path: root/include/linux/kasan.h
diff options
authorAndrey Ryabinin <>2015-03-12 16:26:11 -0700
committerLinus Torvalds <>2015-03-12 18:46:08 -0700
commita5af5aa8b67dfdba36c853b70564fd2dfe73d478 (patch)
treed898e560802ef68b21280539040ccd19dc62678b /include/linux/kasan.h
parentb3c1030d50bad39383fcfa6721bd3c35463b3f3f (diff)
kasan, module, vmalloc: rework shadow allocation for modules
Current approach in handling shadow memory for modules is broken. Shadow memory could be freed only after memory shadow corresponds it is no longer used. vfree() called from interrupt context could use memory its freeing to store 'struct llist_node' in it: void vfree(const void *addr) { ... if (unlikely(in_interrupt())) { struct vfree_deferred *p = this_cpu_ptr(&vfree_deferred); if (llist_add((struct llist_node *)addr, &p->list)) schedule_work(&p->wq); Later this list node used in free_work() which actually frees memory. Currently module_memfree() called in interrupt context will free shadow before freeing module's memory which could provoke kernel crash. So shadow memory should be freed after module's memory. However, such deallocation order could race with kasan_module_alloc() in module_alloc(). Free shadow right before releasing vm area. At this point vfree()'d memory is not used anymore and yet not available for other allocations. New VM_KASAN flag used to indicate that vm area has dynamically allocated shadow memory so kasan frees shadow only if it was previously allocated. Signed-off-by: Andrey Ryabinin <> Acked-by: Rusty Russell <> Cc: Dmitry Vyukov <> Signed-off-by: Andrew Morton <> Signed-off-by: Linus Torvalds <>
Diffstat (limited to 'include/linux/kasan.h')
1 files changed, 3 insertions, 2 deletions
diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index 72ba725ddf9c..5fa48a21d73e 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -5,6 +5,7 @@
struct kmem_cache;
struct page;
+struct vm_struct;
@@ -52,7 +53,7 @@ void kasan_slab_free(struct kmem_cache *s, void *object);
int kasan_module_alloc(void *addr, size_t size);
-void kasan_module_free(void *addr);
+void kasan_free_shadow(const struct vm_struct *vm);
#else /* CONFIG_KASAN */
@@ -82,7 +83,7 @@ static inline void kasan_slab_alloc(struct kmem_cache *s, void *object) {}
static inline void kasan_slab_free(struct kmem_cache *s, void *object) {}
static inline int kasan_module_alloc(void *addr, size_t size) { return 0; }
-static inline void kasan_module_free(void *addr) {}
+static inline void kasan_free_shadow(const struct vm_struct *vm) {}
#endif /* CONFIG_KASAN */