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From:   Muchun Song <songmuchun@bytedance.com>
Date:   Mon, 28 Mar 2022 23:54:12 +0800
Message-ID: <CAMZfGtVkp+xCM3kgLHRNRFUs_fus0f3Ry_jFv8QaSWLfnkXREg@mail.gmail.com>
Subject: Re: [PATCH v2] mm: kfence: fix objcgs vector allocation
To:     Marco Elver <elver@google.com>
Cc:     Alexander Potapenko <glider@google.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        kasan-dev <kasan-dev@googlegroups.com>,
        Linux Memory Management List <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Xiongchun duan <duanxiongchun@bytedance.com>
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On Mon, Mar 28, 2022 at 11:51 PM Muchun Song <songmuchun@bytedance.com> wrote:
>
> On Mon, Mar 28, 2022 at 11:43 PM Marco Elver <elver@google.com> wrote:
> >
> > On Mon, 28 Mar 2022 at 15:28, Muchun Song <songmuchun@bytedance.com> wrote:
> > >
> > > If the kfence object is allocated to be used for objects vector, then
> > > this slot of the pool eventually being occupied permanently since
> > > the vector is never freed.  The solutions could be 1) freeing vector
> > > when the kfence object is freed or 2) allocating all vectors statically.
> > > Since the memory consumption of object vectors is low, it is better to
> > > chose 2) to fix the issue and it is also can reduce overhead of vectors
> > > allocating in the future.
> > >
> > > Fixes: d3fb45f370d9 ("mm, kfence: insert KFENCE hooks for SLAB")
> > > Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> >
> > Reviewed-by: Marco Elver <elver@google.com>
>
> Thanks.
>
> >
> > Btw, how did you test this?
> >

I have tested it with syzkaller with the following configs.
And I didn't find any issues.

CONFIG_KFENCE=y
CONFIG_KFENCE_SAMPLE_INTERVAL=10
CONFIG_KFENCE_NUM_OBJECTS=2550
CONFIG_KFENCE_DEFERRABLE=n
CONFIG_KFENCE_STATIC_KEYS=y
CONFIG_KFENCE_STRESS_TEST_FAULTS=0