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From: Maxim Mikityanskiy <maximmi@mellanox.com>
To: Alexei Starovoitov <ast@kernel.org>,
	"David S. Miller" <davem@davemloft.net>
Cc: "Daniel Borkmann" <daniel@iogearbox.net>,
	"Björn Töpel" <bjorn.topel@intel.com>,
	"bpf@vger.kernel.org" <bpf@vger.kernel.org>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	"Saeed Mahameed" <saeedm@mellanox.com>,
	"Jakub Kicinski" <jakub.kicinski@netronome.com>,
	"Jesper Dangaard Brouer" <hawk@kernel.org>,
	"John Fastabend" <john.fastabend@gmail.com>,
	"Martin KaFai Lau" <kafai@fb.com>,
	"Song Liu" <songliubraving@fb.com>, "Yonghong Song" <yhs@fb.com>
Subject: Re: [PATCH bpf-next] net: Don't uninstall an XDP program when none is installed
Date: Wed, 10 Jul 2019 11:16:05 +0000	[thread overview]
Message-ID: <3124b473-1322-e98e-d5ab-60e584e74200@mellanox.com> (raw)
In-Reply-To: <20190612161405.24064-1-maximmi@mellanox.com>

On 2019-06-12 19:14, Maxim Mikityanskiy wrote:
> dev_change_xdp_fd doesn't perform any checks in case it uninstalls an
> XDP program. It means that the driver's ndo_bpf can be called with
> XDP_SETUP_PROG asking to set it to NULL even if it's already NULL. This
> case happens if the user runs `ip link set eth0 xdp off` when there is
> no XDP program attached.
> 
> The drivers typically perform some heavy operations on XDP_SETUP_PROG,
> so they all have to handle this case internally to return early if it
> happens. This patch puts this check into the kernel code, so that all
> drivers will benefit from it.
> 
> Signed-off-by: Maxim Mikityanskiy <maximmi@mellanox.com>
> ---
> Björn, please take a look at this, Saeed told me you were doing
> something related, but I couldn't find it. If this fix is already
> covered by your work, please tell about that.
> 
>   net/core/dev.c | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/net/core/dev.c b/net/core/dev.c
> index 66f7508825bd..68b3e3320ceb 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -8089,6 +8089,9 @@ int dev_change_xdp_fd(struct net_device *dev, struct netlink_ext_ack *extack,
>   			bpf_prog_put(prog);
>   			return -EINVAL;
>   		}
> +	} else {
> +		if (!__dev_xdp_query(dev, bpf_op, query))
> +			return 0;
>   	}
>   
>   	err = dev_xdp_install(dev, bpf_op, extack, flags, prog);
> 

Alexei, so what about this patch? It's marked as "Changed Requested" in 
patchwork, but Jakub's point looks resolved - I don't see any changes 
required from my side.

  parent reply	other threads:[~2019-07-10 11:16 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-12 16:14 [PATCH bpf-next] net: Don't uninstall an XDP program when none is installed Maxim Mikityanskiy
2019-06-12 18:39 ` Björn Töpel
2019-06-12 21:15 ` Jakub Kicinski
2019-06-13  9:04   ` Björn Töpel
2019-06-13 17:26     ` Jakub Kicinski
2019-07-10 11:16 ` Maxim Mikityanskiy [this message]
2019-07-12 15:44   ` Daniel Borkmann
2019-08-14 14:34     ` [PATCH bpf-next v2] net: Don't call XDP_SETUP_PROG when nothing is changed Maxim Mikityanskiy
2019-08-14 17:57       ` Jonathan Lemon
2019-08-14 22:01       ` Jakub Kicinski
2019-08-17 21:29       ` Daniel Borkmann

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