Re: [PATCH] net/mlx4_en: Fix bpf_prog_add ref_cnt in mlx4
From: Daniel Borkmann <hidden>
Date: 2016-11-09 09:05:41
Also in:
linux-rdma, lkml
On 11/09/2016 08:35 AM, Zhiyi Sun wrote:
There are rx_ring_num queues. Each queue will load xdp prog. So bpf_prog_add() should add rx_ring_num to ref_cnt. Signed-off-by: Zhiyi Sun <redacted>
Your analysis looks incorrect to me. Please elaborate in more detail why you think current code is buggy ... Call path is dev_change_xdp_fd(), which does bpf_prog_get_type() on the fd. This already takes a ref and only drops it in case of error. Thus in mlx4_xdp_set(), you only need priv->rx_ring_num - 1 refs for the rest of the rings, so that dropping refs from old_prog makes sure we release it again. Looks correct to me (maybe a comment would have helped there).
quoted hunk ↗ jump to hunk
drivers/net/ethernet/mellanox/mlx4/en_netdev.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)diff --git a/drivers/net/ethernet/mellanox/mlx4/en_netdev.c b/drivers/net/ethernet/mellanox/mlx4/en_netdev.c index 12c99a2..d25e150 100644 --- a/drivers/net/ethernet/mellanox/mlx4/en_netdev.c +++ b/drivers/net/ethernet/mellanox/mlx4/en_netdev.c@@ -2650,7 +2650,7 @@ static int mlx4_xdp_set(struct net_device *dev, struct bpf_prog *prog) */ if (priv->xdp_ring_num == xdp_ring_num) { if (prog) { - prog = bpf_prog_add(prog, priv->rx_ring_num - 1); + prog = bpf_prog_add(prog, priv->rx_ring_num); if (IS_ERR(prog)) return PTR_ERR(prog); }@@ -2680,7 +2680,7 @@ static int mlx4_xdp_set(struct net_device *dev, struct bpf_prog *prog) } if (prog) { - prog = bpf_prog_add(prog, priv->rx_ring_num - 1); + prog = bpf_prog_add(prog, priv->rx_ring_num); if (IS_ERR(prog)) return PTR_ERR(prog); }
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