Re: [PATCH] vdpa_sim: avoid putting an uninitialized iova_domain

[Jason Wang]

On Mon, Nov 22, 2021 at 8:22 PM Longpeng(Mike) <longpeng2@xxxxxxxxxx> wrote:
>
> From: Longpeng <longpeng2@xxxxxxxxxx>
>
> 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@xxxxxxxxxx>

Acked-by: Jason Wang <jasowang@xxxxxxxxxx>

> ---
>  drivers/vdpa/vdpa_sim/vdpa_sim.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c
> index 5f484fff8dbe..41b0cd17fcba 100644
> --- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
> +++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c
> @@ -591,8 +591,11 @@ static void vdpasim_free(struct vdpa_device *vdpa)
>                 vringh_kiov_cleanup(&vdpasim->vqs[i].in_iov);
>         }
>
> -       put_iova_domain(&vdpasim->iova);
> -       iova_cache_put();
> +       if (vdpa_get_dma_dev(vdpa)) {
> +               put_iova_domain(&vdpasim->iova);
> +               iova_cache_put();
> +       }
> +
>         kvfree(vdpasim->buffer);
>         if (vdpasim->iommu)
>                 vhost_iotlb_free(vdpasim->iommu);
> --
> 2.27.0
>