linux-kernel - Re: [PATCH] igb: Fix NULL pointer dereference in ethtool loopback test

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Message-ID: <aJqBN0xtMzt_cA87@MacBook-Air.local>
Date: Mon, 11 Aug 2025 16:48:07 -0700
From: Joe Damato <joe@...a.to>
To: Tianyu Xu <xtydtc@...il.com>
Cc: anthony.l.nguyen@...el.com, przemyslaw.kitszel@...el.com,
	andrew+netdev@...n.ch, kuba@...nel.org, sdf@...ichev.me,
	intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, tianyxu@...co.com
Subject: Re: [PATCH] igb: Fix NULL pointer dereference in ethtool loopback
 test

On Mon, Aug 11, 2025 at 07:41:53PM +0800, Tianyu Xu wrote:
> The igb driver currently causes a NULL pointer dereference
> when executing the ethtool loopback test. This occurs because
> there is no associated q_vector for the test ring when it is
> set up, as interrupts are typically not added to the test rings.
> 
> Since commit 5ef44b3cb43b removed the napi_id assignment in
> __xdp_rxq_info_reg(), there is no longer a need to pass a napi_id.
> Therefore, simply use 0 as the final parameter.
> 
> Signed-off-by: Tianyu Xu <tianyxu@...co.com>
> ---
>  drivers/net/ethernet/intel/igb/igb_main.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
> index a9a7a94ae..453deb6d1 100644
> --- a/drivers/net/ethernet/intel/igb/igb_main.c
> +++ b/drivers/net/ethernet/intel/igb/igb_main.c
> @@ -4453,8 +4453,7 @@ int igb_setup_rx_resources(struct igb_ring *rx_ring)
>  	if (xdp_rxq_info_is_reg(&rx_ring->xdp_rxq))
>  		xdp_rxq_info_unreg(&rx_ring->xdp_rxq);
>  	res = xdp_rxq_info_reg(&rx_ring->xdp_rxq, rx_ring->netdev,
> -			       rx_ring->queue_index,
> -			       rx_ring->q_vector->napi.napi_id);
> +			       rx_ring->queue_index, 0);
>  	if (res < 0) {
>  		dev_err(dev, "Failed to register xdp_rxq index %u\n",
>  			rx_ring->queue_index);

This LGTM but will probably need to be re-sent with a Fixes tag.

See: https://www.kernel.org/doc/html/v6.16/process/maintainer-netdev.html#tl-dr

If you repost, feel free to add:

Reviewed-by: Joe Damato <joe@...a.to>