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Date:   Thu, 5 Jan 2023 16:47:55 -0800
MIME-Version: 1.0
Subject: Re: [PATCH bpf-next v6 07/17] bpf: XDP metadata RX kfuncs
Content-Language: en-US
To:     Stanislav Fomichev <sdf@google.com>
Cc:     ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org,
        song@kernel.org, yhs@fb.com, john.fastabend@gmail.com,
        kpsingh@kernel.org, haoluo@google.com, jolsa@kernel.org,
        David Ahern <dsahern@gmail.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Willem de Bruijn <willemb@google.com>,
        Jesper Dangaard Brouer <brouer@redhat.com>,
        Anatoly Burakov <anatoly.burakov@intel.com>,
        Alexander Lobakin <alexandr.lobakin@intel.com>,
        Magnus Karlsson <magnus.karlsson@gmail.com>,
        Maryam Tahhan <mtahhan@redhat.com>, xdp-hints@xdp-project.net,
        netdev@vger.kernel.org, bpf@vger.kernel.org
References: <20230104215949.529093-1-sdf@google.com>
 <20230104215949.529093-8-sdf@google.com>
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From:   Martin KaFai Lau <martin.lau@linux.dev>
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On 1/4/23 1:59 PM, Stanislav Fomichev wrote:
> +void *bpf_dev_bound_resolve_kfunc(struct bpf_prog *prog, u32 func_id)
> +{
> +	const struct xdp_metadata_ops *ops;
> +	void *p = NULL;
> +
> +	/* We don't hold bpf_devs_lock while resolving several
> +	 * kfuncs and can race with the unregister_netdevice().
> +	 * We rely on bpf_dev_bound_match() check at attach
> +	 * to render this program unusable.
> +	 */
> +	down_read(&bpf_devs_lock);
> +	if (!prog->aux->offload || !prog->aux->offload->netdev)

nit. !prog->aux->offload->netdev check is not needed. Testing 
!prog->aux->offload should be as good.