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References: <20220530053326.41682-1-songmuchun@bytedance.com> <0563a019-09e3-a176-d4c1-c240f3cf62d0@redhat.com>
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From:   Muchun Song <songmuchun@bytedance.com>
Date:   Mon, 30 May 2022 15:08:40 +0800
Message-ID: <CAMZfGtUMfNjOGJ3j4tgha6SxFymNGDo3CW5NO73ZsMby42BPjg@mail.gmail.com>
Subject: Re: [PATCH] mm: memory_hotplug: fix memory error handling
To:     David Hildenbrand <david@redhat.com>
Cc:     Greg KH <gregkh@linuxfoundation.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        cheloha@linux.vnet.ibm.com, Michal Hocko <mhocko@suse.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Nathan Lynch <nathanl@linux.ibm.com>,
        LKML <linux-kernel@vger.kernel.org>,
        linux- stable <stable@vger.kernel.org>
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On Mon, May 30, 2022 at 2:56 PM David Hildenbrand <david@redhat.com> wrote:
>
> On 30.05.22 07:33, Muchun Song wrote:
> > The device_unregister() is supposed to be used to unregister devices if
> > device_register() has succeed.  And device_unregister() will put device.
> > The caller should not do it again, otherwise, the first call of
> > put_device() will drop the last reference count, then the next call
> > of device_unregister() will UAF on device.
> >
> > Fixes: 4fb6eabf1037 ("drivers/base/memory.c: cache memory blocks in xarray to accelerate lookup")
> > Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> > Cc: <stable@vger.kernel.org>
> > ---
> >  drivers/base/memory.c | 5 ++---
> >  1 file changed, 2 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/base/memory.c b/drivers/base/memory.c
> > index 7222ff9b5e05..084d67fd55cc 100644
> > --- a/drivers/base/memory.c
> > +++ b/drivers/base/memory.c
> > @@ -636,10 +636,9 @@ static int __add_memory_block(struct memory_block *memory)
> >       }
> >       ret = xa_err(xa_store(&memory_blocks, memory->dev.id, memory,
> >                             GFP_KERNEL));
> > -     if (ret) {
> > -             put_device(&memory->dev);
> > +     if (ret)
> >               device_unregister(&memory->dev);
> > -     }
> > +
> >       return ret;
> >  }
> >
>
> See
>
> https://lkml.kernel.org/r/d44c63d78affe844f020dc02ad6af29abc448fc4.1650611702.git.christophe.jaillet@wanadoo.fr
>

I see. Good job by Christophe. Thanks David.