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

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Date:   Tue, 8 Nov 2022 10:33:58 +0100
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     Yuan Can <yuancan@...wei.com>
Cc:     stefanha@...hat.com, mst@...hat.com, jasowang@...hat.com,
        davem@...emloft.net, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org
Subject: Re: [PATCH] vhost/vsock: Fix error handling in vhost_vsock_init()

On Tue, Nov 08, 2022 at 09:13:57AM +0000, Yuan Can 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.

Thanks for this fix!

>
>Fixes: c0cfa2d8a788 ("vsock: add multi-transports support")

Is this the right tag?

It seems to me that since the introduction of vhost-vsock we have the 
same problem (to be solved differently, because with the introduction of 
multi-transport we refactored the initialization functions).

So should we use 433fc58e6bf2 ("VSOCK: Introduce vhost_vsock.ko")?

Thanks,
Stefano

>Signed-off-by: Yuan Can <yuancan@...wei.com>
>---
> 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
>