# Re: \[PATCH\] vdpa\_sim: avoid putting an uninitialized iova\_domain

- From: Stefano Garzarella \<sgarzare@redhat.com\>
- Date: 2021-11-23 08:19:38 
- List: virtualization
- Page: https://ratatoskr.run/virtualization/2021/11/1582427
- Thread: https://ratatoskr.run/lkml/2021/11/1581589/t.md

```text
On Mon, Nov 22, 2021 at 08:22:21PM +0800, Longpeng(Mike) wrote:
>From: Longpeng <redacted>
>
>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 <redacted>
>---
> 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>

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```