Re: [PATCH RFC v2 2/6] mm/slab: Perform init_on_free earlier

[Alexander Popov <alex.popov@linux.com>]

On 30.09.2020 15:50, Alexander Potapenko wrote:
> 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>

Hello!

Can this particular patch be considered for the mainline kernel?


Note: I summarized the results of the experiment with the Linux kernel heap
quarantine in a short article, for future reference:
https://a13xp0p0v.github.io/2020/11/30/slab-quarantine.html

Best regards,
Alexander

>> ---
>>  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
>>
> 
>