Do skb_put() after a new skb has been successfully allocated otherwise
the reused skb leads to skb_panics or incorrect packet sizes.

Fixes: f92e1869d74e ("Add Mellanox BlueField Gigabit Ethernet driver")
Signed-off-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
Changes in v2:
- moved skb_put() after dma_unmap_single()
- added Fixes tag
- fixed typos in commit log

 .../ethernet/mellanox/mlxbf_gige/mlxbf_gige_rx.c    | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlxbf_gige/mlxbf_gige_rx.c b/drivers/net/ethernet/mellanox/mlxbf_gige/mlxbf_gige_rx.c
index afa3b92a6905..0d5a41a2ae01 100644
--- a/drivers/net/ethernet/mellanox/mlxbf_gige/mlxbf_gige_rx.c
+++ b/drivers/net/ethernet/mellanox/mlxbf_gige/mlxbf_gige_rx.c
@@ -245,12 +245,6 @@ static bool mlxbf_gige_rx_packet(struct mlxbf_gige *priv, int *rx_pkts)
 
 		skb = priv->rx_skb[rx_pi_rem];
 
-		skb_put(skb, datalen);
-
-		skb->ip_summed = CHECKSUM_NONE; /* device did not checksum packet */
-
-		skb->protocol = eth_type_trans(skb, netdev);
-
 		/* Alloc another RX SKB for this same index */
 		rx_skb = mlxbf_gige_alloc_skb(priv, MLXBF_GIGE_DEFAULT_BUF_SZ,
 					      &rx_buf_dma, DMA_FROM_DEVICE);
@@ -259,6 +253,13 @@ static bool mlxbf_gige_rx_packet(struct mlxbf_gige *priv, int *rx_pkts)
 		priv->rx_skb[rx_pi_rem] = rx_skb;
 		dma_unmap_single(priv->dev, *rx_wqe_addr,
 				 MLXBF_GIGE_DEFAULT_BUF_SZ, DMA_FROM_DEVICE);
+
+		skb_put(skb, datalen);
+
+		skb->ip_summed = CHECKSUM_NONE; /* device did not checksum packet */
+
+		skb->protocol = eth_type_trans(skb, netdev);
+
 		*rx_wqe_addr = rx_buf_dma;
 	} else if (rx_cqe & MLXBF_GIGE_RX_CQE_PKT_STATUS_MAC_ERR) {
 		priv->stats.rx_mac_errors++;
-- 
2.35.3

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Wed, 24 May 2023 21:49:08 +0200 you wrote:
> Do skb_put() after a new skb has been successfully allocated otherwise
> the reused skb leads to skb_panics or incorrect packet sizes.
> 
> Fixes: f92e1869d74e ("Add Mellanox BlueField Gigabit Ethernet driver")
> Signed-off-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
> ---
> Changes in v2:
> - moved skb_put() after dma_unmap_single()
> - added Fixes tag
> - fixed typos in commit log
> 
> [...]

Here is the summary with links:
  - [v2,net] net: mellanox: mlxbf_gige: Fix skb_panic splat under memory pressure
    https://git.kernel.org/netdev/net/c/d68cb7cf1fd0

You are awesome, thank you!
-- 
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On Wed, May 24, 2023 at 09:49:08PM +0200, Thomas Bogendoerfer wrote:
> Do skb_put() after a new skb has been successfully allocated otherwise
> the reused skb leads to skb_panics or incorrect packet sizes.
> 
> Fixes: f92e1869d74e ("Add Mellanox BlueField Gigabit Ethernet driver")
> Signed-off-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>

Reviewed-by: Simon Horman <simon.horman@corigine.com>