openwrt/target/linux/generic/backport-6.1/750-v6.5-20-net-ethernet-mtk_eth_soc-fix-uninitialized-variable.patch

From e10a35abb3da12b812cfb6fc6137926a0c81e39a Mon Sep 17 00:00:00 2001
From: Daniel Golle <daniel@makrotopia.org>
Date: Sun, 10 Sep 2023 22:40:30 +0100
Subject: [PATCH] net: ethernet: mtk_eth_soc: fix uninitialized variable

Variable dma_addr in function mtk_poll_rx can be uninitialized on
some of the error paths. In practise this doesn't matter, even random
data present in uninitialized stack memory can safely be used in the
way it happens in the error path.

However, in order to make Smatch happy make sure the variable is
always initialized.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
 drivers/net/ethernet/mediatek/mtk_eth_soc.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
+++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
@@ -1987,11 +1987,11 @@ static int mtk_poll_rx(struct napi_struc
 	u8 *data, *new_data;
 	struct mtk_rx_dma_v2 *rxd, trxd;
 	int done = 0, bytes = 0;
+	dma_addr_t dma_addr = DMA_MAPPING_ERROR;
 
 	while (done < budget) {
 		unsigned int pktlen, *rxdcsum;
 		struct net_device *netdev;
-		dma_addr_t dma_addr;
 		u32 hash, reason;
 		int mac = 0;
 
@@ -2168,7 +2168,8 @@ release_desc:
 		else
 			rxd->rxd2 = RX_DMA_PREP_PLEN0(ring->buf_size);
 
-		if (MTK_HAS_CAPS(eth->soc->caps, MTK_36BIT_DMA))
+		if (MTK_HAS_CAPS(eth->soc->caps, MTK_36BIT_DMA) &&
+		    likely(dma_addr != DMA_MAPPING_ERROR))
 			rxd->rxd2 |= RX_DMA_PREP_ADDR64(dma_addr);
 
 		ring->calc_idx = idx;