igc: Fix passing 0 to ERR_PTR in igc_xdp_run_prog()

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'

Reviewed-by: Maciej Fijalkowski <[email protected]>
Reviewed-by: Jacob Keller <[email protected]>
Signed-off-by: Yue Haibing <[email protected]>
Reviewed-by: Simon Horman <[email protected]>
Tested-by: Avigail Dahan <[email protected]>
Signed-off-by: Tony Nguyen <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: Yue Haibing

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;
 		}