netdev - Re: [net-next PATCH 2/2] ixgbe: deleting dfwd stations out of order can cause null ptr deref

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Date:	Fri, 8 Nov 2013 07:31:06 -0500
From:	Neil Horman <nhorman@...driver.com>
To:	John Fastabend <john.fastabend@...il.com>
Cc:	jeffrey.t.kirsher@...el.com, netdev@...r.kernel.org,
	davem@...emloft.net
Subject: Re: [net-next PATCH 2/2] ixgbe: deleting dfwd stations out of order
 can cause null ptr deref

On Fri, Nov 08, 2013 at 12:51:10AM -0800, John Fastabend wrote:
> The number of stations in use is kept in the num_rx_pools counter
> in the ixgbe_adapter structure. This is in turn used by the queue
> allocation scheme to determine how many queues are needed to support
> the number of pools in use with the current feature set.
> 
> This works as long as the pools are added and destroyed in order
> because (num_rx_pools * queues_per_pool) is equal to the last
> queue in use by a pool. But as soon as you delete a pool out of
> order this is no longer the case. So the above multiplication
> allocates to few queues and a pool may reference a ring that has
> not been allocated/initialized.
> 
> To resolve use the bit mask of in use pools to determine the final
> pool being used and allocate enough queues so that we don't
> inadvertently remove its queues.
> 
> # ip link add link eth2 \
> 	numtxqueues 4 numrxqueues 4 txqueuelen 50 type macvlan
> # ip link set dev macvlan0 up
> # ip link add link eth2 \
> 	numtxqueues 4 numrxqueues 4 txqueuelen 50 type macvlan
> # ip link set dev macvlan1 up
> # for i in {0..100}; do
>   ip link set dev macvlan0 down; ip link set dev macvlan0 up;
>   done;
> 
> Signed-off-by: John Fastabend <john.r.fastabend@...el.com>
Acked-by: Neil Horman <nhorman@...driver.com>
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