Re: [patch 022/200] mm/slab: rerform init_on_free earlier

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On Tue, Dec 15, 2020 at 4:04 AM Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> From: Alexander Popov <alex.popov@xxxxxxxxx>
> Subject: mm/slab: rerform init_on_free earlier

Nit: s/rerform/perform

>
> 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.
>
> Link: https://lkml.kernel.org/r/20201210183729.1261524-1-alex.popov@xxxxxxxxx
> Signed-off-by: Alexander Popov <alex.popov@xxxxxxxxx>
> Reviewed-by: Alexander Potapenko <glider@xxxxxxxxxx>
> Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
> Acked-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
> Cc: Christoph Lameter <cl@xxxxxxxxx>
> Cc: Pekka Enberg <penberg@xxxxxxxxxx>
> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> ---
>
>  mm/slab.c |    5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> --- a/mm/slab.c~mm-slab-perform-init_on_free-earlier
> +++ a/mm/slab.c
> @@ -3417,6 +3417,9 @@ free_done:
>  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;
> @@ -3435,8 +3438,6 @@ void ___cache_free(struct kmem_cache *ca
>         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);
> _



-- 
Alexander Potapenko
Software Engineer

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