Date:   Tue, 23 Nov 2021 09:19:29 +0100
From:   Stefano Garzarella <sgarzare@redhat.com>
To:     "Longpeng(Mike)" <longpeng2@huawei.com>
Cc:     mst@redhat.com, jasowang@redhat.com, mgurtovoy@nvidia.com,
        parav@nvidia.com, virtualization@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org, arei.gonglei@huawei.com
Subject: Re: [PATCH] vdpa_sim: avoid putting an uninitialized iova_domain
Message-ID: <20211123081929.6wa3jes3rnm5hh63@steredhat>
References: <20211122122221.56-1-longpeng2@huawei.com>
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On Mon, Nov 22, 2021 at 08:22:21PM +0800, Longpeng(Mike) wrote:
>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>
>---
> drivers/vdpa/vdpa_sim/vdpa_sim.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)

Ooops, thanks for fixing this :-)

With the Fixes tag as suggested:

Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>