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SubjectRe: [PATCH RFC v2 2/6] mm/slab: Perform init_on_free earlier
On Tue, Sep 29, 2020 at 8:35 PM Alexander Popov <alex.popov@linux.com> wrote:
>
> Currently in CONFIG_SLAB init_on_free happens too late, and heap
> objects go to the heap quarantine being dirty. Lets move memory
> clearing before calling kasan_slab_free() to fix that.
>
> Signed-off-by: Alexander Popov <alex.popov@linux.com>
Reviewed-by: Alexander Potapenko <glider@google.com>

> ---
> mm/slab.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/mm/slab.c b/mm/slab.c
> index 3160dff6fd76..5140203c5b76 100644
> --- a/mm/slab.c
> +++ b/mm/slab.c
> @@ -3414,6 +3414,9 @@ 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;
> @@ -3432,8 +3435,6 @@ 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, virt_to_head_page(objp), objp);
> --
> 2.26.2
>


--
Alexander Potapenko
Software Engineer

Google Germany GmbH
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80636 München

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