Re: [PATCH] mm/slab: Perform init_on_free earlier

[Joonsoo Kim]

2020년 12월 11일 (금) 오전 3:37, Alexander Popov 님이 작성:
>
> Currently in CONFIG_SLAB init_on_free happens too late, and heap
> objects go to the heap quarantine not being erased.
>
> Lets move init_on_free clearing before calling kasan_slab_free().
> In that case heap quarantine will store erased objects, similarly
> to CONFIG_SLUB=y behavior.
>
> Signed-off-by: Alexander Popov 
> Reviewed-by: Alexander Potapenko 

Acked-by: Joonsoo Kim 

Re: [PATCH] mm/slab: Perform init_on_free earlier

[David Rientjes]

On Thu, 10 Dec 2020, Alexander Popov wrote:

> Currently in CONFIG_SLAB init_on_free happens too late, and heap
> objects go to the heap quarantine not being erased.
> 
> Lets move init_on_free clearing before calling kasan_slab_free().
> In that case heap quarantine will store erased objects, similarly
> to CONFIG_SLUB=y behavior.
> 
> Signed-off-by: Alexander Popov 
> Reviewed-by: Alexander Potapenko 

Acked-by: David Rientjes 

[PATCH] mm/slab: Perform init_on_free earlier

[Alexander Popov]

Currently in CONFIG_SLAB init_on_free happens too late, and heap
objects go to the heap quarantine not being erased.

Lets move init_on_free clearing before calling kasan_slab_free().
In that case heap quarantine will store erased objects, similarly
to CONFIG_SLUB=y behavior.

Signed-off-by: Alexander Popov 
Reviewed-by: Alexander Potapenko 
---
 mm/slab.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/mm/slab.c b/mm/slab.c
index b1113561b98b..344a101e37e0 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -3416,6 +3416,9 @@ static void cache_flusharray(struct kmem_cache *cachep, 
struct array_cache *ac)
 static __always_inline void __cache_free(struct kmem_cache *cachep, void *objp,
 unsigned long caller)
 {
+   if (unlikely(slab_want_init_on_free(cachep)))
+   memset(objp, 0, cachep->object_size);
+
/* Put the object into the quarantine, don't touch it for now. */
if (kasan_slab_free(cachep, objp, _RET_IP_))
return;
@@ -3434,8 +3437,6 @@ void ___cache_free(struct kmem_cache *cachep, void *objp,
struct array_cache *ac = cpu_cache_get(cachep);
 
check_irq_off();
-   if (unlikely(slab_want_init_on_free(cachep)))
-   memset(objp, 0, cachep->object_size);
kmemleak_free_recursive(objp, cachep->flags);
objp = cache_free_debugcheck(cachep, objp, caller);
memcg_slab_free_hook(cachep, &objp, 1);
-- 
2.26.2