linux-kernel - Re: [PATCH 1/4] 9p: Fix probe failed when modprobe 9pnet

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Message-ID: <12013317.ToeGUHxLYt@silver>
Date:   Mon, 28 Nov 2022 15:27:16 +0100
From:   Christian Schoenebeck <linux_oss@...debyte.com>
To:     mst@...hat.com, jasowang@...hat.com, pbonzini@...hat.com,
        stefanha@...hat.com, axboe@...nel.dk, kraxel@...hat.com,
        david@...hat.com, ericvh@...il.com, lucho@...kov.net,
        asmadeus@...ewreck.org, davem@...emloft.net, edumazet@...gle.com,
        kuba@...nel.org, pabeni@...hat.com, rusty@...tcorp.com.au,
        Li Zetao <lizetao1@...wei.com>
Cc:     lizetao1@...wei.com, virtualization@...ts.linux-foundation.org,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        v9fs-developer@...ts.sourceforge.net, netdev@...r.kernel.org
Subject: Re: [PATCH 1/4] 9p: Fix probe failed when modprobe 9pnet_virtio

On Monday, November 28, 2022 3:10:02 AM CET Li Zetao wrote:
> When doing the following test steps, an error was found:
>   step 1: modprobe 9pnet_virtio succeeded
>     # modprobe 9pnet_virtio      <-- OK
> 
>   step 2: fault injection in sysfs_create_file()
>     # modprobe -r 9pnet_virtio   <-- OK
>     # ...
>       FAULT_INJECTION: forcing a failure.
>       name failslab, interval 1, probability 0, space 0, times 0
>       CPU: 0 PID: 3790 Comm: modprobe Tainted: G        W
>       6.1.0-rc6-00285-g6a1e40c4b995-dirty #108
>       Hardware name: QEMU Standard PC (i440FX + PIIX, 1996)
>       Call Trace:
>        <TASK>
>        ...
>        should_failslab+0xa/0x20
>        ...
>        sysfs_create_file_ns+0x130/0x1d0
>        p9_virtio_probe+0x662/0xb30 [9pnet_virtio]
>        virtio_dev_probe+0x608/0xae0
>        ...
>        </TASK>
>       9pnet_virtio: probe of virtio3 failed with error -12
> 
>   step 3: modprobe virtio_net failed
>     # modprobe 9pnet_virtio       <-- failed
>       9pnet_virtio: probe of virtio3 failed with error -2
> 
> The root cause of the problem is that the virtqueues are not
> stopped on the error handling path when sysfs_create_file()
> fails in p9_virtio_probe(), resulting in an error "-ENOENT"
> returned in the next modprobe call in setup_vq().
> 
> virtio_pci_modern_device uses virtqueues to send or
> receive message, and "queue_enable" records whether the
> queues are available. In vp_modern_find_vqs(), all queues
> will be selected and activated, but once queues are enabled
> there is no way to go back except reset.
> 
> Fix it by reset virtio device on error handling path. After
> virtio_find_single_vq() succeeded, all virtqueues should be
> stopped on error handling path.
> 
> Fixes: 1fcf0512c9c8 ("virtio_pci: modern driver")
> Signed-off-by: Li Zetao <lizetao1@...wei.com>
> ---

As others said, comment should probably be adjusted, apart from that:

Reviewed-by: Christian Schoenebeck <linux_oss@...debyte.com>

>  net/9p/trans_virtio.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c
> index e757f0601304..39933187284b 100644
> --- a/net/9p/trans_virtio.c
> +++ b/net/9p/trans_virtio.c
> @@ -668,6 +668,7 @@ static int p9_virtio_probe(struct virtio_device *vdev)
>  out_free_tag:
>  	kfree(tag);
>  out_free_vq:
> +	virtio_reset_device(vdev);
>  	vdev->config->del_vqs(vdev);
>  out_free_chan:
>  	kfree(chan);
>