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From:   Jason Wang <jasowang@redhat.com>
Date:   Tue, 23 Nov 2021 12:12:49 +0800
Message-ID: <CACGkMEsDmqwWdw51NKftjhcGr6z9ynP8dcqDiaQY=soTXTSBDg@mail.gmail.com>
Subject: Re: [PATCH] vdpa_sim: avoid putting an uninitialized iova_domain
To:     Parav Pandit <parav@nvidia.com>
Cc:     "Longpeng(Mike)" <longpeng2@huawei.com>,
        "mst@redhat.com" <mst@redhat.com>,
        "sgarzare@redhat.com" <sgarzare@redhat.com>,
        Max Gurtovoy <mgurtovoy@nvidia.com>,
        "virtualization@lists.linux-foundation.org" 
        <virtualization@lists.linux-foundation.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "arei.gonglei@huawei.com" <arei.gonglei@huawei.com>
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On Tue, Nov 23, 2021 at 11:12 AM Parav Pandit <parav@nvidia.com> wrote:
>
>
>
> > From: Longpeng(Mike) <longpeng2@huawei.com>
> > Sent: Monday, November 22, 2021 5:52 PM
> >
> > From: Longpeng <longpeng2@huawei.com>
> >
> > The system will crash if we put an uninitialized iova_domain, this could
> > happen when an error occurs before initializing the iova_domain in
> > vdpasim_create().
> >
> > BUG: kernel NULL pointer dereference, address: 0000000000000000 ...
> > RIP: 0010:__cpuhp_state_remove_instance+0x96/0x1c0
> > ...
> > Call Trace:
> >  <TASK>
> >  put_iova_domain+0x29/0x220
> >  vdpasim_free+0xd1/0x120 [vdpa_sim]
> >  vdpa_release_dev+0x21/0x40 [vdpa]
> >  device_release+0x33/0x90
> >  kobject_release+0x63/0x160
> >  vdpasim_create+0x127/0x2a0 [vdpa_sim]
> >  vdpasim_net_dev_add+0x7d/0xfe [vdpa_sim_net]
> >  vdpa_nl_cmd_dev_add_set_doit+0xe1/0x1a0 [vdpa]
> >  genl_family_rcv_msg_doit+0x112/0x140
> >  genl_rcv_msg+0xdf/0x1d0
> >  ...
> >
> > So we must make sure the iova_domain is already initialized before put it.
> >
> > In addition, we may get the following warning in this case:
> > WARNING: ... drivers/iommu/iova.c:344 iova_cache_put+0x58/0x70
> >
> > So we must make sure the iova_cache_put() is invoked only if the
> > iova_cache_get() is already invoked. Let's fix it together.
> >
> > Signed-off-by: Longpeng <longpeng2@huawei.com>
>
> Can you please add the fixes tag here so that older kernels can take this fix?
>

I guess it's 4080fc106750 ("vdpa_sim: use iova module to allocate IOVA
addresses")

Thanks