linux-kernel - Re: [PATCH v2 net 1/4] igc: Fix passing 0 to ERR_PTR in igc_xdp_run

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Message-ID: <ZxJSd4Hj5+TW01cc@boxer>
Date: Fri, 18 Oct 2024 14:20:07 +0200
From: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
To: Yue Haibing <yuehaibing@...wei.com>
CC: <anthony.l.nguyen@...el.com>, <przemyslaw.kitszel@...el.com>,
	<davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>,
	<pabeni@...hat.com>, <ast@...nel.org>, <daniel@...earbox.net>,
	<hawk@...nel.org>, <john.fastabend@...il.com>, <vedang.patel@...el.com>,
	<jithu.joseph@...el.com>, <andre.guedes@...el.com>, <horms@...nel.org>,
	<jacob.e.keller@...el.com>, <sven.auhagen@...eatech.de>,
	<alexander.h.duyck@...el.com>, <intel-wired-lan@...ts.osuosl.org>,
	<netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<bpf@...r.kernel.org>
Subject: Re: [PATCH v2 net 1/4] igc: Fix passing 0 to ERR_PTR in
 igc_xdp_run_prog()

On Fri, Oct 18, 2024 at 10:37:31AM +0800, Yue Haibing wrote:
> igc_xdp_run_prog() converts customed xdp action to a negative error code
> with the sk_buff pointer type which be checked with IS_ERR in
> igc_clean_rx_irq(). Remove this error pointer handing instead use plain
> int return value to fix this smatch warnings:
> 
> drivers/net/ethernet/intel/igc/igc_main.c:2533
>  igc_xdp_run_prog() warn: passing zero to 'ERR_PTR'
> 
> Fixes: 26575105d6ed ("igc: Add initial XDP support")
> Signed-off-by: Yue Haibing <yuehaibing@...wei.com>

Reviewed-by: Maciej Fijalkowski <maciej.fijalkowski@...el.com>

> ---
>  drivers/net/ethernet/intel/igc/igc_main.c | 20 +++++++-------------
>  1 file changed, 7 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
> index 6e70bca15db1..5e44c2546a12 100644
> --- a/drivers/net/ethernet/intel/igc/igc_main.c
> +++ b/drivers/net/ethernet/intel/igc/igc_main.c
> @@ -2123,10 +2123,6 @@ static bool igc_cleanup_headers(struct igc_ring *rx_ring,
>  				union igc_adv_rx_desc *rx_desc,
>  				struct sk_buff *skb)
>  {
> -	/* XDP packets use error pointer so abort at this point */
> -	if (IS_ERR(skb))
> -		return true;
> -
>  	if (unlikely(igc_test_staterr(rx_desc, IGC_RXDEXT_STATERR_RXE))) {
>  		struct net_device *netdev = rx_ring->netdev;
>  
> @@ -2515,8 +2511,7 @@ static int __igc_xdp_run_prog(struct igc_adapter *adapter,
>  	}
>  }
>  
> -static struct sk_buff *igc_xdp_run_prog(struct igc_adapter *adapter,
> -					struct xdp_buff *xdp)
> +static int igc_xdp_run_prog(struct igc_adapter *adapter, struct xdp_buff *xdp)
>  {
>  	struct bpf_prog *prog;
>  	int res;
> @@ -2530,7 +2525,7 @@ static struct sk_buff *igc_xdp_run_prog(struct igc_adapter *adapter,
>  	res = __igc_xdp_run_prog(adapter, prog, xdp);
>  
>  out:
> -	return ERR_PTR(-res);
> +	return res;
>  }
>  
>  /* This function assumes __netif_tx_lock is held by the caller. */
> @@ -2585,6 +2580,7 @@ static int igc_clean_rx_irq(struct igc_q_vector *q_vector, const int budget)
>  	struct sk_buff *skb = rx_ring->skb;
>  	u16 cleaned_count = igc_desc_unused(rx_ring);
>  	int xdp_status = 0, rx_buffer_pgcnt;
> +	int xdp_res = 0;
>  
>  	while (likely(total_packets < budget)) {
>  		struct igc_xdp_buff ctx = { .rx_ts = NULL };
> @@ -2630,12 +2626,10 @@ static int igc_clean_rx_irq(struct igc_q_vector *q_vector, const int budget)
>  			xdp_buff_clear_frags_flag(&ctx.xdp);
>  			ctx.rx_desc = rx_desc;
>  
> -			skb = igc_xdp_run_prog(adapter, &ctx.xdp);
> +			xdp_res = igc_xdp_run_prog(adapter, &ctx.xdp);
>  		}
>  
> -		if (IS_ERR(skb)) {
> -			unsigned int xdp_res = -PTR_ERR(skb);
> -
> +		if (xdp_res) {
>  			switch (xdp_res) {
>  			case IGC_XDP_CONSUMED:
>  				rx_buffer->pagecnt_bias++;
> @@ -2657,7 +2651,7 @@ static int igc_clean_rx_irq(struct igc_q_vector *q_vector, const int budget)
>  			skb = igc_construct_skb(rx_ring, rx_buffer, &ctx);
>  
>  		/* exit if we failed to retrieve a buffer */
> -		if (!skb) {
> +		if (!xdp_res && !skb) {
>  			rx_ring->rx_stats.alloc_failed++;
>  			rx_buffer->pagecnt_bias++;
>  			set_bit(IGC_RING_FLAG_RX_ALLOC_FAILED, &rx_ring->flags);
> @@ -2672,7 +2666,7 @@ static int igc_clean_rx_irq(struct igc_q_vector *q_vector, const int budget)
>  			continue;
>  
>  		/* verify the packet layout is correct */
> -		if (igc_cleanup_headers(rx_ring, rx_desc, skb)) {
> +		if (xdp_res || igc_cleanup_headers(rx_ring, rx_desc, skb)) {
>  			skb = NULL;
>  			continue;
>  		}
> -- 
> 2.34.1
>