diff options
| -rw-r--r-- | include/linux/kasan.h | 7 | ||||
| -rw-r--r-- | mm/slab_common.c | 22 |
2 files changed, 26 insertions, 3 deletions
diff --git a/include/linux/kasan.h b/include/linux/kasan.h index b40ea104dd36..cc8a03cc9674 100644 --- a/include/linux/kasan.h +++ b/include/linux/kasan.h @@ -76,8 +76,11 @@ void kasan_free_shadow(const struct vm_struct *vm); int kasan_add_zero_shadow(void *start, unsigned long size); void kasan_remove_zero_shadow(void *start, unsigned long size); -size_t ksize(const void *); -static inline void kasan_unpoison_slab(const void *ptr) { ksize(ptr); } +size_t __ksize(const void *); +static inline void kasan_unpoison_slab(const void *ptr) +{ + kasan_unpoison_shadow(ptr, __ksize(ptr)); +} size_t kasan_metadata_size(struct kmem_cache *cache); bool kasan_save_enable_multi_shot(void); diff --git a/mm/slab_common.c b/mm/slab_common.c index b7c6a40e436a..a09bb10aa026 100644 --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -1613,7 +1613,27 @@ EXPORT_SYMBOL(kzfree); */ size_t ksize(const void *objp) { - size_t size = __ksize(objp); + size_t size; + + if (WARN_ON_ONCE(!objp)) + return 0; + /* + * We need to check that the pointed to object is valid, and only then + * unpoison the shadow memory below. We use __kasan_check_read(), to + * generate a more useful report at the time ksize() is called (rather + * than later where behaviour is undefined due to potential + * use-after-free or double-free). + * + * If the pointed to memory is invalid we return 0, to avoid users of + * ksize() writing to and potentially corrupting the memory region. + * + * We want to perform the check before __ksize(), to avoid potentially + * crashing in __ksize() due to accessing invalid metadata. + */ + if (unlikely(objp == ZERO_SIZE_PTR) || !__kasan_check_read(objp, 1)) + return 0; + + size = __ksize(objp); /* * We assume that ksize callers could use whole allocated area, * so we need to unpoison this area. |