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>
---
v2: initialize with DMA_MAPPING_ERROR instead of NULL

 drivers/net/ethernet/mediatek/mtk_eth_soc.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/mediatek/mtk_eth_soc.c b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
index 31090490d47ce..6145ddcff206c 100644
--- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
+++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
@@ -2119,11 +2119,11 @@ static int mtk_poll_rx(struct napi_struct *napi, int budget,
 	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;
 
@@ -2300,7 +2300,8 @@ static int mtk_poll_rx(struct napi_struct *napi, int budget,
 		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;
-- 
2.42.0

Hello:

This patch was applied to netdev/net.git (main)
by David S. Miller <davem@davemloft.net>:

On Sun, 10 Sep 2023 22:40:30 +0100 you wrote:
> 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.
> 
> [...]

Here is the summary with links:
  - [net,v2] net: ethernet: mtk_eth_soc: fix uninitialized variable
    https://git.kernel.org/netdev/net/c/e10a35abb3da

You are awesome, thank you!
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