;
}

25
mm/kasan/kasan.h
View File

@ -156,7 +156,7 @@ static inline bool kasan_requires_meta(void)
#ifdef CONFIG_KASAN_GENERIC
#define KASAN_SLAB_FREETRACK 0xFA /* freed slab object with free track */
#define KASAN_SLAB_FREE_META 0xFA /* freed slab object with free meta */
#define KASAN_GLOBAL_REDZONE 0xF9 /* redzone for global variable */
/* Stack redzone shadow values. Compiler ABI, do not change. */
@ -253,6 +253,15 @@ struct kasan_global {
#ifdef CONFIG_KASAN_GENERIC
/*
* Alloc meta contains the allocation-related information about a slab object.
* Alloc meta is saved when an object is allocated and is kept until either the
* object returns to the slab freelist (leaves quarantine for quarantined
* objects or gets freed for the non-quarantined ones) or reallocated via
* krealloc or through a mempool.
* Alloc meta is stored inside of the object's redzone.
* Alloc meta is considered valid whenever it contains non-zero data.
*/
struct kasan_alloc_meta {
struct kasan_track alloc_track;
/* Free track is stored in kasan_free_meta. */
@ -278,8 +287,12 @@ struct qlist_node {
#define KASAN_NO_FREE_META INT_MAX
/*
* Free meta is only used by Generic mode while the object is in quarantine.
* After that, slab allocator stores the freelist pointer in the object.
* Free meta contains the freeing-related information about a slab object.
* Free meta is only kept for quarantined objects and for mempool objects until
* the object gets allocated again.
* Free meta is stored within the object's memory.
* Free meta is considered valid whenever the value of the shadow byte that
* corresponds to the first 8 bytes of the object is KASAN_SLAB_FREE_META.
*/
struct kasan_free_meta {
struct qlist_node quarantine_link;
@ -380,15 +393,15 @@ void kasan_report_invalid_free(void *object, unsigned long ip, enum kasan_report
struct slab *kasan_addr_to_slab(const void *addr);
#ifdef CONFIG_KASAN_GENERIC
void kasan_init_cache_meta(struct kmem_cache *cache, unsigned int *size);
void kasan_init_object_meta(struct kmem_cache *cache, const void *object);
struct kasan_alloc_meta *kasan_get_alloc_meta(struct kmem_cache *cache,
const void *object);
struct kasan_free_meta *kasan_get_free_meta(struct kmem_cache *cache,
const void *object);
void kasan_init_object_meta(struct kmem_cache *cache, const void *object);
void kasan_release_object_meta(struct kmem_cache *cache, const void *object);
#else
static inline void kasan_init_cache_meta(struct kmem_cache *cache, unsigned int *size) { }
static inline void kasan_init_object_meta(struct kmem_cache *cache, const void *object) { }
static inline void kasan_release_object_meta(struct kmem_cache *cache, const void *object) { }
#endif
depot_stack_handle_t kasan_save_stack(gfp_t flags, depot_flags_t depot_flags);

20
mm/kasan/quarantine.c
View File

@ -143,22 +143,10 @@ static void *qlink_to_object(struct qlist_node *qlink, struct kmem_cache *cache)
static void qlink_free(struct qlist_node *qlink, struct kmem_cache *cache)
{
void *object = qlink_to_object(qlink, cache);
struct kasan_alloc_meta *alloc_meta = kasan_get_alloc_meta(cache, object);
struct kasan_free_meta *free_meta = kasan_get_free_meta(cache, object);
unsigned long flags;
if (alloc_meta) {
stack_depot_put(alloc_meta->alloc_track.stack);
stack_depot_put(alloc_meta->aux_stack[0]);
stack_depot_put(alloc_meta->aux_stack[1]);
__memset(alloc_meta, 0, sizeof(*alloc_meta));
}
if (free_meta &&
*(u8 *)kasan_mem_to_shadow(object) == KASAN_SLAB_FREETRACK) {
stack_depot_put(free_meta->free_track.stack);
__memset(&free_meta->free_track, 0, sizeof(free_meta->free_track));
}
kasan_release_object_meta(cache, object);
/*
* If init_on_free is enabled and KASAN's free metadata is stored in
@ -170,12 +158,6 @@ static void qlink_free(struct qlist_node *qlink, struct kmem_cache *cache)
cache->kasan_info.free_meta_offset == 0)
memzero_explicit(free_meta, sizeof(*free_meta));
/*
* As the object now gets freed from the quarantine,
* take note that its free track is no longer exists.
*/
*(u8 *)kasan_mem_to_shadow(object) = KASAN_SLAB_FREE;
if (IS_ENABLED(CONFIG_SLAB))
local_irq_save(flags);

6
mm/kasan/report_generic.c
View File

@ -110,7 +110,7 @@ static const char *get_shadow_bug_type(struct kasan_report_info *info)
bug_type = "use-after-free";
break;
case KASAN_SLAB_FREE:
case KASAN_SLAB_FREETRACK:
case KASAN_SLAB_FREE_META:
bug_type = "slab-use-after-free";
break;
case KASAN_ALLOCA_LEFT:
@ -173,8 +173,8 @@ void kasan_complete_mode_report_info(struct kasan_report_info *info)
memcpy(&info->alloc_track, &alloc_meta->alloc_track,
sizeof(info->alloc_track));
if (*(u8 *)kasan_mem_to_shadow(info->object) == KASAN_SLAB_FREETRACK) {
/* Free meta must be present with KASAN_SLAB_FREETRACK. */
if (*(u8 *)kasan_mem_to_shadow(info->object) == KASAN_SLAB_FREE_META) {
/* Free meta must be present with KASAN_SLAB_FREE_META. */
free_meta = kasan_get_free_meta(info->cache, info->object);
memcpy(&info->free_track, &free_meta->free_track,
sizeof(info->free_track));