[PATCH net] igc: return XSK frame copies on XDP_TX failure

[Paul Moses <p@1g4.org>]

Converting an XSK buffer to an XDP frame allocates a page and returns
the original buffer to its pool. If the TX ring is full or DMA mapping
fails, igc_xdp_xmit_back() returns an error without freeing the copy.
The RX cleaner cannot release it, so the page leaks.

Return the copied frame on TX failure. Save the RX memory type before
conversion so native frames remain RX-owned on failure.

Fixes: fc9df2a0b520 ("igc: Enable RX via AF_XDP zero-copy")
Cc: stable@vger.kernel.org
Signed-off-by: Paul Moses <p@1g4.org>
---
Tested on Intel I225-V with baseline and patched kernels. Physical
pause-frame backpressure caused 46 leaked copies on the baseline.
With the fix, all 72 rejected copies were returned once and freed,
and all 192 copies were accounted for. 

 drivers/net/ethernet/intel/igc/igc_main.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
index 1fb5f3cbe93c..39263fd04aa9 100644
--- a/drivers/net/ethernet/intel/igc/igc_main.c
+++ b/drivers/net/ethernet/intel/igc/igc_main.c
@@ -2487,6 +2487,7 @@ struct igc_ring *igc_get_tx_ring(struct igc_adapter *adapter, int cpu)
 
 static int igc_xdp_xmit_back(struct igc_adapter *adapter, struct xdp_buff *xdp)
 {
+	enum xdp_mem_type mem_type = xdp->rxq->mem.type;
 	struct xdp_frame *xdpf = xdp_convert_buff_to_frame(xdp);
 	int cpu = smp_processor_id();
 	struct netdev_queue *nq;
@@ -2504,6 +2505,10 @@ static int igc_xdp_xmit_back(struct igc_adapter *adapter, struct xdp_buff *xdp)
 	txq_trans_cond_update(nq);
 	res = igc_xdp_init_tx_descriptor(ring, xdpf);
 	__netif_tx_unlock(nq);
+
+	if (res && mem_type == MEM_TYPE_XSK_BUFF_POOL)
+		xdp_return_frame(xdpf);
+
 	return res;
 }
 
-- 
2.56.GIT