[PATCH net] net: ti: icssg-prueth: fix XDP_TX from the AF_XDP zero-copy RX path

[PATCH net] net: ti: icssg-prueth: fix XDP_TX from the AF_XDP zero-copy RX path

[David Carlier]

On XDP_TX from the zero-copy RX path, emac_run_xdp() converts the xsk
buffer via xdp_convert_zc_to_xdp_frame(), which clones the data into a
fresh MEM_TYPE_PAGE_ORDER0 page that is not DMA mapped. Transmitting it
as PRUETH_TX_BUFF_TYPE_XDP_TX derives the DMA address with
page_pool_get_dma_addr(), reading an uninitialized page->dma_addr, so
the device DMAs from a bogus address (corrupt TX, or an IOMMU fault).

Pick the TX buffer type from the frame's memory type: keep
PRUETH_TX_BUFF_TYPE_XDP_TX for page_pool frames and use
PRUETH_TX_BUFF_TYPE_XDP_NDO for the cloned zero-copy frame. The
completion path already unmaps PRUETH_SWDATA_XDPF buffers.

Fixes: 7a64bb388df3 ("net: ti: icssg-prueth: Add AF_XDP zero copy for RX")
Cc: stable@vger.kernel.org
Signed-off-by: David Carlier <devnexen@gmail.com>
---
 drivers/net/ethernet/ti/icssg/icssg_common.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/ti/icssg/icssg_common.c b/drivers/net/ethernet/ti/icssg/icssg_common.c
index 82ddef9c17d5..302e700ea17d 100644
--- a/drivers/net/ethernet/ti/icssg/icssg_common.c
+++ b/drivers/net/ethernet/ti/icssg/icssg_common.c
@@ -804,6 +804,7 @@ EXPORT_SYMBOL_GPL(emac_xmit_xdp_frame);
  */
 static u32 emac_run_xdp(struct prueth_emac *emac, struct xdp_buff *xdp, u32 *len)
 {
+	enum prueth_tx_buff_type tx_buff_type;
 	struct net_device *ndev = emac->ndev;
 	struct netdev_queue *netif_txq;
 	int cpu = smp_processor_id();
@@ -826,11 +827,21 @@ static u32 emac_run_xdp(struct prueth_emac *emac, struct xdp_buff *xdp, u32 *len
 			goto drop;
 		}
 
+		/* In AF_XDP zero-copy mode xdp_convert_buff_to_frame()
+		 * clones the xsk buffer into a fresh MEM_TYPE_PAGE_ORDER0
+		 * page that is not DMA mapped. Such a frame must be mapped
+		 * via the NDO path; only a page pool-backed frame already
+		 * carries a usable page_pool DMA address.
+		 */
+		tx_buff_type = xdpf->mem_type == MEM_TYPE_PAGE_POOL ?
+				PRUETH_TX_BUFF_TYPE_XDP_TX :
+				PRUETH_TX_BUFF_TYPE_XDP_NDO;
+
 		q_idx = cpu % emac->tx_ch_num;
 		netif_txq = netdev_get_tx_queue(ndev, q_idx);
 		__netif_tx_lock(netif_txq, cpu);
 		result = emac_xmit_xdp_frame(emac, xdpf, q_idx,
-					     PRUETH_TX_BUFF_TYPE_XDP_TX);
+					     tx_buff_type);
 		__netif_tx_unlock(netif_txq);
 		if (result == ICSSG_XDP_CONSUMED) {
 			ndev->stats.tx_dropped++;
-- 
2.53.0