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-rw-r--r--mm/kasan/generic.c130
1 files changed, 99 insertions, 31 deletions
diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c
index 4d837ab83f..1900f85760 100644
--- a/mm/kasan/generic.c
+++ b/mm/kasan/generic.c
@@ -25,6 +25,8 @@
#include <linux/sched.h>
#include <linux/sched/task_stack.h>
#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/stackdepot.h>
#include <linux/stacktrace.h>
#include <linux/string.h>
#include <linux/types.h>
@@ -361,6 +363,8 @@ void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
{
unsigned int ok_size;
unsigned int optimal_size;
+ unsigned int rem_free_meta_size;
+ unsigned int orig_alloc_meta_offset;
if (!kasan_requires_meta())
return;
@@ -378,49 +382,77 @@ void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
ok_size = *size;
- /* Add alloc meta into redzone. */
+ /* Add alloc meta into the redzone. */
cache->kasan_info.alloc_meta_offset = *size;
*size += sizeof(struct kasan_alloc_meta);
- /*
- * If alloc meta doesn't fit, don't add it.
- * This can only happen with SLAB, as it has KMALLOC_MAX_SIZE equal
- * to KMALLOC_MAX_CACHE_SIZE and doesn't fall back to page_alloc for
- * larger sizes.
- */
+ /* If alloc meta doesn't fit, don't add it. */
if (*size > KMALLOC_MAX_SIZE) {
cache->kasan_info.alloc_meta_offset = 0;
*size = ok_size;
/* Continue, since free meta might still fit. */
}
+ ok_size = *size;
+ orig_alloc_meta_offset = cache->kasan_info.alloc_meta_offset;
+
/*
- * Add free meta into redzone when it's not possible to store
+ * Store free meta in the redzone when it's not possible to store
* it in the object. This is the case when:
* 1. Object is SLAB_TYPESAFE_BY_RCU, which means that it can
* be touched after it was freed, or
* 2. Object has a constructor, which means it's expected to
- * retain its content until the next allocation, or
- * 3. Object is too small.
- * Otherwise cache->kasan_info.free_meta_offset = 0 is implied.
+ * retain its content until the next allocation.
*/
- if ((cache->flags & SLAB_TYPESAFE_BY_RCU) || cache->ctor ||
- cache->object_size < sizeof(struct kasan_free_meta)) {
- ok_size = *size;
-
+ if ((cache->flags & SLAB_TYPESAFE_BY_RCU) || cache->ctor) {
cache->kasan_info.free_meta_offset = *size;
*size += sizeof(struct kasan_free_meta);
+ goto free_meta_added;
+ }
- /* If free meta doesn't fit, don't add it. */
- if (*size > KMALLOC_MAX_SIZE) {
- cache->kasan_info.free_meta_offset = KASAN_NO_FREE_META;
- *size = ok_size;
- }
+ /*
+ * Otherwise, if the object is large enough to contain free meta,
+ * store it within the object.
+ */
+ if (sizeof(struct kasan_free_meta) <= cache->object_size) {
+ /* cache->kasan_info.free_meta_offset = 0 is implied. */
+ goto free_meta_added;
+ }
+
+ /*
+ * For smaller objects, store the beginning of free meta within the
+ * object and the end in the redzone. And thus shift the location of
+ * alloc meta to free up space for free meta.
+ * This is only possible when slub_debug is disabled, as otherwise
+ * the end of free meta will overlap with slub_debug metadata.
+ */
+ if (!__slub_debug_enabled()) {
+ rem_free_meta_size = sizeof(struct kasan_free_meta) -
+ cache->object_size;
+ *size += rem_free_meta_size;
+ if (cache->kasan_info.alloc_meta_offset != 0)
+ cache->kasan_info.alloc_meta_offset += rem_free_meta_size;
+ goto free_meta_added;
+ }
+
+ /*
+ * If the object is small and slub_debug is enabled, store free meta
+ * in the redzone after alloc meta.
+ */
+ cache->kasan_info.free_meta_offset = *size;
+ *size += sizeof(struct kasan_free_meta);
+
+free_meta_added:
+ /* If free meta doesn't fit, don't add it. */
+ if (*size > KMALLOC_MAX_SIZE) {
+ cache->kasan_info.free_meta_offset = KASAN_NO_FREE_META;
+ cache->kasan_info.alloc_meta_offset = orig_alloc_meta_offset;
+ *size = ok_size;
}
/* Calculate size with optimal redzone. */
optimal_size = cache->object_size + optimal_redzone(cache->object_size);
- /* Limit it with KMALLOC_MAX_SIZE (relevant for SLAB only). */
+ /* Limit it with KMALLOC_MAX_SIZE. */
if (optimal_size > KMALLOC_MAX_SIZE)
optimal_size = KMALLOC_MAX_SIZE;
/* Use optimal size if the size with added metas is not large enough. */
@@ -450,8 +482,35 @@ void kasan_init_object_meta(struct kmem_cache *cache, const void *object)
struct kasan_alloc_meta *alloc_meta;
alloc_meta = kasan_get_alloc_meta(cache, object);
- if (alloc_meta)
+ if (alloc_meta) {
+ /* Zero out alloc meta to mark it as invalid. */
__memset(alloc_meta, 0, sizeof(*alloc_meta));
+ }
+
+ /*
+ * 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)
+{
+ /* 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)
+{
+ if (!kasan_arch_is_ready())
+ return;
+
+ /* Check if free meta is valid. */
+ if (*(u8 *)kasan_mem_to_shadow(object) != KASAN_SLAB_FREE_META)
+ return;
+
+ /* Mark free meta as invalid. */
+ *(u8 *)kasan_mem_to_shadow(object) = KASAN_SLAB_FREE;
}
size_t kasan_metadata_size(struct kmem_cache *cache, bool in_object)
@@ -472,7 +531,7 @@ size_t kasan_metadata_size(struct kmem_cache *cache, bool in_object)
sizeof(struct kasan_free_meta) : 0);
}
-static void __kasan_record_aux_stack(void *addr, bool can_alloc)
+static void __kasan_record_aux_stack(void *addr, depot_flags_t depot_flags)
{
struct slab *slab = kasan_addr_to_slab(addr);
struct kmem_cache *cache;
@@ -489,17 +548,17 @@ static void __kasan_record_aux_stack(void *addr, bool can_alloc)
return;
alloc_meta->aux_stack[1] = alloc_meta->aux_stack[0];
- alloc_meta->aux_stack[0] = kasan_save_stack(0, can_alloc);
+ alloc_meta->aux_stack[0] = kasan_save_stack(0, depot_flags);
}
void kasan_record_aux_stack(void *addr)
{
- return __kasan_record_aux_stack(addr, true);
+ return __kasan_record_aux_stack(addr, STACK_DEPOT_FLAG_CAN_ALLOC);
}
void kasan_record_aux_stack_noalloc(void *addr)
{
- return __kasan_record_aux_stack(addr, false);
+ return __kasan_record_aux_stack(addr, 0);
}
void kasan_save_alloc_info(struct kmem_cache *cache, void *object, gfp_t flags)
@@ -507,8 +566,13 @@ void kasan_save_alloc_info(struct kmem_cache *cache, void *object, gfp_t flags)
struct kasan_alloc_meta *alloc_meta;
alloc_meta = kasan_get_alloc_meta(cache, object);
- if (alloc_meta)
- kasan_set_track(&alloc_meta->alloc_track, flags);
+ if (!alloc_meta)
+ return;
+
+ /* Invalidate previous stack traces (might exist for krealloc or mempool). */
+ release_alloc_meta(alloc_meta);
+
+ kasan_save_track(&alloc_meta->alloc_track, flags);
}
void kasan_save_free_info(struct kmem_cache *cache, void *object)
@@ -519,7 +583,11 @@ void kasan_save_free_info(struct kmem_cache *cache, void *object)
if (!free_meta)
return;
- kasan_set_track(&free_meta->free_track, 0);
- /* The object was freed and has free track set. */
- *(u8 *)kasan_mem_to_shadow(object) = KASAN_SLAB_FREETRACK;
+ /* Invalidate previous stack trace (might exist for mempool). */
+ release_free_meta(object, free_meta);
+
+ kasan_save_track(&free_meta->free_track, 0);
+
+ /* Mark free meta as valid. */
+ *(u8 *)kasan_mem_to_shadow(object) = KASAN_SLAB_FREE_META;
}