Re: [PATCH] tuntap: forbid changing mq flag for persistent device

[David Miller]

From: Jason Wang <jasowang@xxxxxxxxxx>
Date: Wed, 29 May 2013 12:32:11 +0800

> We currently allow changing the mq flag (IFF_MULTI_QUEUE) for a persistent
> device. This will result a mismatch between the number the queues in netdev and
> tuntap. This is because we only allocate a 1q netdevice when IFF_MULTI_QUEUE was
> not specified, so when we set the IFF_MULTI_QUEUE and try to attach more queues
> later, netif_set_real_num_tx_queues() may fail which result a single queue
> netdevice with multiple sockets attached.
> 
> Solve this by disallowing changing the mq flag for persistent device.
> 
> Bug was introduced by commit edfb6a148ce62e5e19354a1dcd9a34e00815c2a1
> (tuntap: reduce memory using of queues).
> 
> Reported-by: Sriram Narasimhan <sriram.narasimhan@xxxxxx>
> Cc: Michael S. Tsirkin <mst@xxxxxxxxxx>
> Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>

Applied, thanks Jason.
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