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

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

[Paul Moses]

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

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

[netdev-bot+sinfo]

Hi!

This is an automated message. This series looks like a fix, but its
commit messages seem to be missing some information:

 - How the issue was discovered, e.g. hit in production, hit during
   development, syzbot report, manual code inspection, LLM or static
   analysis tool scan.

Please do not repost the series just to address the above. Instead,
reply to this email with the missing information, so that reviewers
can take it into account. If the series needs another revision for
other reasons, please include the information in the commit messages
then.

The evaluation is done by an LLM so it may be wrong, if you think
that is the case please reply and explain.