Add proper error checking for dmaengine_desc_get_metadata_ptr() which
can return an error pointer and lead to potential crashes or undefined
behaviour if the pointer retrieval fails.

Properly handle the error by unmapping DMA buffer, freeing the skb and
returning early to prevent further processing with invalid data.

Fixes: 6a91b846af85 ("net: axienet: Introduce dmaengine support")
Signed-off-by: Abin Joseph <abin.joseph@amd.com>
---
 drivers/net/ethernet/xilinx/xilinx_axienet_main.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
index 0d8a05fe541a..1729fd21d83b 100644
--- a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
+++ b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
@@ -1166,8 +1166,17 @@ static void axienet_dma_rx_cb(void *data, const struct dmaengine_result *result)
 	skb = skbuf_dma->skb;
 	app_metadata = dmaengine_desc_get_metadata_ptr(skbuf_dma->desc, &meta_len,
 						       &meta_max_len);
-	dma_unmap_single(lp->dev, skbuf_dma->dma_address, lp->max_frm_size,
-			 DMA_FROM_DEVICE);
+
+	dma_unmap_single(lp->dev, skbuf_dma->dma_address, lp->max_frm_size, DMA_FROM_DEVICE);
+
+	if (IS_ERR(app_metadata)) {
+		if (net_ratelimit())
+			netdev_err(lp->ndev, "Failed to get RX metadata pointer\n");
+		dev_kfree_skb_any(skb);
+		lp->ndev->stats.rx_dropped++;
+		goto rx_submit;
+	}
+
 	/* TODO: Derive app word index programmatically */
 	rx_len = (app_metadata[LEN_APP] & 0xFFFF);
 	skb_put(skb, rx_len);
@@ -1180,6 +1189,7 @@ static void axienet_dma_rx_cb(void *data, const struct dmaengine_result *result)
 	u64_stats_add(&lp->rx_bytes, rx_len);
 	u64_stats_update_end(&lp->rx_stat_sync);
 
+rx_submit:
 	for (i = 0; i < CIRC_SPACE(lp->rx_ring_head, lp->rx_ring_tail,
 				   RX_BUF_NUM_DEFAULT); i++)
 		axienet_rx_submit_desc(lp->ndev);
-- 
2.34.1

On Tue, 26 Aug 2025 23:35:49 +0530 Abin Joseph wrote:
> Subject: [PATCH net-next] net: xilinx: axienet: Add error handling for RX metadata pointer retrieval

Sounds like a fix, please repost as [PATCH net], against the
netdev/net tree.

> Add proper error checking for dmaengine_desc_get_metadata_ptr() which
> can return an error pointer and lead to potential crashes or undefined
> behaviour if the pointer retrieval fails.
> 
> Properly handle the error by unmapping DMA buffer, freeing the skb and
> returning early to prevent further processing with invalid data.
> 
> Fixes: 6a91b846af85 ("net: axienet: Introduce dmaengine support")
> Signed-off-by: Abin Joseph <abin.joseph@amd.com>
> ---
>  drivers/net/ethernet/xilinx/xilinx_axienet_main.c | 14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
> index 0d8a05fe541a..1729fd21d83b 100644
> --- a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
> +++ b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
> @@ -1166,8 +1166,17 @@ static void axienet_dma_rx_cb(void *data, const struct dmaengine_result *result)
>  	skb = skbuf_dma->skb;
>  	app_metadata = dmaengine_desc_get_metadata_ptr(skbuf_dma->desc, &meta_len,
>  						       &meta_max_len);
> -	dma_unmap_single(lp->dev, skbuf_dma->dma_address, lp->max_frm_size,
> -			 DMA_FROM_DEVICE);
> +
> +	dma_unmap_single(lp->dev, skbuf_dma->dma_address, lp->max_frm_size, DMA_FROM_DEVICE);

80 char width is still strongly preferred, at least in networking.
So please don't unwrap this line for no apparent reason :\

> +	if (IS_ERR(app_metadata)) {
-- 
pw-bot: cr