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Message-ID: <e1e25755-432d-fd8d-c3f6-7752f68e037e@huawei.com>
Date:   Thu, 12 Oct 2023 19:31:18 +0800
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Subject: Re: [PATCH RFC] ubi: gluebi: Fix NULL pointer dereference caused by
 ftl notifier
To:     <richard@nod.at>, <miquel.raynal@bootlin.com>, <vigneshr@ti.com>
CC:     <linux-mtd@lists.infradead.org>, <linux-kernel@vger.kernel.org>,
        <chengzhihao1@huawei.com>, <yi.zhang@huawei.com>,
        <yangerkun@huawei.com>
References: <20231010142925.545238-1-wangzhaolong1@huawei.com>
From:   ZhaoLong Wang <wangzhaolong1@huawei.com>
In-Reply-To: <20231010142925.545238-1-wangzhaolong1@huawei.com>
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Friendly ping ...

> If both flt.ko and gluebi.ko are loaded, the notiier of ftl
> triggers NULL pointer dereference when trying to visit
> ‘gluebi->desc’ in gluebi_read().
> 
> ubi_gluebi_init
>    ubi_register_volume_notifier
>      ubi_enumerate_volumes
>        ubi_notify_all
>          gluebi_notify    nb->notifier_call()
>            gluebi_create
>              mtd_device_register
>                mtd_device_parse_register
>                  add_mtd_device
>                    blktrans_notify_add   not->add()
>                      ftl_add_mtd         tr->add_mtd()
>                        scan_header
>                          mtd_read
>                            mtd_read
>                              mtd_read_oob
>                                gluebi_read   mtd->read()
>                                  gluebi->desc - NULL
> 
> Detailed reproduction information available at the link[1],
> 
> In the normal case, obtain gluebi->desc in the gluebi_get_device(),
> and accesses gluebi->desc in the gluebi_read(). However,
> gluebi_get_device() is not executed in advance in the
> ftl_add_mtd() process, which leads to null pointer dereference.