netdev - Re: [PATCH v2] vhost/vsock: Fix error handling in vhost_vsock

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Date:   Wed, 9 Nov 2022 11:32:45 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Yuan Can <yuancan@...wei.com>
Cc:     stefanha@...hat.com, sgarzare@...hat.com, mst@...hat.com,
        davem@...emloft.net, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org
Subject: Re: [PATCH v2] vhost/vsock: Fix error handling in vhost_vsock_init()

On Tue, Nov 8, 2022 at 6:19 PM Yuan Can <yuancan@...wei.com> wrote:
>
> A problem about modprobe vhost_vsock failed is triggered with the
> following log given:
>
> modprobe: ERROR: could not insert 'vhost_vsock': Device or resource busy
>
> The reason is that vhost_vsock_init() returns misc_register() directly
> without checking its return value, if misc_register() failed, it returns
> without calling vsock_core_unregister() on vhost_transport, resulting the
> vhost_vsock can never be installed later.
> A simple call graph is shown as below:
>
>  vhost_vsock_init()
>    vsock_core_register() # register vhost_transport
>    misc_register()
>      device_create_with_groups()
>        device_create_groups_vargs()
>          dev = kzalloc(...) # OOM happened
>    # return without unregister vhost_transport
>
> Fix by calling vsock_core_unregister() when misc_register() returns error.
>
> Fixes: 433fc58e6bf2 ("VSOCK: Introduce vhost_vsock.ko")
> Signed-off-by: Yuan Can <yuancan@...wei.com>

Acked-by: Jason Wang <jasowang@...hat.com>

> ---
> Changes in v2:
> - change to the correct Fixes: tag
>
>  drivers/vhost/vsock.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
> index 5703775af129..10a7d23731fe 100644
> --- a/drivers/vhost/vsock.c
> +++ b/drivers/vhost/vsock.c
> @@ -959,7 +959,14 @@ static int __init vhost_vsock_init(void)
>                                   VSOCK_TRANSPORT_F_H2G);
>         if (ret < 0)
>                 return ret;
> -       return misc_register(&vhost_vsock_misc);
> +
> +       ret = misc_register(&vhost_vsock_misc);
> +       if (ret) {
> +               vsock_core_unregister(&vhost_transport.transport);
> +               return ret;
> +       }
> +
> +       return 0;
>  };
>
>  static void __exit vhost_vsock_exit(void)
> --
> 2.17.1
>