netdev - Re: [PATCH net 1/2] ibmvnic: Add tx check to prevent skb leak

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Date: Tue, 25 Jun 2024 10:58:14 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: Nick Child <nnac123@...ux.ibm.com>, netdev@...r.kernel.org
Cc: nick.child@....com, haren@...ux.ibm.com, ricklind@...ibm.com
Subject: Re: [PATCH net 1/2] ibmvnic: Add tx check to prevent skb leak

On Thu, 2024-06-20 at 10:23 -0500, Nick Child wrote:
> Below is a summary of how the driver stores a reference to an skb during
> transmit:
>     tx_buff[free_map[consumer_index]]->skb = new_skb;
>     free_map[consumer_index] = IBMVNIC_INVALID_MAP;
>     consumer_index ++;
> Where variable data looks like this:
>     free_map == [4, IBMVNIC_INVALID_MAP, IBMVNIC_INVALID_MAP, 0, 3]
>                                                	consumer_index^
>     tx_buff == [skb=null, skb=<ptr>, skb=<ptr>, skb=null, skb=null]
> 
> The driver has checks to ensure that free_map[consumer_index] pointed to
> a valid index but there was no check to ensure that this index pointed
> to an unused/null skb address. So, if, by some chance, our free_map and
> tx_buff lists become out of sync then we were previously risking an
> skb memory leak. This could then cause tcp congestion control to stop
> sending packets, eventually leading to ETIMEDOUT.
> 
> Therefore, add a conditional to ensure that the skb address is null. If
> not then warn the user (because this is still a bug that should be
> patched) and free the old pointer to prevent memleak/tcp problems.
> 
> Signed-off-by: Nick Child <nnac123@...ux.ibm.com>
> ---
>  drivers/net/ethernet/ibm/ibmvnic.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/net/ethernet/ibm/ibmvnic.c b/drivers/net/ethernet/ibm/ibmvnic.c
> index 5e9a93bdb518..887d92a88403 100644

For some reasons, this one was not applied together with patch 2/2.

I'm applying it now.

Cheers,

Paolo