netdev - Re: [PATCH net-next v3 2/4] bpf, mlx5: fix various refcount issues in mlx5e_xdp

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Date:   Mon, 21 Nov 2016 11:30:54 +0200
From:   Saeed Mahameed <saeedm@....mellanox.co.il>
To:     Daniel Borkmann <daniel@...earbox.net>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Brenden Blanco <bblanco@...mgrid.com>,
        Zhiyi Sun <zhiyisun@...il.com>,
        Rana Shahout <ranas@...lanox.com>,
        Saeed Mahameed <saeedm@...lanox.com>,
        Linux Netdev List <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next v3 2/4] bpf, mlx5: fix various refcount issues in mlx5e_xdp_set

On Sat, Nov 19, 2016 at 2:45 AM, Daniel Borkmann <daniel@...earbox.net> wrote:
> There are multiple issues in mlx5e_xdp_set():
>
> 1) The batched bpf_prog_add() is currently not checked for errors. When
>    doing so, it should be done at an earlier point in time to makes sure
>    that we cannot fail anymore at the time we want to set the program for
>    each channel. The batched refs short-cut can only be performed when we
>    don't need to perform a reset for changing the rq type and the device
>    was in opened state. In case the device was not in opened state, then
>    the next mlx5e_open_locked() will aquire the refs from the control prog
>    via mlx5e_create_rq(), same when we need to perform a reset.
>
> 2) When swapping the priv->xdp_prog, then no extra reference count must be
>    taken since we got that from call path via dev_change_xdp_fd() already.
>    Otherwise, we'd never be able to release the program. Also, bpf_prog_add()
>    without checking the return code could fail.
>
> Fixes: 86994156c736 ("net/mlx5e: XDP fast RX drop bpf programs support")
> Signed-off-by: Daniel Borkmann <daniel@...earbox.net>

Acked-by: Saeed Mahameed <saeedm@...lanox.com>