netdev - Re: [PATCH net-next] bpf, mlx4: fix prog refcount in mlx4_en_try_alloc

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Date:   Sat, 12 Nov 2016 23:34:09 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     daniel@...earbox.net
Cc:     alexei.starovoitov@...il.com, bblanco@...mgrid.com,
        tariqt@...lanox.com, zhiyisun@...il.com, netdev@...r.kernel.org
Subject: Re: [PATCH net-next] bpf, mlx4: fix prog refcount in
 mlx4_en_try_alloc_resources error path

From: Daniel Borkmann <daniel@...earbox.net>
Date: Wed,  9 Nov 2016 22:02:34 +0100

> Commit 67f8b1dcb9ee ("net/mlx4_en: Refactor the XDP forwarding rings
> scheme") added a bug in that the prog's reference count is not dropped
> in the error path when mlx4_en_try_alloc_resources() is failing from
> mlx4_xdp_set().
> 
> We previously took bpf_prog_add(prog, priv->rx_ring_num - 1), that we
> need to release again. Earlier in the call path, dev_change_xdp_fd()
> itself holds a reference to the prog as well (hence the '- 1' in the
> bpf_prog_add()), so a simple atomic_sub() is safe to use here. When
> an error is propagated, then bpf_prog_put() is called eventually from
> dev_change_xdp_fd()
> 
> Fixes: 67f8b1dcb9ee ("net/mlx4_en: Refactor the XDP forwarding rings scheme")
> Signed-off-by: Daniel Borkmann <daniel@...earbox.net>

Applied, thanks Daniel.