When an XDP redirect to an AF_XDP socket fails because its RX ring is full, the XSK core frees the buffer. During the subsequent batched refill of a legacy cyclic RQ, mlx5e also releases the WQE's XSK buffer before allocating a replacement. If that refill succeeds only partially, a WQE left without a replacement retains its old buffer pointer. The buffer can meanwhile be allocated to another WQE. A later refill retry can then free the live buffer through the stale pointer and publish the same UMEM frame twice. Mark the WQE as released immediately after the driver-side free. The flag is already cleared when a replacement buffer is assigned, so refill retries no longer release stale pointers. The failure is silent and produces no kernel warning or splat. A standalone legacy cyclic-RQ zero-copy libxsk reproducer, using 64-byte UDP traffic offered at 12 Mpps, detected it: stock stopped after 2,854,914 packets in 4.094 seconds, with 4,542 xdp_rx_ring_full events and 64 ownership/double-publication errors. With this change it processed 356,904,225 packets in 30 seconds despite 571,405 xdp_rx_ring_full events, with no ownership or data errors. Fixes: 3f93f82988bc ("net/mlx5e: RX, Defer page release in legacy rq for better recycling") Cc: stable@vger.kernel.org Suggested-by: Daniel Borkmann Reviewed-by: Dragos Tatulea Signed-off-by: Jerome Tollet --- Changes in v2: - Reorder and tighten the problem statement. - State explicitly that the failure produces no warning or splat. - Add Dragos' Reviewed-by tag. v1: https://lore.kernel.org/netdev/20260819151320.64178-1-jtollet@cisco.com/ drivers/net/ethernet/mellanox/mlx5/core/en_rx.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c index 6fc6605d2..7967a2737 100644 --- a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c @@ -410,8 +410,11 @@ static inline void mlx5e_free_rx_wqe(struct mlx5e_rq *rq, static void mlx5e_xsk_free_rx_wqe(struct mlx5e_wqe_frag_info *wi) { - if (!(wi->flags & BIT(MLX5E_WQE_FRAG_SKIP_RELEASE))) - xsk_buff_free(*wi->xskp); + if (wi->flags & BIT(MLX5E_WQE_FRAG_SKIP_RELEASE)) + return; + + xsk_buff_free(*wi->xskp); + wi->flags |= BIT(MLX5E_WQE_FRAG_SKIP_RELEASE); } static void mlx5e_dealloc_rx_wqe(struct mlx5e_rq *rq, u16 ix) -- 2.55.0