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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Edward Cree <ecree.xilinx@gmail.com>
Cc: Yury Vostrikov <mon@unformed.ru>, bpf@vger.kernel.org,
	Martin Habets <habetsm.xilinx@gmail.com>,
	Thomas Gleixner <tglx@linutronix.de>
Subject: Re: NULL pointer deref inside xdp_do_flush due to
 bpf_net_ctx_get_all_used_flush_lists
Message-ID: <20241001140438.mq8L_5Zh@linutronix.de>
References: <5627f6d1-5491-4462-9d75-bc0612c26a22@app.fastmail.com>
 <20241001133603.G8j39V2l@linutronix.de>
 <09947f9d-0694-fad6-661a-0b24db9aa47a@gmail.com>
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In-Reply-To: <09947f9d-0694-fad6-661a-0b24db9aa47a@gmail.com>

On 2024-10-01 15:01:25 [+0100], Edward Cree wrote:
> On 01/10/2024 14:36, Sebastian Andrzej Siewior wrote:
> > diff --git a/drivers/net/ethernet/sfc/efx_channels.c b/drivers/net/ethernet/sfc/efx_channels.c
> > index c9e17a8208a90..f3288e02c1bd8 100644
> > --- a/drivers/net/ethernet/sfc/efx_channels.c
> > +++ b/drivers/net/ethernet/sfc/efx_channels.c
> > @@ -1260,7 +1260,8 @@ static int efx_poll(struct napi_struct *napi, int budget)
> >  
> >  	spent = efx_process_channel(channel, budget);
> >  
> > -	xdp_do_flush();
> > +	if (spent)
> > +		xdp_do_flush();
> >  
> >  	if (spent < budget) {
> >  		if (efx_channel_has_rx_queue(channel) &&
> 
> Seems reasonable to me.
> Another alternative is to look at budget rather than spent,
>  as that seems like the condition that drives whether we
>  have a real XDP.

If you prefer. What are chances that you had budget but cleaned nothing?

> -ed

Sebastian